OSO.90 - part 1 (translated)

1NORM OS.090PLANTS OF RESIDUAL WATER TREATMENT1, OBJETO……………………………………………………………………….…... 052, ALCANCE……………………………………………………………………..…053, DEFINICION……………………………………………………………………..054, DISPOSITIONS GENERALES………………………………………………174,1 Object of tratamiento……………………………………………………….....174,2 Basic direction for diseño………………………………………….....174,3 Norms for the studies of factibilidad……………………………………..184,4 Norms for the engineering studies básica……………………………….225, SPECIFIC DISPOSITIONS FOR DESIGNS DEFINITIVOS………..235,1 Aspects generales………………………………………………………………..235,2 Works of llegada…………………………………………………………………..245,3 Treatment preliminar……………………………………………………………265.3.1 Cribas………………………………………………………………………………265.3.2 Desarenadores…………………………………………………………………….275.3.3 Measurer and distributors of caudal………………………………………………..285,4 Treatment primario……………………………………………………………….295.4.1 Generalidades…………………………………………………………………….295.4.2 Imhoff…………………………………………………………………..29 tanks5.4.3 Tanks of sedimentación……………………………………………………….315.4.4 Tanks of flotación……………………………………………………………..345,5 Treatment secundarios…………………………………………………………345.5.1. Generalidades…………………………………………………………………….345.5.2. Lagoons of estabilización…………………………………………………………345.5.2.1 Aspects generales………………………………………………………………..345.5.2.2 Lagoons anaerobias……………………………………………………………..355.5.2.3 Lagoons aeradas………………………………………………………………….365.5.2.4 Lagoons facultativas………………………………………………………………..385.5.2.5 Design of lagoons for the removal of organisms patógenos……………..405.5.2.6. General norms for the design of lagunas………………………………….4125.5.3. Treatment with mud processes activados………………………………….435.5.3.1 Aspects generales………………………………………………………………..435.5.3.2 Sedimentador secundario………………………………………………………..485.5.3.3 Ditches of oxidación………………………………………………………………... 505.5.4 Filters percoladores………………………………………………………………..525.5.5 Rotating biological systems of contacto……………………………………….545.6 Other types of tratamiento……………………………………………………….545.6.1 Application on the land and reuso agrícola………………………………..…545.6.2 Intermittent filters of arena……………………………………………………565.6.3 Anaerobic treatment of flow ascendente…………………………………..575,7 Desinfección……………………………………………………………………….605,8 Tertiary water treatment residuales………………………………………605,9 Treatment of lodos……………………………………………………………..615.9.1 Generalidades……………………………………………………………………..615.9.2 Digestion anaerobia……………………………………………………………….625.9.3 Lagoons of lodos………………………………………………………………….635.9.4 Application of muds on terreno…………………………………………….635.9.5 Mud removal of the lagoons of estabilización…………………………645.9.6 Beds of secado…………………………………………………………………643PRACTICAL STANDARDS OF S.090 CONSTRUCTIONPLANTS OF RESIDUAL WATER TREATMENT1 OBJECTThe primary target is to normar the development of projects of treatment ofresidual waters in the levels preliminary, basic and definitive.2 IT REACHES2.1 The present norms are related to the facilities that they requirea plant of municipal residual water treatment and the processes thatthey must experience residual waters before its unloading to the bodyreceiver or to its reusability.3 DEFINITIONS3,1 AdsorptionFisicoquímico phenomenon that consists of the fixation of gaseous substances,dissolved liquid or free molecules in the surface of a solid.3,2 AbsorptionSelective solid fixation and concentration dissolved insidesolid material, by diffusion.3,3 AcidityThe capacity of a watery solution to react with ions hidroxilountil pH of neutralization.3.4 Water-bearingGeologic formation of porous material able to store an appreciable oneamount of water.3,5 VentilationProcess of oxygen transference of the air to the water by natural means(natural flow, cascades, etc.) or artificial (mechanical agitation or diffusion ofcompressed air).3,6 Mechanical ventilationOxygen introduction of the air in a liquid by action of an agitatormechanic.3,7 Prolonged ventilationA modification of the treatment with activated muds that it facilitates4mineralización of mud in the ventilation tank.3,8 Adensador (Espesador)Treatment to remove liquid of muds and to reduce its volume.3,9 AffluentWater or another liquid that enter to reservorio, plant of treatment ortreatment process.3,10 Residual waterWater that has been used by a community or trains and that contains materialorganic or inorganic dissolved or in suspension.3,11 Domestic residual waterWater of domestic, commercial and institutional origin that contains remaindersphysiological and other originating ones of the human activity.3,12 Municipal residual waterThey are domestic residual waters. It is possible to be included under this definition todomestic residual water mixture with waters of pluvial drainage or withresidual waters of industrial origin, whenever these fulfillrequirements to be admitted in the systems of type sewage systemcombined.3.13 AnaerobicCondition in which there is presence of air or free no oxygen.3,14 AnalysisThe examination of a substance to identify its components.3,15 Application in the landApplication of residual water or muds partially treated, under conditionscontrolled, in the land.3,16 BacteriaGroup of unicellular microscopic organisms, with bacterial chromosomeonly, binary division and that takes part in the processes of stabilization oforganic matter.3.17 Bases of designData set for the final and intermediate conditions of the design thatthey serve for the sizing of the treatment processes. The datathey include generally: populations, volumes, concentrations and I contribute to percápita of residual waters. The parameters that usually determinebases of the design are: DBO, fecales solids in suspension, coliformes andnutrients.3,18 BiodegradaciónTransformation of the organic matter in composed less complexes, by5action of microorganisms.3,19 BiopelículaBiological film adhered to an average solid and that carries out the degradationof the organic matter.3,20 By-passSet of used elements to turn aside the water residual of a processor plant of treatment in conditions of emergency, maintenance or ofoperation.3,21 Camera of contactExtended tank which the residual water treated enters in contact withagent disinfectant.3,22 Activated charcoalCarbonáceos grains that have a high capacity of selective removalof soluble compounds, by adsorption.3,23 Load of the designRelation between volume and concentration of a specific parameter that is usedin order to determine the proportions a process of the treatment.3,24 Surface loadingVolume or mass of a parameter by area unit that is used stopsto determine the proportions a process of the treatment.3.25 Of great volume tipMaximum volume in a given interval.3.26 Hour maximum volumeVolume at the time of Maxima unloads.3.27 Of great volume meansAverage of the daily volumes in a certain period.3,28 CertificationProgram of the organization of control to credit the capacity of the personnel ofoperation and maintenance of a treatment plant.3,29 ClarificationProcess of sedimentation to eliminate sedimentables solids of the waterresidual.3,30 CloraciónApplication of chlorine or composed of chlorine to the residual water for disinfection andin some cases for chemical oxidation or control of scents.3,31 Coagulation6Colloidal particle agglomeration (< 0,001 mm) y dispersas (0,001 a 0,01mm) in visible clots, by addition of a coagulant.3,32 CoagulantSimple electrolyte, usually inorganic salt, that contains a cationmultivalente of iron, aluminum or calcium. It is used to destabilizecolloidal particles favoring its agglomeration.3,33 ColiformesGram not esporuladas negative bacteria of form extended able ofto ferment lactose with gas production to 35 +/- 0.5 ºC (coliformes totals).Those that have the same properties to 44,5 +/- 0.2 ºC in 24 hoursthey denominate fecales coliformes (now also denominated coliformestermotolerantes).3,34 CompensationProcess by which residual water is stored and cushions the variationsextreme of unloading, homogenizando themselves its quality and being avoided of great volumetip.3.35 Heavy sieveDevice of parallel bars of separation generally uniforms (4 to 10cm) to remove floating solids of great size.3.36 It sifts AverageStructure of parallel bars of separation uniforms (2 to 4 cm) to removefloating solids and in suspension; one is used generally in the treatmentpreliminary.3,37 Criteria of designGuides of engineering who specify objectives, results or limits that mustto be fulfilled in the design of a process, structures or component of a system.3,38 Roadside ditch of coronationOpened channel, had generally, that is located in a plant oftreatment with the purpose of collecting and turning aside waters pluvial.3,39 Biochemical demand of oxygen (DBO)Amount of oxygen that requires the microorganisms for the stabilizationof the organic matter under conditions of specific time and temperature(generally 5 days and to 20ºC).3,40 Chemical demand of oxygen (DQO)Measurement of the amount of oxygen required for the chemical oxidation oforganic matter of the residual water, using like oxidating inorganic saltsof permanganato or dichromate of potassium.3,41 Density of energyRelation of the installed power of a aerador and the volume, in a tank ofventilation, aerada lagoon or digestor aerobe.73,42 Residual water purificationPurification or removal of objectionable substances of residual waters; it applies to processes of treatment of liquids exclusively.3.43 Accidental spillNot planned direct or indirect unloading of a liquid that containsundesirable substances that cause well-known adverse effects in the quality ofreceiving body. This unloading can be result of an accident, effectnatural or unsuitable operation.3,44 DesarenadoresDesigned camera to reduce the speed of the residual water and to allowmineral solid removal (sand and others), by sedimentation.3,45 Controlled unloadingRegulation of the unloading of the crude residual water to eliminateextreme variations of volume and quality.3.46 Acid remainderUnloading that an appreciable amount of acidity contains and pH low.3.47 Dangerous remainderRemainder that has one or more of the following characteristics: corrosive,reagent, explosive, toxic, inflammable or infectious.3.48 Industrial remainderRemainder originated in the manufacture of a specific product.3,49 Mud dehydrationProcess of removal of the water contained in muds.3,50 DisinfectionThe destruction of present microorganisms in residual watersby means of the use of an agent disinfectant.3,51 DiffuserPorous plate, tube or another device, through which air is injectedtablet or other gases in bubbles, to the liquid mass.3,52 DigestionBiological decomposition of the organic matter of the mud that produces onemineralización, liquefaction and partial gasificación.3,53 Aerobic digestionBiological decomposition of the organic matter of mud, in the presence ofoxygen.3,54 Anaerobic digestion8Biological decomposition of the organic matter of mud, in absence ofoxygen.3,55 Final dispositionDisposition of the efluente or the mud treated about a treatment plant.3,56 Rotating distributorMovable device that turns around a central axis and is made up ofhorizontal arms with orifices that unload the residual water on a filterbiological. The action of unloading of the orifices produces the movementmetropolitan newspaper.3,57 Age of mudParameter of design and own operation of the activated mud processesthat it is from the relation of the mass of present volatile solids intank of ventilation divided by the mass of removed volatile solids ofsystem per day. The parameter is expressed in days.3,58 Efficiency of the treatmentRelation between the mass or removed concentration and the mass or concentrationapplied, in a process or plant of treatment and for a parameterspecific. It can express in decimal or percentage.3,59 EfluenteLiquid that leaves a treatment process.3,60 Final EfluenteLiquid that leaves a plant of residual water treatment.3,61 Submarine emissaryComplementary pipe and accessories that allow the disposition ofresidual waters pretreated in the sea.3.62 EmitterChannel or pipe that receives residual waters of a sewage system systemuntil a plant of treatment or a plant of treatment until a pointof final disposition.3,63 Bacteriological examinationAnalysis to determine and to quantify the number of bacteria in watersresidual.3,64 Factor of loadOperational parameter and of design of the activated mud process that isto divide the mass of the substrate (kg DBO/d) that it feeds a tank onventilation, between the mass of microorganisms in the system, represented bymass of volatile solids.3.65 Biological filter9Synonymous of “filtro percolador”, “lecho bacterial of contacto” or "biofiltro".3.66 Percolador filterSystem in which the settled residual water is applied on meansfilter of synthetic heavy or material stone. The film of microorganismsthat it is developed on filter means stabilizes the organic matter ofresidual water.3,67 Nonprecise sourceSource of dispersed contamination.3,68 Point sourceAny defined source that unloads or can unload polluting agents.3,69 Degree of treatmentEfficiency of removal of a plant of residual water treatment stopsto fulfill the requirements of quality of the receiving body or the norms ofreuso.3,70 EqualizationTo see compensation.3,71 Environmental impactChange or effect on the atmosphere that is from a specific action.3.72 RaincoatThat it prevents the passage of a liquid.3,73 InterceptorChannel or pipe that receives the residual water volume of unloadingscross-sectional and it leads them to a treatment plant.3,74 Superficial irrigationApplication of residual waters in the land in such a way that they flow from oneor several points until the end of a lot.3,75 IVL (Volumetric mud Index)Volume in milliliters occupied by a gram of solids, in dry weight, ofwater mixes mud/after a sedimentation of 30 minutes in a cylindergraduated as 1000 mililiter.3,76 Aerada lagoonPool for the residual water treatment in which oxygen is injectedby mechanical action or compressed air diffusion.3,77 Aerobic lagoonPool with high production of biomass.3,78 Anaerobic lagoonPool with high laid-down load in which the treatment takes place in10oxygen absence. This type of lagoon requires later treatmentcomplementary.3,79 Lagoon of high production of biomassPool of form normally extended, with a short period of retention,depth reduced and with mixture facilities that maximize the productionof seaweed. (Other used terms but that are tending to the disuse are:“laguna aerobic ", “laguna fotosintética” and “laguna of discharge tasa”).3,80 Lagoon of stabilizationPool in which unloading residual waters and in where one takes placeestalibilización of organic matter and the bacterial reduction.3,81 Lagoon of controlled unloadingPool of treated residual water storage, normally stopsreuso agriculturist, in who the treated efluente dams up to be used inshe forms discontinuous, during the periods of greater demand.3,82 Mud lagoonPool for storage, digestion or removal of the liquid of mud.3,83 Lagoon of maturationPool of stabilization to treat the secondary efluente or watersresidual previously treated by a system of lagoons, in whereit produces an additional reduction of bacteria. The terms “lagunas ofpulimento” or “lagunas of acabado” they have the same meaning.3,84 Facultative lagoonPool whose oxygen content varies in agreement with the depth andhour of the day.In the superior layer of a facultative lagoon a symbiosis exists betweenseaweed and bacteria in the presence of oxygen, and in the inferior layersit produces an anaerobic biodegradación.3,85 Bacterial beds of contact(Synonymous of “filtros biológicos” or percoladores “filtros).3,86 Bed of dryingTanks of depth reduced with sand and burden on you drain, destined athe mud dehydration by filtration and evaporation.3,87 Mixed LicorMixture of activated mud and liquid remainder, under ventilation in the process ofactivated muds.3,88 Activated mudConstituted mud mainly of biomass with some amount of solidsinorganic that recirculates of the bottom of the secondary sedimentador to the tank ofventilation in the treatment with activated muds.113,89 Activated mud of excessPart of the activated mud that retires of the process of treatment of watersresidual for its later disposition (Vg espesamiento, digestion ordrying).3,90 Crude mudRetired mud of the tanks of primary or secondary sedimentation, thatit requires later treatment (espesamiento or digestion).3,91 Digested mudMud mineralized through the aerobic or anaerobic digestion.3.92 Residual water handlingHarvesting work set, treatment and disposition and actions ofoperation, monitoreo, control and monitoring in relation to residual waters.3,93 Filter meansGranular material through as passes the water residual in orderpurification, treatment or preparation.3,94 Heavy metalsMetallic elements of HD (for example, mercury, chromium, cadmium,lead) generally toxic, in low concentrations to the man, plants andanimals.3,95 Mortality of the bacteriaReduction of the bacterial population normally expressed bykinetic coefficient of first order in d-1.3.96 Compound sampleCombination of alicuotas of individual samples (normally in 24 hours)whose partial volume is determined in proportion to the volume of the residual water tomoment of each sampling.3.97 Precise sampleSample taken at random to one hour determined, its use is obligatory forexamination of a parameter that normally cannot be preserved.3,98 Automatic MuestreadorEquipment that takes individual samples, at intervals predetermined.3,99 SamplingTaking of samples of predetermined volume and with the technique ofcorresponding preservation for the parameter that is going away to analyze.3,100 Intestinal nematodesParasites (Áscaris lumbricoides, Trichuris trichiura, Necator americanus andAncylostoma duodenale, among others) whose eggs require of a periodlatent of development before causing to infection and its infectiva dose she is minimum12(an organism). They are considered like the organisms of greaterpreoccupation in any scheme of residual water reusability.They must be used like indicating microorganisms of all the agentssedimentables pathogens, of greater to so large minor (even cystsamibianos).3,101 NutrientAny substance that to the being assimilated by organisms, promotes hisgrowth. In residual waters one normally talks about nitrogen andphosphorus, but also can be other essential elements.3,102 Works of arrivalDevices of the plant of treatment immediately after the emitter andbefore the treatment processes.3,103 Dissolved oxygenOxygen concentration solubilizado in a liquid.3.104 ParasiteProtozoario organism or nematodo that living in the human being canto cause diseases.3,105 Period of nominal retentionRelation between the volume and the efluente volume.3.106 pHLogarithm with negative sign of the ion concentration hydrogen,expressed in masses by liter.3.107 Plant of treatmentInfrastructure and processes that allow the residual water purification.3.108 Plant pilotPlant of treatment on scale, used for the determination ofkinetic constants and parameters of design of the process.3,109 Equivalent populationThe population considered when relating the load of a parameter (generallyDBO, solids in suspension) with the corresponding contribution per capita (gDBO/(hab.d) or g SS/ (hab.d)).3,110 Percentage of reductionTo see efficiency of the treatment (3.58).3,111 Pre-cureProcesses that prepare residual waters for their later treatment.

OSO.90 - part 2 (translated)

3,112 Biological processAssimilation by bacteria and other microorganisms of the organic matter ofremainder, for its stabilization.133,113 Activated mud processResidual water treatment in which a mixture is put under ventilation(licor mixed) of activated mud and residual water. The mixed licor isput under sedimentation for its later recirculation or mud dispositionactivated.3,114 Anaerobic reactor of ascending flowContinuous process of anaerobic residual water treatment in whichremainder circulates in ascending form through a mud mantle or filter,for the partial stabilization of the organic matter. The remainder flows ofprocess by the superior part and normally obtains gas like by-product.3.115 Oxygen requirementNecessary amount of oxygen for the aerobic stabilization of the matterorganic and used in the reproduction or cellular synthesis and the metabolismendogenous.3,116 Reuso of residual watersResidual water use properly treated for an intentionspecific.3,117 Final sedimentationTo see secondary sedimentation.3,118 Primary sedimentationRemoval of settleable material present in crude residual waters.This process requires the later treatment of praised/poured off mud.3,119 Secondary sedimentationProcess of separation of the biomass in suspension produced inbiological treatment.3,120 Combined systemSystem of sewage system that receives residual water and rainwater ofdomestic or industrial origin.3,121 Individual system of treatmentSystem of treatment for a house or a reduced number of houses.3.122 Active solidsPart of the volatile solids in suspension that representmicroorganisms.3,123 SSVTAVolatile solids in suspension in the ventilation tank.3,124 Séptico tankIndividual system of residual water disposition for a house orset of houses that combines the sedimentation and the digestion. The efluenteit is arranged by percolación in the land and settled solids and14accumulated they are removed periodically in manual or mechanical form.3,125 Rate of filtrationSpeed of application of the residual water to a filter.3.126 ToxicsChemical composed elements or able to cause damage by contact orsistémica action to plants, animals and to the man.3,127 Advanced treatmentProcess of fisicoquímico or biological treatment to reach a degree oftreatment superior to the secondary treatment. It can imply the removal ofseveral parameters like:_ solid removal in suspension (microsifted, chemical clarification,filtration, etc.);_ removal of organic complexes dissolved (absorption, oxidationchemistry, etc.);_ inorganic compound removal dissolved (distillation,electrodiálisis, ionic interchange, inverse osmosis, chemical precipitation,etc.);_ removal of nutrients (nitrificación-denitrificación, degassing ofammoniac, chemical precipitation, assimilation, etc.).3,128 Anaerobic treatmentStabilization of an organic remainder by action of microorganisms inoxygen absence.3,129 Biological treatmentProcesses of treatment that intensifies the action of the microorganisms stopto stabilize the organic matter present.3,130 Conventional treatmentProcess of well-known and used affluent treatment actually. Generallyone talks about processes of primary or secondary treatment frequently andthe disinfection by means of cloración is included. The processes are excluded fromtertiary or advanced treatment.3,131 Joint treatmentDomestic and industrial residual water treatment in the same plant.3,132 Mud treatmentProcesses of stabilization, mud preparation and dehydration.3,133 Treatment in the landApplication on the land of residual waters partially dealt withthe aim to reach an additional treatment.3,134 Preliminary treatment15To see pre-cure.3,135 Primary treatmentRemoval of a considerable amount of matter in suspension without includingcolloidal and dissolved matter.3,136 Chemical treatmentApplication of chemical compounds in residual waters to obtainwished result; it includes/understands the processes of precipitation, coagulation,mud flocculation, preparation, disinfection, etc.3,137 Secondary treatmentLevel of treatment that allows to obtain the removal of organic matterbiodegradable and solid in suspension.3,138 Tertiary treatmentAdditional treatment to the secondary one. To see advanced treatment (To see 3,127).4 GENERAL DISPOSITIONS4,1 Object of the treatment4.1.1 The objective of the treatment of residual waters is to improve its quality stopsto fulfill the norms of quality of the receiving body or the norms ofreusability.4.1.2 The objective of the mud treatment is to improve its quality for its dispositionend or its advantage.4,2 Basic direction for the design4.2.1 The fundamental requirement before coming to the preliminary or definitive design froma plant of residual water treatment, is to have made the studyof the receiving body. The study of the receiving body will have to considermore unfavorable conditions. The treatment degree will be determined ofagreement with the norms of quality of the receiving body.4.2.2 In the case of advantage of efluentes of plants of treatment ofresidual waters, the treatment degree will be determined in accordance withthe requirements of quality for each type of advantage according tonorm.4.2.3 Once determined the degree of required treatment, the design it mustto take place in agreement with the following stages:4.2.3.1 Study of feasibility, the same one that has the following components:16_ domestic and industrial residual water Characterization;_ basic information (geologic, geotécnica, hidrológica and topographic);_ determination of the present and future volumes;_ I contribute per capita present and future;_ selection of the treatment processes;_ presizing of treatment alternatives;_ evaluation of environmental impact and vulnerability before disasters;_ técnicoeconomica feasibility of the alternatives and selection of the plusfavorable.4.2.3.2 Definitive design of the plant that includes/understands_ additional studies of characterization that are required;_ geologic, geotécnicos and topographic studies in detail;_ studies of tratabilidad of residual waters, with the use of plants ascale of laboratory or pilot, when the case amerite;_ sizing of the processes of treatment of the plant;_ sanitary hydraulic design;_ structural design, mechanics, electrical and architectonic;_ flat and technical memory of the project;_ referential budget and formula of readjustment of prices;_ engineering specifications for the construction and_ manual of operation and maintenance.4.2.4 According to the size and importance of the installation that is going away to design,they will be able to combine the two mentioned stages of design, previous authorizationof the competent authority.4.2.5 All plant of treatment will have to count on perimetric wall and measures ofsecurity.4.2.6 According to the size and importance of the treatment system, it will haveto consider infrastructure complementary: houses of monitoring, warehouse,laboratory, house of the operator and other facilities that indicatecompetent organism. These facilities will be obligatory for thosedesigned systems of treatment for an equal or greater population of 25000inhabitants and others of so large minor that the competent organism considersof importance.4,3 Norms for the feasibility studies4.3.1 The técnicoeconomica feasibility studies are obligatory for allcities with sewage system system.4.3.2 For the domestic residual water characterization it will be made, for eachimportant unloading, five campaigns of measurement and hour sampling of 24hours of duration and one will determine the volume and temperature in the field. campaigns must take place in days different from the week. Fromhour sampling compound samples will be satisfied; all the samplesthey will have to be preserved according to the standard methods for analysis17of residual waters. In the compound samples it will be determined likeminimum the following parameters:_ biochemical demand of oxygen (DBO) 5 days and 20ºC;_ chemical demand of oxygen (DQO);_ coliformes fecales and totals;_ parasitic (mainly intestinal nematodes);_ solid totals and in suspension including the volatile component;_ ammoniacal and organic nitrogen; and_ solid sedimentables.4.3.3 The statistical analysis of the generated data will take place and if they arerepresentative, it will be come to extend the characterization campaigns.4.3.4 For the determination of volumes of the unloadings they will take place likeminimum five additional campaigns of hour measurement during the 24 hoursof the day and in days that are considered representative. With those datait will come to determine of great volume the average and hour maximumrepresentative of each unloading. The volumes will be related topopulation present contributor of each unloading to determinecorresponding contributions per capita of residual water. In case of existingindustrial unloadings within the sewage system system, will calculatedomestic and industrial volumes separately. Of being possiblethey will carry out measurements to determine the amount of water of infiltration tosewage system system and the contribution of illicit connections of pluvial drainage.In systems of sewage system of combined type the contribution will have to studypluvial.4.3.5 In case of new systems the of great volume means of design will be determinedtaking as it bases the served population, the water dowries stophuman consumption and the contained factors of contribution in the norm ofsewage system networks, considering itself in addition the infiltration volumes andI contribute industrialists.4.3.6 For communities without sewage system system, the determination ofcharacteristics must take place more calculating the mass of the parametersimportant, from the contributions per capita according to it is indicated in the following onepicture.CONTRIBUTIONS PER CAPITA FOR DOMESTIC RESIDUAL WATERSPARAMETERS- DBO 5 days, 20ºC, g/(hab.d) 50- Solid in suspension, g/(hab.d) 90- NH3 - N like N, g/(hab.d) 8- N total Kjeldahl like N, g/(hab.d) 12- total Phosphorus, g/(hab.d) 3- Coliformes fecales. Nº of bacteria/(hab.d) 2x1011- Salmonella Sp., Nº of bacteria/(hab.d) 1x108- Nematodes intes., Nº of eggs/(hab.d) 4x105184.3.7 In the communities in where sampling has been made, it will be relatedmass of DBO polluting agents, solids in suspension and nutrients,coliformes and parasites with the populations contributors, to determineit contributes per capita of the indicated parameters. The contribution per capita domestic eindustrialist will calculate separately.4.3.8 In cities with sépticos tanks one will evaluate the volume and mass ofdifferent parameters from the mud of sépticos tanks that it can be unloadedto the plant of residual water treatment. This boosting charge will betake into account for the design of the processes of the following form:_ for systems of stabilization lagoons and ditches of oxidation,unloading will be accepted to the entrance of the plant._ for other types of plants with mud treatment, the unloading will beaccepted to the entrance of the process of digestion or in the beds ofdrying.4.3.9 With the collected information the bases of the design will be determined ofplant of residual water treatment. A horizon will be considered ofdesign (period of design) between 20 and 30 years, the same one that will beproperly justified before the competent organism. The design basesthey consist of determining for present, future conditions (final of the periodof design) and intermediate (every five years) the values of the following onesparameters._ population total and served by the system;_ of great volume means of domestic, industrial origin and of infiltration tosystem of sewage system and pluvial drainage;_ of great volume hour maximum and minimum;_ contributes per capita of domestic residual waters;_ contributes per capita of DBO, nitrogen and solids in suspension;_ mass of unloading of polluting agents, such as: DBO, nitrogen andsolids; and_ concentrations of polluting agents like: DBO, DQO, solids insuspension and coliformes in the residual water.4.3.10 The of great volume means of design will be determined adding the of great volume average ofdomestic residual waters, plus the volume of industrial efluentesadmitted to the system of sewage system and of great volume means of infiltration. pluvial water volume will not be considered for this case. The volumesin excess caused by the pluvial drainage they will be turned aside before the entranceto the plant of treatment by means of lightening structures.4.3.11 In no case the residual water unloading will be allowed without treatment aa receiving body, even though the studies of the receiving body indicate thatthe treatment is not necessary. The minimum treatment that will have to receiveresidual waters before their unloading, will have to be the primary treatment.4.3.12 Once determined the treatment degree, it will be come to the selection from19the processes of treatment for residual waters and muds. One will occurspecial consideration to the removal of intestinal parasites, in case ofto require itself. Processes will be selected that can be constructed andmaintained without greater difficulty, reducing to the minimum mechanization andautomatization of the units and avoiding the import of parts to the maximumand equipment.4.3.13 For the selection of the processes of treatment of residual watersit will use as it guides the values of the following picture:Removal (%)Removal(cycles log10)Process of treatmentDBOSolids insuspensionBacteriaHelmintosPrimary sedimentation25-3040-700-10-1Activated muds (a)70-9570-950-20-1Percoladores filters (a)50-9070-900-20-1Aeradas lagoons (b)80-90(c)1-20-1Ditches of oxidation (d)70-9580-951-20-1Lagoons of stabilization(e)70-85(c)1-61-4(a) preceded and followed of sedimentation(b) includes secondary lagoon(c) dependent of the type of lagoonssedimentation (d) followed(e) depending on the number of lagoons and other factors like: temperature,period of retention and forms of the lagoons.4.3.14 Once selected the processes of treatment for residual watersand muds, will be come to the sizing of alternatives. In this stageit will determine the number of units of the processes that are going away to construct inthe different phases from implementation and other components of the plant oftreatment, like: pipes, channels of interconnection, constructions stopouter operation and control, adjustments, etc. Also, they will be determinedheadings of operation and maintenance, as consumption of energy and personnelnecessary for the different phases.4.3.15 In the técnicoeconomica study of feasibility the different ones will be analyzedalternatives in relation to the type of technology: requirements of the land,teams, energy, necessity of personnel specialized for the operation,trustworthiness in operations of medium repair and situations ofemergency. The conditions will be analyzed in which it will be admittedtreatment of industrial residual waters. For the economic analysis20they will determine the direct, indirect costs and of operation and maintenance ofthe alternatives, in agreement with an appropriate method of comparison. they will determine the greater costs of the treatment of industrial efluentesadmitted and the mechanisms to cover these costs.In case of being required, the impact will be determined in approximate form oftreatment on the tariffs. With this information it will be come to the selectionof the most favorable alternative.4.3.16 The feasibility studies will have to be accompanied of evaluations ofthe environmental impacts and of vulnerability before disasters of each one ofthe alternatives, as well as the corresponding measures of mitigación.4,4 Norms for the studies of basic engineering4.4.1 The intention of the studies of basic engineering is to develop informationadditional so that the definitive designs can be conceived with the greater onesecurity degree. Between the works that can be made in this levelthey find:4.4.2 Additional studies of characterization of residual waters or remaindersindustrialists who can require themselves to collect data that have the greater oneconfidence degree.4.4.3 Geologic and geotécnicos studies that are required for the designs oflaying of foundations of the different units from the treatment plant. studies of ground mechanics are of particular importance in the design ofstabilization lagoons, specifically for the design of the docks,waterproofing of the bottom and earthwork in general.4.4.4 Of greater importance, mainly for cities of great size and withprocess of biological treatment, is the tratabilidad studies, for one orseveral of the domestic or industrial residual water unloadings thatadmit.4.4.4.1 The purpose of the studies of biological tratabilidad is to determine in formexperimental the behavior of the biomass that will carry out the work ofbiodegradación of the organic matter, as opposed to different conditionsclimatic and of feeding. In some circumstances one will beto determine the behavior of the treatment process, in front of substancesinhibiting or toxic. The most important results of these studies are:_ the kinetic constants of biodegradación and mortality of bacteria;_ the requirements of energy (oxygen) of the process;_ the amount of produced biomass, the same one that must treat andto arrange itself later; and_ the environmental conditions of design of the different processes.4.4.4.2 These studies must be carried out for cities with one obligatorilypresent population (referred the date of the study) greater to 75000 inhabitants and21others of so large minor that the competent organism considers ofimportance by its possibility of growth, the immediate water use ofreceiving body, the presence of industrial unloadings, etc.4.4.4.3 The tratabilidad studies will be able to be carried out in plants on scale oflaboratory, with a capacity of around 40 l/d or plants on scale pilotwith a capacity of around 40-60 m3/d. The type, size and sequenceof the studies they will be determined in agreement with the specific conditionsof the remainder.4.4.4.4 For the treatment with activated muds, including the oxidation ditches andaeradas lagoons will settle down at least three conditions of operationof “edad of lodo” in order to cover an interval with values between the conditionsinitials until the end of the operation. In these studies they will take placemeasurements and determinations necessary to validate the results withsuitable balance of energy (oxygen) and nutrients.4.4.4.5 For the biological filters at least three conditions will settle down oforganic operation of “carga volumétrica” for the same criterion previouslyindicated.4.4.4.6 The tratabilidad for stabilization lagoons will take place in a lagoonnear, in case of existing. A model of appropriate temperature will be usedfor the zone and the weather datas of the station will be processed morenear, for the simulation of the temperature. Additionally it will be determined,in experimental form, the coefficient of mortality of fecales coliformes andcorresponding factor of temperature correction.4.4.4.7 For industrial remainders the type of biological tratabilidad will be determined orfísicoquimica that is required in agreement with the nature of the remainder.4.4.4.8 When it is considered advisable are made in additional form, studies ofinorganic tratabilidad to develop criteria of design of other processes,like for example:_ tests of sedimentation in columns, for the design ofprimary sedimentadores;_ tests of sedimentation and espesamiento, for the design ofsecondary sedimentadores;_ tests of chemical metering for the neutralization process;_ tests of jars for físicoquimico treatment; and_ tests of tratabilidad for several concentrations of remaindersdangerous.5 SPECIFIC DISPOSITIONS FOR DEFINITIVE DESIGNS5,1 General aspects5.1.1 In the case of cities with system of combined sewage system, the design of22treatment system will have to be subject to a careful analysis stopsto justify the sizing of the processes of the plant for conditionsover the average. The volume of design of arrival works andpreliminary treatments will be the maximum schedule calculated without the contributionpluvial.5.1.2 An overflow will be included before the entrance to the plant so that it works whenvolume exceeds the hour maximum volume of design of the plant.5.1.3 For the definitive design of the treatment plant one will be due to count likeminimum with the following basic information:_ detailed topographical survey of the zone where they will be locatedunits of treatment and the zone of unloading of the efluentes;_ studies of agricultural development urban or that can exist in the zonechosen for the treatment;_ necessary geologic and geotécnicos data for the structural design ofthe units, including the phreatic level;_ hidrológicos data of the receiving body, including the maximum level offlood for possible protective installations;_ climatic data of the zone; and_ availability and trustworthiness of the service of electrical energy.5.1.4 The product of the definitive design of a plant of water treatmentresidual it will consist of two documents:_ the definitive study and_ technical file.These documents will have to appear having in consideration thathiring of the execution of works will have to include the beginning ofthe treatment plant.5.1.4.1 The documents to appear include/understand:_ technical memory of the project;_ the indicated basic information in numeral 5.1.3;_ the results of the study of the receiving body;_ results of the characterization of residual waters and the testsof tratabilidad of being necessary;_ sizing of the treatment processes;_ results of the evaluation of environmental impact; and_ manual of operation and maintenance.5.1.4.2 The technical file will have to contain:_ Flat at level of work execution, within which, without characterlimitante must be included:- general planimetry of the work, location of the units oftreatment;23- hydraulic and sanitary designs of the processes and interconnectionsbetween processes, which include/understand plant planes, cuts,hydraulic profiles and other constructive details;- flat structural, mechanical, electrical and architectonic;- flat of general works like protective installations, ways,inner adjustments, laboratories, house of the operator, house ofguardianía, perimetric walls, etc.;_ descriptive memory._ engineering specifications_ analysis of unit costs_ metrados and estimated_ formulas of readjustments of prices_ documents related to the processes of licitation, awarding,work supervision, reception and other that the competent organismconsider of importance.

OSO.90 - part 3 (translated)

5.1.5 The systems of lagoons must be located in a sufficiently extensive area andoutside the influence of subject channels to torrents and avenues, and in the case ofnot to be possible, protective installations will be due to project. The area will have to bethe most moved away possible of the populated centers, recommending itselffollowing distances:_ 500 ms like minimum for anaerobic treatments;_ 200 ms like minimum for facultative lagoons;_ 100 ms like minimum for systems with aeradas lagoons; and_ 100 ms like minimum for activated muds and percoladores filters.The distances must be justified in the study of environmental impact. project must consider an area of protection around the system oftreatment, determined in the study of environmental impact.The designer will be able to justify smaller distances to the recommended ones ifhe includes in the design processes of control of scents and other contingenciesdetrimental.5.1.6 From item 5,2 in ahead the criteria are detailed that will be used stopsthe sizing of the treatment units and structurescomplementary. The values that are included are referential and arebased on the state-of-the-art of the technology of water treatmentresidual and they could be modified by the previous designer presentation, tocompetent authority, of the justification sustentatoria based oninvestigations and the technological development. The results ofinvestigations made in the local level could be incorporated to the normwhen this one is updated.5,2 Works of arrival5.2.1 To the set of structures located between the distributing point of the emitter andprocesses of preliminary treatment denominate arrival structures to him. In24general terms these structures must be determine the proportions for the volumemaximum schedule.5.2.2 A structure of reception of the emitter will be due to project that allowsto obtain suitable speeds and to dissipate energy in the case of lines ofimpulsion.5.2.3 Immediately after the reception structure it will be locateddevice of deflection of the plant. The existence, size and considerations ofdesign of these structures will be justified properly consideringprocesses of the plant and the operation in conditions of maintenancecorrective of one or several of the processes. For stabilization lagoonsthey will have to project these structures for the periods of drying and removalof muds.5.2.4.1 The location of the pumping station (in case of existing) will depend on the typeof the pump. For the case of pumps of the type screw, this can beplaced before the preliminary treatment, preceded of heavy sieves with onesmaller opening to the spiral passage. For the case of centrifugal pumps withoutdisintegrator, the pumping station will have to be located after the process ofsifting.5,3 Preliminary treatmentThe units of preliminary treatment that can be used in the treatmentof municipal residual waters they are the sieves and the desarenadores.5.3.1. Sieves5.3.1.1 The sieves must be used in all plant of treatment, even in the plusessimple.5.3.1.2 Sieves of manual cleaning will be designed preferredly, unlessamount of sifted material justifies those of mechanized cleaning.5.3.1.3 The design of the sieves must include:_ a platform of operation and drainage of the material sifted with railingsof security;_ illumination for the operation during the night;_ sufficient space for the temporary storage of the sifted materialin suitable sanitary conditions;_ technical solution for the final disposition of the sifted material; and_ the floodgates necessary to put outside operationanyone of the units.5.3.1.4 The design of the channels will take place for the conditions of maximum volumeschedule, being able to consider the following alternatives:25_ three channels with sieves of equal dimension, as which one will serve asby pass in case of emergency or maintenance. In this case two ofthe three channels will have the capacity to lead the maximum schedule;_ two channels with sieves, each one determine the proportions for the maximum volumeschedule;_ for small facilities can be used a channel with sieves with bypass for the case of emergency or maintenance.5.3.1.5 For the design of sieves of grates the following ones will be taken into accountaspects:a) Bars of rectangular section of 5 to 15 mm of thickness will be used of30 to 75 mm wide. The dimensions depend on the length ofI sweep and the cleaning mechanism.b) the espaciamiento between bars will be between 20 and 50 mm. For localitieswith an inadequate system of harvesting of solid remaindersit recommends a espaciamiento nongreater to 25 mm.c) the dimensions and espaciamiento between bars will be chosen of waythat the speed of the channel before and through the bars isadapted. The speed through the clean bars must staybetween 0.60 to 0.75 m/s (based on hour maximum volume). speeds must be verified for the minimum volumes, average andmaximum.d) Determined the dimensions will be come to calculate the speed ofchannel before the bars, the same one that must stay between 0.30 and0,60 m/s, being 0.45 m/s a value commonly used.e) In the determination of the hydraulic profile the pressure drop a will calculatetraverse of the sieves for conditions of hour maximum volume and 50%of the obstructed area. The obtained most unfavorable value will be used toto apply the correlations for the calculation of pressure drop. The brace ofwater in the channel before the sieves and the free edge will be verified stopsconditions of hour maximum volume and 50% of the area of sievesobstructed.f) the rake of the bars of the sieves of manual cleaningit will be between 45 and 60 degrees with respect to the horizontal.g) the calculation of the amount of sifted material will be determined in agreementwith the following table.Opening(mm)Amount (liters of materialsifting l/m3of residual water)20 0,03825 0,02335 0,0122640 0,009h) to facilitate the installation and the maintenance of the cleaning sievesmanual, the grates will be installed in lateral guides with profilesmetalists in “U”, resting at heart in a profile “L” or ontop formed by a small launching slip of concrete.5.3.2 Desarenadores5.3.2.1 The inclusion of desarenadores is obligatory in the plants that they havesedimentadores and digestores. For systems of stabilization lagoonsuse of desarenadores is optional.5.3.2.2 The desarenadores will be preferredly of manual cleaning, without incorporatingmechanisms, except in the case of desarenadores for facilitiesgreat. According to the removal mechanism, the desarenadores can be agravity of horizontal or helical flow. First they can be designedas channels of extended form and rectangular section.5.3.2.3 The desarenadores of horizontal flow will be designed to remove particlesof average diameter equal or superior to 0.20 mm. For the effect one is due to treatto control and to maintain the speed of the flow around 0.3 m/s with onetolerance + 20%. The rate of application will have to be between 45 and 70 m3/m2/h,having to verify itself for the conditions of the place and the maximum volumeschedule. When coming out and entered of the desarenador it will be anticipated, to each side, byexcept an additional length equivalent to 25% of the theoretical length. relation between the length and the height of the water must be like minimum 25. The heightof the water and free edge it must be verified for the hour maximum volume.5.3.2.4 The control of the speed for different water braces will take place withinstallation of a garbage dump when coming out of the desarenador. This it can be of typeproportional (sutro), trapezial or a measurer of critical regime (Parshall orPalmer Bowlus). The speed must be verified for the minimum volume,average and maximum.5.3.2.5 Two units are due to provide with alternating operation like minimum.5.3.2.6 For desarenadores of manual cleaning the facilities are due to includenecessary (floodgates) to put outside operation anyone ofunits. The dimensions of the part destined to the sand accumulationthey must be determined based on the anticipated amount of material andfrequency of wished cleaning. The minimum frequency of cleaning will be ofonce for week.5.3.2.7 The desarenadores of hydraulic cleaning are not recommendable unlessadditional facilities for the drying of the sand are designed (pools orlagoons).5.3.2.8 For the design of desarenadores of helical flow (or Geiger), the parametersof design properly they will be justified before the competent organism.275.5.3.3 Measurer and Distributors of Volume5.3.3.1 After the sieves and desarenadores one is due to include in obligatory formmeasurer of volume of critical regime, being able to be of the type Parshall or PalmerBowlus. The use of garbage dumps will not be accepted.5.3.3.2 The volume measurer must include a well of registry for the installation oflimnígrafo. This mechanism must be installed in a house withappropriate safety measures.5.3.3.3 The structures of volume distribution must allow the distribution ofvolume considering all its variations, in proportion to the capacity ofinitial process of treatment for the case of the conventional treatment and inproportion to the areas of the primary units, in the case of lagoons ofstabilization. In general these facilities do not have to allow the accumulationof sand.5.3.3.4 The distributors can be of the following types:_ camera of distribution of central entrance and ascending flow, withcircular or square garbage dump and installation of manual floodgates,during conditions of medium repair._ distributing with partitions in critical regime, the same one that will be located inchannel._ others properly justified before the competent organism.5.3.3.5 For the facilities before indicated the design one will take place forconditions of hour maximum volume, having to verify hisoperation for conditions of minimum volume at the beginning of the operation.5,4 Primary Treatment5.4.1 Majorities5.4.1.1 The objective of the primary treatment is the organic solid removal einorganic sedimentables, to diminish the load in the biological treatment.The solids removed in the process process must be before hisfinal disposition.5.4.1.2 The processes of the primary treatment for residual waters can be:Imhoff tanks, tanks of sedimentation and tanks of flotation.5.4.2 Imhoff Tanks5.4.2.1 They are tanks of primary sedimentation in which the digestion is gotten upof muds in a compartment located in the inferior part.5.4.2.2 For the design of the zone of sedimentation it will be used the following criteria:a) The area required for the process will be determined with a load28superficial of 1 m3/m2/h, calculated on the basis of of great volume means.b) the period of nominal retention will be of 1.5 to 2.5 hours. The depthit will be the product of the surface loading and the period of retention.29c) the bottom of the tank will be of cross-sectional section in form of V andslope of the sides, with respect to the horizontal axis, will have between 50 and60 degrees.d) In the central edge will leave an opening for the solid passage of0,15 ms to 0.20 ms. One of the sides will have to extend so thatprevent the gas passage towards the sedimentador; this prolongation will haveto have a horizontal projection of 0.15 to 0.20 ms.f) the free edge will have a minimum value of 0,30m.g) the structures of entrance and exit, as well as other parameters ofdesign, will be such that for the rectangular sedimentadoresconventional.5.4.2.3 For the design of the compartment of storage and mud digestion(zone of digestion) one will consider the following criteria:a) The volume muds will be determined considering the reduction of 50% ofvolatile solids, with a density of 1.05 kg/l and a content averageof 12.5% solids (to the weight). The compartment will be determine the proportionsin order to store muds during the process of digestion according totemperature. The following values will be used:TEMPERATURE (ºC)TIME OFDIGESTION (DAYS)5110107615552040_ 2530b) Alternatively will determine the volume of the mud compartmentconsidering a volume of 70 liters by inhabitant for the temperatureof 15ºC. For other temperatures this unitary volume mustto multiply by a factor of relative capacity according to the values ofthe following table:30to peak altitude of muds it will have to be 0.50 ms below the bottom ofsedimentador.d) the bottom of the compartment will have the form of a pyramid trunk,whose walls will have an inclination of 15º to 30º with respect tohorizontal.5.4.2.4 For the design of the free surface between the walls of the digestor and the ones ofsedimentador (zone of foam) the following criteria will be followed:a) The free espaciamiento will be of 1.00 ms like minimum.b) total the free surface will be at least 30% of the total surface oftank.5.4.2.5 The facilities for the digested mud removal must be designed init forms similar the primary sedimentadores, considering that muds areretired for drying in intermittent form. For the effect they are due to have init counts the following recommendations:a) The minimum diameter of the pipes of mud removal will be of 200mm.b) the pipe of mud removal must be 15 cm over the bottomof the tank.c) For the hydraulic removal of mud requires at least one loadhydraulics of 1.80 ms.5.4.3 Tanks of Sedimentation5.4.3.1 The small tanks of sedimentation, of diameter or nongreater side mustto be projected without mechanical equipment. The form can be rectangular,to circulate or square; the rectangular ones will be able to have several hoppers andcircular or square a central hopper, as it is the case ofsedimentadores Dormund type. The inclination of the walls of the hoppers will beof at least 60 degrees with respect to horizontal. The parameters ofdesign is similar to those of sedimentadores with mechanical equipment.TEMPERATURE (ºC)CAPACITY FACTORRELATIVE52,0101,4151,0200,7> = 250,5315.4.3.2 The greater tanks of sedimentation will use mechanical equipment formud sweeping and transport to the processes of mud treatment.5.4.3.3 The parameters of design of the tank of primary sedimentation and hisefficiencies must preferredly be determined experimentally.When conventional tanks of primary sedimentation are designed withoutexperimental datas will be used the following criteria of design:a) The channels of distribution and entrance to the tanks must be designedfor the hour maximum volume.b) the area requirements must be determined using surface loadingsbetween 24 and 60 m/d based on of great volume means of design, which is equivalentat a speed of sedimentation from 1.00 to 2.5 m/h.c) the period of nominal retention will be of 1.5 to 2.5 hours (recommendable <2 hours), based on the daily maximum volume of design.d) the depth is the product of the surface loading and the period ofretention and must be between 2 and 3.5 m.s (recommendable 3 ms).e) Wide the long relation/must be between 3 and 10 (recommendable 4) andlong relation/depth between 5 and 30.f) the hydraulic load in the 500 garbage dumps will be from 125 to m3/d by meterlinear (recommendable 250), based on the daily maximum volume of design.g) the efficiency of removal of the sedimentation process can be consideredin agreement with the following table:Recommended percentage of removalPeriod of retentionnoun (hours)200 DBO 100 to 300 mg/l DBO 200 to mg/lDBO SS * DBO SS *1,5 30 50 32 562,0 33 53 36 603,0 37 58 40 644,0 40 60 42 66Total solid SS * = in suspension.h) the volume of primary muds must calculate for the end of the period ofdesign (with of great volume means) and to evaluate itself for every 5 years of operation.The solid removal of the process will be obtained from the following table:Solid concentrationType of mudprimaryGravitySpecific Rank%RecommendedWith sewage systemtoilet1,03 4 - 12 6,0With sewage systemcombined1,05 4 - 126,5With activated mudof excess1,03 3 - 104,032i) the retirement of muds of the sedimentador must take place in cyclical form eideally by gravity. Where it is not had hydraulic loadit must retire by pumping in cyclical form. For primary mudit recommends:_ rotating pumps of positive displacement;_ diaphragm pumps;_ piston pumps; and_ centrifugal pumps with open impeller.For a suitable operation of the plant, he is recommendable to installcyclical motors of variable speed and each 0.5 switches who work a4 hours. The system of mud conduction will be able to include, of being necessary,device to measure the volume.j) the volume of the mud hopper must be verified formud storage of two consecutive cycles. The speed inpipe of exit of primary mud must be at least 0.9 m/s.5.4.3.4 The mechanism of mud sweeping of rectangular tanks will have onespeed between 0.6 and 1.2 m/min.5.4.3.5 The characteristics of the circular tanks of sedimentation will befollowing:_ depth: of 3 to 5 ms_ diameter: of 3.6 to 4.5 ms_ pending of bottom: from 6% to 16% (recommendable 8%).5.4.3.6 The mechanism of mud sweeping of the circular tanks will have oneincluded/understood tangential tip speed between 1.5 and 2.4 m/min or onespeed of rotation of 1 to 3 revolutions per hour, being two a valuerecommendable.5.4.3.7 The system of entrance to the tank must guarantee the uniform distribution ofliquid through the cross-sectional section and must be designed so in form thatavoid short circuits.5.4.3.8 The hydraulic load in the exit garbage dumps will be from 125 to 500 m3/d bylinear meter (recommendable 250), based on the daily maximum volume of design.5.4.3.9 A system of harvesting of creams will be due to design, the ones that mustto store itself in a special well before being transported to the process ofdigestion.5.4.3.10 The minimum slope of the 1.7 mud hopper will be vertical to 1.0 horizontal. Incase of rectangular sedimentadores, when the hopper is too muchwide, a cross-sectional one will be due to provide sweeping from the end topoint of mud extraction.335.4.4 Tanks of FlotationThe flotation process is used in residual waters to remove particlesfine in suspension and of low density, using the air like agent offlotation. Once the solids have been elevated to the surface of the liquid,they are removed in a skimmed operation of. The process requires the greater onemechanization degree that the conventional tanks of sedimentation; hisuse will have to be justified before the competent organism.5,5 Secondary Treatment5.5.1 Majorities5.5.1.1 For effects of the present norm of design they will be considered likesecondary treatment the biological processes with a removal efficiencyof soluble DBO greater to 80%, being able to be of biomass in suspension oradhered biomass, and includes the following systems: stabilization lagoons,activated muds (including the ditches of oxidation and other variants), filtersbiological and rotatory modules of contact.5.5.1.2 The selection of the type of secondary treatment, will have to be properlyjustified in the feasibility study.5.5.1.3 Between the methods of biological treatment with biomass in suspensionthey will prefer those that are of easy operation and maintenance and thatreduce to the minimum the use of complicated mechanical equipment or that nocan be repaired locally. Between these methods they are the systems ofstabilization lagoons and the ditches of oxidation of intermittent operation andcontinuous. The activated mud system conventional and the compact plantsof this type they could be used only in the case in that one demonstrates thatother inconvenient alternatives are technique and economically.5.5.1.4 Between the methods of biological treatment with adhered biomass they will be preferredthose that are of easy operation and that they lack complicated equipment orof difficult repair. Among them they are the percoladores filters and the modulesrotatory of contact.5.5.2 Lagoons of Stabilization5.5.2.1 General Aspectsa. The stabilization lagoons are pools designed forresidual water treatment by means of natural biological processesof interaction of the biomass (seaweed, bacteria, protozoarios, etc.) andcontained organic matter in the residual water.b. The treatment by stabilization lagoons is applied when the biomassof the seaweed and the nutrients that unload the efluente they can beassimilated by the receiving body. The use of this type of treatmentit recommends specially when a high degree of removal is required34of pathogenic organisms.For the cases in which the efluente is unloaded to a lake ordam, will have to evaluate the possibility of eutroficación of the bodyreceiver before its consideration like alternative of unloading or inall case is due to determine the postratamiento necessities.c. For the domestic and industrial residual water treatmentthey will consider solely the systems of lagoons that you have unitsanaerobic, aeradas, facultative and of maturation, in the combinationsand number of units that are detailed in the present norm.d. The discharge lagoons will not be considered like treatment alternativeproduction of biomass (known like aerobic lagoons orphotosynthetic), because its purpose is to maximize the production ofseaweed and not the treatment of the liquid remainder.5.5.2.2 Anaerobic Lagoonsa. The anaerobic lagoons are used generally like first unitof a system when the land availability is limited or fordomestic residual water treatment with high concentrations andindustrial remainders, in which case can occur several unitsanaerobic in series. The use is not recommendable anaerobic lagoonsfor 15 smaller temperatures of ºC and presence of high content ofsulphates in residual waters (greater to 250 mg/l).b. Due to the high loads of design and to the reduced efficiency, it isnecessary the additional treatment to reach the treatment degreerequired. In the case of using secondary facultative lagoons hissuperficial laid-down load does not have to be over the values limitfor facultative lagoons. Generally the area of the units in seriesof the system it does not have to be uniform.c. In the sizing of anaerobic lagoons it is possible to be usedfollowing recommendations for 20 temperatures of ºC:_ volumetric laid-down load from 100 to 300 g DBO/(m3.d);_ period of nominal retention of 1 to 5 days;_ depth between 2,5 and 5 ms;_ 50% of efficiency of DBO removal;_ greater surface loading of 1000 kg DBO/ha.día.d. A minimum number of two units in parallel will be due to design stopsto allow the operation in one of the units while mud is removedof the other.e. The mud accumulation will calculate with a nonsmaller contribution of 40l/hab/año. One will be due to indicate, in the descriptive and manual memory ofoperation and maintenance, the period of cleaning assumed in the design.35In no case the volume of accumulated muds will be due to allow thatsurpass 50% of the brace of the lagoon.f. For effects of the calculation of the bacterial reduction one will be assumednull reduction in anaerobic lagoons.g. It will have to verify the values of volumetric laid-down load and loadssuperficial for the conditions of beginning of operation and cleaning ofmuds of the lagoons. These values must be included/understood betweenrecommended in point 3 of this article.

OSO.90 - part 4 (translated)

5.5.2.3 Aeradas Lagoonsa. The aeradas lagoons are used generally like first unit ofa treatment system in where the availability of the land islimited or for the treatment of domestic remainders with dischargesindustrial concentrations or remainders whose residual waters arepredominantly organic. The use of the lagoons aeradas in serieshe is not recommendable.b. The following types of aeradas lagoons are distinguished:_ aeradas Lagoons of complete mixture: the same ones that maintainsbiomass in suspension, with a HD of installed energy(> 15 W/m3). They are considered like a incipiente mud processactivated without separation and mud recirculation and the presence ofseaweed is not apparent. In this type of lagoons the depth variesbetween 3 and 5 ms and the period of retention between 2 and 7 days. For theseunits the use of aeradores of low speed is recommendable ofrotation. This it is the only case of aerada lagoon for which it existsa sizing methodology._ facultative aeradas Lagoons: which maintain the biomass inpartial suspension, with a density of installed energy smaller thanthe previous ones (1 to 4 W/m3, recommendable 2 W/m3). This type oflagoon presents/displays mud accumulation frequently, being observedthe appearance of gas bubbles of great size in the surface byeffect of the mud digestion at heart. In this type of lagoonsthe periods of retention vary between 7 and 20 days (variation averagebetween 10 and 15 days) and the depths are at least 1.50 ms. Inwarm climates and with good insolation an appreciable one is observedgrowth of seaweed in the surface of the lagoon._ facultative Lagoons with mechanical agitation: they are appliedto units exclusively overloaded of the facultative type inwarm climates. They have one lowers density of energy installed (oforder of 0.1 W/m3), the same one that serves to overcome the effectsadverse of the thermal stratification, in absence of the wind. conditions of design of these units are the same ones that stopsfacultative lagoons. The use of the aeradores can be intermittent.36c. Both first types of aeradas lagoons before mentioned, canto be followed of designed facultative lagoons with the purpose of treatingthe efluente of the primary lagoon, assimilating a great amount of solidsin suspension.d. For the design of aeradas lagoons of complete mixture they will be observedfollowing recommendations:_ the criteria of design for the process (kinetic coefficient ofdegradation, constant of autooxidación and oxygen requirements stopsyntheses) must ideally be determined throughexperimentation._ Alternatively will determine the proportions the lagoon aerada for the efficiencyof soluble removal of established DBO in conditions of the month morecold and with a constant of degradation around 0.025 (1/(mg/lXv.d)) to 20ºC, in where Xv are the volatile solid concentrationassets in the lagoon._ the oxygen requirements of the process (for synthesis and breathingendogenous) it will be determined for conditions of the hottest month.These will be corrected to conditions standard, by temperature andelevation, according to indicated in numeral 5.5.3.1 item 6._ will select the type of more advisable aerador, preferring itselfsuperficial mechanical aereadores, in agreement with hischaracteristics, speed of rotation, yield and cost. capacity of required and installed energy will be determinedselecting an even number of aeradores of equal size andspecified efficiencies._ For the removal of coliformes will be used the same coefficient ofnet mortality that the specified one for the facultative lagoons. quality of the efluente will be determined more for the conditions of the monthcold. For the effect the factor of dispersion will be able to be determined byaverage of the following relation:d = 2881 xs PRL2In where:PR is the expressed period of nominal retention in hours and L islength between the entrance and the exit in meters.In case of being used another correlation it will have to be justified beforecompetent authority.375.5.2.4 Facultative Lagoonsa. Its location like unit of treatment in a system of lagoonsit can be:_ As lagoon only (case of cold climates in which the load ofdesign is so low that it allows a suitable removal of bacteria)or followed of a secondary or tertiary lagoon (normally referredlike maturation lagoon), and_ Like a secondary unit after anaerobic lagoons oraeradas to process its efluentes to a greater degree.b. The criteria of design referred to temperatures and mortality of bacteriathey are due to determine in experimental form. Alternatively and whenthe experimentation is not possible, will be able to be used the following criteria:_ the temperature of design will be the average of the coldest month(temperature of the water), determined through correlations oftemperatures of the existing air and water._ In case of not existing those data, will determine the temperature ofwater adding to the temperature of the air a value that will be justifiedproperly before the competent organism, the same one that dependsof the meteorological conditions of the place._ In where it does not exist no data will be used the temperature average ofair of the coldest month._ the coefficient of bacterial mortality (net) will be adopted betweeninterval from 0.6 to 1.0 (l/d) for 20ºC.c. The load of design for facultative lagoons is determined withfollowing expression:CD = 250 xs 1.05 (T – 20)In where:CD is the surface loading of design in kg DBO/(ha.d)T is the temperature of the water average of the coldest month in ºC.d. Alternatively it can be used other correlations that will have to bejustified before the competent authority.e. The designer will have to adopt a load of smaller design todetermined previously, if factors exist like:_ the existence of abrupt variations of temperature,_ the form of the lagoon (the lagoons of extended form is sensible avariations and must have minors loads),38_ the existence of industrial remainders,_ the type of sewage system system, etc.f. In order to at heart avoid the growth of aquatic plants with roots,depth of the lagoons must be greater of 1.5 ms. For the design ofprimary a facultative lagoon, the designer will have to provide a heightadditional for the mud accumulation between periods of cleaning of 5 a10 years.g. For primary facultative lagoons the volume is due to determine ofaccumulated mud considering a 80% of solid removal insuspension in the efluente, with a reduction of 50% of volatile solidsby anaerobic digestion, a density of the 1.05 mud kg/l andcontent of solids from 15% to 20% to the weight. With these data it mustto determine the frequency of removal of mud in the installation.h. For the design of facultative lagoons that receive the efluente of lagoonsaeradas the following recommendations are due to consider:_ the oxygen balance of the lagoon must be positive, having init counts the following components:• the oxygen production by photosynthesis,• the superficial reaeración,• the assimilation of volatile solids of the affluent,• the assimilation of the soluble DBO,• the consumption by solubilización of solids in the digestion, and• the net consumption of I oxygenate of anaerobic solids._ is due to determine the volume of accumulated mud fromsolid concentration in suspension in the efluente of the lagoonaereada, with a reduction of 50% of volatile solids by digestionanaerobic, a density of the 1.03 mud kg/l and a content ofsolids 10% to the weight. With these data one is due to determinefrequency of removal of mud in the installation.i. In the calculation of removal of the organic matter (DBO) it will be possible to be usedany methodology properly sustained, with indication ofit forms in which the DBO concentration is determined (total or soluble).In the use of correlations of load of DBO applied to removed DBO,one is due to consider that the removed load of DBO is the differencebetween the total DBO of the affluent and the soluble DBO of the efluente. It stopslagoons in series are due to take in consideration that in the lagoonprimary the greater removal of organic matter takes place. concentration of DBO in the following lagoons is not predictable, hadto the influence of the populations of seaweed of each unit.395.5.2.5 Design of Lagoons for Removal of Pathogenic Organismsa. The dispositions that are detailed apply for any type oflagoons (in individual form or for lagoons in series), sincebacterial mortality and removal of parasites it happens in allunits and not only in the maturation lagoons.b. In relation to the parasites of residual waters, the nematodesintestinal they are considered like indicators, so that its removalit implies the removal of other types of parasites. For a suitable oneremoval of intestinal nematodes in a system of lagoon is requireda period of nominal retention of 10 days like minimum in one ofunits.c. The reduction of bacteria in any type of lagoons must, inpossible, to be determined in terms of fecales coliformes, likeindicators. For such effect, the designer must use the flow modeldispersed with the net coefficients of mortality for the different typesof units. The use of the model of complete mixture with coefficientsglobal of mortality he is not acceptable for the design of the lagoons inseries.d. The factor of dispersion in the model of dispersed flow can be determinedaccording to the form of the lagoon and the value of the temperature. The designerhe will have to justify the used correlation.The following values are referential for wide the long relation /:Long relation - wide Factor of dispersion d1 1,002 0,504 0,258 0,12e. The net coefficient of mortality can be corrected with the following onerelation of dependency of the temperature.KT = K20 x 1.05 (T - 20)In where:KT is the net coefficient of mortality to the temperature of water Taverage of the coldest month, in ºCK20 is the net coefficient of mortality to 20 ºC.405.5.2.6 General norms for the design of systems of lagoonsa. The period of design of the treatment plant must be included/understoodbetween 20 and 30 years, with stages of implementation of around 10years.b. In the conception of the project the following ones are due to followconsiderations:_ the design must be conceived at least with two units in parallelin order to allow the operation of one of the units during the cleaning._ the conformation of units, geometry, forms and number of cellsit must be chosen based on the topography of the site, and in individual ofan optimal earthwork, is to say of a suitable balancebetween the stuffed cut and for the docks._ the form of the lagoons depends on the type of each one ofunits. For the anaerobic and aeradas lagoons they are recommendedsquare or slightly rectangular forms. For the lagoonsfacultative one recommends extended forms; it is suggestedminimum long-wide relation is of 2._ In general, the type of entrance must not very be simplest possible andmoved away of the edge of the slopes, having to project with unloadingon the surface._ In the exit is due to install a device of measurement of volume(garbage dump or measurer of regime I criticize), with the purpose of being ableto evaluate the operation of the unit._ Before the exit of the primary lagoons is recommendedinstallation of a screen for the retention of creams._ the interconnection between the lagoons can take place by means of usingsimple pipes after the garbage dump or channels with a measurer ofcritical regime. This last alternative is the one of smaller loss ofload and of utility in flat lands._ the corners of the docks must be well-off to diminishaccumulation of creams._ the wide one of the berm on the docks must be at least of 2.5 msin order to allow the circulation of vehicles. In the primary lagoonswide it must so be that it allows the circulation of heavy equipment, as muchin the stage of construction like during the mud removal._ does not recommend the design of pipes, valves, floodgatesmetallic of drained of the lagoons because they are deteriorated bylack of use. For the drained one of the lagoons it is recommended41temporary installation of siphons or another alternative system of lowcost.c. The recommended free edge for the stabilization lagoons is of 0,5m. For the case in which surge by the action can be produced ofwind will be due to calculate a greater height and to design the protectioncorresponding to avoid the process of erosion of the docks.d. The operation of the lagoons is due to verify in the design stopsthe following special conditions:- During the conditions of putting in initial operation, the balancehydric of the lagoon (affluent - evaporation - efluente infiltration >)it must be positive during the first months of operation.- During the periods of cleaning, the applied surface loading onthe lagoons in operation do not have to exceed the fully factored loadcorresponding to the temperatures of the period of cleaning.e. For the design of the docks one is due to consider the following onesdispositions:_ is due to carry out the number of drillings necessary to determinethe type of ground and the layers to cut itself in the earthwork.In this stage the tests of ground mechanics will take place thatthey are required (the permeability in the site is due to include) foradapted design of the docks and forms of waterproofing. It stopsto determine the number of test pits will be had in considerationtopography and geology of the land, being observed like minimumfollowing criteria:• The minimum number of test pits is of 4 by hectare.• For the systems of several cells the minimum number of test pitsit will be determined by the number of cuts of the axes of the docksplus a perforation in the center of each one unit. For landsof rough topography in which pronounced cuts are requiredthe drillings will be increased when they are necessary.• The docks must be designed verifying that do not take placevolcamiento and that exists stability in the conditions moreunfavorable of operation, including drained fast and an earthquake.• The subpressures in the outer sides are due to calculate ofslopes to verify if the outer slope of the docks isadapted and to determine the necessity of controls like:waterproofing, coverings or filters of drainage.• In general the inner slopes of the docks must have oneinclination between 1:1,5 and 1:2. The outer slopes are lessinclined, between 1:2 and 1:3 (vertical one: horizontal).• Of the data of the drillings the type of material a is due to specifyto be used in the compaction of the docks and castrates ofwaterproofing, determining itself in addition the quarries todifferent materials that are required.42• The vertical interval of relief of the bottom of the lagoons and the phreatic levelit will have to be determined considering the constructive restrictions and ofcontamination of underground waters according tovulnerability of the water-bearing one.One will be due to design, if outside necessary, the system ofwaterproofing of the bottom and slopes, having to justify the solutionadopted.f. The following facilities are due to consider additional:_ House of the operator and equipment depot and tools._ Laboratory of residual water analysis for the control oftreatment processes, for cities with more than 75000 inhabitantsand others of so large minor that the competent organism considersnecessary._ For the aeradas lagoons is due to consider additionallyconstruction of an operation house, with area of office, factory andspace for the mechanical-electrical controls, in which it mustto settle a board of operation of the motors and other controlsthat they are necessary._ basic a weather station that allows the measurement ofenvironmental temperature, direction and speed of wind, precipitation andevaporation._ For the aeradas lagoons is due to consider the illumination and to assurethe supplying of energy in continuous form. For the effectit must study the convenience of installing a generator set._ the system of lagoons must be protected against damages by effect ofrun-off, designing itself roadside ditches of rainwater interceptionin case that the topography of the land therefore requires it._ the plant must count on perimetric wall of protection and signboardsadapted.5.5.3 Treatment with Activated Muds5.5.3.1 General aspectsto Next common aspects of the process are norman as muchconventional with muds activated like of all its variations.b. For effects of the present norms they are considered like optionsthose that have an efficiency of removal from 75 to 95% of the DBO.Between the possible variations the ventilation will be able to be selectedprolonged by oxidation ditches, in reason to his low cost. selection of the type of process will be justified by means of a technical studyeconomic, the one that will consider at least the following aspects:_ quality of the efluente;_ requirements and costs of preliminary and primary treatments;_ requirements and costs of ventilation tanks and sedimentadores43secondary;_ requirements and costs of the land for the facilities (includesunits of treatment of residual water and free mud, areas, etc.);_ cost of the mud treatment, including the amount of generated mudin each one of the processes;_ cost and life utility of the equipment of the plant;_ operational costs of each alternative (including the monitoreo ofcontrol of the processes and the quality of the efluentes);_ difficulty of the operation and described requirement of personnel.c. For the design of any variant of the activated mud process,they will have in consideration the following general dispositions:_ the fundamental criteria of the process like: age of mud,oxygen requirements, mud production, efficiency and density ofbiomass must be determined in experimental form according tothe indicated thing in article 4.4.4._ In where he is not requisite to develop these studies, will be able to be useddesign criteria._ to determine the efficiency is considered to the mud processactivated jointly with the secondary or efluente sedimentadorseparated liquid of the biomass._ the design of the ventilation tank takes place for the conditions ofof great volume means. The process will have to be in capacity to givequality established for the efluente in the conditions of the month morecold.d. For the ventilation tank one will verify the values of the following onesparameters:_ period of retention in hours;_ age of muds in days;_ volumetric load in kg DBO/m3;_ removal of DBO in %;_ volatile solid concentration in suspension in the tank ofventilation (SSVTA), in kg SSVTA/m3 (this parameter alsoit knows like volatile solids in suspension of the mixed licor -SSVLM);_ load of the mass in kg DBO/Kg SSVTA. day;_ rate of recirculation or rate of return in %.e. In case of not requiring the tratabilidad tests, they will be able to be usedfollowing referential values:44TYPE OFPROCESSPERIOD OFRETENTION(h)AGE OFMUD(d)LOADVOLUMETRICkg (DBO/m3.día)Conventional 4 - 8 4 -15 0.3 - 0,6Ventilationstaggered3 - 6 5 -15 0.6 - 0,9High load 2 - 4 2 - 4 1.1 - 3,0Ventilationprolonged16 - 48 20 - 60 0.2 - 0,3Mixture completes 3 - 5 5 - 15 0.8 - 2,0Ditch of oxidation 20 - 36 30 - 40 0.2 - 0,3Additionally one will be due to have in consideration the following parameters:TYPE OFPROCESSRemovalof DBOConcentracióSSTA nkg/m3Load ofmass kgDBO/ (kgSSVTA.día)Rate ofrecirculación %Conventional 85 - 90 1.5 - 3.0 0.20 - 0.40 25 - 50Ventilationstaggered85 - 95 2.0 - 3.5 0.20 - 0.40 25 - 75High load 75 - 90 4.0 - 10 0.40 – 1,50 30 - 500Ventilationprolonged75 - 95 3.0 - 6.0 0.05 – 0,50 75 - 300Mixture completes 85 - 95 3.0 - 6.0 0.20 – 0,60 25 - 100It settles ofoxidation75 - 95 3.0 - 6.0 0.05 – 0,15 75 - 300NOTE: The selection of another process will have to be justified properly.f. For the determination of the capacity of oxigenación of the processthey will have to consider the following dispositions:_ the oxygen requirements of the process must calculate forconditions of operation of temperature monthly average more dischargeand they must be sufficient to supply oxygen for the synthesis oforganic matter (DBO removal), for the endogenous breathing andfor the nitrificación._ These requirements are given in conditions of field and must becorrected to conditions standard of zero percent of saturation,standard temperature of 20 ºC and one atmosphere of pressure, with the useof the following relations:N20 = NC/FF = and x Q T - 20 (CSC x ß - Ci)/9,0245CSC = CS (P - p)/(760 - p)p = exp (1.52673 + 0.07174 T - 0.000246 T 2)P = 760 exp (- and/8005)CS = 14.652 - 0.41022 T + 0.007991 T 2 - 0.000077774 T3In where:N20 = requisite of oxygen in standard conditions, kg O2/dRequisite NC = of oxygen in conditions of field, kg O2/dF = correction factorAnd = correction factor that relates the coefficients ofoxygen transference of the remainder and the water. Its valueproperly it will be justified according to the type of ventilation.Generally this value is in the rank of 0.8 a0,9.Q = factor of temperature dependency whose value is takenlike 1.02 for compressed air and 1.024 by ventilationmechanics.CSC = concentration of oxygen saturation in conditions offield (P pressure and temperature T).ß = correction factor that relates the concentrations ofsaturation of the remainder and the water (in conditions offield). Its value properly will be justified according totype of ventilation system. Normally it is assumedvalue of 0.95 for the mechanical ventilation.Ci = oxygen level in the ventilation tank. Normallyit is assumed between 1 and 2 mg/l. Under no circumstance ofoperation will allow a smaller oxygen level of 0,5mg/l.CS = concentration of oxygen saturation in conditions tolevel of the sea and temperature T.P = atmospheric Pressure of field (to the elevation of the place),mm Hg.p = steam pressure of the water to the temperature T, mm Hg.And = Elevation of the site in meters on the level of the sea._ the use of other relations must be justified properly beforecompetent organism._ the correction to standard conditions for the ventilation systemswith compressed air he will be similar to the previous thing, but in addition it must havein account the characteristics of the diffuser, the air flow anddimensions of the tank.46g. The selection of the type of aereador will have to be justified properly technicaland economically.h. For the systems of mechanical ventilation the following ones will be observeddispositions:_ the installed capacity of energy for the ventilation will be determinedrelating the oxygen requirements of the process (kg O2/d) andyield of the selected aereador (kg O2/Kwh) both inconditions standard, with the respective correction by efficiency inmotor and reducer. The number of ventilation equipment will be likeminimum two and preferredly of equal capacity consideringthe standardized capacities of manufacture._ the yield of the aereadores must be determined in a tank withclean water and a density of energy between 30 and 50 W/m3. yields will have to be expressed in kg O2/Kwh and the following onesconditions:_ a pressure atmosphere;_ zero percent of saturation;_ temperature of 20 ºC._ the motor-reducing set must be selected for a regime ofoperation of 24 hours. A factor is recommended on watch of1,0 for the motor._ the installed capacity of the equipment will be previously determined,but without the efficiencies of the motor and reducer of speed._ the ventilation rotor must be of stainless steel or another materialresistant to the corrosion and approved by the competent authority._ the density of energy (W/m3) will be determined relatingcapacity of the equipment with the volume of each tank of ventilation. density of energy must allow a speed of circulation ofmixed licor, so that the sedimentation does not take place ofsolids._ the location of the aeradores must so be that an interaction existsof its areas of influence.i. For systems with compressed air diffusion it will be come in formsimilar, but considering the following factors:- the type of diffuser (fine or heavy bubble);- the constants characteristic of each diffuser;- the yield of each unit of ventilation;- the air flow in standard conditions;- the location of the diffuser with respect to the depth of the liquid, and47wide of the tank.- altitude above sea level.The required power will be determined considering the load ondiffuser plus the pressure drop by the flow of the air throughpipes and accessories. The design capacity will be 1.2 timesnominal capacity.

OSO.90 - part 5 (translated)

5.5.3.2 Secondary Sedimentadora. The criteria of design for the secondary sedimentadores mustto determine itself experimentally.b. In absence of sedimentation tests, one is due to considerfollowing recommendations:- the design is due to carry out for hour maximum volumes;- for all the variations of the activated mud process(excluding prolonged ventilation) one recommends the following onesparameters:The hydraulic loads previously indicated are based onvolume of the residual water without considering the recirculation, sincesame it is retired of the bottom at the same time and it does not have influence inrate of climb of the sedimentador.c. For circular secondary decantadores they are due to considerfollowing recommendations:- the decantadores with capacities of up to 300 m3 can bedesigned without mechanism of type mud sweeping, having to beLOAD OFSURFACEm3/m2.dLOADkg/m2.hTYPE OFTREATMENTAverageMáx.AverageMáx.DEPTHmSedimentation acontinuation ofactivated muds(excludedventilationprolonged)16-3240-483,0-6,09,03,5-5Sedimentation acontinuation ofventilationprolonged8-1624-321,0-5,07,03,5-548conical or piramidal, with a minimum inclination of the walls ofhopper of 60 degrees (Dormund type). For these cases the removal ofmuds must be done through pipes with a minimum diameterof 200 mm.- the circular decantadores with mechanism of mud sweepingthey must be designed with a central hopper for mud accumulationof at least 0.6 ms of diameter and Maxima depth of 4 ms.The walls of the hopper must have an inclination of at least60 degrees.- the bottom of the circular decantadores must have an inclinationof around 1:12 (vertical one: horizontal).- the diameter of the zone of entrance in the center of the tank must beapproximately 15 to 20% of the diameter of the decantador. walls of the entrance well do not have to be deepened more than 1 mbelow the surface to avoid the drag muds.- the tip speed of the sweeping one of muds must beincluded/understood between 1.5 to 2.5 m/min and nongreater of 3 revolutionsfor hour.d. The rectangular secondary decantadores will be the second optionafter the circular ones. For these cases one is due to considerfollowing recommendations:- wide the long relation/must be 4/1 like minimum.- the wide relation/depth must be included/understood between 1 and2.- For the small facilities (up to 300 m3) it will be possible to be designedrectangular sedimentadores without mechanisms of mud sweeping,in which case inverted pyramids with angles will be designedminimums of 60º with respect to the horizontal.e. For oxidation ditches the design of the ditch is admitted withbuilt-in secondary sedimentador, for which the designer will haveto justify the design criteria properly.f. In order to facilitate the mud return, the following ones are due to considerrecommendations:- For circular decantadores, the return of mud will be continuous andit will be able to use centrifugal pumps or of positive displacement. installed capacity of the pumping station of return mudshe will be at least 100% over the operational capacity. pumping capacity will be sufficiently flexible (with motors ofvariable speed or number of pumps) so that it canto operate the plant in all the conditions throughout the life ofit plants.- For rectangular decantadores with mechanism of sweeping ofmovement toward the front, will consider the mud removal init forms intermittent, between periods of trips of the mechanism.- the return mud must be pumped to a distribution camera49with manual floodgates and garbage dumps to separate the mud ofexcess.- Alternatively the process can be controlled unloading mudof excess directly of the ventilation tank, using the age ofmud like control parameter. For example if the age of mud isof 20 days, 1/20 of the volume of the tank will be due to reject ofventilation every day. This is the only form of operation in the caseof ditches of oxidation with built-in sedimentador. In this casethe mixed licor must be retired in intermittent form (from 6 to 8retirements) to a tank of concentration (in the case of ditch ofoxidation) or to a espesador, in the case of other systems of lossage of mud.5.5.3.3 Ditches of oxidationa. The oxidation ditches are adapted for small and greatcommunities and constitute a special form of prolonged ventilationwith low costs of installation inasmuch as the use is not necessary ofprimary movement and the mud stabilized in the process can beemptied directly in drying beds. This type of treatmentit is in addition to simple operation and able to absorb variations abruptof load.b. The criteria of design for the oxidation ditches are such thatwhich has been enunciated in the previous chapter (activated muds) init refers parameters of design of the reactor and secondary sedimentador andrequirements of I oxygenate. In the present I capitulate occur recommendationsadditional own of this process.c. For the populations of up to 10000 inhabitants they are possible to be designedditches of conventional type, with horizontal rotors. For this caseit must consider the following recommendations:- the form of the conventional ditch is made oval, with a simple onepartition of soportante level in half. For a suitable onedistribution of the lines of flow, recommends the installation ofat least two located semicircular partitions inends, to 1/3 of the wide one of the channel.- the entrance can be a simple tube with free unloading, locatedpreferably before the rotor. If it is had more than two ditchesit will have to consider a box of distribution of volumes.- the horizontal rotor to select itself must be of so characteristic thatallow the circulation of the liquid with a speed of at least25 cm/seg. In this case the depth of the ditch will not have to begreater of 1.50 ms for a suitable transference at the moment. Nothe deepening of the channel underneath the zone is necessary ofventilation.- the rotors are cylindrical bodies of several types, supported inboxes of bearing in its ends, thus its lengthit depends on the structure and stability of each model. It stopsrotors of greater length of 3.0 ms the use of supports is recommendedintervals. The supports in the ends must have50obligatorily boxes of autoalineantes, able buns ofto absorb the deflections of the rotor without causing mechanical problems.- the determination of the characteristics of the rotor like diameter,length, speed of rotation and depth of immersion, mustto take place so that the requirements can be provided ofoxygen to the process in all the possible operative conditions.To the effect one is due to have the curves characteristic ofyield of the model considered in conditions standard. standard yields of horizontal rotors are of the order of1,8 to 2.8 kg O2/Kwh.- the normal procedure is to design the first garbage dump of exitof the ditch, the same one that can be of fixed or adjustable height andto determine the interval of immersions of the rotor for the different onesconditions of operation.- For facilities of up to 20 l/s can be considered the use ofditches of intermittent operation, without secondary sedimentadores.In this case storage is due to provide with the remainder byperiod of up to 2 hours, or in the interceptor or a ditchaccessory.- the motor-reducing set must be chosen in such a way thatspeed of rotation is between 60 and 110 RPM and that the speedperipheral of the rotor m/s is around 2.5.d. For greater populations of 10000 inhabitants one will be due to considerobligatorily the ditch of deep oxidation (reactor of orbital flow)with aeradores of vertical axis and low speed of rotation. Theseaereadores have the characteristic to transfer to the liquid mass init forms efficient so that they distribute a suitable speed and a flowof helical type. For this case they are due to considerfollowing recommendations:- the depth of the ditch will be of 5 ms and the wide one of 10 ms likemaximum. The density of energy will have to be superior to 10 W/m3- the reactors can have varied forms, wheneverlocate the aeradores in the ends and tangential form toseparation partitions. They occur as it guides following the wide ones anddepths of the channels:Equivalent inhabitants Wide, m Depth, m10000 5.00 1,5025000 6.25 2,0050000 8.00 3,5075000 8.00 4,00100000 9.00 4,50200000 10.00 5,00In relation to the form of the channels the following ones occurrecommendations:51- the depth of the channel must be between 0.8 and 1.4 times the diameterof the selected rotor;- the wide one of the channels must be between 2 and 3 times the diameter ofselected rotor;- the developed length of the channel does not have to exceed 250 ms;For the aereadores of vertical axis the following ones occurrecommendations:- the speed of rotation for the small aereadores must be of36 to 40 RPM and for the great aereadores of 25 to 40 RPM.- the distance between the aim of the dividing partition and the ends ofimpeller vanes must be around 1.5% of the total diameter ofrotor (including the trowels).- the depth of immersion of the rotor must be of 0.15 to 0.20 ms.- the density of energy in the zone of total mixture must be of 20 a60 W/m3.Ditches of oxidation of continuous operation can be consideredwith zones of denitrificación before a zone of ventilation. Foreffect is necessary to consider the following aspects:- In the design of secondary sedimentadores, for ditches withdenitrificación is due to assure a fast retirement mud, stopsto prevent the flotation of the same one.- the exit garbage dump must be located at the end of the zone ofdenitrificación.5.5.4 Percoladores filters5.5.4.1 The percoladores filters will have to be designed so that it is reduced to the minimumthe use of mechanical equipment. For it one will prefer the following onesoptions: stone beds, distribution of the primary efluente (treated inImhoff tanks) by means of fuzes or mechanisms of whirling armself-propelled, sedimentadores secondary without mechanisms of sweeping (withmud hoppers) and return of secondary mud to the primary treatment.5.5.4.2 The previous treatment to the percoladores filters will be: sieves, desarenadores andprimary sedimentation.5.5.4.3 The filters could be of discharge or low load, for which they will be had inconsideration the following parameters of design:Type of loadParameterLow DischargeHydraulic load, m3/m2/d 1.00 - 4.00 8,00 - 40,00Laid-down load, kg DBO/m3/d 0.08 - 0.40 0.40 - 4,80Depth (stone bed), m 1.50 - 3.00 1.00 - 2,00(average plastic), m Up to 12 msReason of recirculation 0 1.00 - 2,00525.5.4.4 In the filters of low load the metering must take place by means ofsiphons, with an interval of 5 minutes. For the filters of high loadmetering is continuous by effect of the recirculation and in case of being usedsiphons, the metering interval will be inferior of 15 seconds.5.5.4.5 Any system of distribution will be used that guarantees the distributionuniform of the primary efluente on the surface of contact means.5.5.4.6 When fixed fuzes are used, it will be located them in the vertices of trianglesequilateral that covers all the surface with the filter. The sizing ofpipes will depend on the distribution, the one that can be intermittent or continuous.5.5.4.7 Any means of contact will be allowed that promotes the development ofgreater amount of Biopelícula and that allows the free circulation of the liquid and ofair, without producing obstructions. When small stones are used,minimum size will be of 25 mm and the maximum of 75 mm. For great stones,its size will oscillate between 10 and 12 cm.5.5.4.8 A ventilation system will be designed so that a circulation existsnatural of the air, by temperature difference, through the system of drainageand through the contact bed.5.5.4.9 The drainage system must fulfill the following objectives:• to provide a hardware to means with contact;• to collect the liquid, for which the bottom must have a slope between1 and 2%;• to allow an suitable air recirculation.5.5.4.10 The drainage system will have to fulfill the following recommendations:• The channels of water harvesting will have to work with a bracemaximum of 50% in relation to its Maxima conduction capacity, andfor minimum braces it will have to ensure speeds drag.• Wells of ventilation in the ends of the central channel must be located ofventilation.• In case of filters of great surface wells must be designed ofventilation in the periphery of the unit. The surface opened of thesewells m2 by each 250 will be of 1 m2 of bed surface.• The false bottom of the drainage system will have a nonsmaller area of orificesto 15% of the total area of the filter.• In filters of low load without recirculation, the drainage system will haveto design itself so that the bed can be flooded to controldevelopment of insects.5.5.4.11 Facilities of secondary sedimentation are due to design. The intention ofthese units are to separate the biomass in excess produced in the filter. design could be similar to the one of the primary sedimentadores with the conditionof which the design load is based on the flow of the plant plus the flow ofrecirculation. The surface loading does not have to exceed 48 m3/m2/d based onthe maximum volume.535.5.5. Rotating Biological systems of Contact5.5.5.1 They are units that have means of contact placed in modules discs orcylindrical modules that rotate around their axis. The modules discs orcylindrical they are submerged generally up to 40% of his diameter, ofway that when rotating allows that the Biopelícula is put in contactalternadamente with the primary efluente and the air. The conditions ofapplication of this process is similar to those of the biological filters in whichone talks about efficiency.5.5.5.2 Necessarily the previous treatment to the biological systems of contactit will be: sieves, desarenadores and primary sedimentador.5.5.5.2 The rotatory modules can have following means of contact:• wood discs, located plastic material or metal in parallel formso that they provide a high faying surface for the developmentof the Biopelícula;• stuffed cylindrical meshes of light material.5.5.5.4 For the design of these units it will be observed the following onesrecommendations:• hydraulic load between 0.03 and 0.16 m3/m2/d.• the tip speed of rotation for municipal residual watersm/s must stay around 0.3.• the minimum volume of the units must be of 4.88 liters by each m2of contact means surface.• for modules in series a minimum of four units will be used.5.5.5.5 The efluente of these systems must treat in a secondary sedimentadorin order to separate the originating biomass of the biological reactor. The criteria ofdesign of this unit is similar to those of the secondary sedimentador ofbiological filters.5.6 Other Types of Treatment5.6.1 Application on the land and reuso agriculturist5.6.1.1 The application in the pretreated residual water land is a type oftreatment that can or not to produce a final efluente. If agriculturist exists reusoone will be due to fulfill the requirements of the effective legislation.5.6.1.2 The study of feasibility of these systems must include the aspects agricultural andof grounds considering at least the following thing:• ground evaluation: problems of salinity, infiltration, drainage, watersunderground, etc.;• evaluation of the quality of the water: possible problems of toxicity,tolerance of cultures, etc.;54• types of cultures, forms of irrigation, necessities of storage,infrastructure works, costs and yield.5.6.1.3 The three main processes of application in the land are: irrigation to rateslow, fast infiltration and superficial flow.5.6.1.4 For systems of irrigation of slow rate the following parameters are suggested ofdesign:to Grounds will be chosen that have a good drainage and a permeability nogreater of 5 cm/d.b. Slope of the land: for cultures 20% at the most and forestsup to 40%.c. Depth of napa phreatic: minimum 1.5 ms and preferably more of3 ms.d. Required pre-cure: according to the lineamientos of the previous numeral.and Requirements of storage: one is due to analyze carefullycarrying out a hydric balance. The variables to consider itself are byless:- infiltration capacity- rain regime- type of ground and culture- evapotranspiración and evaporation- applicable hydraulic load- periods of rest- additional treatment that takes place in the storage.f. The nitrogen load will be verified so that when carrying out the balancehydric, the calculated nitrate concentration in underground watersmg/l is inferior of 10 (like nitrogen).g. The laid-down load will be between 11 and 28 kg DBO/(ha.d), to preventexaggerated development of biomass. The low loads will be used withsecondary efluentes and the high loads with primary efluentes.h. The periods of rest usually it varies between 1 and 2 weeks.i. For defense of the quality of the underground water the cultures will be preferredwith high nitrogen use.5.6.1.5 For the systems of fast infiltration the following ones are recommendedparameters:to Grounds able are required 60 to infiltrate from 10 to cm/d, like sand,the sandy slime, muddy sands and burden fine. It is also requiredsuitable knowledge of the variations of the phreatic level.b. The required pre-cure is primary like minimum.c. The water table must be between 3 and 4.5 ms of depth like minimum.d. The hydraulic load can vary between 2 and 10 cm per week,depending on several factors.and The necessary storage is due to determine considering55variables indicated in the previous numeral. One is due to maintain periodsof rest between 5 and 20 days to maintain conditions aerobic inground. The periods of application will be chosen maintaining onerelation between 2:1 to 7:1 between the rest and application.f. The recommended laid-down load must stay between 10 and 60 kgDBO/(ha.d).