2012 Coleman Anaerobic Digestion SSO vs WWTP

ANAEROBIC DIGESTI DIGESTI ON - COMPARI SON OF OF DESI DESI GN CONSI CONSI DERATI ONS ONS BETWEEN BETWEE N A BIOS BI OSOL OLII DS AND AND ORGANIC ORGANIC SOLI OL I D WASTES WASTES DIGESTI DIGESTI ON FACI L IT Y P. Co C olem leman, an, PhD PE PEng, ng, AEC A ECOM OM J . Blis Blisc chke, M S, AECOM AEC OM

ABSTRACT

A naerobic robic dige digesti stion on is is a wel well un unde derstood rstood biosoli biosolids treatmen entt technol technology. ogy. The The primary benefits fits are the production ion of renewable energy and the reduction ion of materi teria al to be dis dispose posed of. Howeve However, r, biosol biosolids ids are a minor sourc source e of diges digestible tible material when compared with organic solid wastes, industrial wastes, agricultural wastes wastes (e.g. (e.g. man manure) ure) and en energy ergy crops. This his paper per wi will present the desi design gn of the the new Di Disco Source Sepa Separated Organic Organicss (SSO) (SSO) A naerobic robic Dige Di gestio stion n Processi Processing Facility Facility in the the City of Toron Toronto and contra trast it with with the the design of a typ typical ical Biosolids osolids Dige Digesti stion on Facil cility. Issu I ssue es such such as pre-processi pre-processing ng options options,, dige digester ster desi design, gn, end product product quality, quality, proces processs water water balance an and d biogas biogas producti production on are discussed 1.

I NT RODUC T I ON

On vaca vacati tion, on, in in 117 1176, 6, Al A llesa esandro ndro Vol V olta ta col collected gas gas rel release ased from from L ake Maggi ggiore (Italy) (I taly) an and d showed showed that that it it was flam fl ammable ble. V olta olta experim ri mented nted with with this this marsh gas gas bui buillding ding a pistol pistola a which which was an earl early y precursor of the inter nternal combus combusti tion on engine. engine. A centur century y la later Becha Becham mp dem demonstrated a microbi crobial al ori origin gin of this this gas gas using using an an ethan ethanol ol--base based d me media dia inoculated inoculated with with rabbit feces eces (Spe (Speece ece 2008). 2008). I n 186 1860, 0, Louis L ouis Moura Mourass bui built lt a closed closed containe containerr with with a wa water ter seal in in which orga organi nic c matter (excrem (excremen ent) t) disa disappe ppeared. ared. Thi T hiss system, later ater referr referred ed to as the Mouras Automatic Scavenger, was considered an elegant solution to the treatment of sewag sewage e sol soliids. However, However, eviden evidence ce sugge suggests that that many many people people alrea already reli relied on this method of treatm treatmen ent. t. I t is is bel believed eved that that the first first purposepurpose-bui built anae anaerobic robic dige digeste sterr was bui buillt in in 1859 1859 for an Ind Indiian leper leper colony colony (Speece (Speece 2008 2008). ). Thir Thirtty one years lat later, W. D. Scott-Mon -Moncrieff ieff co constructed a tank with ith an empty pty space at the botto bottom m and a submerged bed of stones stones on the upper upper part part creating probably one of the first anaerobic filters. The The firs first noteworthy link linking ing of of liqu liquefac faction ion of of sewage so solids lids an and ga gas production/utilization did not occur until 1895. Cameron constructed a septic tank in Exete Exeterr (U (UK) that that produced gas gas that powered ne nearby arby gas gas lights. li ghts. Tod Today, anaerobic systems are used to produce renewable energy fro from high igh strength industrial effluents, agricultural material, municipal wastes, organic WEAO 2012 Technical Conference, Ottawa, Ontario

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industri ndustrial al byproducts byproducts and and bi biosoli osolids. ds. A na nae erobic robic dige digestion stion provi provides des a means eans to reduce reduce polluti poll ution on from from organi organic wastes wastes whil while producing a rene renewabl wable fuel – biogas. biogas. Biogas can used to produce heat, steam, electricity and replace fossil-based vehicle fuels. 2.

M I CROBI OL OGY

Anaerobic digestion (see Figure 1) can be divided into four steps (Henze, van L oosdrecht et al. 2008): 1. Hydrolysis: Enzymes excreted by fermentative bacteria break down compl complex ex undissolve undissolved d material into into less compl complex, ex, dissol dissolved ved compounds compounds that can pass pass through through cell cells wall walls and membranes of fermen entati tative ve bacteri bacteria. a. Whe When n diges digesti tion on source separa separated ted organi organics, approximately 15% of ammonia is released into solution at this step step (Zha (Zhang ng,, Walker Walker et al. 2010). 2010). 2. Acidogenesis: Dissolved compounds within fermentative cells are converted to simpler compounds and excreted. These include vola volatil ti le fatty aci acids, ds, am ammonia onia, alcohols alcohols (e.g. etha ethanol), nol), la lactic ctic aci acid, d, carbon dioxide and hydrogen sulfide. 3. Acetoge cetogenes nesiis: (intermediary acid production) digestion products are converted into acetate, hydrogen, and carbon dioxide. 4. M ethanogenesis nesis: Acetate, hydrogen, carbon dioxide plus carbonate, for form mate or methan methanol are converted converted into into metha methane ne and carbon dioxide (i.e. biogas). Typically, 70% of the methane is produced produced from rom acetate acetate (by aceticl aceticlasti astic c metha methanogens nogens)) and 30% from carbon dioxide and hydrogen (by hydrogenotrophic methanogens). 3.

FE EDST OCK

The There are a number of or organic fee feedstocks suita itable for for anaerob robic dige igestion ion (Figu (Figure 2). I n a typ typical ical Nor North Ame America rican city, ity, the responsibility ibility for for these feedstocks is spread across city departments (e.g. solid waste vs. water and sewage). sewage). The heref refor ore, e, the management of the these se feedstocks feedstocks is is fragme fragmented nted and opportunity opportunity to cooperate cooperate to obtain the bes bestt soluti solution on for for a city city is is more ore often often than not missed. A typica typicall SSO dige digeste sterr produce produces abou aboutt 110 m3 of biogas per wet tonne of material terial processe processed which which is is abou aboutt 80% of the biogas pote potential ntial of the SSO. SSO. This is is 3 about about 0.8 0.8 to 1.0 m /kg volatile matter destroyed which is similar to the biogas yield for sewage sludge. The yield will change depending on what organics are prese present nt in in the SSO an and d how the SSO is prepa prepared red for dige digesti stion on (e.g. hydrol hydrolyse ysed). d). WEAO 2012 Technical Conference, Ottawa, Ontario

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Unlike SSO, the organic make up of sewage will only vary significantly from one site to another if there is a significant industrial discharge to the sewer system. Apart from from the vari varia abil bility in in the feed cha characteri racteristi stics, cs, the other other dif differences rences betw betwee een n SSO and sewag sewage e sludge sludgess ar are (1) water water content and and (2) contaminants in in the feedstock. Sewage sludge consists of three types of materials: raw volatile solids (VS), biomass solids (e.g. waste activated sludge), and inert material. The inert material consi consists sts of materi aterial al tha thatt arrives arri ves with with the sewag sewage e and and material crea created ted in in the process (e.g. iron phosphates). Scree Screenings nings an and d grit, grit, if not removed fro from m the raw sewage sewage,, create create problem problems in the digester. Screenings form rafts on the water surface and interfere with rotating equ equiipment (e.g. pumps, ps, mixers). Plas Plasti tics, cs, if i f they they ma make it into the the fina finall dige digested sted product, can lim li mit the the use of the end pr product. Gri Grit increa increase sess equi equipm pmen entt wear and settles out in the digester reducing the volumetric capacity. The The prim rimary processing ing challen llenge for for se sewage treatment slud ludges is water. Sewage Sewage sludg sludge e is dil dilute. In I n North North Am America erica di digesters gesters are are fe fed a sludg sludge e mix at about 4% sol soliids (Krau (K rause se 2010 2010)): A typical typical desi design susta sustaiined-peak d-peak load loadiing rate rate for me mesophi sophillic dige digeste sters rs is is 3 1.9 to 2.5 kg volatile solids/m /d (0.12 to 0.16 lb volatile solids/d/cu ft). The The upper limit of th the volat latile solids lids loa loading ing rate typica ically is determine ined by the rate at at which which toxic toxic materia terials— part partiicula cularly rl y ammonia onia— accum accumula ulate or methane form formers wash out. A limit limitin ing g value lue of 3.2 kg volatile latile 3 solids/m /d (0.20 lb volatile solids/d/cu ft) is often used. The The more dilut ilute the sewage slud ludge, the more energy is require ired to heat the feed and to maintain the temperature in the digester. Thickening the sludge to about about 6% decreases decreases the heat demand. and. I n some circ circum umstances, stances, it is i s possibl possible e to heat heat a prope properly rly insulate nsulated diges digester ter fed at 6% solids olids using only only the the wast waste e heat from a properly sized biogas co-generation engine. In Europe Europe,, whe where me mechanic chanical al thick thicke ening ning of prim primary sludg sludge e is is more comm common, dige digesters sters are fed fed with with sludge sludge at 5% to 8% sol soliids. Thi Thiss is is because cause a thickening belt or rotary drum can reliably achieve 6% and 9% dried solids when thickening waste activated sludge and primary sludge respectively. The average dige digeste sterr VS V S load loadiing is betwee between n 3 and 4 kg VS/ VS/m m3/d. /d. The The experien ience in in th the wa wastewater ind industry wit with h “h “high igh so solids lids dig dige estion ion” started with the first thermal hydrolysis plant installed at Hias, Norway in 1995 (Fjærgård and and Sande Sanderr 1999). Attempts to load load conventi conventional onal diges digesters ters at at highe higherr rates without pasteurizing or hydrolyzing the sludge failed because of foaming or souring (Brown and Sale 2002).

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A number of thermal hydrolysis installations have followed including one to be built for District of Columbia Water and Sewer Authority (Washington, DC). The feed concentration is about 10% solids. The volatile solids load to the dige digester ster is is between 5 and and 6 kg VS/ V S/m m3/d. /d. The The constitu ituents of th the collected SSO (e.g. each household has a separate bin) bin) and the the organic fraction fraction of mun unici icip pal solid olid was wastes tes (OFM (OFMSW) (e.g. (e.g. wha what is left afte after the material terial is i s mechani chanicall cally y processe processed d at at a material terial recovery recovery facil cility) varies from jurisdiction to jurisdiction. Even the SSO collected in neighboring communities can be different due to dif different erent rules rules as to what can can be be put into into a green bi bin. For example, ple, the Region egion of Peel Peel an and d the City of Toronto both have have green green bin programs. The T he City of of Tor Toronto allo llows the use of pla plasstic bags and accepts diap iapers in the green bin. in. The The Regi egion of Pe Peel only only allows allows certif certified composta compostable plastic bags in the green green bin and insists nsists that that diap diapers ers are are dispose disposed with with the regul regular ar garbag garbage. e. 4.

CITY OF OF TORO TORON NTO SSO ANAE ANAERO ROB BIC DIGE DIGES STION TION FACILITI FACILITI ES

The The Cit City of Toro Toronto ha has on one op operating ing an anaerob robic dig dige estion ion pro proc cessing ing facil facility ity (Duffe (Dufferin) rin) and is curre currently build ilding a secon cond one one at the the Disco Disco Road Road Tra Transfer fer Station ion site ite. I n the the City City of Toronto’s Duffe Dufferin rin Fa Facil cility, the the was waste arrive arrivess as as ‘ra ‘raw’ w’ SSO on the tip floor with plastic bags, heavy debris (e.g. rocks) and grit (Figure 3). The moisture content varies by season. The moisture content is typically around 68%. The The materia rial is pulpe lped using ing a mix of fre fresh and recycled led water as a preconditioning step for ‘wet’ digestion (with a total solids [TS] content of typically less ess than than 15%). 15%). At the Toronto facil faciliitie ties, the pulp is digested digested and the dige digesta state te is 3 dewate dewatered. red. The maxim aximum loading oading rate is about about 5 kg VS/ VS/m m /d. At other non-BTA facilities, the pulp is dewatered and only the liquid is digested. 5. USE OF OF WAS WASTEW TEWATE ATER R SIMULATIO SIMULATION N SOFTWAR FTWARE E TO DES DESIGN IGN SSO PROCESSING FACILITIES

Wastewa Wastewater ter treatm treatmen entt pla plant sim simula ulation tion software software (e.g. Bi BioWi oWin, GPSGPS-X X) was deve develloped to model model the the processing processing of liquid quid wastes wastes (see (see Figure 4 as an exam example). ple). Because the Disco Road Road Facil acility incl include udess awastewate wastewaterr treatm treatmen entt plan plantt and anaerobic digesters, AECOM modeled the facility using both BioWin and GPS-X S-X. Both Both these pack packag ages es include nclude sophisti sophisticated cated pH and diges digester ter models that that involve complex water chemistry calculations. AECOM also recently modeled a facility that received, digested and dewa dewatere tered d raw sludge cake del delivered vered by truck to the fa facil cility. In this case, case, in order order to set the inputs necessary for the anaerobic digestion model, AECOM modeled WEAO 2012 Technical Conference, Ottawa, Ontario

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the wastewater wastewater treatment treatment plant and then then im imported ported the output fro from m the WWT WWTP plan plantt mode modell to the biosoli biosolids proces processi sing ng facil cility mode modell. For the most part, this this approach approach work worked ed.. However, this this app approach roach cann cannot ot be use used for for an SSO facil cility. The desi designe gner therefore refore must ust start start with with sol soliids, vola volatil ti le soli solids and and moisture oisture content content infor inform mation. tion. The The nit nitrrogen an and ph phosphorus co content is es estimated fro from lite literature va value lues (e.g. %N//wet soli %N solids) and from rom histori historic c sewage sewage an and d cake discharge discharge data data from from an existing facility. Measuring the characteristics of the feedstock directly is expe expens nsiive and and labor labor in i ntensi tensive ve (Ja (J ansen nsen,, Spli Spliid et et al. 2004 2004)) The The two most difficu ifficult decisio ision ns to be made by an SSO fac facilit ility modeler ler are (1) how to set the the diss dissolved olved solids olids so tha that the the anaerobic robic dige digester ter mode odel funct fun ction ionss and (2) (2) how to charact racte erize COD, N and P was waste fract fraction ionss whe when entering the feedstock into the model. The The knowled ledge of SS SSO an and OFMSW FMSW ch characterist istics ics is limite ited compared to what is known about domestic sewage. Commercial simulation software package packagess need need to allow allow the the modeler to to “dumb down” the the model to refl reflect ect the limited infor inform mation on the model inputs. nputs. For For example, ple, it it may may not not be ne necess cessary ary to model the dige digester ster pH. pH. What What is more ore importan portantt is is modeli odeling the ammonia onia concentrati concentration on in in the diges digester, centrate and and wastewater wastewater trea treatment tment plant as well well as the varying levels in the process water buffer tanks. 6.

PRE PROCE SSI NG NG

Most wastewater trea treatment tment plants plants screen screen and and de-grit grit the the raw sewage at the head of the treatment process. However, in jurisdictions where there is a strict rule about plastics in biosolids used on agricultural land, the sludge is screened a second time through a 5mm to 10mm screen prior to thickening. SSO SSO also also contain contain containm containments that need need to be removed oved before before the material is digested. digested. The T hese contami contamina nants nts are are more dif difficult cult to man anag age e than than scree screenings nings in in sewage sewage sludge sludge.. Conse onseque quently, ntly, there there are are a number ber of proprie proprietary ‘wet’ ‘ wet’ ana nae erobic robic dige digesti stion on proces processe sess on the market (Fi (F igure 5) 5) – each with with its its own appro approach ach to mana nagi ging ng contam contamina nants nts.. Thi Thiss pap pape er wil will focus focus on on the the BTA process process which which is ins install talle ed at one one Tor Toronto facility ility (Du (Duffe fferin) in) and will be be soon ins installed at a second Tor Toronto facilit ility (Disco Road). The The Duffe Dufferin rin SSO Fac Facility ility, commiss ission ioned in 2002, was origin igina ally desi design gne ed to process process 25,000 25,000 wet wet tonne tonnes pe per year year (T (TPY ). The The facil cility is is curr curre ently ntly processi processing ng close close to 40,000 40,000 wet wet TPY TPY . The T he facil cility is is to be expande xpanded to process process up to 55,000 55,000 TPY . The The ne new w Disco Di sco Road facili acil ity is is des desiigned to process process 75,000 75,000 wet TPY. Bot Both site ites use the ‘we ‘wet’ BTA Pr Process (BTA (BTA 20 2011). Figu Figure 6 illus illustrates in a simpl simpliified flow flow diagram diagramtheBTA Proce Process ss.. WEAO 2012 Technical Conference, Ottawa, Ontario

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Other preprocessing options include pasteurization (to meet strict disi disinf nfecti ection on stand standards) ards) and/o and/orr physical physical/c /che hemical mical trea treatmen tmentt of the sludg sludge e to make make it more digestabl digestable. e. There are compa comparabl rable e options options for other organics organics feedstocks (e.g. SSO). The The ‘we ‘wet’ BTA pre-tr -treatment st step ge generates a waste su suspension ion in th the Pulper (Figure 7) by adding primarily recycled water to the ‘raw’ SSO. During the pulping process the plastic bags are broken open and removed along with with othe other li l ight/ ght/ffloatin loating ma materi terial al using using a rake rake.. The soso-cal called Li Light ght Fra Fraction ction that incl include udess the plasti plastic c bags bags are are washed washed and and pressed/depressed/de-watered. watered. Hea Heavy materi terial (e.g. (e.g. ston tones, glas glass, batte tteries ries, cutle cutlery) ry) also call calle ed Hea Heavy Fraction Fraction sinks sinks to the the bottom of the pul pulpe perr whe where re it it is is removed through a he heavy avy fracti fraction on trap. The T he pulp, at about 8-10% solids, is then passed to a de-gritting step. The pulp is passed through hydrocycl hydrocyclones as as a key com component ponent of the grit grit rem removal system to remove finer particles. The pulp is then fed into the digester directly or temporarily stored in a suspe suspensi nsion on buffer buffer tank tank before before bei being ng fe fed to the dige digester. ster. 7.

DI GE GE ST ER DESI GN GN

Sewage digesters come in one of three shapes (Figure 8): cylindrical (height height diam diameter) an and d egg egg shape shaped. Most digesters for ‘wet’ SSO digestion are cylindrical in shape. This is the most economi economical shape for the size size of these these types of dige di gesters. sters. The The dige digesters sters are are normally constructed from coated steel or concrete. This is because solid waste facilities differ from wastewater treatment plants in two ways: (1) expected asset life is shorter and (2) the feedstock can be diverted during facility shutdown becaus because e the the feedstock feedstock can be be diverted diverted to anothe anotherr site site or stockpi stockpilled. ed. Thi T hiss is is not the case for raw sewage. Unconf nconfine ned d gas, gas, confi confine ned d gas, gas, draft draft tube, tube, pump, line nea ar motion otion and and big big blad blade e are are used in in sewage sewage dige digeste sters. rs. This his sai said, as the thickness thickness of the the feed feed increases ncreases,, mixing xing moves away away fro from m turbulen turbulentt towards lam lamina narr systems. In I n the latter atter case, case, the mixer tends tends to “fol “fold” d” the the material terial much lilike a cook uses a spatula tula when mixing cake batter. SSO digester designers tend to shy away from mixers involving rotating equipm quipmen entt when the SSO SSO conta contaiins contaminants that that wil will wra wrap aro around und rota rotating ting shafts. For exam xample, ple, Duffe Dufferin rin and Dis Disco Road Road both use use gas lance lancess to mix the the digester. 8.

PROCESS ESS DESIG ESIGN N AND AND INHIB INHIBITIO ITION N

The The destruction ion of organic fee feedstsocks containin ining g nitr itrogen relea leases ammonia into solution. The larger the mass fraction of nitrogen in the feedstock, WEAO 2012 Technical Conference, Ottawa, Ontario

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the greater greater the relea release of nitro nitroge gen n per per mass ass of volati volatille soli solids des destro troye yed. d. Am A mmonia onia + exists in in the dige digester ter in both its ionic form (NH 4 ) and and its free free form form (NH (NH3). Free ammonia onia is is toxic toxic pri primaril arily to the hydrogen hydrogentr trophi ophic c meth methan anoge ogens ns.. The degree degree of this toxicity is dependent partly on the availability of certain micronutrients (Chen, Cheng et al. 2008). Conventi onventional onal sewag sewage e diges digesters ters operate operate with with amm ammonia onia concentr concentra ations tions between between 800 to 1,500 mg/L g/L as N. N. A recent surv survey ey of dige digesters sters downstr downstrea eam of therm thermal al hydrolysi hydrolysiss plants plants condu conducted cted for for DC DC WASA report report ammonia onia concentra concentrati tions ons betwe betwee en 2,000 2,000 to 3,000 mg/L. g/L . This is i s typical typical of of ammonia onia concentrations observed in SSO digesters. The The hypothesis is that dige igesters acclimatize ize to these high igh ammonia concentrati concentrations ons by (a) red reduci ucing ng the pH of of the dige digester ster by accumul ccumulati ating ng highe higher volatile acid concentrations and (b) by growing different bacteria. 9.

DI S SC CO ROA D F A CI L LT TY

The The Dis Disco Roa Road SSO Fac Facilit ility is design igned to process 75,00 ,000 wet tonnes of SSO per year (Figure 9). The The material ial is receive ived 5 days per week, 16 hours per day. The The dige igesters and an d the wastewa wastewater trea treatmen tmentt plan plantt Seq Seque uenci ncing ng Batch Batch Rea Reactors ctors (SB (SBR Rs) are fed 24 hours per per day, day, 7 days per per week. The tran transi siti tion on from from 16/5 to 24/7 operati operation on is is mediated ediated by the suspensi suspension on buff buffer tank, the the proces processs water water 1 tank and and the SBR SBR feed buff buffer tank. tank. The suspens suspensiion buf bufffer tank tank holds holds en enough ough SSO SSO to fe feed the diges digesters ters over the wee weekend. The The pro proces cesss water water 1 tan tank and the SBR SBR feed eed buff buffer tank store centrate to be used for pulping and to feed the SBR during the week. The The materia rial is fed fed by a fro front end loa loader int into one of tw two hoppers which ich feed thre three e BTA pul pulpers. pers... The The SSO is pulpe lped and the Ligh Light Fra Fraction ion and Hea Heavy Fra Fraction ion are removed. The The pulpe lped materia rial is de de-gri -grittted by by pa passing ing it th through a total of three hydrocycl hydrocyclones ones as part part of the grit grit removal system. The T he dede-gritted gritted pulp pulp is is then pumped ped to an an air mixed suspen suspensi sion on buffer buffer tank. tank. The suspen suspensi sion on buffer buffer tank tank is is sized sized to store store en enough ough pulp pulp to fee feed d two digeste digesters rs through through the weekend. weekend. The The three residu idues (Lig (Ligh ht Fra Fraction ion, Hea Heavy Fra Fractio tion, Clas Classified Gri Gritt) ar are compressed and loaded into residue trailers. The The ho homogeneous an and co contamina inant-fr -free pu pulp is pu pumped to to on one of of two cyli cyl indrical ndrical conf confiine ned d gas gas mixed dige digeste sters rs (5,300 (5,300 m3 each). The T he dige digeste sters rs are mixed using using gas gas lan lances ces.. The hydrauli hydraulic retenti retention on in in the diges digesters ters is is greater than 15 days. WEAO 2012 Technical Conference, Ottawa, Ontario

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The The dige igestate is dewatered by by tw two of of th three centrifu ifuges. The The centrifu rifug ges only only use polyme polymer when centrate (PW1+ (PW1+) is bei being produced for the waste wastewate waterr trea treatmen tmentt plan plant. t. Between etween 65% to 70% of the centrate centrate is is recycled recycled and and used used to pulp the incoming SSO. The balance is sent to one of two 750 m3 SBRs. Approxim pproximatel ately 2/3 of the SBR SBR effl efflue uent nt is is then then re-used re-used in the process. process. The The bal balan ance ce is discharged to the sanitary sewer. The The dewatered dige igestate is loa loaded in trailers and taken to another site ite for for further processing (composting). 9.1

Wat Water Ba Balan lance

Most wastewater treatment plants (WWTPs) have two process waters: potable water and effluent. This is because there is an abundance of good quality water available at a WWTP. This This is not th the case at a solid organic waste anaerobic treatment facility ility where there is a water water shortage in process water water of highe higher quali quality. For this this rea reason, the Disco Road SSO facility has five different quality process waters driven by the site-spe site-specif cific requirem requiremen entt to reduce the am amount of potabl potable water water to the the greatest extend extend feasibl sible e (Tab (T ablle 1) and and only to to treat the required required volum volume e of wate waterr to the required quality. Wate Waterr enters ters the the proce process ss in i n one one of thre three e ways ways:: with the the SSO, rai rainwate waterr (NPW (NPW)) harvested rvested from the roof of the facil cility (non (non--potable potable water) water) and and nea nearby transfer station and potable water (PW). Potable water is used to prepare polymers, rinse instruments, and irrigate biofilt iofilte ers. rs. Non Nonpotable water is used to humidify idify odorous air and wash floors/equipment. SBR SBR effl efflue uen nt (Proce (Process ss Wate Waterr 2) is used used to wash wash the L ight ght Fra Fraction ction an and the Grit as wella s to top up condensate and overflow traps. The target effluent quality is 350 tota total suspended solids (TSS) and 100 mg/L TKN. Cen Centrate whe when the the centrifuges are not using polymer (Process Water 1) is recycled and used to pulp the SSO. Process Water1 is typically 1.5% to 2% solids. The dirtiest water collected via floor and pulper drains (Process Water 0) is used to pulp the SSO. Water lea leaves ves the process in in one of three ways: ways: with with dewatere dewatered d dige digestate state and residu residue es, as SBR SBR efflue uen nt discha discharged rged to sewer wer and the the biofi biofilter drai drainage to sewer.


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Table Table 1: Proc Process Wat Water Grade

Source

Use

PROCESS PROC ESS WATE R 0 (PW0) (PW0) Fr om Pulpe Pul per Sump Sump

Prima Pr imarr y Source: Source:

Used i n pulpe ulper(s) r(s) for for pulping SSO so that the solids soli ds and liliquors are captured captured and digeste digested; d; this this is the only use

PROCESS PROC ESS WATE R 1 (PW1) (PW1) C entrate ntr ate with with no polyme polymer addition additi on that has been passed thr ough a 2mm Bow Sieve


Floor drains Delivery truck sumps This This is the the “dirt “dirtie iesst” or lowe lowest gra grade of Residuals liquors Process Water, Water, and is comp comprise ri sed d of untreated floor fl oor drainage drainageand liquors li quors passed passed Secondar Secondary y Source: through the pulper sump sieve screw for for None gross particl rti cle e removal. Condensate drains & screened centrate

Used for maki making ng pulp once the pulper pulper sump has been drawn drawn down

Secondar Secondary y Source:

The The Pro Process Wat Water 1 is ma mainly inly centrate that has passed through the Bow Bow Si eve* for particle removal. SBR FEE F EE D (PW1+) Centrate with polymer addition that has been passed thr ough a 2mm Bow Bow Sieve

The The solids lids con content of of PW1 PW1+ is lowe lower th than PW1. PW1+ is produc produced ed exclusi exclusive vely ly to feed the WTP PROCESS PROC ESS WATE R 2 (PW2) (PW2) WT P effluen effl uentt to meet meet Sewer Bylaw Byl aw

Parameter BOD5 TSS Tot Total Pho Phosphorus rus TKN

Not to exceed 300 mg/L 350 mg/L 10 mg/L 100 mg/L

WTP WTP Effluen Ef fluentt (PW2) (P W2)


Fed to WTP to produce produce PW2

Screened centrate from a centrifuge that is dosed with polymer for solids capture Secondar Secondary y Source:

Settled PW1 Prima Pr imarr y Source: Source:

Sprays and washi washing, ng, top up traps

WTP WTP efflue effl uent Secondar Secondary y Source:

topped up using Non-potab N on-potabll e water if the the need arises (not (not normally anticipated)

The The BOD5 should be inhibited for nitrification to obtain carbonaceous demand NON-POTABLE NON-POTABLE WATER (NPW) (NPW)


Rainwater

Rain Rain water water from roof

Floo Fl oorr / Truc T ruck k / Facility Facil ity Washing Washing Polymer dilution

Secondar Secondary y Source:

Top Topped up up us using ing City City wa water in prolonged dry periods POTABLE WAT ER (PW)

10.

City Water

Odour control unit (I rr rri gati on sprays) and and instrum i nstrument ent ri rinsing.

CONCL US USI ON ONS

The The primary differences be between dige igestion ion of se sewage solids lids and source separated organ organiics are: Types an and ma mass of of contam tamina inants: SSO contains more debris and grit 1. Type than than sewage sewage sludge sludge which which must must be removed prior prior to diges digesti tion. on. Sewage sludge has less grit because grit is removed from the raw sewage in the headworks.


Page 9

2. Ammonia concentration in digester : The ammonia concentrations in SSO SSO diges digesters ters is is comparabl parable e to sewage sewage diges digesters ters fed fed with with therma thermally hydrol hydrolyze yzed d soli solids. ds. xing syste system ms: Mixing equipment using rotating equipment (e.g. jet 3. M ixing mixing) xing) are are not used used in SSO dige di geste sters rs when the SSO SSO contai contains ns contaminan nants ts that that wi will wra wrap aro around und rotating rotating equipm quipmen ent. t.

4. Water balance: Water must be added to the SSO (pulping) prior to digestion whil while wate waterr is removed se sewage wage soli solids prior prior to digesti digestion. on. 11.

RE FE RE NC E S

Brown, S. and R. Sale (2002). "Operating a High-Rate Digester: Southern Water Expe Experien rience." ce." J ourna ournal CI CI WE WEM M 16: 16: 116-120 116-120.. BTA (2011 (2011). ). "Welcome "Welcome to to BT BTA I nte nternational tional Gmb GmbH!". Retrieved July J uly 31, 31, 2011, from http://bta-international.de/. Chen, Chen, Y., Y ., J . J . Ch Cheng, et et al. al. (2008 (2008). ). "Inihibtion "I nihibtion of ana anaerobic digestion digestion process: A review." Bioresource technology 99: 4044-4064. Fjærgård, rgård, T. T . and and O. Sande Sander (19 (1999 99)). Fi Five Y ears' Experi xperien ence ce with with the the CAMBI Process at HIAS. 4th European Biosolids and Organic Residuals Conference, November 1999 Henze, M., M. C. M. van Loosdrecht, et al. (2008). Biological Wastewater Tre Treatment. Prin Princ ciple ipless, Mod Modelling lling and Design ign Lon London, UK, IWA Pub Publish lishing ing. Ja J ansen, J . l. C., H. Spliid Spliid,, et al. al. (20 (2004). "Ass "Assessment of of sampling ling an and chemical analysis of source-separated organic household waste." Waste Management 24: 541-549. 541-549. Kraus rause e, T. T . L., Ed. (20 (2010 10). ). Design Design of Mun uniicipa cipall Waste Wastewa wate terr Trea T reatment Plan Plants, WEF Man Manual of Pra Practice ice No. No. 8, ASCE ASCE Man Manuals and Rep Reports on Engineering Practice No. 76, Fifth Edition. Alexandria, Virginia, Water Environm nvironmen entt Federation. deration. Speece, R. E. (2008). Anaerobic Biotechnology and Odor/Corrossion Control for M unicipaliti nicipalitie es an and In I ndust dustri rie es Nash Nashvi villle, TN, Archa rchae Pres Press. Zhang Zhang,, Y., Y ., M. M . Walker, et et al. al. (20 (2010 10). ). Te Techni chnical cal Re Report. Optimi Optimizing zing Processes for the Stable Opertaion of Food Waste Digestion. Defra Porject Code: WR1208.


Page 10 10

Substrate Protein e.g. Keratin

Carbohydrates e.g. e.g. S ucrose ucrose

1

Hydrolysis

1

Amino Acids, S ugars

2

Fermentation

Lipids e.g. Fats

1

Fatty Acids, Alcohols

2

2

2

Intermediary P roducts (Propionate, (P ropionate, Butyrate Butyrate etc) etc)

Anaerobic Oxidation

3

Hydrogen Carbon Dioxide Dioxide

Acetate

Homoacetogenesis 4b

4a

Aceticlastic Methanogensis

Hydrogenotrophic Methanogensis

Methane C arbon Dioxide Dioxide

FI GURE 1 ANAEROBIC ANAEROBI C DI DI GESTI GESTI ON PROCESS PROCESS


Page 11 11

Dry Digestion

-

>15% TS

Organic Wastes

Wet Wet Digestion Criteria:

<15% Feedstock Total Total SolTS Solids ids (TS)

(manure, commercial, residential)

- Paper/Card Paper/Cardboard board - Ener Energy gy Crops Crops -Yard Waste

Aerobic Treatment

Anaerobic Treatment

-(leaves, grass, trimmings)

- Wood Waste

FI GURE 2 FEEDSTOCK FEEDSTOCK

RA W SSO

PUL PED SSO

FI GURE 3 SOURCE SEPA SEPARAT RAT ED ORGANICS ORGANIC S (SSO)


Page 12 12

SSO

Digester Cake

SBR#1

Centrate+

SBR#2 Cake+

FIGU FI GURE RE 4

BIOWIN™ M ODEL ODEL L AY OUT OUT FOR DI SCO SSO PROCESS PROCESSI NG FACI L I TY 1999 Radeberg, D 1999 Fürstenwalde, D

2003 Madrid, E

1996 Wels, A 1996 Rügen, D

Lohse (Linde KCA) 1995 Dietrichsdorf, D 1996 Karlsruhe, D 1996 Schwabach, Schwabach, D 1997 Münster 1997 Erkheim, D (1997 München, D) 1998 Wadern-L, D

1991 Helsingør, DK

B TA

BTA (MAT)

1986 - 1995 Garching, D Pilot Plant

2002 Barcelona, E Ecoparque I

2000 Newmarket, CAN 2001 Mertingen, Mertingen, D 2001 Pulawy, Pl 2002 Parramatta, AUS 2002 Toronto, CAN CAN 2002 Verona, I 2002 Villacidro, I

2005 Hita, JPN 2005 Lissabon, P 2005 Burgos, E 2005 Camposampiero, I 2005 Salto des Negro, E

2003 Ie per, B 2003 Ko-Sung Ko-Sung,, K ore orea a 2003 Mülheim (Ruhr), (Ruhr), D 2003 Pamplona, E

BTA (MAT)

BTA

2007 Ecoparque Ecoparque I, E

2005 Ge scher, scher, D 1999 Boden, D 2003 Palma, E 2006 Ecoparque Ecoparque III, E 2005 Västeras,S rosno, no, Pl 2003 Avila, E 2005 Deißlingen, D 2006 K ros Volkenschw.,D hw.,D 2006 Tuleda,E 2008 Wien, A 2004 Lanzarote Lanzarote,E ,E 2005 Volkensc

(1993 Baden-Baden, D) 1992 Kaufbeuren, D

Biostab (Ros Roca) 2005 Schaumburg, D

Horstmann

mann)

2008 Jaén, E 2008 Voghera, I 2008 Gran Canaria, E 2008 Alicante, E 2006 Wiefels, D 2006 Lübeck, D 2006 León, E 2006 Schw. Elster, D

1999 Nordhausen, D

Haase Lohse (AMB)

198 4

1 986

1988

1 990

199 2

1 994

199 6

1 99 8

2000

200 2

20 04

2 006

FIGU FIGURE 5 EV EVO OLUTIO LUTION N OF ‘WET ‘WET’’ ANAE ANAER ROBIC DIGES IGESTIO TION N OF SOL I DS WASTES


Page 13 13

2006 Deiderode, D

20 08

FI GURE 6 BTA PROCESS PROCESS


Page 14 14

FIGU FI GURE RE 7 BTA PUL PUL PER AND AND GRIT REM OVAL SYSTEM

D >H

Cylindrical Unconfined Gas Confined Gas Draft Tube Pump

D
D
Double Cone

Egg

Big Blade Rev Draft Tube Confined Gas

Big Blade Rev Draft Tube Confined Gas

FI GURE 8 DIGESTER SHAPES SHAPES AND M I XI NG SY STEM S


Page 15 15

FI GURE 9 NEW DI DI SCO ROAD SS SSO PROCESS PROCESSI NG FACI L I TY


Page 16 16

2012 Coleman Anaerobic Digestion SSO vs WWTP

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