| Anaerobic ammonia oxidation(ANAMMOX)process is a new efficient,energy-saving and economical biological wastewater denitrification technology.However,how to solve the problem of operation obstacles caused by special environment(low temperature)conditions in practical application is the key research direction in the field of sewage control engineering nowadays.In this paper,the effects of pH and salinity on the performance of ANAMMOX process and the characteristics of sludge granules under low temperature(15 C)stress were investigated.The following conclusions were drawn:(1)Start-up and operation characteristics of ANAMMOX process were studied.With mature anaerobic ammonia oxidation sludge as inoculum,the rapid start-up of ANAMMOX can be achieved in only 9 days.After 80 days,the granulation of ANAMMOX can be achieved,and the reactor operation efficiency is stable.After raising the load,the TN removal load reaches about 3.14 kg/(m3 d)when the influent NH4+-N and NO2--N concentrations are 150 mg/L and 180 mg/L.(2)The effect of temperature on ANAMMOX process was studied.An efficient and stable ANAMMOX reactor was used as the research object to study the effect of step-by-step cooling on the denitrification efficiency and sludge characteristics of ANAMMOX process.When the temperature was 30?,the removal of TN from sludge was the largest,reaching 1.866 kg/(m3·d).The nitrogen removal efficiency of ANAMMOX becomes worse when the temperature decreases gradually from 30? to 15?.The TN removal rate of ANAMMOX was 1.14 kg/(m3 d)under the impact of low temperature at 15?.Compared with 30?,the TN removal rate of ANAMMOX had been reduced from 90%to 63%.In the process of gradual cooling,the physical properties of granular sludge change correspondingly with the decrease of temperature.The BW of granular sludge decreases gradually from 51%to 9.8%.The settling capacity of granular sludge decreases from 46.57 m/h to 39.6 m/h,and the flocculability of granular sludge decreases obviously.(3)The short-term effects of different cooling methods,pH and salinity on the ANAMMOX reaction were studied by sequential batch experiments.The results showed that both low temperature and high temperature could reduce the anaerobic ammonia oxidation reaction,and the optimum temperature of anaerobic ammonia oxidation reaction was 30?.Sudden cooling mode could seriously destroy the anaerobic ammonia oxidation reaction.At low temperature of 15?,high pH promoted the denitrification efficiency of ANAMMOX bacteria in the range of pH 7.2?9.2.Low salinity could stimulate the activity of ANAMMOX,while high salinity could inhibit the activity of ANAMMOX.The interaction can inhibit the activity of ANAMMOX.It was found that the nitrogen removal efficiency(NRR)of the reactor was twice as high as that of the reactor without adjusting the pH at 15? and pH 8.1 When salinity is 4 g/L at 15?,the nitrogen removal efficiency(NRR)of the reactor is 1.79 times that of the reactor without salinity adjustment at 15?.(4)The long-term effects of pH and salinity on denitrification efficiency and sludge characteristics of ANAMMOX at low temperature were studied by continuous flow test.Nitrogen removal efficiency was the highest at 15? and pH 8.2.The removal rates of ammonia nitrogen and nitrite nitrogen were about 10%higher than those of the control group(15?,pH 7.6).Under the condition of 4g/L salt concentration at low temperature,the denitrification efficiency of anaerobic ammonia oxidation was improved.Compared with that without adding salinity at low temperature,the removal load of TN was 0.89kg/(m3·d),and the efficiency was increased by 8%.However,excessive pH and salinity have a serious inhibitory effect on the denitrification efficiency of ANAMMOX.Both pH and salinity can promote EPS secretion.At low temperature,appropriate pH can increase the ratio of PN to PS,and the highest corresponding pH is 8.1.Salinity stimulates the production of EPS from anaerobic ammonia oxidation sludge,and the composition of PN and PS of EPS increases.In the range of 0 g/L to 12 g/L,the PN/PS ratio showed an upward trend.Under the condition of 20g/L,the ratio of PN/PS decreased significantly.The settling and flocculating properties of granular sludge can be significantly improved by appropriate pH.The BW value of granular sludge increases gradually from 9.8%to 17.9%,the ZSV value reaches the maximum at pH 8.1,and the ESS value shows an upward trend.Proper salinity can improve sludge sedimentation and flocculation.Under the condition of 4-12g/L,the BW value of granular sludge increases and ZSV value decreases. |
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