operational performance of the anaerobic baffled reactor used to treat wastewater from a peri

85 Pages·2010·3.87 MB·English

OPERATIONAL PERFORMANCE OF THE
ANAEROBIC BAFFLED REACTOR
USED TO TREAT WASTEWATER
FROM A PERI-URBAN COMMUNITY
OCTOBER 2010
Operational Performance of the
Anaerobic Baffled Reactor
Used to Treat Wastewater
from a Peri-Urban Community
by
Kerri Hudson
AResearchReportsubmittedtotheFacultyofEngineeringandtheBuilt
Environment,UniversityoftheWitwatersrand,Johannesburginpartialfulfilmentofthe
requirementsforthedegreeofMasterofScienceinEngineering.
Johannesburg
October2010
PREFACE
The work presented in this dissertation was performed at the University of KwaZulu-
Natal,HowardCollegeCampus,fromMay2004toFebruary2005. Theworkwassuper-
visedbyKatherineFoxonandProfessorC.A.Buckley(PollutionResearchGroup, Uni-
versity of KwaZulu-Natal), and co-supervised Professor P. Marjanovic (School of Civil
andEnvironmentalEngineering,UniversityoftheWitwatersrand).
This study is part of a broader Anaerobic Baffled Reactor (ABR) research programme
fundedbytheWaterResearchCommission(Projectnumber: K5/1248),andthevarious
partsoftheworkwerecompletedbydifferentmembersoftheprojectteam. Manycom-
ponentsofthisprojecthavebeenpublishedbydifferentmembersoftheprojectteam.
The author was part of the project team as a research assistant responsible for the gen-
eral maintenance and operation of the ABR, as well as monitoring of Chemical Oxygen
Demandandsolidslevelsintheinfluent,effluentandeachcompartment. Itwasagreed
with the Pollution Research Group that the author could use some of her own data as
wellasothersupportingdatafromtheprojectfortheresearchcomponentofaMaster’s
degreethroughtheUniversityoftheWitwatersrand.
As far as this research project is concerned, the microbial work was performed by Sud-
hir Pillay at the School for Life and Environmental Sciences, and Ammonia, Nitrogen,
PhosphorousandalkalinityanalyseswereperformedbyDiveshaMoodleyattheSchool
of Chemistry. All other data and photographs presented herein, operation of the ABR
Preface ii
andsamplecollectionandanalysiswereperformedbytheauthor,KerriHudson.
All of the work presented in this Research Report is original, unless otherwise stated.
It has not (in whole or in part) been previously submitted by the author to any tertiary
instituteaspartofadegreerequirement.
KerriHudson:
Date:
ACKNOWLEDGMENTS
Iwouldliketothankthefollowingforalltheinputandassistancetheyhavegivendur-
ingthisproject:
• ProfessorChrisBuckley(HeadofthePollutionResearchGroup,SchoolofChemi-
calEngineering)fortheopportunitytoworkontheABRprojectwiththePollution
ResearchGroup,andforhissupervisionandvaluableinputintothisstudy.
• Katherine Foxon (ABR project leader, Pollution Research Group) for her contin-
uedassistance,patienceandsupervision,revisionofdataandresults,andwithout
whomIwouldnothavecompletedmyresearch.
• Sudhir Pillay (School of Life and Environmental Sciences, UKZN) for his input
withthemicrobialanalysesandparticipationinsamplingexpeditions.
• Divesha Moodley (School of Chemistry, UKZN) for her input with the chemical
analyses.
• NicholasDuPreezandtherestofmyfamilyfortheirsupportandencouragement,
andallmyotherfriendsandcolleaguesfromChemEngatUKZN.
”Water is fundamental for life and health. The human right to water is indispensable for
leading a healthy life in human dignity. It is a pre-requisite to the realization of all other
humanrights.”
–––TheUnitedNationsCommitteeonEconomic,CulturalandSocialRights–––
ABSTRACT
An estimated 37% of the population in South Africa are currently without basic sanita-
tionfacilities. Poorsanitationmayleadtothespreadofdiseaseandincreasedcontami-
nationofgroundandsurfacewaterresources. Thedemandforbasicservicescontinues
to exceed supply and limited progress has been made in elimination of backlogs. As a
result, various low-cost sanitation alternatives, are being investigated, including urine
diversiontoiletsandVentilatedImprovedPit(VIP)latrines. Researchisalsobeingcon-
ducted for the use of anaerobic baffled reactors to treat water from peri-urban commu-
nitiesandindustrialwastewater,withpositiveresults.
TheAnaerobicBaffledReactor(ABR)isahighrateanaerobicreactor,whichhasaseries
of hanging and standing baffles that form several equal volume compartments to force
thewastewaterupanddownthrougheachcompartmentasitflowsfromtheinlettothe
outlet of the reactor. The ABR has been found to treat high strength organic loads, and
has consistently high Chemical Oxygen Demand (COD) removal. It does not require
externalpowerandmeetstheotherrequirementsforasanitationalternative.
ThisstudyformspartofalargerWaterResearchCommission(WRC)Project,conducted
by the Pollution Research Group at the University of KwaZulu-Natal, which investi-
gated the feasibility of ”the anaerobic baffled reactor for sanitation in dense peri-urban
areas”. The objective of this study is to monitor the performance of the ABR in a peri-
urbanarea.
Abstract vi
The pilot reactor used for this study was constructed at the University of KwaZulu-
Natal, and was set up at the Kingsburgh Wastewater Treatment Works. A submersible
pumpwas used to pump wastewater fromthe influent channel into the feed box of the
ABR. The flow rate of the influent was regulated by a programmable logic controller,
whichallowedforarelativelyconstantflowof1.6l/mintotheABR,wheretheunused
feedoverflowedbackintothechannel.
Over an operational period of 6 months, samples from the influent and effluent of the
ABR were collected and analysed on a regular basis. The influent and effluent results
werecomparedinordertomonitortheperformanceoftheABR.Thefollowingparame-
terswereinvestigated:
• ChemicalOxygenDemand
• Solids
• pH
• Alkalinity
• Phosphates
• TotalKjeldahlNitrogen
• Faecalcoliforms
There were no major stoppages during the study period, and only a few minor flow
incidents, as a result sufficient data was obtained to monitor the performance of the
reactor. Thehydraulicretentiontimewasapproximately42hours.
The percentage removal of COD by the ABR shows that the average reduction in COD
is 83%, and removal rates were consistently between 78% and 90%. Solids were consis-
tentlylowintheeffluent,showingaremovalefficiencyof40%-70%.
On site measurements for pH presented an average of 7.2 for the influent, and an av-
erage of 6.5 for the effluent samples. Alkalinity concentrations of were averaged to 256
mgCaCO /lfortheinfluentsamplesand246mgCaCO /lfortheeffluentsamples. The
3 3
Abstract vii
alkalinityresultsforthisstudywerelowwhencomparedtotypicalanaerobictreatment
systems, suggesting that the ABR was poorly buffered, however this did not appear to
influencethetreatmentperformanceoftheABR.
TherewasaslightdecreaseinPhosphates;howeverthiswasnotconsideredasignificant
decrease. AnaerobicdigestionhasnomechanismtoremovePhosphatesorPhosphorous,
as a result this decrease is attributed to the relatively few number of samples. A slight
reduction on TKN was observed due to treatment by the ABR; however no significant
trendswerenoted.
TherewasasignificantreductioninE.colibyanaverageof76%. Theaverageremovalof
86%ofcoliformswassignificant. AlthoughasignificantreductionofE.coliandcoliforms
was found, the concentration of faecal coliforms found in the effluent are substantially
higher than the DWA guideline for irrigation, which is 1 cfu/100ml, or approximately
10000E.colicells.
Significant concentrations of nutrients were still present in the effluent, and as a result,
intermsoftheDepartmentofWaterAffairs(DWA)waterqualityguidelines,ABRefflu-
ent is unsuitable for discharge to surface or groundwater, and may not be used for any
activitythatmaycontaminatesuchwaterresources.
TheABRachievedsignificantremovaloffaecalcoliforms,however,therewerestillhigh
concentrations of indicator organisms in the effluent, and when compared to the DWA
guidelinesfordischargetonaturalwaterresources,andforirrigationanddomesticuses,
theseexceededtheguidelineconcentrationsandareconsideredarisktohumanhealth.
Therefore,theeffluentmaynotbedischargedorusedwithoutfurthertreatment.
Overall, theABRprovedtobeasturdytreatmentsystemwithmanybiologicalandhy-
draulicadvantagesovertheconventionaltreatmentsystems(Foxonetal.,2005). Further
theABRwouldhavelowerinstallation,operationandmaintenancecostsincomparison
withconventionaltreatmentsystems,anditprovidesaviablealternativeforcommuni-
tieswithdrysanitationthataspiretowaterbornesanitation(Foxonetal.,2005).
However,theABRwasnotfoundtotreatwastewatertosuitablechemicalandmicrobi-
ologicalstandardsasastandalonetreatmentalternativeforanyenduse,includingirri-
Abstract viii
gation. FortheABRtobecomeapossibletreatmentalternative, suitablepost-treatment
and appropriate uses and/or discharge practises would have to be investigated. The
ABRhasnomeansforpreventionofthebuild-upoforforremovalofsolids,andanABR
treatment system would therefore require a pre-treatment step or maintenance plan for
screeningandremovalofgritandotherundesirablematerial.