Co m p ile d b y :
Waste Stabilisation Ponds
Publ i shed on SSWM (ht t p: / / www.sswm.i nfo)
D o r o t h e e Sp u h le r ( s e e c o n in t e r n a t io n a l
g m b h )
W a ste or W a stew a ter Sta bilisa tion Pon d s (W SPs) a re a rt ificia l m a n -m a d e la g oon s in w h ich
bla ck w a ter, g rey w a ter or fa eca l slu d g e a re trea ted by n a tu ra l occu rrin g p rocesses a n d th e in flu en ce of
sola r lig h t, w in d , m icroorg a n ism s a n d a lg a e. Th e p on d s ca n be u sed in d iv id u a lly or in series of a n
a n a erobic, fa cu lta tiv e a n d a erobic (m a tu ra tion ) p on d . W SPs a re low -cost for O & M a n d BOD a n d
p a th og en rem ov a l is h ig h . H ow ev er, la rg e su rfa ce a rea s a n d exp ert d esig n a re req u ired . Th e efflu en t
still con ta in s n u trien ts (e.g . N a n d P) a n d is th erefore a p p rop ria te for th e reu se in a g ricu ltu re
(irrig a tion ) or a q u a cu ltu re (e.g . fish - or m a crop h y te p on d s) bu t n ot for d irect rech a rg e in su rfa ce
w a ters.
In Out
Bl ackwat er, Faecal Sl udge, Greywat er, Br ownwat er, Faeces, Excr et a
Sl udge, Fer t i gat i on Wat er, Bi ogas (i f anaerobi c pond i s covered)
In tro d u ctio n
Fi gur e 1: Typi cal scheme of a wast e st abi l i sat i on syst em: An anaer obi c, f acul t at i ve and mat ur at i on pond i n ser i es. Sour ce: adapt ed f r om TILLEY et al . (2008)
Tre a tm e n t M e ch a n is m a n d Ba s ic D e s ign Prin cip le s
The di ff er ent t ypes of WSP can be used i ndi vi dual l y, but t he most ef fi ci ent and common syst em gener al l y consi st s of t hree ponds i n ser i es: f i rst an anaerobi c; t hen a facul t at i ve pond and fi nal l y an aer obi c or mat urat i on pond. Onl y sl i ght l y pol l ut ed wast ewat er may be di schar ged di r ect l y i nt o pri mary f acul t at i ve ponds. Thi s can be done al so wi t h more heavi l y pol l ut ed wast ewat er i n si t uat i ons when anaer obi c ponds are unaccept abl e because of odour nui sance.
In essence, anaerobi c and f acul t at i ve ponds ar e desi gned for BOD (Bi ol ogi cal Oxygen Demand) r emoval and mat urat i on ponds for pat hogen removal , al t hough some BOD removal occur s i n mat urat i on ponds and some pat hogen removal i n anaer obi c and facul t at i ve ponds. Dependi ng on t he r equi rement f or t he f i nal eff l uent , onl y anaerobi c and facul t at i ve ponds ar e necessar y i n some i nst ances.
Anaerobic Treatment Ponds (APs)
Mi ni wast e st abi l i sat i on ponds consi st i ng of a anaer obi c (r i ght ), f acul t at i ve (mi ddl e) and aer obi c pond (l ef t ) at t he CREPA headquar t er, i n Ouagadougou, Bur ki na Faso and a l ar ge-scal e wast e st abi l i sat i on pond syst em i n Mai ne (USA). Sour ce: SPUHLER (2006) (l ef t ) and
ht t p: / / www. l agoonsonl i ne. com/ cor i nna-mai ne. ht m [ Accessed: 07. 02. 2010]
Anaer obi c Treat ment Ponds ar e deep ponds (2 t o 5 m) devoi d of di ssol ved oxygen, where sl udge i s deposi t ed on t he bot t om and anaer obi c bact er i a break down t he or gani c mat t er by anaerobi c di gest i on, r el easi ng met hane and car bon di oxi de. Vi r uses, bact eri a, hel mi nt h, Ascar i s eggs and ot her pat hogens can al so be i nact i vat ed by sedi ment at i on when associ at ed wi t h sol i ds. N, P and K can al so be r educed by sl udge for mat i on and t he r el ease of ammoni a i nt o t he ai r. However, t he mai n funct i on of anaer obi c ponds i s BOD r emoval , whi ch can be reduced 40 t o 85 % (WSP 2007).
As a compl et e pr ocess, t he anaer obi c pond ser ves t o:
Set t l e undi gest ed mat er i al and non-degradabl e sol i ds as bot t om sl udge Di ssol ve or gani c mat er i al
i s set t l ed t o t he gr ound i n non-bi odegradabl e deat h al gae mat er i al . Phosphor us can al so be r emoved by preci pi t at i on as i norgani c P, but i t can al so r et ur n t hrough mi ner al i zat i on and r esol ubi l i sat i on i nt o t he wat er col umn. As a compl et e process, t he facul t at i ve pond ser ves t o:
Fur t her t r eat wast ewat er t hrough sedi ment at i on and aer obi c oxi dat i on of organi c mat er i al Reduce odour
Reduce some di sease-causi ng mi croorgani sms i f pH r ai ses St ore r esi dues as bot t om sl udge
FPs l ose ammoni a i nt o t he ai r at hi gh pH; and set t l e some ni t r ogen and phosphorus i n t he sl udge.
FPs can resul t i n t he r emoval of 80 t o 95% of t he BOD5 (WSP 2007), whi ch means an overal l r emoval i n t he or der of 95% over t he t wo ponds (AP and FP). Tot al ni t rogen r emoval i n WSP syst ems can reach 80% or mor e, and ammoni a r emoval can be as hi gh as 95%. The HRT for a facul t at i ve pond l i es bet ween 5 t o 30 days (WSP 2007). Somet i mes t wo or mor e consecut i vel y smal l er f acul t at i ve ponds are const r uct ed i nst ead of a very l ar ge one, because i t i s mor e pr act i cal for de-sl udgi ng. To remove t he al gae fr om aer obi c pond, effl uent s’ r ock fi l t r at i on, gr ass pl ot s, fl oat i ng macrophyt es and her bi vorous fi sh can be used, but most commonl y, t he effl uent fl ows di r ect l y i n a f i nal mat urat i on pond.
Aerobic / Maturation Ponds (MPs)
Pat hways of BOD r emoval i n f acul t at i ve wast e st abi l i sat i on ponds. Sour ce: ht t p: / / npt el . i i t m. ac. i n/ cour ses/ Webcour se-cont ent s/ IIT-KANPUR / wast eWat er / Lect ur e%2040. ht m#Cl assi f i cat i on and ht t p: / / www. r pi . edu/ dept / chem-eng/ Bi ot ech-Envi r on/ FUNDAMNT/ st r eem/ oxpond. j pg
[ Accessed: 07. 02. 2010]
Wher eas anaer obi c and facul t at i ve ponds ar e desi gned f or BOD r emoval , mat ur at i on or pol i shi ng ponds are essent i al l y desi gned f or pat hogen r emoval and r et ai ni ng suspended st abi l i sed sol i ds (MARA et al . 1992; SASSE, 1998; TILLEY et al . 2008). The si ze and number of mat ur at i on ponds depends on t he r equi r ed bact eri ol ogi cal qual i t y of t he fi nal ef fl uent . The pr i nci pal mechani sms for f aecal bact eri al r emoval i n facul t at i ve and mat urat i on ponds ar e HRT, t emperat ur e, hi gh pH (> 9), and hi gh l i ght i nt ensi t y. Faecal bact er i a and ot her pat hogens di e off due t o t he hi gh t emper at ure, hi gh pH or r adi at i on of t he sun l eadi ng t o sol ar di si nfect i on (CURTIS et al . 1992).Regar di ng vi r us removal , l i t t l e i s defi ni t el y known but i t i s gener al l y recogni sed t hat i t occur s by adsorpt i on on t o set t abl e sol i ds (i ncl udi ng t he pond al gae) and consequent sedi ment at i on i n t he anaerobi c and f acul t at i ve pond. Some macr oor gani sms such as pr ot ozoan cyst s and hel mi nt h eggs are al so r emoved by sedi ment at i on. Mat urat i on ponds ar e shal l ower (1 t o 1.5 m), wi t h 1 m bei ng opt i mal . The r ecommended hydr aul i c r et ent i on t i me i s 15 t o 20 days (WSP 2007). If used i n combi nat i on wi t h al gae and/ or fi sh har vest i ng, t hi s t ype of pond i s al so ef fect i ve at r emovi ng t he maj or i t y of ni t r ogen and phosphorus fr om t he effl uent (TILLEY et al . 2008). Some f ur t her i nfor mat i on on t he physi cal desi gn i s gi ven i n ARTHUR (1983) and IRC (2004).
Cost Consideration
t echnol ogi es and onl y l ow-t ech i nf rast r uct ur e. Thi s makes t hem part i cul arl y sui t abl e for devel opi ng count r i es wher e many convent i onal wast ewat er t r eat ment pl ant s have fai l ed because wat er and sewer ut i l i t i es di d not gener at e suff i ci ent revenue t o pay t he el ect r i ci t y bi l l for t he pl ant (IRC 2004). However, exper t desi gn i s st i l l r equi red. Furt her, t he ponds can be combi ned wi t h aquacul t ur e t o l ocal l y pr oduce ani mal f eed (e. g. duckweed) or fi sh (e.g. fi shponds). Bi ogas (met hane and car bon di oxi de) may al so be r ecover ed f or use when anaerobi c ponds ar e covered wi t h a fl oat i ng pl ast i c membrane (PENA VARON 2004).
Op e ra tio n a n d M a in te n a n ce
Resour ce Recover y and Reuse. Sour ce: EWARDS (1990) i n ROSE (1999)
Sol i ds i n t he r aw wast ewat er, as wel l as bi omass pr oduced, wi l l set t l e out i n f i rst -st age anaer obi c ponds and i t i s common t o r emove sl udge when i t has reached hal f dept h i n t he pond. Thi s usual l y occurs aft er 1 up t o 10 or 20 years of oper at i on. In cer t ai n i nst ances, anaer obi c ponds become covered wi t h a t hi ck scum l ayer, whi ch i s t hought t o be benefi ci al but not essent i al , and may gi ve r i se t o i ncreased fl y br eedi ng.
To pr event scum for mat i on, excess sol i ds and gar bage need t o be r emoved before t he wast ewat er ent er s t he ponds; and pr e-t r eat ment (wi t h gr ease t r aps) i s essent i al t o mai nt ai n t he ponds (TILLEY et al . 2008). Care shoul d be t aken t o ensur e t hat pl ant mat er i al does not fal l i nt o t he ponds as t hi s i ncr eases t he BOD cont ent of t he wat er. Unl ess i t i s t he purpose of t he pond, veget at i on or macrophyt es shoul d be r emoved as i t may provi de a br eedi ng habi t at for mosqui t oes and pr event l i ght fr om penet r at i ng t he wat er col umn. (TILLEY et al . 2008). The WHO (WHO 2005 i n MOREL & DINER 2006) does not pr omot e pond syst ems i f appropri at e mosqui t o cont rol measur es ar e not guar ant eed.
If t he wat er i s r eused for i rr i gat i on, t he sal i ni t y of t he ef fl uent shoul d be cont rol l ed r egul ar l y i n or der t o prevent negat i ve i mpact on t he soi l st r uct ur e.
H e a lth As p e cts
To pr event l eachi ng, t he ponds shoul d have a l i ner. The l i ner can be cl ay, asphal t , compact ed eart h, or anot her i mper vi ous mat er i al . Al t hough effl uent s fr om mat ur at i on ponds are general l y l ow i n pat hogens, t he ponds shoul d i n no way be used f or r ecr eat i on or as a di rect sour ce of wat er f or consumpt i on or domest i c use. A berm can prot ect f rom erosi on or t he i nvasi on by veget at i on and a f ence can pr ot ect t he l agoons fr om peopl e and ani mal s and pr event t hat garbage i s t hrown i n.
For t he r est ri ct ed and unr est ri ct ed reuse of t he effl uent i n agri - and aquacul t ur e, pl ease r efer t o t he WHO (2006) gui del i nes.
Can t r eat hi gh-st r engt h wast ewat er t o hi gh qual i t y eff l uent si mple met hodology t o help t he desi gner i n prepari ng adequat ely det ai led desi gns.
VARON, M. P. ; MARA, D. D. (2004): Wast e St abi li sat i on Ponds. (pdf present at i on). Delf t : Int ernat i onal Wat er and Sani t at i on Cent re . URL
[ Accessed: 17. 05. 2012] . PDF
Thi s document prov i des i nf ormat i on and i nst ruct i ons on w ast e st abi li sat i on ponds. Vari ous case st udi es are ment i oned, e. g. t he w ast ew at er-f ed f i shponds i n Calcut t a i n Indi a.
Int ernat i onal Dev elopment Research Cent er Canada (IDRC). PDF
The report suggest s t hat emergi ng t rends i n low -cost , decent rali sed nat urally-based i nf rast ruct ure and urban w ast ew at er management w hi ch promot e t he recov ery and reuse of w ast ew at er resources are i ncreasi ngly relev ant . Technologi es f or t hese sani t at i on opt i ons are present ed. The concept of managi ng urban w ast ew at er f low s at a decent rali sed or "i nt ermedi at e" lev el, based on mi cro w at ersheds, i s explor ed. Ef f luent t reat ment st andards t hat are current ly accept ed i n order t o prot ect publi c healt h and saf et y are rev i ew ed.
TILLEY, E. ; LUETHI, C. ; MOREL, A. ; ZURBRUEGG, C. ; SCHERTENLEIB, R. (2008): Compendi um of Sani t at i on Syst ems and Technologi es. Duebendorf and Genev a: Sw i ss Federal Inst i t ut e of Aquat i c Sci ence and Technology (EAWAG). URL [ Accessed: 15. 02. 2010] . PDF
Thi s compendi um gi v es a syst emat i c ov erv i ew on di f f erent sani t at i on syst ems and t echnologi es and descri bes a w i de range of av ai lable low -cost sani t at i on t echnologi es.
WAFLER, M. (2008): Trai ni ng Mat eri al on Anaerobi c Wast ew at er Treat ment . Aarau: Seecon GmbH. PDF
Thi s t rai ni ng manual emphasi zes basi cs of bi ogas t echnology as w ell as desi gn pri nci ples and t echni cal consi derat i ons. A sample desi gn exerci se and some t echni cal draw i ngs and sket ches are also gi v en.
WSP (Edi t or) (2007): Phi li ppi nes Sani t at i on Source Book and Deci si on Ai d. pdf present at i on. Washi ngt on: Wat er and Sani t at i on Program. PDF
Thi s Sani t at i on Sourcebook di st i ls some of t he core concept s of sani t at i on i n a user-f ri endly f ormat so t hat t he book can serv e as a pract i cal ref erence t o sani t at i on prof essi onals and i nv est ment deci si on-makers, part i cularly t he local gov ernment s. The annexe cont ai ns a pract i cal collect i on of f act sheet s on select ed sani t at i on syst em opt i ons.
WSP (Edi t or) (2008): Technology Opt i ons f or Urban Sani t at i on i n Indi a. A Gui de t o Deci si on-Maki ng. pdf present at i on. Washi ngt on: Wat er and Sani t at i on Program. URL [ Accessed: 26. 03. 2010] . PDF
These gui dance not es are desi gned t o prov i de st at e gov ernment s and urban local bodi es w i t h addi t i onal i nf ormat i on on av ai lable t echnologi es on sani t at i on. The not es also ai d i n maki ng an i nf ormed choi ce and explai n t he sui t abi li t y of approaches.
