Treatment Mechanism and Basic Design Principles

  Waste Stabilisation Ponds

  Publ i shed on SSWM ( ht t p: / / www.sswm.i nfo )

  Co m p ile d b y : 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, Sl udge, Fer t i gat i on Wat er, Bi ogas (i f anaerobi c pond Faeces, Excr et a i s covered)

In tro d u ctio n

  Wast ewat er st abi l i sat i on ponds are l arge man-made basi ns i n whi ch gr eywat er, bl ackwat er or faecal sl udge can be t r eat ed t o an ef fl uent of r el at i vel y hi gh qual i t y and apt for t he reuse i n agr i cul t ur e. The t r eat ment , i n opposi t i on t o convent i onal t r eat ment processes such as act i vat ed sl udge syst em t akes days t o week (MARA & PEARSON 1998 i n ROSE 1999), but WSPs pr ovi de a good opt i on for a (semi -) cent r al i sed t r eat ment i n devel opi ng count r i es because of t he l ow capi t al and part i cul arl y l ow O & M (Oper at i on and Mai nt enance) cost s. In addi t i on, i t i s one of t he few l ow-cost nat ur al processes whi ch pr ovi des good t r eat ment of pat hogens (DFID 1998). The effl uent of WSP i s r el at i vel y ri ch i n nut r i ent s (ni t r ogen and phosphor us) and r epr esent s an i mmedi at e r esour ce for reuse i n agri cul t ure or aquacul t ur e (ROSE 1999). Exper i ence f rom ar ound t he wor l d has shown t hat WSPs are ver y oft en t he most cost -eff ect i ve wast ewat er t reat ment met hod, but t hei r maj or di sadvant age i s t hat avai l abi l i t y of l ar ge ar eas of l and far away f rom homes and publ i c spaces i s r equi r ed (DFID 1998). Anaerobi c ponds requi r e approxi mat el y 4 m2/ m3 dai l y fl ow and f acul t at i ve aer obi c ponds r equi r e 25 m2/ m3 dai l y fl ow (SASSE 1998). WSPs make use of t he sun, wi nd, gr avi t y, and bi ol ogi cal act i vi t y t o achi eve t r eat ment . The pri nci pl es behi nd WSP oper at i on are si mpl e and t hey pl ace no st r ai n on t echni cal r esources or l abour (WHO, 1987). However, bot h t he pr ocess desi gn and t he physi cal desi gn of WSPs have t o be car r i ed out ver y car eful l y by compet ent desi gn engi neer s si nce WSPs ar e more t han j ust holes i n t he ground (PENA VARON 2004).

  

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 Break down bi odegr adabl e organi c mat er i al BOD r emoval i n anaer obi c ponds i s gover ned by t he same mechani sms t hat occur i n al l ot her anaerobi c r eact ors (MARA et al . 1992) and anaerobi c ponds do not or onl y r arel y cont ai n al gae. The process (as i n sept i c t anks) r el i es on t he sedi ment at i on of set t abl e sol i ds and subsequent anaer obi c di gest i on i n t he r esul t i ng sl udge l ayer.

  Duri ng anaer obi c di gest i on, bi ogas i s produced whi ch coul d be col l ect ed by cover i ng t he anaer obi c pond wi t h a fl oat i ng pl ast i c membr ane (PENA VARON 2004, WAFLER 2008). The r ecover ed bi ogas can be used f or heat i ng, cooki ng or, i f suffi ci ent amount s can be col l ect ed f or ener gy pr oduct i on.

  3 APs can recei ve or gani c l oads usual l y i n t he range of 100 t o 350 g BOD/ m / day (PENA VARON 2004). They shoul d not be oper at ed bel ow 10° C, and t he l oad, whi ch can be t r eat ed i ncr eases l i near l y wi t h t emper at ur e r i se (e.g.

  3

  3

  100 g/ m / day at 10° C and 300g/ m / day at 20° C). The desi gn t emper at ur e shoul d be t he mean of t he col dest mont h of t he year (PENA VARON 2004). A HRT of one day shoul d be suf fi ci ent for a BOD5 l ower t han 300

  3 mg/ m / day at 20° C, but t he r ecommended HRT r ange var i es f rom 2 t o 5 days (WSP 2007).

  For hi gh-st r engt h i ndust r i al wast es, up t o t hree anaerobi c ponds i n ser i es mi ght be necessary. The opt i mum pH for di gest i on l i es at 6 t o 8 and aci di c wast ewat ers t hus requi r e neut r al i si ng pr i or t o t r eat ment . Due t o i t s

  3 t oxi ci t y t o anaer obi c bact er i a, ammoni a concent r at i ons should not exceed >80 mg NH -N/ L.

  Pond BOD Removal Pat hogen Removal HRT Anaer obi c Pond 50 t o 85%

  1 t o 5 days Facul t at i ve Pond 80 t o 95%

  5 t o 30 days Mat ur at i on Pond 60 t o 80% 90% 15 t o 20 days

  Compar i son of t he t r eat ment per f or mance of di f f er ent wast e st abi l i sat i on ponds. Sour ce: WSP (2007) Facultative Treatment Ponds (FPs)

  Facul t at i ve Tr eat ment Ponds ar e t he si mpl est of al l WSPs and consi st of l ar ge shal l ow ponds (dept h of 1 t o 2m) wi t h an aer obi c zone cl ose t o t he sur face and a deeper, anaer obi c zone. There ar e t wo t ypes of facul t at i ve ponds: pri mary facul t at i ve ponds t hat recei ve raw wast ewat er (aft er gri t r emoval ), and secondary facul t at i ve ponds r ecei vi ng set t l ed wast ewat er usual l y f rom t he anaer obi c pond. In pri mary facul t at i ve ponds, t he funct i ons of anaer obi c and secondar y facul t at i ve ponds ar e combi ned. Thi s t ype of pond i s desi gned gener al l y for t he t reat ment of onl y sl i ght l y pol l ut ed wast ewat er and i n sensi t i ve l ocat i ons where anaer obi c ponds’ odour woul d be unaccept abl e. FPs ar e desi gned for BOD removal on t he basi s of l ow sur face l oadi ng (unl i ke anaer obi c ponds whi ch are desi gned accordi ng t o t hei r vol umet r i c l oad) and can t reat wat er i n t he BOD range of 100 t o 400 kg/ ha/ day

  2 cor respondi ng t o 10 t o 40 g/ m / day at t emper at ures above 20° C (MARA and PEARSON, 1998).

  The facul t at i ve ponds ar e cover ed by al gae. The al gae gr ow usi ng t he sunl i ght and t hey produce oxygen i n excess t o t hei r own requi r ement s, whi ch t hey t ransf er t o t he wat er. It i s t hi s excess of oxygen t hat i s used by bact er i a t o f ur t her br eak down t he or gani c mat t er vi a aer obi c di gest i on (oxi dat i on) t r ansformi ng t he or gani c pol l ut ant s i nt o CO . Addi t i onal l y t o aerobi c and anaer obi c di gest i on of BOD, i n t he facul t at i ve ponds "sewage

  The al gal pr oduct i on of oxygen occur s near t he sur face of aer obi c ponds t o t he dept h t o whi ch l i ght can penet r at e (i .e. t ypi cal l y up t o 500 mm). Addi t i onal oxygen can be i nt r oduced by wi nd due t o ver t i cal mi xi ng of t he wat er. Oxygen i s unabl e t o be mai nt ai ned at t he l ower l ayers i f t he pond i s t oo deep, and t he col our t oo dar k t o al l ow l i ght t o penet r at e ful l y or i f t he BOD and COD i n t he l ower l ayer i s hi gher t han t he suppl y. As a r esul t of t he phot osynt het i c act i vi t i es of t he pond al gae, t her e i s a di urnal var i at i on i n t he concent rat i on of di ssol ved oxygen. At peak sun r adi at i on, t he pond wi l l be most l y aerobi c due t o al gal act i vi t y, whi l e at sunr i se t he pond wi l l be pr edomi nant l y anaer obi c. Peak al gae act i vi t y al so r esul t s i n a pH r i se t o above 9 si nce car bonat e and bi car bonat e i ons r eact t o provi de mor e carbon di oxi de f or t he al gae, l eavi ng an excess of hydroxyl i ons. A pH above 9 for 24 hours can pr ovi de a 100% ki l l of E. col i and t hus, most pat hogeni c bact eri a ( ht t p:/ / ponce.sdsu.edu/ ai wps.ht ml ). At hi gh pH, ammoni ac, comi ng fr om t he hydrol ysi s of or gani c ni t r ogen i s t ransf or med t o ammoni a, whi ch i s vol at i l i sed t o t he ai r. Ther e i s l i t t l e evi dence f or ni t ri f i cat i on and deni t ri f i cat i on. But ammoni a, as wel l as phosphor us i s al so i ncor por at ed i nt o new al gal bi omass and part of t hi s 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

  Accor di ng t o t he Int er nat i onal Wat er and Sani t at i on Cent r e (IRC), st abi l i sat i on ponds are t he most cost -ef fect i ve (semi -)cent ral i sed wast ewat er t reat ment t echnol ogy for t he r emoval of pat hogeni c mi cr oor gani sms. However, t hi s depends on t he avai l abi l i t y of l and and i t s pri ce. St abi l i sat i on ponds al so have t he advant age of ver y l ow operat i ng cost s si nce t hey use no energy compar ed t o ot her wast ewat er t reat ment 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.

  At a Gla n ce

  In a fi r st pond (anaer obi c pond), sol i ds and set t l eabl e or gani cs set t l es t o t he bot t om formi ng a sl udge, whi ch i s, di gest ed anaerobi c by mi cr oor gani sm. In a second pond (facul t at i ve pond), al gae gr owi ng on t he sur face provi de t he wat er wi t h oxygen l eadi ng

  

Working Principle t o bot h anaer obi c di gest i on and aer obi c oxi dat i on of t he organi c pol l ut ant s. Due t o t he

  al gal act i vi t y, pH r i ses l eadi ng t o i nact i vat i on of some pat hogens and vol at i l i sat i on of ammoni a. The l ast ponds ser ves for t he r et ent i on of st abi l i sed sol i ds and t he i nact i vat i on of pat hogeni c mi croorgani sms vi a heat i ng r i se of pH and sol ar di si nfect i on. Al most al l wast ewat ers (i ncl udi ng heavi l y l oaded i ndust r i al wast ewat er ) can be

  Capacity/ Adequacy t r eat ed, but as hi gher t he organi c l oad, as hi gher t he r equi red sur face. In t he case of hi gh sal t cont ent , t he use of t he wat er for i r r i gat i on i s not r ecommended.

  90% BOD and TSS; hi gh pat hogen r educt i on and r el at i vel y hi gh r emoval of ammoni a and

  Performance

  phosphor us; Tot al HRT: 20 t o 60 days

  Costs Low capi t al cost s wher e l and pr i ces ar e l ow; very l ow oper at i on cost s

Self-help Desi gn must be car ri ed out by exper t . Const r uct i on can t ake pl ace by semi - or unski l l ed

Compatibility l abour ers. Hi gh sel f-hel p compat i bi l i t y concerni ng mai nt enance.

  Ver y si mpl e. Removi ng veget at i on (t o pr event BOD i ncr ease and mosqui t o br eat h) scum

  O&M and fl oat i ng veget at i on fr om pond sur faces, keepi ng i nl et s and out l et s cl ear, and repai r i ng any embankment damage. Reliability Rel i abl e i f ponds ar e mai nt ai ned wel l , and i f t emper at ur es are not t oo l ow. Main strength Hi gh effi ci ency whi l e ver y si mpl e oper at i on and mai nt enance.

  Large surf ace ar eas requi r ed and needs t o be pr ot ect ed t o pr event cont act wi t h human

  Main weakness

  or ani mal s

A p p lic a b ilit y Wast ewat er for t r eat ment i n aerobi c ponds shoul d have a BOD5 cont ent bel ow 300 mg/ l (SASSE 1998)

  Facul t at i ve and anaerobi c ponds may be char ged wi t h hi gh-st rengt h wast ewat er. However, bad odour cannot be avoi ded r el i abl y wi t h hi gh l oadi ng r at es. WSPs ar e especi al l y appr opr i at e for rur al communi t i es t hat have l ar ge, open and unused l ands, away fr om homes and publ i c spaces and wher e i t i s feasi bl e t o devel op a l ocal col l ect i on syst em. They ar e not appr opr i at e for ver y dense or ur ban areas. WSPs ar e part i cul arl y wel l sui t ed for t r opi cal and subt r opi cal count r i es because t he i nt ensi t y of t he sunl i ght and t emperat ur e are key fact or s for t hei r ef fi ci ency (IRC 2004). In col d cl i mat es, t he HRT and l oadi ng may be adj ust ed, but when mean t emper at ures f al l bel ow 12 ° C dur i ng several mont h of t he years, WSPs seem not t o be appr opr i at e (ARTUHR 1983). WSP ar e al so r ecommended f or t he t r eat ment i n or der t o reuse t he ef fl uent i n agr i cul t ur e and aquacul t ur e, because of i t s eff ect i veness i n r emovi ng nemat odes (wor ms) and hel mi nt h eggs (WHO 2006, Vol ume II), whi l e preser vi ng some nut r i ent s. If r euse i s not possi bl e, WSPs may not be adequat e f or areas sensi t i ve t o eut r ophi cat i on (UNEP 2004).

A d v a n t a g e s

  Can be bui l t and r epai red wi t h l ocal l y avai l abl e mat eri al s No ext ernal energy r equi red for oper at i on Low i n const r uct i on and ver y l ow operat i ng cost s Hi gh reduct i on i n pat hogens

  Can t r eat hi gh-st r engt h wast ewat er t o hi gh qual i t y eff l uent Gener al l y rel i abl e and wel l -funct i oni ng Eff l uent can be r eused i n aquacul t ur e or for i r r i gat i on i n agr i cul t ur e

D i s a d v a n t a g e s

  Requi res l ar ge open l and sur faces f ar away fr om homes and publ i c spaces Requi res exper t desi gn and super vi si on May pr omot e breedi ng of i nsect s i n t he pond (e. g. f l i es, mosqui t oes) De-sl udgi ng (nor mal l y every few year s) and cor rect di sposal of t he sl udge needs t o be guarant eed If t he ef fl uent i s r eused, sal i ni t y needs t o be moni t or ed If t he nut r i ent s i n t he eff l uent can not be r eused (e.g. i n agr i cul t ur e), di schar ge can cause eut r ophi cat i on Anaer obi c ponds can cause bad odour s i f poor l y desi gned Not al ways appr opr i at e for col der cl i mat es

R e fe r e n c e s

  

ARTHUR, J. P. (1983): Not es i n t he Desi gn and Operat i on of Wast e St abi li zat i on Ponds i n Warm Cli mat es of Dev elopi ng Count ri es . Washi ngt on:

The World Bank. PDF

Anaerobi c, f acult at i v e and mat urat i on ponds as w ells as aerat ed lagoon syst ems are present ed as an appropri at e solut i on i n dev elopi ng

count ri es w here sew erage syst ems are present . The t echni cal cont ent w as rev i ew ed by Prof . Duncan Mara (Uni v ersi t y of Leeds, England).

Det ai led desi gn, operat i on and mai nt enance gui dance i s gi v en. Hence, t hi s paper can be usef ul as a t echni cal manual.

CURTIS, T. P. ; MARA, D. D. ; SILVA, S. A. (1992): Inf luence of pH, Oxygen, and Humi c Subst ances on Abi li t y of Sunli ght t o Damage Faecal Coli f orms

i n Wast e St abi li zat i on Pond Wat er. In: Appli ed and Env i ronment al Mi crobi ology 58, 1335-1343. URL [ Accessed: 02. 04. 2010] . PDF

Thi s sci ent i f i c art i cle descri bes how solar li ght and oxygen lead t o damage of f aecal coli f orms i n w ast e st abi li zat i on ponds. Humi c subst ances

absorb t he energy of t he sunli ght and react w i t h surroundi ng oxygen, leadi ng t o t he f ormat i on of t oxi c react i v e oxygen speci es (ROS).

  

DFID (Edi t or) (1998): Gui dance Manual on Wat er Supply and Sani t at i on Programmes. London: Wat er, Engi neeri ng and Dev elopment Cent re

(WEDC) f or t he Depart ment f or Int ernat i onal Dev elopment (DFID). URL [ Accessed: 04. 01. 2011] . PDF

Thi s manual has been prepared as a t ool t o help i mprov e DFID's (Depart ment f or Int ernat i onal Dev elopment s, Uni t ed Ki ngdom) support f or

w at er supply and sani t at i on proj ect s and programmes i n dev elopi ng count ri es. It s part i cular f ocus i s on how DFID assi st ance can best meet t he

needs of t he urban and rural poor f or w at er supply and sani t at i on serv i ces.

EWARDS, P. (Edi t or); PULLIN, R. (Edi t or) (1990): Wast ew at er-f ed aquacult ure. . Calcut t a, Indi a: Int ernat i onal semi nar on w ast ew at er

reclamat i on and reuse f or aquacult ure. URL [ Accessed: 18. 01. 2011] . PDF

MARA, D. D. ; PEARSON, H. (1998): Desi gn Manual f or Wast e St abi li zat i on Ponds i n Medi t erranean Count ri es. Leeds: Lagoon Technology

Int ernat i onal Lt d.

  

MARA, D. D. ; ALABASTER, G. P. ; PEARSON, H. W. ; MILLS, S. W. (1992): Wast e St abi li zat i on Ponds: A Desi gn Manual f or East ern Af ri ca. . Leeds:

Lagoon Technology Int ernat i onal.

MOREL, A. ; DIENER, S. (2006): Greyw at er Management i n Low and Mi ddle-Income Count ri es, Rev i ew of di f f erent t reat ment syst ems f or

households or nei ghbourhoods. Duebendorf : Sw i ss Federal Inst i t ut e of Aquat i c Sci ence (EAWAG), Depart ment of Wat er and Sani t at i on i n

Dev elopi ng Count ri es (SANDEC). URL [ Accessed: 19. 05. 2010] . PDF

Thi s report compi les i nt ernat i onal experi ence i n greyw at er management on household and nei ghbourhood lev el i n low and mi ddle-i ncome

count ri es. The document ed syst ems, w hi ch v ary si gni f i cant ly i n t erms of complexi t y, perf ormance and cost s, range f rom si mple syst ems f or

si ngle-house appli cat i ons (e. g. local i nf i lt rat i on or garden i rri gat i on) t o rat her complex t reat ment t rai ns f or nei ghbourhoods (e. g. seri es of

v ert i cal and hori zont al-f low plant ed soi l f i lt ers).

WHO (Edi t or) (1987): Wast ew at er st abi li zat i on ponds: Pri nci ples of planni ng and pract i ce. . Alexandri a: World Healt h Organi zat i on Regi onal

Of f i ce f or t he East ern Medi t erranean. PDF

The book has been di v i ded i n t w o part s. Part A prov i des a comprehensi v e summary concerni ng t he v ari ous aspect s of const ruct i ng, operat i ng

and mai nt ai ni ng pond syst ems. It also consi ders aspect s such as management and saf et y. Part B i s i nt ended f or persons maki ng t he preli mi nary

desi gns on w hi ch cost est i mat es and, hence, choi ces can be made. In part i cular, t he appendi x and annex prov i de a w orki ng example and a

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.

  

ROSE, D. G. (1999): Communi t y-Based Technologi es f or Domest i c Wast ew at er Treat ment and Reuse- opt i ons f or urban agri cult ure. Ot t aw 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.

  

For further readings, case studies, awareness raising material, training material, important weblinks or

the related powerpoint presentation, see www.sswm. info/ category/ implementation-tools/ wastewater-

treatment/ hardware/ semi-centralised-wastewater-treatments/ w