Anaerobic Ammonium Oxidation Process For Denitrification Treatment Of Seawater-containing Sewage

Saline wastewater containing ammonia nitrogen emissions increased day by day, which added tremendous pressure on the environment. It was hard to treat saline wastewater by traditional biochemical nitrogen removal processes. Anammox process, as a cost-effective and environment-friendly nitrogen removal approach, has shown an overwhelmingly potential advantage in treating wastewater with high salinity concentration compared to other conventional nitrogen processes. In this paper, anammox process was used to study the nitrogen removal of wastewater containing seawater, and achieved some results:The adaptation of freshwater anammox bacteria to seawater. The results showed that anammox bacteria could remain active and maintain high nitrogen removal efficiency in any proportion of seawater through acclimation. When seawater proportion was not more than 40%, the seawater almost had no effect on the stability and the nitrogen removal efficiency of the reactor, besides, the activity of ANAMMOX bacteria was enhanced. The maximum specific activity of ANAMMOX bacteria, achieving in the reactor with 30% seawater, was 21.3% up compared with reactor with 10% seawater. When seawater proportion was more than 40%, the nitrogen efficiency of reactor began to decay. However, with sufficient time to adapt, the efficiency would recover. During this period, the reaction of the reactor to seawater could be divided into three phases: sensitive period, interim stable period and recovery period.The recovery capability of anammox bacteria that suffered inhibition of high salt environment contained 100% seawater concentration. The results showed that the nitrogen removal performance of anammox reactor suffered inhibition of high salinity concentration would enter a period of stable nitrogen removal efficiency again after an interim stable period and a recovery period, and the nitrogen removal rate(NRR) could be 0.52 kg N/(m~3·d), which were similar to that containing 10% seawater. The modified Logistic model and modified Gompertz model were revised and its' suitability were improved. The re-modified Logistic model was suggested to use to simulate the NRR recovery process of anammox reactor that suffered inhibition of 100% seawater concentration. The doubling time of NRR was estimated at 11.359 d by establishing the prediction formula for the recovery time of NRR.Effects of nitrite on anammox bacteria at salt environment contained 100% seawater concentration. The results showed that anammox process began to be inhibited when the influent nitrite concentration was 170mg/L, and the ammonia nitrogen removal efficiency decreased 8.41%. The fitting of modified Logistic model showed that influent nitrite less than 151.49mg/L would increase the nitrogen removal rate while influent nitrite higher than 170mg/L would inhibit the nitrogen removal rate. The model of Luong suited to fit the inhibition kinetics with higher nitrite concentration which affected nitrogen removal efficiency. The maximum substrate removal rate(NRRmax) obtained by Luong model was 0.53 kg N/(m~3·d), and the half-saturation constant(KS) was 0.10 mg/L. The maximum allowable effluent nitrite concentration above which cells do not grow(Sm) was predicted to be 338.22 mg/L and the correlation(n) was 0.97801. When anammox process was used to treat wastewater containing 100% seawater, it was suggested that the effluent of nitrite concentration should be lower than 338.22 mg/L.