Inhibition Of Thiocyanate And Quinoline On Anammox Granules

The anaerobic ammonium o xidation（anammox）process has the practical application value in treating coke wastewater with high-strength ammonium,and considerable amouts of typical inhibitors could be introduced to anammox reactors.In this paper,the short-and long-term effects of thiocyanate（SCN^-）on anammox granules were evaluated,and the recovery strategies were proposed.And then,the effect of SCN^-shock on the performance of anammox process was investigated.Finally,the responses of anammox granules to quinoline exposure were tracked.The performane of nitrogen removal and granule characteristics were evaluated under quinoline and quinoline gradient domestication was applied to improve anammox properties.The main results are as follows:（1）The feasibility of using anammox granules to treat industrial wastewater containing SCN^-was examined in this paper.Anammox activity decreased with increasing thiocyanate concentration and pre-exposure time in batch tests.A modified noncompetitive model was used to fit the data for thiocyanate inhibition,and the 50%inhibition concentration(IC₅₀)of thiocyanate on anammox was 620.4 mg L^-1.In continuous-flow experiments,the influent thiocyanate concentration of test reactor（R₁）in phase II gradually increased from 10 to 120 mg L^-1,and the average nitrogen removal efficiency（NRE）of R₁ was maintained at 83.0±7.82%.This robustness was attributed to the self-adaptation ability of anammox granules through long-term acclimatization.The NRE was decreased to 57.1%under 130 mg L^-1 thiocyanate within two days.Under thiocyanate stress,the SAA,settling velocity and heme c content of the anammox granules significantly decreased,and the extracellular polymeric substances（EPS）content slightly increased.In batch tests,after exposure to 10 mg L^-1 Fe（III）for 24 h,a critical SAA(301.9 mg N g^-1VSS d^-1)was observed with relatively optimal recovery efficiency（119.9%）.In continuous-flow experiments,Fe（III）had important function of shield agent.The long-term performance inhibition could be reversed in the presence of 10 mg L^-1 Fe（III）,and the SAA increased 17.4%.（2）The robustness of an anammox process under individual and combined thiocyanate（SCN^-）and hydraulic shocks was investigated.In the test of individual SCN^-shocks,the reactor performance was stable at a relatively lower SCN^-concentration(300 mg L^-1)after exposure to SCN^-shocks for 1.5 and 3 h;the higher NO₂^--N of effluent was reached to 65.4 mg L^-1 after exposure to SCN^-shocks(900 mg L^-1)for 3 h.In the test of hydraulic shocks,the reactor performance in hydraulic shock tests was robust,and the relative low SAA loss ratios（9.2%and 4.0%）were observed in shocks 7 and 8.The results indicated that the performance of the reactor was functionally redundant when the NLR was abruptly doubled,allowing the reactor performance to immediately return to normal levels in the recovery period.In the test of combined SCN^-and hydraulic shocks,the maximum loss percentage of SAA was42.6%in the test of SCN^-shock(900 mg L^-1)for 3 h.The effect of anammox performance was increased with shock strength.Shock tests had certain degree influence on anammox granules.The heme c content in combined SCN^-and hydraulic shocks(300 mg L^-1,0.5 HRT,3 h)was adversely affected,with maximum loss percentage of 22.7%.However,the EPS content during the shock period increased in varying degrees and antagonized exogenous disturbances.（3）In this study,the quinoline was select to evaluate the acute toxicity,long-term effects on anammox granules and the strategy of domesticate culture.In batch tests,the SAA of anammox granules under different quinolone concentration was invested,and the IC₅₀ of quinoline at an initial total nitrogen level of 200 mg L^-1was found to be 13.1 mg L^-1 by non-competitive inhibition model.The response of anammox granules to pre-exposure to quinoline was in relation to metabolic status,and the co-existed of quinoline and NO₂^--N had a rapid detrimental effect,with 64.5%of the full effect occurring with 12 h.In continuous-flow experiments,the nitrogen removal rate（N RR）of reactor decreased from 2.5 to 1.5 kg N m^-3 d^-1 within 3 days presence of 10 mg L^-1 quinoline.The NRR and NRE of reactor were recovered to 2.6kg N m^-3 d^-1 and 83.1%by decreasing the quinoline and substrate concentration.Then,after cultivated and acclimated by adding quinoline in the effluent,the anammox granules could tolerate 10 mg L^-1 quinoline.When the quinoline concentration was increased to 10 mg L^-1,the NRR and NRE were 2.4±0.3 kg N m^-3 d^-1 and 92.2±5.3%,respectively.Under quinoline stress,the SAA,EPS and heme c content were decreased to 60.4%,79.3%and 77.9%,respectively,and settling velocity persistently increased to 108.5%.