High rate thermophilic anaerobic membrane bioreactor for wastewater treatment | |
| Author | Wijekoon, Kaushalya C. |
| Call Number | AIT Thesis no.EV-10-05 |
| Subject(s) | Membrane reactors Thermophilic bacteria Sewage--Purification--Biological treatment |
| Note | A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Thermophilic anaerobic wastewater treatment is an attractive solution for higher strength wastewaters could achieve higher microbial growth rate; high loading rates in smaller reactor. But thermophilic application of well known existing high rate anaerobic reactors has hindered due to excessive biomass washout. Therefore membrane bioreactor concept in thermophilic anaerobic wastewater treatment has become a promising technology. This assures total biomass retention; consequently ensure handling high loading rates. Two stage AnMBR treatment systems ensure optimum growth conditions of acid formers and methanogens. This enhances the microbial activity, consequently the biogas production. In this study, performances of two stage AnMBR at thermophilic condition (55°C) was studied. After seed sludge acclimatization, system was operated in three loading rates such as 5, 8 and 12 kg COD/m³.d. Operated HRT of the system was 2 days, which is distributed as 16 h for hydrolytic reactor and 32 h for methanogenic reactor. Wastewater flow rate of the system was 4.5 L/d. Molasses based synthetic wastewater was used as the feed concentration was increased to increase the loading rate. Feed wastewater concentration which used in three loading rates were 10, 16 and 24 kg COD/m³ respectively. MF membrane with nominal pore size of 0.1 μm was used in external partial sedimentation mode. Filtration cycle was maintained as 2 min filtration and 30 sec drain off. Hydrolytic reactor was operated at 1.8 g/L of MLVSS concentration and methanogenic reactor was at 10 g/L. Microbial activity, biogas productivity and methane yield was increased with the increased loading rate. Highest biogas productivity was 5 times the reactor volume, which is comparable with existing high rate anaerobic reactors. Methane composition was almost 60 % in all three loading rates. Highest methane yield was 0.35 m³CH4/ g CODr. Higher VFA production was observed and average of 6900 mg/L was and propionic is negligible. Hydrolytic reactor acidification was increased with increasing loading rate from 65 to 71.3 % indicating good performances of hydrolytic reactor with increasing loading rate. Reactor achieved 96 % of BOD removal in first and second loading rates while COD removal was about 80 %. However, reactor COD removal was reduced to 61 % while BOD removal was reduced to 89 % in the third loading rate due to insufficient microbial concentration. In addition, NH3 accumulation in reactor was observed with increasing loading rate due to the higher TN concentration in feed. |
| 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 and Management (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Annachhatre, Ajit P. ;Preeda Pakpian; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship (Japanese Government); |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2010 |