Response of nitrifying biofilm to inhibitory shock loads | |
| Author | Rajbhandari, Binod Kumar |
| Call Number | AIT Thesis no.EV-01-3 |
| Subject(s) | Nitrification inhibitors Sewage--Purification--Nitrogen removal |
| 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 |
| Abstract | Response of nitrifying biofilm to inhibitory shock loads was investigated using aniline as an inhibitory compound. Effect of bulk aniline concentration as well as exposure time on activity of nitrifying biofilm was investigated. A lab scale continuous down flow biofilm reactor with flow rate of 20 ml/min and hydraulic retention time of 32.55 min was operated for this purpose. Experiment were conducted under the conditions where ammonium and DO were not limiting factor. While inhibitor concentration in feed was varied to quantify the inhibitory effects on nitrifying biofilm. Synthetic wastewater containing constant NH4-N concentration of about 25 mg/l was used as feeding solution. pH of the system was maintained between 6.8 to 7.5. Pure oxygen was supplied and maintained DO between 9 to 18 mg/l. Recirculation ratio of 1 :6 was applied to achieve completely mix condition. Experiments were conducted with various possible combinations of feed aniline concentration varied between 2-10 mg/l and exposure time of 6-18 times of HRT (space-time). The experimental results revealed that the degree of inhibition to nitrifiers depends upon concentration as well as exposure time of toxic compound. Aniline concentration higher than 6 mg/l was found to be significantly toxic to nitrifiers. The maximum observed reduction in nitrification rate due to aniline application rate of 2, 4, 6, 8 and 10 mg/l exposed to 12 HRT were around 9, 20, 25, 62 and 80% respectively. Effluent nitrate concentration was found to be varying exponentially during exposure as well as recovery phase. It was observed that lower concentration of aniline with long exposure might have higher degree of inhibition than higher aniline concentration with short exposure. In case of 6mg/l of feed aniline exposed to 18HRT effluent N03-N concentration was reduced by about 11.2mg/l. While about 8.7mg/l reduction in effluent N03-N was observed at 8mg/l of feed aniline exposed to 6HRT. Maximum effluent N03-N reduction of about 13mg/l and 15.5mg/l was found due to feed aniline concentration of 8mg/l exposed to 9HRT and 12 HRT respectively. While the reduction was about 1 O. lmg/l due to feed aniline concentration of 1 Omg/l exposed to 6HRT. Empirical models with exponential reduction and recovery of biofilm activity during exposure and recovery stage were found to yield satisfactory results. |
| Year | 2001 |
| 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) | Annachhatre, Ajit P. |
| Examination Committee(s) | Chongrak Polprasert ;Mark, Ole |
| Scholarship Donor(s) | Her Majesty the Queen of Thailand |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2001 |