| Author | Sinha, Banashri |
| Call Number | AIT Diss. no.EV-07-03 |
| Subject(s) | Nitrification
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the
degree of Doctor of Technical Sciences in
Enviromnental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | The partial nitrification process involves part ial nitrification of ammonium to nitrite. The effluent from partial nitrification process containing a mixture of ammonium and nitrite in equal prop01tion is ideally suited as the influent for the ANaerobic AMMonium OXidation (ANAMMOX) process. Therefore, partial nitrification process was initiated in a CSTR independent of the sludge age and experiments were conducted to optimize the operational parameters for 50% conversion of the ammonium nitrogen to nitrite nitrogen with negligible nitrate formation in the reactor. The lab-scale experiments were carried out in a continuously stirred aerated reactor which was made of borosilicate glass with working volume of 5 liters. The reactor was well-equipped with a pH controller, a temperature controller, a level controller and a DO recorder. Studies on different parameters including DO, temperature and pH was carried out for optimizing 50% conversion of the ammonium nitrogen to nitrite nitrogen. From the experiments it was found that a temperature of 35°C, a DO of 0.3-0.5 mg/l and pH of 8 were the most important operating parameters for partial nitrification during nitrogen removal in biological processes. The experimental set-up was successfully operated at the above-mentioned operational parameters with increasing NH4N concentration in the influent feed for 110 days (Phase I; 50 - 350 mg/l) and for 133 days (Phase II; 280-680 mg/l). The sludge retention time was not monitored and the recirculation ratio was maintained at 3: 1. During the second phase, the highest effluent N02 N of 346.3 mg/l was obtained at a loading rate of 3.9 kg/m 3 of ammonium nitrogen in the form of NH4Cl.The ratio between nitrite nitrogen and ammonium nitrogen in the effluent was mostly around 1.0-1 .5 during the steady-state. It was also found that minimal nitrate nitrogen formation took place in the reactor during the overall operation of the reactor in both the phases. Thus, the effluent was ideally suited for further treatment by Anammox process. Microbial characterization was carried out during the second phase using molecular techniques - Quinone profile, FISH, PCR-DGGE and Sequencing, and the structure of the floe viewed under SEM and TEM from the seed sludge to the stable state operation period. There was an increase in the UQ-8 content from 24. 8% in seed sludge to 61.2% in Day 136 sample and a decrease in the other types of Quinone content from 69.7% in seed sludge to 36.2 % in Day 136 sample. This clearly reflects that there is an increase in the Nitrosomonas population with time and some of the biomass contributing towards other types of Quinone in the seed sludge couldn't flourish in the reactor with time. SEM Image revealed that 80-90% of the population viewed under the SEM showed clusters of sho1t rod-shaped and slightly tapering spherical cells which are the characteristics of nitrifier population. TEM showed the extensive presence of dividing small rod-shaped cells and spherical cells which could be assumed to be Nitrosomonas and Nitrosospira due to their resemblance with the structure. The FISH images indicated that in the seed sludge there were approximately only 2-3 % of nitrifiers which gradually increased to 8-9 % of AOB and 2-3 % of NOB on Day 21 and then finally on Day 95, 48-53 % of AOB and 6-8 % of NOB could be seen. Presence of Nitrosomonas, Nitrosospira and Pseudoxanthomonas were confirmed by Sequencing.
During the Phase IV, aniline was added into the reactor through the influent feed. There was an immediate inhibition and the efficiency of ammonium removal came down from 51.1 % to 2.3 % within 4 days of operation when 20 mg/l of aniline was added. Sludge samples were taken from the reactor before and after addition of aniline (7 days) for quinine profile analysis. It was found that there was an increase in the % of UQ-9 and a decrease in the UQ-8. The inhibition effect could be removed only after 22 days of operation of the reactor with normal SWW as well as washing of the sludge with water. Aniline was then added to the reactor with increased concentration in steps (1, 2, 5, 10, 15, 20, 30, 40 mg/l). It was found that the process was inhibited slowly and complete inhibition took place at 40 mg/l. So it can be said that acclimatised sludge is better adapted to dosage of aniline than a sudden shock dosage. SEM Images showed that a particular type of bacterium was present in huge numbers as well as the presence of some other spiral type were observed which were not present in the reactor during the uninhibited period. TEM images revealed that the inner structure of 80-90% of the cells was disrupted and hence disintegration of the enzyme system might be the cause for total inhibition of the partial nitrification process after addition of aniline. PCR-DGGE also showed the formation of 2-3 new bands and dissolving of 2 bands in the aniline inhibited sample as compared to the uninhibited sample. Presence of aniline-tolerant Nitrosomonas strains were confirmed by Sequencing, though the strains were not identified. |
| Year | 2007 |
| Type | Dissertation |
| 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) | Annachhatre, Ajit P. ; |
| Examination Committee(s) | Athapol Noomhorm ;Shipin, Oleg ;Rao, Bhamidimarri |
| Scholarship Donor(s) | ARRPET WWTM Project, Sweden ;
AIT Fellowship ; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2007 |