OSO.90 - part 6 (translated)

5.6.1.6 For the systems of superficial flow the following ones are recommendedparameters:to Argillaceous grounds of low permeability are required.b. The slope of the land must be between 2 and 8% (preferably 6%).A uniform surface without broken or natural channels is required, ofway that the residual waters can be distributed in a layer ofuniform thickness in all the area of application. The surface will haveto cover with grass or any other type with similar vegetation that isresistant to the conditions of flood and that provides an atmosphereadapted for the development of bacteria.c. The phreatic level must be 0.6 ms underneath like minimum, to allowa suitable ventilation of the zone by roots.d. The required pre-cure is primary like minimum.and Laid-down loads of up to 76 kg DBO can be used/(ha.d).The AS must be intermittent, with a 2:1 relationbetween the periods of rest and application. Before the cut oruse of the vegetation for animal food is due to allowperiod of rest of 2 weeks like minimum.5.6.2 Intermittent Sand filters5.6.2.1 Are units used for the solid removal, DBO and some types ofmicroorganisms.5.6.2.2 In case of being used east process, the following ones are due to considerrecommendations:to Pre-cure: primary like secondary recommendable minimum and.b. Hydraulic load: of 0,08 to 0,2 m3/m2/d for primary efluente and of 0.2 a0,4 m3/m2/d for secondary efluente.c. Filter bed: washed granular material with less 1% by weight oforganic matter. The sand will have an effective size of 0.35 to 1.0 mm anda coefficient of uniformity smaller than 4 (preferably 3,5). depth of the bed will be able to vary between 0.60 and 0.90 ms.d. The drainage system consists of tubes with open meetings or withperforations and a tube of ventilation to the end waters above. slope of the tubes will be of 0.5 and 1%. Under the pipes it will be placeda bed of support constituted by gravel or crushed stone from 0.6 to 3,8cm of diameter.e. The distribution of the affluent will take place by means of canals or byaspersion. Protective concrete plates are due to place stopsto prevent the erosion of filter means.56f. The affluent must be dosed with a minimum frequency of 2 times to the day,flooding the filter up to 5 cm of depth.g. The minimum number of units is two. For continuous operation, one ofthe units must be able to treat all the volume, while the otherunit is in maintenance or alternatively it is due to providestorage of the remainder during the period of maintenance.5.6.3 Anaerobic treatments of Ascending Flow5.6.3.1 The anaerobic treatment of ascending flow is a modification of the processof developed anaerobic contact for several decades and it has been consisting ofreactor in which the efluente is introduced through a system oflocated distribution at heart and that flows upwards crossingaverage of anaerobic contact. In the superior part a zone exists ofseparation of liquid and gaseous phase and the clarify efluente leaves by the partsuperior. The dwell times of these processes are relativelyshort. Basically diverse types of the reactors, most usual exist are:a. The one of fluidizado bed, in which the contact means are a materialto granulate (normally sand). The efluente is applied to one at heartcontrolled rate (it is required generally of recirculation) to producethe fluidización of contact means and the biomass are developed aroundof grains of means.b. The reactor of ascending flow with mud mantle (well-known like RAFAor UASB by the abbreviations in English) in which the remainder flows in formascending through a zone of mud mantle.5.6.3.2 In order to determine the conditions of application it is required to analyze the advantagesand disadvantages of the process. The main advantages of the process are:- elimination of the sedimentation process;- relatively short period of retention;- production of biogas; and- applicability to remainders of high concentration.The main disadvantages of the process are:- specialized operational control and of high cost;- very limited removal of bacteria and apparently null removal ofparasites;- sensitivity of the anaerobic systems to abrupt changes of load andtemperature;- difficult application of the process to remainders of low concentration;- operational missions that imply the necessity of described operationfor the control of the process;- deterioration of the structure by effect of the corrosion;- necessity of later treatment, mainly because the processit transforms organic nitrogen to ammoniac, which imposes onedemand of additional oxygen and presents/displays the toxicity possibility; e- insufficient information for residual waters of low load.57After a realistic analysis of great amount of information on the processthe following conditions of application settle down:a. The practice of these processes in the residual water treatment ofcities of several sizes do not have a sufficiently long filelike considering them like an established technology. The variantof fluidizados beds it presents/displays minor experience that the flow variantascending with mud mantle.b. Nevertheless, the use of such for the treatment of remaindersconcentrated industrialists it seems acceptable at the moment.c. Previous to the definitive design he is recommendable that the design criteriabe experimentally determined by means of the use of plants pilot.5.6.3.3 Since the systems of fluidizados anaerobic beds require of the greater onedegree of mechanization and specialized operation, its use will have to bejustified before the competent authority. The design criteriathey will determine through plants pilot.5.6.3.4 In order to orient the design of anaerobic reactors of ascending flow they occurfollowing referential parameters:a. The previous treatment must be desarenadores sieves and.b. Loads of the design.- 1.5 to 2.0 kg DQO/(m3.día) for domestic residual waters.- 15 to 20 kg DQO/(m3.día) for concentrated organic remainders(industrial remainders).c. Sedimentador- Surface loading 1.2 to 1.5 m3/(m2.h), calculated on the basis of the volumemaximum schedule.Height:- 1.5 ms for domestic residual waters.- 1.5 to 2.0 ms for remainders of high laid-down load.Inclination of walls: 50 to 60º- gas Baffle plates: in the central edge of the sedimentadores it will be leftan opening for the passage of solids of 0.15 to 0.20 ms one of the sidesit will have to extend so that it prevents the gas passage towardssedimentador; this prolongation must have a horizontal projectionof 0.15 to 0.20 ms.- Speed of passage by the openings:3 m3/(m2.h) for remainders of high laid-down load, calculated on the basis ofhour maximum volume.5 m3/(m2.h) for domestic residual waters, calculated on the basis ofhour maximum volume.d. Anaerobic reactor- Rate of climb: 1,0 m3/(m2.h), calculated on the basis of the volumemaximum schedule.- Height of the reactor:585 to 7 ms for remainders of high laid-down load3 to 5 ms for domestic residual waters.and System of feeding:A uniform distribution of the residual water will be due to logar at heartof the reactor. For such effect it will have to be provided with a minimum amount offeeding points:- 2 to 5 m2/punto of feeding, for efluentes of high loadorganic.- 0.5 to 2 m2/punto of feeding, for residual watersdomestic.The feed pipes must be to a height of 0.20 mson the base of the reactor.f. Gas collectorsIn the superior part of the system an area must exist to release the gasproduced. This area could be located around the sedimentadorin the transverse direction or longitudinal. The speed of the gas in thisarea must be the sufficiently high thing to avoid the accumulation offoam and the excessive turbulence that causes the drag solids.The speed of exit of the gas will be between the following values:- 3 to 5 m3 of gas/(m2.h), for remainders of high laid-down load.- 1 m3 of gas/(m2.h), for domestic residual waters.With not reaching these speeds one will be due to provide to the reactor withsystems of dispersion and foam retirement.g. The overall height of the anaerobic reactor (RAFA) of ascending flow will besum of the height of the sedimentador, the height of the anaerobic reactor andfree edge.h. Volume of the RAFA: for domestic residual waters it is recommendedto design a modular system with units in parallel. It is recommendedmodules with a maximum volume of 400 m3. In no case it will haveto project modules of more than 1500 m3 to favor the operation andmaintenance of such.5.6.3.5 For the design of these units the designer will have to justifydetermination of values for the following aspects:to Efficiencies of removal of the organic matter, coliformes andintestinal nematodes.b. The amount of biological mud produced and the form of final disposition.c. Uniform distribution of the unloading.d. The produced amount of gas and the devices for control and handling.e. The minimum requirements of postratamiento.59f. For this type of process the manual of operation will be due to present/display andmaintenance, with indication of the parameters of control of the process,the sizing of the personnel and the minimum qualifications ofpersonnel of operation and maintenance.5,7 Disinfection5.7.1 The reduction of bacteria will take place through treatment processes.Only in the case that the receiving body demands a high qualitybacteriological, the disinfection of secondary efluentes will be considered ortertiary, in intermittent or continuous form. The disinfection of remainderscrude or efluentes primary an option is not considered technicallyacceptable.5.7.2 For the design of cloración facilities the designer will have to sustaindifferent aspects:• the dose of chlorine;• the time of contact and the design of the corresponding camera;• the details of the metering facilities, injection, storageand safeties.5.7.3. The use of other techniques of disinfection (ultraviolet radiation, ozone andothers) will have to be sustained in the feasibility study.5,8 Tertiary residual water treatmentWhen the degree of the treatment fixed in agreement with the conditions ofreceiving body or of advantage is greater than the one than canto obtain by means of the secondary treatment, methods will be due to use oftertiary or advanced treatment.The technique to use will have to be sustained in the feasibility study. designer will have to sustain his criteria of design through tests oftratabilidad.Between these methods the following ones are included:to Inverse osmosisb. Electrodiálisisc. Distillationd. Coagulationand Adsorptionf. Removal by foamg. Filtrationh. Extraction by reliablei. Ionic interchangej. Chemical oxidationk. Precipitationl. Nitrificación - Denitrificación605,9 Mud treatment5.9.1 Majorities5.9.1.1 In order to come to the design of facilities of mud treatment, it will be madea calculation of the mud production in the processes of treatment ofit plants, being due to consider the following recommendations:• The calculation will be made for volumes and average concentrations andtemperatures corresponding to the coldest month.• For primary muds one will determine the volume and mass of solids insuspension total and volatile having in consideration the percentageof removal, solid content and densities.• For processes of biological treatment like those of activated muds andbiological filters the mass of biological muds will be determined producedby synthesis of the organic matter except the amount destroyed byendogenous breathing.• In the mud processes activated with mud unloading directlyfrom the ventilation tank, the volume of mud will be determinedproduced from the parameter of age of mud. In this caseconcentration of the excess mud is the same one that the one of the tank ofventilation.• In the mud processes activated with unloading of the excess mudbefore the ventilation tank, the volume of mud will be determinedproduced from the mud concentration reciculado of the bottom ofsecondary sedimentador.5.9.1.2 One will have in consideration in addition the amounts to muds of sourcesexteriors, like sépticos tanks.5.9.1.3 Muds of oxidation ditches and prolonged ventilation do not require another oneprocess of dehydration treatment that the one, generally in beds ofdrying.5.9.1.4 Muds of other systems of treatment of activated muds and filtersbiological they need to be stabilized. For the effect processes will be chosenthat they are of low cost and simple operation and maintenance.5.9.1.5 The biological mud stabilization will be sustained with a technical studyeconomic.5.9.1.6 For the anaerobic digestion one will consider the following alternatives:• anaerobic digestion in two stages with gas recovery.• opened systems of anaerobic digestion (without gas recovery),like:• open conventional digestores and mud lagoons.5.9.1.7 For the stabilized mud disposition the following ones will be consideredoptions:61• drying beds;• lagoons of mud drying;• disposition in the land of mud without dehydrating; and• others with previous technical justification.5.9.1.8 The designer will have to justify technique economically and the system ofstorage, final disposition and dehydrated mud use.5.9.2. Anaerobic Digestion5.9.2.1 The anaerobic digestion is a process of mud treatment that it has byobject the stabilization, reduction of the volume and inactivación of organismspathogens of muds. Mud already stabilized can be processed withoutproblems of bad scents. The application will be evaluated carefully of thisprocess when the temperature is smaller of 15ºC or when presence existsof biological toxics or inhibitors.5.9.2.2 The process of anaerobic digestion for the following ones will be due to considercases:• for muds of primary plants;• for primary and secondary mud of plants of treatment with filtersbiological;• for primary and secondary mud of activated mud plants,excepting the cases of plants of prolonged ventilation.5.9.2.3 When it wishes to recover the gas of the process, a process can be designed ofdigestion of two stages, considering the following recommendations:• The volume of digestion of the first stage will be determined adoptinga load of 1.6 to 8.0 kg SSV/(m3.d), the same ones that correspond avalues of high rates. In warm climates higher loads will be used andin climates temperings lower loads will be used.• The solid content in mud has great influence in the time ofsolid retention. The time of solid retention will be verified ofthe first stage, in agreement with the values that are indicated and if it isnecessary it will be come to readjust the load:Temperature, ºC Time of retention, dAverage of the coldest month18 2824 2030 1435 (*) 1040 (*) 10(*) Valid for systems with heating.62Temperature, ºC Time of retention in daysAverage of the coldest month15 6020 4725 3730 33- the open digestores can be square circular tanks orlagoons of muds and in no case will have to set out systems withheating.- the application of these systems is not recommendable stopssmaller monthly temperatures average of 15 ºC.5.9.3. Lagoons De Lodos5.9.3.1 The mud lagoons can be used like digestores or stopsdigested mud storage. Its depth is included/understood between 3and 5 ms and their surface will be determined with the use of a surface loading between0,1 and 0.25 kg SSV/(m2.d). In order to avoid the presence of bad scents they mustto use loads towards the low side.5.9.3.2 The parameters of sizing of a lagoon of mud digestion arethose of digestores of low load.5.9.3.3 The mud lagoons must be designed considering the following thing:• the docks and bottoms of these lagoons will have preferablywaterproof covering;• the slopes of the docks can be more inclined than those of lagoonsof stabilization;• devices for the removal of the mud digested are due to include inbottom and of the sobrenadante, in at least three superior levels;• devices of cleaning and facilities of circulation will be due to include ofvehicles, approach ramps, etc.5.9.4. Application of muds on the land5.9.4.1 Stabilized muds contain nutrients that can be taken advantage oflike conditioning of grounds.5.9.4.2 Stabilized muds can directly be applied in liquid stateon the land, whenever at least 55% have been removed ofsuspended volatile solids.5.9.4.3 The lands where muds are applied will have to be located at least a500 ms of the nearest house. The land will have to be prote'ge' againstrainwater run-off and must not have access of the public.5.9.4.4 The land must have an inferior slope of 6% and its ground must have63a rate of infiltration between 1 to 6 cm/h with good drainage, of compositionalkaline or neutral chemistry, must be deep and of fine texture. The phreatic levelit must be located at least to 10 ms of depth.5.9.4.5 It will have to consider at least the following aspects:• heavy metal concentration in muds and compatibility withpermissible maximum levels;• amount of cations in muds and capacity of ionic interchange;• types of culture and forms of irrigation, etc.5.9.5. Mud removal of the Lagoons of Stabilization5.9.5.1 For the mud removal of the primary lagoons, it will be come to the drainageby means of the use of siphons or another device. The lagoons will have to be draineduntil reaching a level that allows the exhibition of mud to the atmosphere. operation of drying must take place in the dry station. During thisoperation the residual water must ideally treat overloading othersunits in parallel.5.9.5.2 The mud of the bottom must be let dry outdoors. The drying mechanismit is exclusively by evaporation and its duration depends on the conditionsenvironmental, mainly of the temperature.5.9.5.3 Dry mud can be removed in manual form or with the aid of equipmentmechanic. In the design of lagoons he will have to consider the approach rampsof heavy equipment for the mud removal.5.9.5.4 Dry mud must be stored in batteries of up to 2 ms by a minimum time of6 months, previous to its use like conditioning of grounds. Of not being usedit will have to be arranged in a sanitary filling.5.9.5.5 Alternatively the mud of primary lagoons will be able to be removed by dredged orpumping to a lagoon of mud drying.5.9.5.6 The designer will have to specify the frequency of the period of removal ofmuds, this value will have to be briefed in the manual of operation ofit plants.5.9.6. Beds of Drying5.9.6.1 The drying beds are generally the simplest and economic method ofto dehydrate stabilized muds.5.9.6.2 Previous to the sizing of the beds one will calculate the mass and volume ofstabilized muds.In the case of oxidation ditches the solid content in mud isknown. In the case of digested muds anaerobically, it will be determinedmass of muds considering a reduction from 50 to 55% of volatile solids.The specific gravity of digested muds varies between 1.03 and 1,04. Although64the solid content in digested mud depends on the type of mud,following values occur as it guides:• for digested primary mud: from 8 to 12% of solids.• for the digested mud of biological processes, including primary mud: of6 to 10% of solids.5.9.6.3 The requirements of area of the drying beds are determined adopting onedepth of application between 20 and 40 cm and calculating the number ofapplications per year. For the effect one is due to consider the following onesperiods of operation:• period of application: 4 to 6 hours;• period of drying: between 3 and 4 weeks for warm climates and between 4 and 8weeks for colder climates;• period of removal of dry mud: between 1 and 2 weeks it stopsfacilities with manual cleaning (depending on the form ofbeds) and between 1 and 2 days for paved facilities in whichthey are possible to be removed dry mud, with equipment.5.9.6.4 Additionally the area requirements will be verified consideringfollowing recommendations:Type of solid digested mud kg/(m2.año)Primary 120 - 200Primary and percoladores filters 100 - 160Primary and activated muds 60 - 100Ditches of oxidation 110 - 2005.9.6.5 For the design of drying beds the following ones are due to considerrecommendations:• They can be constructed of rubblework, concrete or earth (withdocks) with useful total depth of 50 to 60 cm. The wide one of the bedsit is generally of 3 to 6 ms, but for great facilities it canto exceed the 10 ms.• The drainage means are generally are of 0.3 ms of thickness and mustto have the following components:• The means of recommended support are constituted by a layer of 15cm formed by bricks placed on filter means, with onefull separation of 2 to 3 cm of sand. The sand is the filter means andit must have an effective size of 0.3 to 1.3 mm and a coefficient ofuniformity between 2 and 5. Underneath the sand one is due to placegravel layer graduated between 1.6 and 51 mm (1/6” and 2”), of 0.20 ms ofthickness.• You drain them must be constituted by tubes of 100 mm of diameterinstalled underneath the gravel.• Alternatively it is possible to be designed beds paved with slabs ofconcrete or slabs prefabricated, with a 1.5% slope towardscentral channel of drainage. The dimensions of these beds are: of 5 a6515 ms of wide, by 20 to 45 ms of length.• For each bed a pipe is due to provide with unloading with hisrespective valve of floodgate and loseta at heart to preventdestruction of the bed.