| Author | Shakya, Sheelva |
| Call Number | AIT Thesis no.EV-10-26 |
| Subject(s) | Sewage--Purification--Anaerobic treatment
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| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Anaerobic digestion is one of the attractive pre-treatment methods for solid waste management. Hydrolysis of solid waste is a rate-limiting step in an anaerobic process and its intensification usually leads to faster digestion, reduction of reactor size and improvement of system efficiency. Thus, this study is an attempt to improve liquefaction of high solid waste into dissolved organic fraction (leachate) and then treatment of leachate through anaerobic digestion into methane under mesophilic condition. For the experimental purpose, organic fraction of municipal solid waste (OFMSW) (food waste 40%, fruit waste 20%, vegetable waste 27%, leave waste 8%, and paper waste 5%) was used as the main feedstock. This study consists of three experiments: pilot scale semi continuous experiment, batch test and Biochemical Methane Potential (BMP)study. The pilot scale experiment used two types of reactors: flushing reactor and anaerobic reactor. Solid waste was loaded in the flushing reactor and leachate was separated using a mesh of 6 mm pore size. The reactor was operated under various leachate recirculation rates to increase the concentration of dissolved organic load. Subsequently, separated leachate was treated in an anaerobic reactor to produce methane gas. The anaerobic reactor was operated under three organic loading rates 6, 8 and 10 kg COD/m³.d. Furthermore, batch test was conducted in parallel to evaluate the performance of the flushing reactor and BMP test to assess the methane production potential of leachate. Based on the results obtained it can be concluded that recirculation of leachate in solid waste improves the hydrolysis and acidification reaction. Anaerobic treatment of leachate achieved COD removal of 90 % and maximum biogas productivity, which is 6 times the reactor size, at the highest loading rate. Gas volume and methane content increased from 30 to 63 L/d and 61 to 66 % respectively, which indicate the anaerobic reactor performed well under these loading rates. In addition, methane yield of 0.42 m³ CH₄/kg CODr.d shows this type of fresh leachate has higher energy potential than landfill leachate. Furthermore, the test result from BMP test showed that OFMSW leachate has a higher methane yield when compared with OFMSW and it indicates that the leachate contains high percentage of organic rich substrate for methane production thus it is better than the waste itself. Moreover, throughout the experimental period the biological activity of anaerobic reactor was around 0.9 g CODr/g MLVSS.day that indicates a potential of the reactor to take higher organic load. Hence, the flushing mechanism can be an attractive solution for degradation of high OFMSW, which intensifies energy recovery and pollution control, and this will ultimately, increase the life span of landfill. |
| Year | 2010 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Preeda Pakpian;Anal, Anil Kumar; |
| Scholarship Donor(s) | United Nations Environment Programme (UNEP); |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2010 |