| Author | Adhikari, Radha |
| Call Number | AIT Thesis no.EV-06-33 |
| Subject(s) | Refuse and refuse disposal--Thailand--Pathum Thani
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-06-33 |
| Abstract | Various aspects of Anaerobic Digestion (AD) technology have been the focus of research in recent years. Shortening the digestion time with enhanced process efficiency is one of the integral concerns in AD technology. In line with this concern, experimental investigations were conducted on anaerobic digestion of organic fraction of municipal solid waste (OFMSW) in two different modes of operation, namely; sequential batch anaerobic composting (SEBAC), and continuous anaerobic digestions. Digesters in both cases were pilot scale reactors, and they operated under thermophilic condition. In SEBAC, the pre-stage nm was initially operated under mesophiic condition (37 °C) until it stabilized, and the system was shifted to thermophilic condition (55 °C) by gradually increasing the temperature at the rate of 2 °C per day. The process behavior in transient condition revealed that long time acclimatization of inoculums can be avoided if temperature shift is gradual. Three SEBAC cycles were nm with the cross-circulation rates of 0.34, 0.46 and 0.58 m3 leachate / m3 of waste volume per day for which increasing specific methane yields of 184, 217 and 239 L CH4 /kg VS, respectively were observed. These values correspond to the 63%, 74%, 82% process efficiency calculated based on the laboratory BMP assay. As the start-up period decreased from 7 days in cycle I to 5 days in cycle III, the digestion time shortened by 5 days. Higher re-circulation rates not only produced higher biogas but also did so in shorter digestion period. The research also reaffirms the earlier findings that the biogas production rate in thermophilic temperature is considerably higher than the mesophilic. In the later half of the research, a simple continuous reactor that operates on draw-feed mode is described. The reactor was operated under therniophilic condition with the feeding rate of 1.9 kg, 2.7 kg, 3.5 kg and 4.25 kg VS/ m3. day, respectively. The highest biogas production of 1.07 L/day/waste volume was obtained for the organic loading rate of 3.5 kg VS/ m3.day, which slightly reduced to 1.04 L/day/waste volume when the loading to increased to 4.25 kg VS. m3/day as the system showed signs of over loading. The highest specific gas production observed was 335 L/kgVS for the smallest organic loading rate of 1.9 kg VS/m3 day . The energy balance studies conducted for both SEBAC and continuous digesters indicate that both systems are energy surplus systems. Finally, the residue from AD was tested for its nutrient value, calorific value, and heavy metal contents. The percentage of nitrogen and phosphorus in the digestate confirms that AD keeps the value of nutrients intact for fertilizer and that all heavy metal concentrations fall below the WHO standard (proposed, 1997) of compost for developing countries. The calorific value of the digestate was found to be 13.8 MJ/kg it has potential to be used as Refused derived fuel (RDF). |
| Year | 2006 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. EV-06-33 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Visvanathan, Chettiyappan |
| Examination Committee(s) | Annachhatre, Ajit P.;Aramaki, Toshiya |
| Scholarship Donor(s) | Government of Norway (Norad) |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2006 |