Application of membrane bioreactor systems for landfill leachate treatment | |
| Author | Boonchai Wichitsathian |
| Call Number | AIT Diss. no.EV-04-03 |
| Subject(s) | Bioreactor landfills Membrane reactors Sanitary landfills--Leaching |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-04-03 |
| Abstract | Landfill leachate is a complex wastewater with considerable variation in both quality and quantity. The composition and concentration of pollutants are influenced by the types of waste deposited, hydrogeological factors, and more significantly by the age of the landfill site. In general, leachate is highly contaminated with organic contaminants measured as chemical oxygen demand (COD) and biochemical oxygen demand (BOD), and also with high ammonium nitrogen concentration. Biological processes have been found ineffective for leachate from relatively old landfill. In leachate containing high concentrations of organic and nitrogen compounds such cases result in possible serious environmental problems near the landfill site. This research was undertaken to investigate the performance of a membrane bioreactor (MBR) using mixed yeast culture (YMBR) and mixed bacteria culture (BMBR) in treating raw leachate containing high organic and nitrogen concentrations. The inhibition effects of ammonium nitrogen and lead on yeast and bacteria cultures were determined by measuring the oxygen uptake rate (OUR) using the respirometric method. Furthermore, for both YMBR and BMBR, treating the stripped leachate, they were assessed the treatment efficiency to compare the results with those treating the raw leachate. The inhibition experiment revealed that a bacteria culture was very sensitive to ammonium nitrogen when it was compared to a yeast culture. Also the values ofbiokinetic coefficients showed that the specific growth rate(μ) in bacteria system was influenced. At ammonium concentration of 2,000 mg/L, the response of OUR inhibition in a bacteria system was approximately 37% whereas it was around 6% in a yeast system. Furthermore, both yeast and bacteria cultures were also sensitive to lead. In a MBR, treating raw leachate, the COD removal rate for BMBR was slightly lower than the YMBR for varied hydraulic retention time (HRT) at high volumetric loading rate. The average COD removal efficiency in BMBR was 62±2% while in YMBR was 65±2%. The YMBR could obtain higher COD removal rate at higher volumetric loading rate than the BMBR. This indicated that the yeast system can treat leachate containing high organic and nitrogen concentrations. The average TKN removal efficiency for both BMBR and YMBR systems was from 14-25% and 19-29%, respectively. The nitrite and nitrate concentrations (N02- and N03-) were found to be very low. The comparative evaluation of treatment performance of MBR, treating stripped leachate, was examined. The COD removal of both BMBR and YMBR was above 70% at HRT 16 hand 24 h. As a result, the pretreatment with ammonia stripping prior to BMBR showed more significant improvement in· terms of COD removal when it was compared to YMBR. This could be confirmed that the trend of inhibition effect on bacteria was dependent upon the ammonium nitrogen concentration. The range of BOD concentration of effluents from both YMBR and BMBR, treating the stripped leachate was from 30-55 mg/L. This level followed the present effluent standard. Although BOD could be reduced to lower values with these methods, the treated leachate still contained a large quantity of refractory organic compounds. This might be due to the contribution of the slowly biodegradable organics and non-biodegradable organics contained in the leachate. Therefore, they should be further treated in a post treatment for elevating the final effluent to meet the present effluent standard or even increasing the biodegradable organics. Under the same operating conditions, the YMBR could run under transmembrane pressure (TMP) 1.3-2.5 times lower than the BMBR with the significantly reduced membrane fouling rate. This might be due to the soluble extracellular polymeric substances (soluble EPS). Hence, yeast system could enhance membrane performance and had the potential to improve the treatment system due to reduction of operational problems. In addition, bacteria sludge showed a better dewatering quality compared to that of the yeast sludge. |
| Year | 2004 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-04-03 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering (EV) |
| Chairperson(s) | Visvanathan, Chettiyappan; |
| Examination Committee(s) | Preeda Parkpian;Kier, Josef Tran; Athapol Noomhorm;Gtinthert, F.W.; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2004 |