Laboratory Simulation of Anaerobic Digestion of Municipal Solid Waste

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<ul><li><p>This article was downloaded by: [The UC Irvine Libraries]On: 24 October 2014, At: 20:23Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>Journal of Environmental Science and Health, PartA: Toxic/Hazardous Substances and EnvironmentalEngineeringPublication details, including instructions for authors and subscription information:</p><p>Laboratory Simulation of Anaerobic Digestion ofMunicipal Solid WasteProfessor Stanislaw Ledakowicz a &amp; Katarzyna Kaczorek aa Department of Process and Environmental Technology , Technical University of Lodz ,Lodz, PolandPublished online: 06 Feb 2007.</p><p>To cite this article: Professor Stanislaw Ledakowicz &amp; Katarzyna Kaczorek (2004) Laboratory Simulation of AnaerobicDigestion of Municipal Solid Waste, Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances andEnvironmental Engineering, 39:4, 859-871, DOI: 10.1081/ESE-120028398</p><p>To link to this article:</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all the information (the Content) containedin the publications on our platform. However, Taylor &amp; Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor &amp; Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.</p><p>This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms &amp; Conditions of access and use can be found at</p><p></p></li><li><p>JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH</p><p>Part AToxic/Hazardous Substances &amp; Environmental Engineering</p><p>Vol. A39, No. 4, pp. 859871, 2004</p><p>Laboratory Simulation of Anaerobic Digestionof Municipal Solid Waste</p><p>Stanislaw Ledakowicz* and Katarzyna Kaczorek</p><p>Department of Process and Environmental Technology,</p><p>Technical University of Lodz, Lodz, Poland</p><p>ABSTRACT</p><p>Landfill processes were simulated in lab-scale bioreactorslysimeters. The</p><p>changes in leachate characteristics as well as the influence of the leachate</p><p>recirculation on the processes taking place in the landfill were investigated.</p><p>Lysimeters were filled with material simulating municipal waste in the city of</p><p>Lodz, Poland. Compost in the amount of 30%w/w and the methanogens</p><p>inoculum were added in order to enhance a development of methanogenic phase.</p><p>Leachate produced in lysimeters was recirculated once, twice a week, or everyday.</p><p>The leachate composition and biogas changes showed trends confirming that the</p><p>bench-scale lysimeters appeared suitable to simulate processes taking place in the</p><p>landfill. It was also proved that leachate recirculation accelerate these processes.</p><p>Key Words: Biogas; Landfill; Leachate; Lysimeter; Recirculation.</p><p>INTRODUCTION</p><p>Landfilling is the most common method of waste disposal in Poland (95%).According to the current Polish legislation landfilling should be the last solution for</p><p>*Correspondence: Professor Stanislaw Ledakowicz, Department of Process and</p><p>Environmental Technology, ul. Wolczanska 213, Technical University of Lodz, 93 005</p><p>Lodz, Poland; Fax: (48 42) 631 37 38; E-mail:</p><p>859</p><p>DOI: 10.1081/ESE-120028398 1093-4529 (Print); 1532-4117 (Online)</p><p>Copyright &amp; 2004 by Marcel Dekker, Inc.</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>The</p><p> UC</p><p> Irv</p><p>ine </p><p>Lib</p><p>rari</p><p>es] </p><p>at 2</p><p>0:23</p><p> 24 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>ORDER REPRINTS</p><p>MSW treatment. Although recycling of materials and composting reduce the amount</p><p>of landfilled MSW, landfilling is the only option for many materials.[1] The research</p><p>concerning the landfill behavior is still of the great importance in Poland.According to Stegmann[2] the construction and operation of landfill test cells or</p><p>large-scale lysimeters are very time-consuming, costly, and not easy to control. The</p><p>laboratory scale experiments enable the measurements of gas production and</p><p>leachate quality. It is possible to vary parameters and study their influence on the</p><p>anaerobic processes taking place in landfills. Figure 1 emphasises similarity in the</p><p>leachate composition time changes between real landfill (literature data according to</p><p>Oleszkiewicz[3] and lab-scale lysimeters (own investigation).On the other hand Youcai et al.[4] claim that uses of laboratory scale lysimeters</p><p>to roughly simulate a field landfill in terms of the trends are reasonable and reliable,</p><p>when the scale is sufficiently large. However, exact values for parameter in real</p><p>landfill should be monitored directly in situ from the landfill.Among the number of factors influencing the landfill processes the leachate</p><p>recirculation is the most important. Landfill leachate is generated as a result of water</p><p>from precipitation, surface run-off, and filtration or intrusion of groundwater</p><p>percolating through landfill.[5] There are a lot of ex-situ methods for the landfill</p><p>leachate treatment. However, the leachate is known as wastewater whose treatment</p><p>is very complicated, expensive and involving various processes.[6] In-situ leachate</p><p>treatment can be the cost effective and simple method. Moreover, water is necessary</p><p>in all bioprocesses. In this particular case water is essential for transporting substrate</p><p>to and waste products from the microorganisms. In the absence of flushing waste</p><p>products would accumulate to toxic concentrations around the microorganisms.</p><p>Water is also required for nutrient transport and heat transport.[7] The leachate</p><p>recycle may be used to assure the most suitable moisture content in MSW as well as</p><p>moisture flow.</p><p>0</p><p>5</p><p>10</p><p>15</p><p>20</p><p>25</p><p>0 50 100 150 200 250</p><p>Time in lysimeter (day)</p><p>BO</p><p>D5 </p><p>(gO</p><p>2 (d</p><p>m3 )</p><p>-1)</p><p>23456789101112</p><p>pH (</p><p> - )</p><p>Figure 1. Comparison between real landfill and lab-scale lysimeters. ___ BOD5 landfill; _ _</p><p>BOD5 lysimeter; ___ pH landfill; _ _ pH lysimeter.</p><p>860 Ledakowicz and Kaczorek</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>The</p><p> UC</p><p> Irv</p><p>ine </p><p>Lib</p><p>rari</p><p>es] </p><p>at 2</p><p>0:23</p><p> 24 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>ORDER REPRINTS</p><p>The leachate recirculation back into the landfill body has been claimed tostrongly improve biodegradation of the waste.[8] On the other hand the progressiveaccumulation of salts in the leachate may negatively affect microorganismsactivity.[9] Although the leachate recirculation is an area that has attracted a lot ofthe investigations, further investigations on the leachate recirculation are stillnecessary.</p><p>This article shows results of the MSW landfill simulation in the bench-scalelysimeters as well as the leachate recirculation impact on the processes taking place inthe landfills.</p><p>EXPERIMENTAL PROCEDURES</p><p>The reactors in volume of 15 dm3 were used as lysimeters to simulate landfillprocesses. The reactors equipment enables the leachate recirculation, measurementof biogas content and volumes, collection of leachate and gas samples and wateraddition. The experimental set-up is illustrated in Fig. 2. Five such lysimeterswere placed in a termostated roomthe temperature was constant in the range 2021C.</p><p>Each lysimeter was charged with about 5 kg of simulated MSW prepared bymixing different components according to MSW composition typical for the city ofLodz. Fruits and vegetables amounted to 29.9%w/w of the total feed; the remainingwet weight of the feed was paper (20.1%w/w), plastics (13.9%w/w), textiles(4%w/w), metal (4.2%w/w) and other inorganic materials (11.7%w/w). Allcomponents were cut into maximum size of 25 cm.</p><p>In order to enable a development of methanogenic phase the compost in theamount of 30%w/w was added to the bulk mass of waste as well as separate layers.Average packing density of waste in the reactors was approximately 500 kg dm3.</p><p>1 - reactor body filled with waste2 - water addition system3 - leachate recirculation system4 - gas volume measurement system5 - biogas analyzer6 - leachate sampling port</p><p>valveperistaltic pump</p><p>1</p><p>2</p><p>34</p><p>6</p><p>5</p><p>CH2 C2O</p><p>H2S</p><p>Figure 2. Scheme of the lab-scale lysimeter.</p><p>Anaerobic Digestion of Municipal Solid Waste 861</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>The</p><p> UC</p><p> Irv</p><p>ine </p><p>Lib</p><p>rari</p><p>es] </p><p>at 2</p><p>0:23</p><p> 24 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>ORDER REPRINTS</p><p>The porosity was 34%v/v. at the beginning of the experiment and 26%v/v after theexperiment.</p><p>A methanogens inoculum was added in the amount of 200mL pro reactor on the60th day. The inoculum was a sludge taken from an anaerobic digester at themunicipal wastewater treatment plant.</p><p>Two runs of experiments were performed. In the first run the leachate wasrecirculated twice a week. The main research stress was put on the AdvancedOxidation Processes (AOPs) influence on the leachate biodegradation in thelysimeters. The results are to be presented in the other publication.</p><p>In the second run the leachate in the one of the lysimeters was recirculated daily,in the second once per week, while the waste in the third one was completelysubmerged in the leachate.</p><p>The biogas probes were analyzed with the gas analyzer LMS GasData, biogasproduction was measured by Ritter gas meter. The following analytical methodswere applied to the leachate:</p><p> pH (pH-meter WTW pH 540 GLP), redox potential (redox electrode, pH-meter WTW pH 540 GLP), biological oxygen demand BOD5 (dillution method, standard method</p><p>[10]), chemical oxygen demand COD (standard dichromate method, Hach), volatile fatty acids VFA (distillation method, Buchi distillation unit), ammonia nitrogen N-NH4</p><p> (distillation method, Buchi distillation unit), total Kiejdahl nitrogen TKN (Buchi digestion unit), total phosphorus Pt (method 8048, Hach), total organic carbon TOC (coulometeric method, Strohlein coulometer) toxicity (ToxAlert, Vibrio fischeri NRRL B-11177, Merck).</p><p>RESULTS AND DISCUSSION</p><p>The acidogenic and methanogenic phases were visible both in the leachate andbiogas composition changes. The acidogenic phase was distinguished from themethanogenic phase due to pH and redox potential changes in the leachate togetherwith the increase in the biogas production and the biogas composition. The redoxpotential change from positive to negative value is considered as the beginning of themethanogenic phase. It can be seen from Fig. 3 that redox potential dropped belowzero simultaneously with biogas curve rapid rise.</p><p>The addition of compost and the methanogens inoculum as well as theleachate recirculation led to the process acceleration. The acidogenic phase inthe lysimeters lasted about 80 days, while it takes usually few years in the reallandfill. After 250 days of the lysimeter operation the biogas production wasnegligible.</p><p>Although, the processes took much shorter time than in the real landfill,the leachate main characteristic is similar to the literature values (Table 1).Moreover, the biogas composition changes were analogous to the landfill gasvariation.</p><p>862 Ledakowicz and Kaczorek</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>The</p><p> UC</p><p> Irv</p><p>ine </p><p>Lib</p><p>rari</p><p>es] </p><p>at 2</p><p>0:23</p><p> 24 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>ORDER REPRINTS</p><p>Acidogenic Phase</p><p>In this phase, hydrolysis and acidification, as quantified by production of COD,VFA, TOC, and BOD5 in the leachate, were the predominant reactions duringfermentation of solid waste. Similar trends for all parameters were observeda steeprise of their concentration in the acidogenic phase. As it can be seen from Fig. 4, theBOD5 concentration significantly increased from 12 2 g O2 dm3 to about 20 g O2dm3. In the same time interval the COD concentration rose from 25 5 g O2 dm3to 35 5 g O2 dm3 (Fig. 4), VFA from 3 0.5 g CH3COOH dm3 to 16 0.5 gCH3COOH dm</p><p>3 and TOC from 2 0.5 g C dm3 to 9 0.5 g C dm3 (Fig. 5). Suchan extremely high leachate contamination by carbon compounds is typical for a socalled young leachate.</p><p>In this particular study the concentrations additionally increased due to theleachate recirculation. The pH decreased from the value 6 on the seventh day tominimum value 5.3 on the 55th day and then the pH started to increase (Fig. 6).The leachate buffering was not necessary. The BOD5/COD ratio was in the</p><p>0</p><p>10</p><p>20</p><p>30</p><p>40</p><p>50</p><p>60</p><p>70</p><p>0 50 100 150 200 250</p><p>Time (day)</p><p>Cum</p><p>ulat</p><p>ive </p><p>gas </p><p>prod</p><p>ucti</p><p>on </p><p>(dm</p><p>3 kg</p><p>-1)</p><p>-180-160-140-120-100-80-60-40-2002040</p><p>Red</p><p>ox p</p><p>oten</p><p>tial</p><p> (m</p><p>V)</p><p>Figure 3. The gas production and redox potential changes. ___ Gas production; g redox</p><p>potential.</p><p>Table 1. Main characteristics of leachate.</p><p>Parameter Unit Range (real landfill)[11] Range (this study)</p><p>pH () 5.38.5 5.47.1</p><p>BOD5 (mg O2 dm3) 10090,000 7520,000</p><p>COD (mg O2 dm3) 150100,000 10006000</p><p>Chlorides (mg Cl dm3) 304000 350520</p><p>Ammonia nitrogen (mg N dm3) 11500 10200</p><p>Total Kiejdahl nitrogen (mg N dm3) 505000 50350</p><p>Total phosphorus (mg P dm3) 0.130 625</p><p>Anaerobic Digestion of Municipal Solid Waste 863</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>The</p><p> UC</p><p> Irv</p><p>ine </p><p>Lib</p><p>rari</p><p>es] </p><p>at 2</p><p>0:23</p><p> 24 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>ORDER REPRINTS</p><p>range 0.40.6 (Fig. 4) which indicate that leachate is amenable for biodegradation bymicroorganisms. However, the lack of nitrogen and phosphorus compounds wasobserved. The ratio of COD/Total Kiejdahl Nitrogen (COD/TKN) ranged between70 and 160, while the ratio of COD/Total Phosphorus (COD/P) was between 1500and 4500.</p><p>The leachate was also characterized by high toxicity. As it can be seen fromFig. 6, the toxicity increased from 70% on the 7th day of operation to 100% on the50th day in all the reactors and levelled off at 100% until the 80th day.</p><p>It can be seen in Fig. 7 that the biogas production was negligible during almostall of the acidogenic phase. Figure 7 also shows the time changes in the biogascomposition. Due to the degradation of the organic material oxygen was consumedwithin the short time, which resulted in a rapid carbon dioxide production. The</p><p>0</p><p>5</p><p>10</p><p>15</p><p>20</p><p>25</p><p>30</p><p>35</p><p>0 50 100 150 200 250</p><p>Time (day)</p><p>CO</p><p>D (</p><p>g O</p><p>2 (d</p><p>m3 )</p><p>-1),</p><p> VFA</p><p> (g</p><p>CH</p><p>3CO</p><p>OH</p><p> (dm</p><p>3 )-1</p><p>), T</p><p>OC</p><p> (g </p><p>C (</p><p>dm3 )</p><p>-1)</p><p>Figure 5. COD, VFA, and TOC changes. ^ COD; g VFA; mTOC.</p><p>0</p><p>5</p><p>10</p><p>15</p><p>20</p><p>25</p><p>30</p><p>35</p><p>40</p><p>0 50 100 150 200 250</p><p>Time (day)</p><p>BO</p><p>D5,</p><p> CO</p><p>D (</p><p>g O</p><p>2 (d</p><p>m3 )</p><p>-1)</p><p>0</p><p>0,1</p><p>0,2</p><p>0,3</p><p>0,4</p><p>0,5</p><p>0,6</p><p>0,7</p><p>BO</p><p>D5/</p><p>CO</p><p>D r</p><p>atio</p><p> ( -</p><p> )</p><p>Figure 4. BOD5, COD, and BOD5/COD ratio changes. ^ BOD5; g COD;...</p></li></ul>