Achieving stable partial nitrification by combining heat-shock sludge and intermittent gradient aeration
A novel strategy combining heat shock and intermittent gradient aeration was proposed to achieve partial nitrification.The impact of the combined strategy on nitrifying bacteria was explored in a 120-day experiment.Furthermore,the long-term stability of partial nitrification under the combined strategy was optimized by adjusting the sludge discharge ratio as the primary variable.The results demonstrated that intermittent gradient aeration(DO:2.0mg/L//DO:1.2mg/L//DO:0.5mg/L)could rapidly restore the activity of ammonia-oxidizing bacteria impaired by thermal treatment without external carbon source added,and NAR achieved over 80%in 5days.During the stabilization phase,SAOR and SNPR were 30.12 and 6.69mg N/(gVSS⋅h),respectively.And the effluent ammonia concentration was below 0.1mg/L with nitrite and nitrate concentration of 53.42 and 8.01mg/L.Further analysis showed that the NAR remained at 88.96%when the sludge discharge ratio was set at 1%,while it tended to decrease with the discharge ratio of 0.5%or another value of 1.5%.
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