Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes

Download Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes

Post on 24-Nov-2016

219 views

Category:

Documents

5 download

Embed Size (px)

TRANSCRIPT

<ul><li><p>st</p><p>echn</p><p>d Rd., Wuri Dist., Taichung City 41401, Taiwan, ROC, China</p><p>ed theuitabletimula20 and</p><p>fferent solid retention time (SRT) on municipal solid waste (MSW) anaerobic</p><p>ganic compounds such as PAHs and PCDD/Fs (Huang and Huang,2008; Lin et al., 2008). Both BA and FA could be used as aggregate,backll, soil amendment and cement additives (Ciof et al., 2011)after careful pretreatment, toxicity and TCLP test (Lin and Chen,2006).</p><p>attractive option for the renewable energy utilization. Among bio-mass, MSW (containing lignocellulic materials (Goh et al., 2010)) isthought to have the potential for renewable energy production.MSW is generally treated with thermal and biological methodsthat could recover the electricity or energy utilization. When trea-ted with incinerators, FA and BA will be produced needing thecareful treatment to prevent the secondary pollution. As MSWtreated with biological process such as landlling or composting,leachate or odor production become environmental problemsand might increase the treatment cost. Thus, anaerobic digestion</p><p> Corresponding author. Tel.: +886 4 23323000x4469; fax: +886 4 23742365.</p><p>Bioresource Technology 125 (2012) 233238</p><p>Contents lists available at</p><p>Bioresource T</p><p>elsE-mail address: hmlo@cyut.edu.tw (H.M. Lo).Received in revised form 8 August 2012Accepted 10 August 2012Available online 31 August 2012</p><p>Keywords:MSWFABASRTAnaerobic digestion</p><p>digestion with various MSW incinerator y ash (FA) and bottom ash (BA) addition. Results showed thatbiogas production rates (BPRs, 200 to 400 mL/gVS) with organic loading rate of 0.053 gVS/gVSreactor(Day 1435, SRT 20 days, SRT20) at FA 1 g/d (FA1), BA 12 g/d (BA12) and BA 24 g/d (BA24) dosed bio-reactors increased after adaptation. BPRs with SRT10 and SRT5 decreased while BPRs with SRT40showed to increase compared to initial BPRs (200 mL/gVS) with SRT20. SRT5 operation reduced theBPRs (10 90 mL/gVS) signicantly and only BA12 and BA24 dosed bioreactors could recover theBPRs (100 200 mL/gVS) after SRT20 operation (Day 613617) compared to FA1 and FA3 and con-trol. Released levels of Co, Mo and W at BA12 and BA24 dosed bioreactors showed most potential toimprove MSW anaerobic digestion.</p><p> 2012 Elsevier Ltd. All rights reserved.</p><p>1. Introduction</p><p>MSW has been treated mostly by incineration while partly bylandlling, anaerobic digestion, composting, gasication and re-source recovery. The MSWI could reduce the MSW volume andhave the potential to produce the steam and electricity while italso produces the residues such as BA and FA. MSWI BA and FAwere reported to contain various metals oxides and recalcitrant or-</p><p>Renewable energy has currently been the inevitable trend forthe replacement of fossil fuel and nuclear energy due to the reduc-tion need of carbon dioxide emission and treatment difculty ofhigh level nuclear radiological waste. Solar, hydro, tidal, geother-mal, wind, biorenery and biomass energy are thought to be thepotential renewable energy resource in the future. However, it ap-pears currently that energy transfer efciency of solar, tidal, geo-thermal and wind is limited. Thus, biomass energy becomes anReceived 16 June 2012</p><p>Article history: This study investigated diMingdao High School, 497, Sec. 1, ZhongshaneDepartment of Occupational Safety and Health</p><p>h i g h l i g h t s</p><p>" Suitable MSWI ashes addition improv" Biogas enhancement was due to the s" Co, Mo and W were mostly found to s" MSW anaerobic digestion favored SRT</p><p>a r t i c l e i n f o0960-8524/$ - see front matter 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.biortech.2012.08.084Medical University, 91 Hsueh-Shih Rd., Taichung 40402, Taiwan, ROC</p><p>MSW anaerobic digestion.released metals levels.te MSW biogas production.SRT40 operation.</p><p>a b s t r a c tbGraduate Institute of Biochemical Science and Technology, Chaoyang University of Technology, 168, Gifeng E. Rd., Wufeng District, Taichung 41349, Taiwan, ROCcCentral Vocational Training Center, Bureau of Employment and Vocational Training, Councils of Labor Affairs, No.100, Gongyecyu 1st Rd., Situn District, Taichung 407, Taiwan, ROCEffects of different SRT on anaerobic digeMSWI ashes</p><p>H.M. Lo a,e,, H.Y. Chiu b,c, S.W. Lo a,d, F.C. Lo eaDepartment of Environmental Engineering and Management, Chaoyang University of T</p><p>journal homepage: www.ll rights reserved.ion of MSW dosed with various</p><p>ology, 168, Gifeng E. Rd., Wufeng District, Taichung 41349, Taiwan, ROC</p><p>SciVerse ScienceDirect</p><p>echnology</p><p>evier .com/locate /bior tech</p></li><li><p>echnof MSW is thought to be a promising biological treatment methodthat could benet both methane production and digestate utiliza-tion after nutrition examination and biotoxicity test.</p><p>Anaerobic digestion performance of MSW, sludge etc. might beaffected by several factors such as pH, temperature, organic mattercontent, carbon/nitrogen ratio, nutrients and particle size (Lo et al.,2012a,b), solid retention time (SRT) and organic loading rate(OLR)(Zhang et al., 2011; Luste and Luostarinen, 2010; Ferreret al., 2010; Pakarinen et al., 2011; Lee and Rittmann, 2011), pre-treatment of acids, alkali, ultrasonication, radiation, microwaveand ozonation (Raque et al., 2010; Nizami et al., 2009; Coelhoet al., 2011; Devlin et al., 2011), inoculums source (Elbeshbishyet al., 2012), digester conguration (Nizami and Murphy, 2010; Ka-e and Kim, 2011; Rubio-Loza and Noyola, 2010), microbial com-munity (Martn-Gonzlez et al., 2011; Shin et al., 2010; Trzcinskiet al., 2010; Sasaki et al., 2011), co-digested materials (Asamet al., 2011; Li et al., 2011), methane solubility (Serra et al., 2006)and recalcitrant matters (Barret et al., 2010; Bertin et al., 2011; Pat-erakis et al., 2012; Yuzir et al., 2012). Literatures showed that stud-ies on the co-digestion or co-disposal of MSW and MSWI asheswere few (Lo et al., 2010; Lo et al., 2009; Lo et al., 2012a,b; Boniet al., 2007). Results of those investigations indicated that suitableMSWI ashes addition could enhance the biogas production due tothe suitable metals levels released as nutrients for anaerobic diges-tion at a SRT of 20 days. Recently, Lo et al. (2012a,b) have incorpo-rated lots of metals ions levels on the integrated understanding ofstimulation or inhibition of anaerobic digestion or fermentativeprocess. In addition, Lo et al. (2012a,b) also pointed out that recal-citrant compoundsmight be adsorped onto sludge and biodegradedby microorganisms. Nevertheless, studies on different SRT or OLRfor MSW anaerobic co-digestion of MSW and MSWI ashes werefew and that it might show potential useful information for theco-digestion practice of MSW and MSWI ashes with various SRT.</p><p>This study aimed to investigate the various MSWI ashes addi-tion on the MSW anaerobic digestion at various SRT with com-pletely stirred tank reactors (CSTR). Results could provide theuseful information for the anaerobic co-digestion of MSWI asheswith MSW for practical operation.Nomenclature</p><p>BA: Bottom ash MSWI: MSW incineratorBA12: BA 12 g/d OLR: Organic loading rateBA24: BA 24 g/d PAHs: Polyaromatic hydrocarbonsBPRs: Biogas production rates PCDD/Fs: Polychlorinated</p><p>dibenzodioxins/furansCOD: Chemical oxygen demand SRT: Solid retention dayCSTR: Completely stirred tank reactors SRT10: SRT 10 days</p><p>234 H.M. Lo et al. / Bioresource T2. Methods</p><p>2.1. MSWI ashes, MSW and anaerobic sludge seeding</p><p>Materials used in this study were MSWI FA and BA, MSW andanaerobic sludge seeding.MSWI asheswere obtained from an incin-erator located in central Taiwan. Characteristics ofMSWI ashes suchas particle size, pH, loss of ignition, metal content, metals com-pounds, PAHs, PCDD/Fs can be found in Table S-1 and S-2 and re-ferred to Lo et al. (2012a,b). Basic characteristics of MSW andanaerobic sludge seeding were presented in Table 1. MSW (6000 gdry weight) comprised of ofce paper (30%), newspaper (30%), yardwaste (35%) and food waste (5%) was cut into less than 0.5 mm andblended with distilled water (94 L, 94000 g) to make the MSW TS6% (VS 4%). This composition proportionally represents typicalorganic fractions of MSW and could prevent the interference ofunavoidable substances on the effects of anaerobic digestion ofMSWwithMSWI ashes. Elemental analysis of syntheticMSW in thisstudy by elementary analyzer (Heraeus varioIII-NCH) such as C, H, Oand N etc., were measured to be about 46, 6, 41 and 1.4%(C38.3H60O25.63N), respectively. Compared to Taichung city and Tai-wanMSW, Taichung city and TaiwanMSW had the close C(%), N(%),S(%), Cl(%) values of about 20.55 and 17.38, 0.50 and 0.47, 0.47 and0.5, 0.0625 and 0.07, respectively. C (46%) and N (1.4%) of syntheticMSW in this study showed higher compared to those of Taichungcity and TaiwanMSW. However, C/N ratios of Taichung city, Taiwanand synthetic MSW were found to have close values in the order of41.1, 39.68 and 32.86 suitable for anaerobic digestion. A C/N ratio of32.86 between 25 and 50 was reported to be suitable for the MSWcomposting and anaerobic digestion. Basic characteristics of MSWsuch as pH (pH207, Lutron), ORP (pHmeter SP-2300, SUNTEX), elec-trical conductivity (EC, Con 400 series, SUNTEX), TS (DS45, DengYing), VS (CMF, 304, Cheng Jang) and metal content such as Ca,Mg, K, Na, Cd, Cr, Cu, Ni, Pb and Znwere also analyzed (ICP-OES, IRIS,Intrepid II, Thermal Electron Corporation) by Standard Methods(AWWA, 1995) as presented by Lo et al. (2012a,b). Basic character-istics and metal content measured in MSW were also analyzed inanaerobic sludge seeding as can be seen in Table 1. Microorganismsof Clostridiales sp., Methanonosarcina barkeri and Methanomicrobi-ales archaeon were found in sludge seeding shown in Table 1.MSW and sludge seeding were measured to have TS 5.6% (VS4%) and TS 3% (VS 1%), respectively. VS content was thoughtto be the source of biogas production potential (Lo et al., 2012a,b).In general, substrates (carbohydrate, fat, protein and lipid) such asMSW can be biodegraded to be biogas and other matters viahydrolysis, acidogenesis, acetogenesis and methanogenesis asshown in Appendix I. The formula of MSW is calculated to beC38.3H60O25.63N by elemental analysis. Thus, the theoretical biogasproduction (1.03124 L/gVS) such as methane, carbon dioxide andammonia can be obtained via equation S-4 in Appendix I. MSW bio-degradation in batch mode follows the rst order reaction (Lo et al.,EC: Electrical conductivity SRT20: SRT 20 daysFA: Fly ash SRT40: SRT 40 daysFA1: FA 1 g/d SRT5: SRT 5 daysFA3: FA 3 g/d VA: Volatile acidsICP-OES: Inductively coupled plasma-optical emission spectros-</p><p>copy VS: Volatile solidMSW: Municipal solid waste</p><p>ology 125 (2012) 2332382010). Detailedmechanisms and kinetics can be seen in Appendix I.</p><p>3. Experimental</p><p>Anaerobic reactors were 5 L plastic bottle with a working vol-ume of 4 L. Acclimatization of anaerobic sludge seeding to theMSW was the rst step to start the experiment. Two liter of anaer-obic sludge (VS 1%) was obtained from FuTien municipal waste-water treatment plant in Taichung, central Taiwan. It was placedonto the anaerobic reactor, then 100 mL synthetic MSW was putonto the anaerobic reactor daily. Biogas production was monitoredand collected with the gas collector by water replacement method.After 20 day later, the total working volume 4 L was reached and aSRT of 20 days was operated. About 40 day later, as the BPRs were</p></li><li><p>WCl(%) 0.0625</p><p>echnP(%) 0.1402K(%) 0.125C/N ratio 41.1lignin(%)a-cellulose(%)hemicellulous(%)ash content(%)low heating value(kcal/kg)Ca(mg g1) 162.97 8.33Mg(mg g1) 25.27 1.00K(mg g1) 121.10 2.00Na(mg g1) 31.80 1.67Cd(mg g1) 0.01 0.00Cr(mg g1) 0.02 0.00Cu(mg g1) 0.02 0.00Ni(mg g1) 0.25 0.01Pb(mg g1) 0.08 0.00Zn(mg g1) 3.18 0.07Clostridiales sp. (AB198476.1)Methanosarcina barkeri (HQ591417.1)Table 1Basic characteristics of MSW and anaerobic sludge seeding.</p><p>Taichung city MS</p><p>pH 5.49 0.05ORP(mV) 14.35 0.9EC(mS/cm) 6.83 0.25TS(%) 60 2VS(%) 0.16 0.02C(%) 20.55H(%) 3.06O(%) 18.53N(%) 0.50S(%) 0.47</p><p>H.M. Lo et al. / Bioresource Tobserved steadily, then experiment started to proceed. Accordingto the experimental design, FA 1 g/d (FA1), FA 3 g/d (FA3), BA12 g/d (BA12) and BA 24 g/d (BA24) (referring to the test amountLo et al. (2012a,b)) were carry out to examine the effects of MSWIashes on MSW anaerobic digestion. Anaerobic reactors withoutashes addition were used as the control. All bioreactors were con-ducted with duplicate totally accounting for 10 bioreactors andthey were placed on an oven maintained at a temperature of35 C suitable for anaerobic digestion.</p><p>Experiment was progressed for about 667 days with variousSRT operation in six stages. The period of six stages were day 1435, 435505, 505538, 538551, 551613 and 613667 operatedat a SRT of 20, 10, 40, 20, 5 and 20 days (SRT20, SRT10, SRT40,SRT20, SRT5 and SRT20) with a corresponding OLR about 2(0.053), 4 (0.111), 1 (0.0256), 2 (0.053), 8 (0.25) and 2 gVS/Lbioreac-tor (0.053 gVS/gVSbioreactor), respectively.</p><p>3.1. Anaerobic parameters</p><p>Parameters analysis in the control and dosed bioreactors in-cluded biogas production, pH, EC, VS, alkalinity, volatile acids(VA) and chemical oxygen demand (COD) and metals ions levels.Biogas was measured by biogas collectors with water replacementmethod. pH and EC were analyzed by pH 207 (Lutron) and Con 400series (SUNTEX). VS was measured by a 550 C furnace (CMF-307,Cheng Jang). COD was measured by a COD titration equipment(765 Dosimat, Metrohm). Metals levels were measured by ICP-OES (ISIS Intrepid II, Thermo). VA and alkalinity were measuredby titration methods. All analytical methods followed the standardmethods for the examination of water and wastewater (AWWA,1995) and Lo et al. (2012a,b).</p><p>Uncultured Methanomicrobiales archaeon (CU917177.1)</p><p>a Goh et al. (2010).b Taiwan EPA (2011).c Nielsen et al. (1999), Akarsubasi et al. (2005), Baker et al. (2003) and Lo et al. (2012Taiwan MSWb Synthetic MSW Anaerobic sludge seeding</p><p>7.90 0.22 6.86 0.0972.70 4.52 17.25 1.340.34 0.01 1.96 0.055.59 0.19 2.78 0.393.96 0.34 0.74 0.40</p><p>17.38 46641</p><p>0.47 1.40.50.07</p><p>39.68 32.8617.7a</p><p>47.4a</p><p>6.9a</p><p>12.3a</p><p>1844110.03 0.30 12.99 0.557.84 0.13 2.25 0.1565.31 0.01 2.20 0.0714.98 0.80 0.69 0.03</p><p>0.0003 0.10 0.05 0.01 0.000.001 0.28 0.04 0.11 0.020.001 0.12 0.03 0.20 0.04</p><p>0.07 0.00 0.06 0.000.02 2.53 0.10 0.07 0.000.03 5.16 0.35 1.34 0.12</p><p>Sulte reducingc</p><p>Methane producingc</p><p>ology 125 (2012) 233238 2354. Results and discussion</p><p>4.1. Biogas production with various SRT</p><p>BPRs were shown in Fig. 1. Results showed that BPRs with aSRT20 operation (OLR, 2 gVS/L; 0.053 gVS/gVS) at all bioreac-tors began to decrease compared to initial BPRs about 140 days ex-cept the FA1 dosed bioreactors which lasting for more 40 days until180 days. BPRs at most BA12 and BA24 dosed bioreactors appearedto increase from day 205 compared to those of initial control untilday 435 with the same SRT20 (Fig. 1c and d). The BPRs were foundbetween 50 and 400 mL/gVS. Some BPRs between day 435 and505 with a SRT10 were found highest (800 1000 mL/L) com-pared to those of initial control (400 mL/L) (40...</p></li></ul>