Feasibilily of Anaerobic Sewage Treatmenit in Sanitation Strategies in

156 Pages·2012·13.26 MB·English

Prof GJ.Alaerts IHEReportSerie~2O
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S~Veenstra
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Feasibilily of Anaerobic Sewage
Treatmenit in Sanitation Strategies in
~DeveIopingCountries
NEI
HASKONING
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RoyalDutchCofl3ultIflQ
Engineers andArchitecis
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I~. International Institute for
Hydrauljcand Environmental
Engineering W.g.rilng.n — AgricoI~o~,U~.Iv.r.~V
DELFT
341. 5—9OFE—7797

KlngdomoftheNetheilands
MlntstryofForeignAffairs
DirectorateGeneralofInternatIonalCooperation 1990
DPO/OT
Feasibility of Anaerobjc Sewage
Treatment in Sanitation Strategies in
Developincj Countries
LIBRARY, INTEPNATI~~ALREFE~ENCE
CENTRt- F- WATER SUP~LY
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Feasibility of Anaerobic Sewage
Treatment in Saniltation Strategies in
DeveJoping Countries
LJBRARY RFFERENCE CENTRE
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ACknowledgment
This reportwas writtenandediled by
ProL G.J. Alaerts
Mr. S.Veenstra
Mr. M. Bentvelsen
Mr. L.A. vanDuiji
(International Institute for Hydraulic
andEnvironmental Engineering Delft)
-
with coniributions from
Mr. M. Lmdfield
Mr H.Specker
(Netherlands Economie Institute Rotterdam)
-
Mr. L. vanVelsen
Mr. L Wildschut
(Haskoning ConsultingEngineers Nijmegen)
-
Prof. 0. Lettinga
Dr. L. HulshoffPol
Ms. M.Zuidema
(Agricultural UniversityWageningen Wagenmgen)
-
Forfurtherinquiries andto orderadditionalcopies.
InternationalInstitute for
Hydraulic andEnvironmental
Engineering
P0. Box 3015
2601 DA Delft
The Netherlands
Phone [phone],
Fax [phone],
Telex 38099ihe ni
Executive Summary
Backgroundand scope ofsettleablematenal,etc )setby this technologymay
lead to the development of a new comprehenslve
1. Sanitation is equally importantas the provisionof sanitation programme affecting notably sewerage
safe drinking water to improvepublic health. More- design and institutional management aspects which
overadequatedisposal ofliquid wastefiows reduces wouldfavourprogrammeswithtreatmentatinterme-
environmental pollution and thereby contributes to diatescale;
theweIl-beingofthe people. Duringthe past decade — as a technology with different merits anddraw-
insufficientattentionwaspaidtosanitationintropical backs in function of its possible role m the mam
developing andnewly indusirialisingcountnes, this sanitation strategies (with public health, environ-
has ofteri resulted in limited public health benefits mental health,andre-useobjectives).
from investments made in water supply schemes. (Chapters 1 and2).
Rapidurbanisationinmostofthesecountriesledto
sometimesveryhighpopulationdensities,puttingthe 4. This study reviews as much as possible available
“accomodationcapacity”ofthesurroundingenviron- documentedexperienceondifferentanaerobicreactor
mentunderstressandendangeringpublichealth.This types. Because up to now most larger-scale pilot
emphasizes the needforappropriateandnewsanita- experimentinghasbeencarried Outwiih theso-called
nonapproachestothespecificconditionsinurbanand Up-flow Anaerobic Sludge Blanket (UASB) reactor.
pen-urban areas. thisreactortypereceivesmostattention. Someofthe
(Chapters 1 and 2). conciusions however pertain equally well to other
reactor types
2.The Section Research andTechnology (DPO/OT) Though It iS ackinwledged that anaerobic ponds
of the Dutch Directorate-General for International cnn be considered anaerobic reactors as well, here
Cooperation (DGIS) has in the past 10 years sup- high-rate reactors with low land requirements and
portedseveral projects (inColombia, Indonesia and higherefficiencies are emphasized.
India)aimingatdemonstratmgthefeasibilityofandat The technologyis reviewedfor itsappropriateness
theoptimizationofanaerobicreactorsfortreatmentof andrelevanceinlowcostprogrammes.Specialatten-
domestic waste water Anaerobic waste water treat- tion was therefore given toits techmcal, economie,
mentis alreadyappliedon numerou,s(some200-300) financial andinstitutional aspects.
industrial waste waters Other documented research (Chapters 2and3).
on itsapplicationondomestic wastewater,notably in
Brazil, India and P.R. China, confirms interestmg 5. Infirstinstancetheassessment,andthisreport,ai-e
potentials. Therefore the International Institute for organisedfollowing theunitscaleatwhichsanitation
HydraulicandEnvironmentalEngineering(IHE),Delft, is implemented (i) on-site sanitation, (ii) sewage
TheNetherlands,wasrequestedbyDGIStoassessthe collection with off-site or ceniralised treatment, and
feasibility ofanaerobicsewagetrealmentfortropical (iii)intermediate-scaleprogrammes Intermediatemeans
developing countries treatment units serving a small to an intermediate
numberofhouseholds (sometens to some hundreds)
3.This studyconsidersanaerobictieatment technol- (“communal treatment”), or a combined sanitation
ogyfromdifferentpoinis ofview programmeinwhichpartofthewasteis treatedon-site
as atreatment technology, whichmeans that the (onetreatmentsharedby anumberofhousehoids)and
—
study focusses on treatment efficiency andefficacy, the resulting,partially Ireated flow, is further tmans-
andcompares thesewithconventional (usuallyaero- portedandpolishedinasecondtreatmentstepoff-site
bie) altematives; Contrary to alternative treatment technologies,
as atechnology whichmay inaddition affectfa- anaerobictreatmentappears tooffer, at least inprin-
—
vourably thedesign cnterlaofthe sewagecollection ciple,theuniqueopportunity ofapplicationatallthese
network;inotherwords,thenewboundaryconditions thee levels.
(in terms ofoptima!scaleofoperation, management Which treatmenttechnology is mostfeasiblefor a

ExecutveSummary
given case is determined by a nunibemof situational determme thespatial servingareaofareactor. Sonie
determinants,andtheobjectivesofaparticularsanita- tens ofhouseholds (“shared”) om hundreds ofhouse-
nonstrategy(public health,diffementdegreesofenvi- holds (“communal”)can be connected to one tmeat-
ronmentprotection,shallowground waterprotection, ment unit, whose eifluent needs to be further trans-
re-use) A landscape- and selection matnx can be ported This effluenthowever will not contam much
developed,allowmg to indicate the conditionsunder settleable solids and is to be considemed partially
which anaerobic treatment is the most appropriate treated (but toa highem degree than with alternative
option. systems).
(Chapter 7). This option is more expensive. The reactor can
acceptmixed (grey)waste wateroronlyblack waste
Appilcatlon Inon-sitesanitation water
(Chapter4)
6. On-site sanitation should provide for disposal of
toilet (black) waste waiem as well as of(kitchen and 8.Thesame considemationspertaintopublicfacilities
bathroom)sullage. Blackwaste wateris characterized (atoilet/bathing facility foranumberofhouseholds).
bylowflow,highstrength(intermsofBODandCOD)
and high pathogen content Sullage is higher in vol- 9.The operationandmaintenance (caretaking) ofan
umebut containslowerBODandCODconcentration individuâ) anaemobicreacioris comparableto thatof
(yet itspollution badis ofequalimportance) septictanksandleachingpits,andfacestherefore liie
The benefitofanaerobic treatmenttechnology re- samedifficulties (poormaintenanceanddesludging).
lates to better degradation of BOD and COD and Ameactomwhichis shar~doris communaloffersthe
hence better quality of the reactor effluent as corn- advantages that (i) a caretakem cao be paid by the
pared toalternative treatment(septictankomleaching connectedhouseholds,andcan then beheldaccount-
pits) However,formanysituations effluentquality is able, that(ii) caretakers are asmaller andmore“pro-
irrelevantaseffluent(blackwaste water)ispercolated fessional” group to be approached by local govern-
(leached)intothesoil 1fleachingconbeapplzed,that mentfore g trainingpurposes,thanindividualhouse-
is ifpopulation densityis notexcessivelyelevated,the holds, and that (iii) such meactors can be located
simple leaching optionssen’ing oneorafew house- stmategicallytoallowforeasiemaccess(andlowercost)
holds are commonly cheaper than any anaerobic by desludging carts
option In these cases sullage is genemally drained (Chapter4).
away over thesurface (gutters, drains).
The majorandadditional consideration toopt for ApplicatlonatIntermédiate level
leachingis apublichealthstrategy inkeeppathogens
in the undergroundwherethey slowly die off 10. Intermediate-scale means collection of(usually)
(Chapter4). grey waste water in shallow or smail-bore sewefs
followedbylocal(pre-)treatment.Theeffluentis theo
7.Againsttheabovecheapestoptionpleadtheshallow tmansportedoutside thecity in acheapsewemordrain
ground water protection (fordrinking purposes)and asmostsettleablesohdshavebeenremoved Off-site
the environmental stmategies In an envimonmental post-treatment,possiblyinstabilizationpondsoncheap
strategyis must bemecognized thatsullagemepresents land, is a usefulandfeasible option.
considerable pollucion andshould,iffinancially pos- In densily populated, unplanned residential ameas
sible,betmeatedbeforedischargeintoareceivingnver. shalbow or small-home sewers become more cost-
Also, it is still insufficiently acknowledgedthat the effectivethan on-site sanitation
leachmg bed of cheap on-site systems easily dogs (Chapter6).
leadingitsownertoshort-cimcuittheeffluenttothesur-
face drain or sewer Though exact figures are not 11.Thelocaltreatmentcanprobablybestbe achieved
available,thismaybebothindevelopingandindustn- by communal anaerobic reactors, to which some
alisedcountriestherulematherthantheexception.This hundreds of households are connected Anaemobic
adds tothe pollution bad in drainsandsewems meactomsoftheUASBtypehaveshowntooperatewell
1fan environmental strategyis~elected(above a andmeliably at such scale, yielding reasonable treal-
public health strategy) the quality of effluent to be ment efficiency mi BOD and COD (60-80). As
drainedawaybecomesofhigherconcernandanaero- pathogenmemoval is aspooras withalternativetreat-
hictreatmentmaybecomerelevant l3ecausethewaste ment options (withthe exceptionof20-25dayreten-
water mustbe drained, sewerage designcntena will tionponds), theeffluentofthelocaltreatmentneedsto