Partial Nitritation Reactor Research Articles

Completely Autotrophic Nitrogen-Removal for Treatment of High Ammonia Leachate

This study focused on the feasibility of autotrophic nitrogen removal to treat high ammonia leachate, using combined partial Nitritation and Anammox process. In partial nitritation reactor, the optimal operation condition was found with influent ammonium concentration of 1200 mg/L, DO about 3 mg/L, HRT 3 days and temperature about 31°C at the ratio of NO2-N / NH4-N effluent kept at 1.1, which is a prerequisite for the application of Anammox. In Anammox reactor, more than 85% ammonium is removed at HRT 8 days, temperature 28±1°C, and pH 8. The removal rate of nitrogen and COD in combined partial Nitritation and Anammox process are 90% and 74%, respectively. Thus, a combined process of partial nitritation and a subsequent Anammox could be an alternative solution for ammonium removal for leachate.

High-rate nitrogen removal from livestock manure digester liquor by combined partial nitritation–anammox process

In this study, combination of a partial nitritation reactor, using immobilized polyethylene glycol (PEG) gel carriers, and a continuous stirred granular anammox reactor was investigated for nitrogen removal from livestock manure digester liquor. Successful nitrite accumulation in the partial nitritation reactor was observed as the nitrite production rate reached 2.1 kg-N/m(3)/day under aerobic nitrogen loading rate of 3.8 kg-N/m(3)/day. Simultaneously, relatively high free ammonia concentrations (average 50 mg-NH(3)/l) depressed the activity of nitrite oxidizing bacteria with nitrate concentration never exceeding 3% of TN concentration in the effluent of the partial nitritation reactor (maximum 35.2 mg/l). High nitrogen removal rates were achieved in the granular anammox reactor with the highest removal rate being 3.12 kg-N/m(3)/day under anaerobic nitrogen loading rate of 4.1 kg-N/m(3)/day. Recalcitrant organic compounds in the digester liquor did not impair anammox reaction and the SS accumulation in the granular anammox reactor was minimal. The results of this study demonstrated that partial nitritation-anammox combination has the potential to successfully remove nitrogen from livestock manure digester liquor.

Innovative treatment system for digester liquor using anammox process

This study demonstrated that partial nitritation using nitrifying activated sludge entrapped in a polyethylene glycol (PEG) gel carrier, as a pretreatment to anammox process, could be successfully applied to digester liquor of biogas plant at a nitrogen loading rate of 3.0 kg-N/m 3/d. The nitritation process produced an effluent with a NO 2–N/NH 4–N ratio between 1.0 and 1.4, which was found to be suitable for the subsequent anammox process. A high SS concentration (2000–3000 mg/l) in the digester liquor did not affect partial nitritation treatment performances. Effluent from this partial nitritation reactor was successfully treated in the anammox reactor using anammox sludge entrapped in the PEG gel carrier with T-N removal rates of greater than 4.0 kg-N/m 3/d. Influent BOD and SS contents did not inhibit anammox activity of the anammox gel carrier. The combination of partial nitritation and anammox reactors using PEG entrapped nitrifying and anammox bacteria was shown to be effective for the removal of high concentration ammonium in the digester liquor of a biogas plant.

Landfill leachate treatment with a novel process: Anaerobic ammonium oxidation (Anammox) combined with soil infiltration system

A novel combined process was proposed to treat municipal landfill leachate with high concentrations of ammonium and organics. This process consisted of a partial nitritation reactor (PNR), an anaerobic ammonium oxidation (Anammox) reactor (AR) and two underground soil infiltration systems (USIS-1 and USIS-2). Based on the optimum operating conditions obtained from batch tests of individual unit, the combined process was continuously operated on a bench scale for 166 days. Partial nitritation was performed in a fixed bio-film reactor (PNR, working volume = 12 L). Ammonium nitrogen-loading rate (Nv) and DO were combined to monitor partial nitritation, and at T = 30 ± 1 °C, Nv = 0.27–1.2 kg/(m 3·d), DO = 0.8–2.3 mg/L, the ratios of nitrite nitrogen (NO 2 −-N) to ammonium nitrogen (NH 4 +-N) were successfully kept close to 1.0–1.3 in the effluent. Nitrate nitrogen (NO 3 −-N) less than 43 mg/L was observed. The effluent of PNR was ideally suited as influent of AR. Sixty-nine percent COD cr from the raw leachate was degraded in the PNR. Anammox was carried out in a fixed bio-film reactor (AR, working volume = 36 L). At T = 30 ± 1 °C, Nv = 0.06–0.11 kg/(m 3·d), about 60% NH 4 +-N and 64% NO 2 −-N in the influent of AR were simultaneously removed. Inhibition of high-strength NO 2 −-N (up to 1011 mg/L) should be responsible for the low removal rate of nitrogen. About 35% aquatic humic substance (AHS) was degraded in the AR. With the same working volume (200 L), USIS-1 and USIS-2 were alternately performed to treat the effluent from AR at one cycle of about 30 days. At hydraulic loading rate (HLR) = 0.02–0.04 m 3/m 3·d, pollutant loading rates (PLR) = NH 4 +-N ≤ 14 g/m 3·d, TN ≤ 25 g/m 3·d, and COD cr ≤ 13 g/m 3·d, average removal efficiencies of 88% NH 4 +-N, 67% TN and 55% COD cr were obtained. Overall, raw leachate with 1430–2720 mg NH 4 +-N/L, 1524–2912 mg TN/L and 1165–2599 mg COD cr/L, was treated by the process and the effluent with 22–58 mg NH 4 +-N/L, 108–300 mg TN/L and 32–250 mg COD cr/L was obtained with average removal efficiencies of 97% NH 4 +-N, 87% TN and 89% COD cr. The test results indicated that the combined system could work stably over a long period under the operating conditions, and that the process was feasible for the leachate treatment. AR should be the key to the performance of the combined process.

Combined partial nitritation and Anammox biofilm system as a sustainable solution for supernatant treatment

Nowadays, as the effluent water regulations become more stringent, there is a need to treat wastewater in the most efficient manner and according to sustainability principles. One of the possibilities to meet this challenge is treatment of side streams, which are usually returned to the main influent of Wastewater Treatment Plants (WWTP) increasing the total load. Following processes occurring in natural ecosystems a new biological technology - combination of partial nitritation and Anammox processes - for treatment of nitrogen-rich supernatant coming from digested sludge dewatering has been developed. The first stage of the process is an oxidation of half of the ammonium to nitrite (partial nitritation process). The following stage - Anammox process - is an anaerobic oxidation of ammonium and nitrite nitrogen to dinitrogen gas. The process has been successfully tested in a technical-scale pilot plant with a continuous supply of supernatant at Himmerfjärden WWTP. Kaldnes rings were provided for biofilm growth. Almost two-year experiences in operation of the two-stage process have been presented in this paper. The results showed that a proper adjustment of dissolved oxygen (DO) concentration in the bulk liquid and a pH value drop in the partial nitritation reactor is essential to obtain the ammonium-to-nitrite ratio (NAR) in the effluent close to 1.3 as required for the Anammox process. It took four months to recover the Anammox bacteria activity after NO2-N inhibition.

Combined partial nitritation/Anammox system for treatment of digester supernatant

One-year (2004) comprehensive investigations in a semi-industrial pilot plant (5 m3) were carried out with the aim of assessing the influence of operational parameters on the partial nitritation/Anammox system performance. In the system designed as a moving-bed biofilm reactor, the influent nitrogen load to the Anammox reactor was progressively increased and a stable Anammox bacterial culture was obtained. Interaction between subsequent aerobic and anaerobic conditions in the partial nitritation and Anammox reactors, respectively, granted conditions to remove nitrogen through the nitrite route. It implies that the oxygen supply can be limited to a high extent. A control strategy for the partial nitritation step relied on concomitant adjustment of the air supply with a variable influent nitrogen load, which can be monitored by both pH and conductivity measurements. In the Anammox reactor, an influent nitrite-to-ammonium ratio plays a vital role in obtaining efficient nitrogen removal. During the 1-year experimental period, the Anammox reactor was operated steadily and average nitrogen removal efficiency was 84% with 97% as the maximum value.