Effects of spiked metals on the MSW anaerobic digestion

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<ul><li><p> http://wmr.sagepub.com/Waste Management &amp; Research</p><p> http://wmr.sagepub.com/content/30/1/32The online version of this article can be found at:</p><p>DOI: 10.1177/0734242X10383079 2012 30: 32 originally published online 29 September 2010Waste Manag Res</p><p>Banks, CY Lin, WF Liu, PH Chen, CK Chen, HY Chiu, HY Wu, TW Chao, YR Chen, DW Liou and FC LoHM Lo, CF Chiang, HC Tsao, TY Pai, MH Liu, TA Kurniawan, KP Chao, CT Liou, KC Lin, CY Chang, SC Wang, CJ</p><p>Effects of spiked metals on the MSW anaerobic digestion </p><p>Published by:</p><p> http://www.sagepublications.com</p><p>On behalf of: </p><p> International Solid Waste Association</p><p> can be found at:Waste Management &amp; ResearchAdditional services and information for </p><p> http://wmr.sagepub.com/cgi/alertsEmail Alerts: </p><p> http://wmr.sagepub.com/subscriptionsSubscriptions: </p><p> http://www.sagepub.com/journalsReprints.navReprints: </p><p> http://www.sagepub.com/journalsPermissions.navPermissions: </p><p> http://wmr.sagepub.com/content/30/1/32.refs.htmlCitations: </p><p> What is This? </p><p>- Sep 29, 2010 OnlineFirst Version of Record </p><p>- Jan 6, 2012Version of Record &gt;&gt; </p><p> at UNIV OF SOUTHERN CALIFORNIA on April 9, 2014wmr.sagepub.comDownloaded from at UNIV OF SOUTHERN CALIFORNIA on April 9, 2014wmr.sagepub.comDownloaded from </p></li><li><p>Research Article</p><p>Effects of spiked metals on the MSWanaerobic digestion</p><p>HM Lo1, CF Chiang2, HC Tsao3, TY Pai1, MH Liu1, TA Kurniawan4,KP Chao5, CT Liou6, KC Lin7, CY Chang8, SC Wang1, CJ Banks9,CY Lin10, WF Liu11, PH Chen1, CK Chen1, HY Chiu1, HY Wu1,TW Chao1, YR Chen1, DW Liou1, and FC Lo5</p><p>AbstractThis study aimed to investigate the effects of eight metals on the anaerobic digestion of the organic fraction of munici-</p><p>pal solid waste (OFMSW) in bioreactors. Anaerobic bioreactors containing 200mL MSW mixed completely with 200mL</p><p>sludge seeding. Ca and K (0, 1000, 2000 and 6000mgL1) and Cr, Ni, Zn, Co, Mo and W (0, 5, 50 and 100mgL1)of various dose were added to anaerobic bioreactors to examine their anaerobic digestion performance. Results showed that</p><p>except K and Zn, Ca (;728 to ;1461mgL1), Cr (;0.0022 to ;0.0212mgL1), Ni (;0.801 to ;5.362mgL1), Co(;0.148 to ;0.580mgL1), Mo (;0.044 to ;52.94mgL1) and W (;0.658 to ;40.39mgL1) had the potential toenhance the biogas production. On the other hand, except Mo and W, inhibitory concentrations IC50 of Ca, K, Cr, Ni,</p><p>Zn and Co were found to be ;3252, ;2097, ;0.124, ;7.239, ;0.482, ;8.625mgL1, respectively. Eight spiked metalsshowed that they were adsorbed by MSW to a different extent resulting in different liquid metals levels and potential</p><p>stimulation and inhibition on MSW anaerobic digestion. These results were discussed and compared to results from</p><p>literature.</p><p>KeywordsMetals, municipal solid waste, anaerobic digestion, IC50, biogas</p><p>Date received: 6 February 2010; accepted: 8 August 2010</p><p>Introduction</p><p>Municipal solid waste (MSW) has been found to contain</p><p>more metals in Taiwan recently. MSW may be recycled or</p><p>be treated with incineration, composting, pyrolysis, gasica-</p><p>tion, anaerobic digestion or landlling. Among them, anaer-</p><p>obic digestion was reported to have the potential for energy</p><p>recovery, digestate utilization and greenhouse gas mitigation</p><p>(Mller et al., 2009; Gohlke, 2009; Young et al., 2010). As it</p><p>is treated with anaerobic digestion, various metals present in</p><p>the MSW may have the potential to aect the microbial</p><p>activity, causing eects on biological treatments to a certain</p><p>extent, thus resulting in a varying anaerobic process perfor-</p><p>mance. Several researchers have reported that organic</p><p>1Department of Environmental Engineering and Management,Chaoyang University of Technology, Wufong Township, TaichungCounty, Taiwan, ROC.2Institute of Environmental Health, China Medical University,Taichung, Taiwan, ROC.3Department of Business Administration, Asia University, Wufeng,Taichung, Taiwan, ROC.4Laboratory of Applied Environmental Chemistry (LAEC), Departmentof Environmental Sciences and Forestry, University of EasternFinland, Mikkeli, Finland.5Department of Occupational Safety and Health, China MedicalUniversity, Taichung, Taiwan, ROC.6Department of Safety, Health and Environmental Engineering,Hungkuang University, Sha Lu, Taichung, Taiwan, ROC.</p><p>7Department of Occupational Safety and Health, Chung Shan MedicalUniversity, Taichung, Taiwan, ROC.8General Education Center, National Taitung Junior College, TaitungCity, Taiwan, ROC.9Department of Civil Engineering and the Environment, SouthamptonUniversity, Southampton, UK.10Department of Soil and Water Conservation, National Chung HsingUniversity, Taichung, Taiwan, ROC.11Department of Electrical Engineering, Feng Chia University,Taichung, Taiwan, ROC.</p><p>Corresponding author: HM Lo, Department of EnvironmentalEngineering and Management, Chaoyang University of Technology,168, Gifong E. Rd., Wufong Township, Taichung County 41349,Taiwan, ROC.Email: hmlo@cyut.edu.tw; huangmu@yahoo.com</p><p>Waste Management &amp; Research</p><p>30(1) 3248</p><p> The Author(s) 2012Reprints and permissions:</p><p>sagepub.co.uk/journalsPermissions.nav</p><p>DOI: 10.1177/0734242X10383079</p><p>wmr.sagepub.com</p><p> at UNIV OF SOUTHERN CALIFORNIA on April 9, 2014wmr.sagepub.comDownloaded from </p></li><li><p>matters and metals could aect the anaerobic process (Kuo</p><p>and Genthner, 1996; Kida et al., 2001; Ren and Frymer,</p><p>2003; Gikas, 2007; Li and Fang, 2007; Yue et al., 2007;</p><p>Chen et al., 2008; Lin and Shei, 2008; Altas, 2009; Fermoso</p><p>et al., 2009; Tan et al., 2009; Ma et al., 2009; Worm et al.,</p><p>2009; Yuan et al., 2010). These substances included ammo-</p><p>nia, sulde, chlorophenols, halogenated aliphatics, N-substi-</p><p>tuted aromatics, long chain fatty acids, lignins and lignins</p><p>related compounds, light metal ions and heavy metals.</p><p>These mentioned literatures indicated that dierent sub-</p><p>strate, various metals levels and recalcitrant organic com-</p><p>pounds might aect the microbial diversity and bioreactor</p><p>performance. Furthermore, the anaerobic biodegradation</p><p>rate would be aected by metals uptake (Gurgel et al.,</p><p>2008), substrate compositions, microbial community and</p><p>operational conditions. Other investigations focusing on the</p><p>synergistic/antagonistic eects or mechanisms of heavy</p><p>metals on anaerobic digestion or fermentation process has</p><p>also been reported by several researchers (Takashima and</p><p>Speece, 1990; Peier et al., 1994; Espinosa et al., 1995;</p><p>Wang 1995; Artola et al., 1997; Becker and Peier, 1997;</p><p>Lin et al., 1998; Zhang et al., 2003; Malik, 2004). However,</p><p>adverse or benecial eects of metals on MSW anaerobic</p><p>digestion are not many and are not systematically investi-</p><p>gated (Banks and Lo, 2003; Lo, 2005; Lo and Liao, 2007;</p><p>Yue et al., 2007; Chen et al., 2008; Lo et al., 2009a, b). Due to</p><p>the potential existence of metals in MSW and as it is treated</p><p>with anaerobic digestion, it is therefore necessary to assess</p><p>their potential eects on MSW anaerobic digestion.</p><p>This study aims to investigate the eects of selected metals</p><p>on the MSW anaerobic digestion. Selected metals include</p><p>alkali metals of Ca and K, heavy metals of Cr, Ni and Zn,</p><p>and trace metals of Co, Mo and W. The results of the present</p><p>studies are evaluated and compared with those of other</p><p>investigations. The ndings reported in this study are</p><p>expected to provide the baseline data and useful information</p><p>for the anaerobic digestion of MSW and/or anaerobic</p><p>co-digestion of MSW/sludge containing metals.</p><p>Materials and methods</p><p>Municipal solid waste substrate</p><p>To minimize possible interferences with selected metals on</p><p>MSW digestion, MSW that contained ;6% total solids</p><p>(TS) and ;5% volatile solids (VS) was prepared according</p><p>to previous studies (Banks and Lo, 2003; Lo, 2005; Lo and</p><p>Liao, 2007; Lo et al., 2009a, b). Based on the weight propor-</p><p>tion, the MSW was comprised of oce paper (30%), news-</p><p>paper (30%), yard waste (35%) and food waste (5%). This</p><p>composition proportionally represents typical organic frac-</p><p>tions of MSW. In addition, the chemical constituents of C,</p><p>H, O, N and others of MSW were determined to be around</p><p>46, 6, 41, 1.4 and 5.6%, respectively. The carbon/nitrogen</p><p>(C/N) ratio of this synthetic MSW (32.86) was also similar</p><p>to that of typical MSW in Taiwan (39.86). A C/N ratio</p><p>ranging from 25 to 50 has been reported to be suitable</p><p>for the composting and anaerobic digestion of MSW</p><p>(Lo et al., 2009a, b). The food/micro-organisms (F/M)</p><p>ratio is important for the biological treatment process.</p><p>Generally, 0.51 kgBOD (m3 day)1 of volume loading and0.20.4 kgBOD (kgMLSS (Mixed liquor suspended solids)</p><p>day)1 of sludge loading were thought suitable for wastewa-ter biological treatment. In this study, F/M ratio was thought</p><p>to be the initial MSW/initial sludge seeding (200mL</p><p>(;5%VS MSW)/200mL (;2.5% VS sludge seeding)) equal</p><p>to 10 gVS MSW/5 gVS sludge. The experiment was done in</p><p>batch mode. In the MSW anaerobic digestion, a C/N ratio of</p><p>25 was suitable for anaerobic digestion and composting. This</p><p>C/N ratio of 25 was close to that of 32.6 in this study. The C/</p><p>N ratio and F/M ratio and anaerobic bacterial community</p><p>were important factors that will aect the anaerobic diges-</p><p>tion process. The MSW samples were stored in a refrigerated</p><p>storage chamber at 4 8C to minimize any further changes that</p><p>might occur in their physico-chemical properties prior to the</p><p>experiments.</p><p>Anaerobic sludge seeding</p><p>To initiate the MSW anaerobic digestion, 200mL of anaer-</p><p>obic sludge (;TS 3%, ;VS ;2.5%) was added into tested</p><p>batch bioreactors containing 200mL MSW substrate</p><p>(TS;6%;12 g, VS;5%;10 g). The sludge wasobtained from Fu-Tien municipal wastewater treatment</p><p>plant located at Taichung City in central Taiwan. The</p><p>plant collects ;50 00055 000m3 day1 sewage and adoptsaerobic activated sludge process (hydraulic retention time</p><p>(HRT), 6 h). The sludge from the rst (HRT, 1.5 hrs) and</p><p>the second sedimentation tank (HRT, 4 hrs) is processed to</p><p>a gravity thickener (solid retention time (SRT), &gt; 12 h) and</p><p>then sent to the anaerobic digesters (SRT, &gt; 30 days) for</p><p>anaerobic digestion. The anaerobic sludge was taken from</p><p>anaerobic digester and their metal contents and basic param-</p><p>eters such as pH, TS and VS, etc. have been reported in</p><p>previous studies (Lo and Liao, 2007, Lo et al., 2009b). The</p><p>metals content of the sludge used for seeding and the MSW</p><p>are presented in Table 1.</p><p>Experimental</p><p>About 200mL MSW substrate and 200mL sludge seeding</p><p>and the designate spiked metal amounts were mixed comple-</p><p>tely in 500mL anaerobic bioreactors (plastic bottles). The</p><p>bioreactors with working volume of 400mL were operated</p><p>to test the toxicity and response of eight selected metals on</p><p>MSW anaerobic digestion. Bioreactors were maintained at</p><p>35 8C oven which was suitable for anaerobic digestion. The</p><p>anaerobic bioreactors had an exit for biogas collection using</p><p>the water replacement method. Initial pHs were ;66.5 and</p><p>Lo et al. 33</p><p> at UNIV OF SOUTHERN CALIFORNIA on April 9, 2014wmr.sagepub.comDownloaded from </p></li><li><p>the initial VS of the MSW and sludge used for seeding were</p><p>;5% and ;2.5%, respectively. Tested metal compounds</p><p>were CaCl2, K2SO4, CrCl66H2O, NiSO46H2O,ZnSO47H2O, CoSO47H2O, Na2MoO42H2O, andNa2WO42H2O which were purchased from Merck Co. TheCaCl2 and K2SO4 were weighted and spiked directly into the</p><p>batch bioreactors according to the Ca and K of the desig-</p><p>nated added amounts of 1000, 2000 and 6000mgL1, respec-tively. For example, Ca 1000mgL1 was prepared by adding1107.59mgCaCl2 into the batch bioreactors. 1107.59mg (X)</p><p>was calculated by X3 (Ca/CaCl2)/0.4 L 1000mgL1, thatis, X3 (40.08/110.98)/0.4 L 1000mgL1. Similarly, theCrCl66H2O, NiSO46H2O, ZnSO47H2O, CoSO47H2O,Na2MoO42H2O and Na2WO42H2O were spiked accordingto the Cr, Ni, Zn, Co, Mo and W of the designated added</p><p>amounts of 5, 50 and 100mgL1, respectively. Controlbioreactors without metals addition (0mgL1) wereemployed for comparison.</p><p>Forty-four bioreactors for each metal of three various</p><p>spiked amounts and control were used. They were used for</p><p>biogas measurement and 100mL mixture (MSW and sludge</p><p>seeding) were taken one by one (on day 1, 5, 8, 15, 19, 29, 33,</p><p>36, 43, 47 and 50) for each individual metal and parameter</p><p>analysis over the whole digestion period. The required total</p><p>bioreactors for each metal including control and three dier-</p><p>ent added amounts (0, 1000, 2000 and 6000mgL1 or 0, 5, 50and 100mgL1) were 113 4 44 and the total bioreactorsfor the eight metals were 443 8 352. The bioreactors weremaintained within a homeostatic oven with a constant tem-</p><p>perature around 358C. Anaerobic digestion of 200mL MSW</p><p>(VS ;5%;10 g VS) nearly reached the biochemical meth-ane potential (BMP) after 50 days. The biogas production</p><p>was around 455mL (;455mL/10 gVS;45.5mLg1 VS).During the digestion period, biogas production in each</p><p>bioreactor was recorded daily by biogas collectors using the</p><p>water replacement method. A sample of 100mL of MSW</p><p>substrate and sludge seeding mixture was collected in each</p><p>sacriced bioreactor and was ltered through a 0.45mm mem-</p><p>brane for metal and parameter analysis on day 1, 5, 8, 15, 19,</p><p>29, 33, 36, 43, 47 and 50, respectively. The metal concentration</p><p>in each bioreactor was measured by ICP-OES (Inductively</p><p>Coupled Plasma Optical Emission Spectrometry, IRIS</p><p>Intrepid II, Thermal Electron Corporation). The analytical</p><p>method followed the manual of the manufacturer. Briey</p><p>speaking, the ICP-OES equipment was set at the required oper-</p><p>ational conditions. Incident energy was 1100W and reective</p><p>energy was </p></li><li><p>Results and discussion</p><p>Biogas production and anaerobic parameters</p><p>Theotal biogas production measured using the water replace-</p><p>ment method is presented in Figure 1. The composition</p><p>of biogas production was normally comprised of CH4(;5070%), CO2 (;3050%), H2S (</p></li><li><p>and dosed metals minus the metals concentration in the</p><p>liquid phase. The mass balance of the metals in the liquid</p><p>and solid phase can be found in Table 2.</p><p>From Figures 2 and 3 and Table 3, it was shown that</p><p>Ca (;728 to ;1461mgL1, average ;1035mgL1),Cr (;0.0022 to ;0.0212mgL1, average ;0.0148mgL1),Ni (;0.801 to ;5.362mgL1, average ;1.842mgL1), Co(;0.148 to ;0.580mgL1, average ;0.307mgL1),Mo (;0.044 to ;52.94mgL1) and W (;0.658 to;40.39mgL1) had the potential to enhance the biogasproduction. By dividing the highest levels to the lowest</p><p>ones, Mo and W showed wider stimulation ranges whereas</p><p>Ca, Cr, Ni and Co showed narrower stimulation ranges in</p><p>comparison to those of Mo and W. The IC50 concentrations</p><p>showed the order of Ca&gt;K&gt;Co&gt;Ni&gt;Zn&gt;Cr. Typical</p><p>metal levels in the biogas plant will vary with the dierent</p><p>digested substrate, metals adsorption and operating condi-</p><p>tions. Typical metal levels in the organic fraction of MSW</p><p>(OFMSW) anaerobic digestion or waste compost can be</p><p>found in Lo et al. (2010), Iglesias et al. (2000) or Farrell</p><p>and Jones (2009) (Table 4). On the other hand, inhibitory</p><p>concentrations (IC50) of Ca, K, Cr, Ni, Zn and Co were</p><p>found to be ;3252, ;2097, ;0.124, ;7.239, ;0.482,</p><p>;8.625mgL1, respectively. The Mo and W that wasdosed under 100mgL1 showed stimulatory results ratherthan inhibitory eects (Figure. 3 (E-a) and (F-a)). The</p><p>alkali metals Ca and K showed higher IC50 values than</p><p>those of the heavy...</p></li></ul>