Nitrification performance evaluation of activated sludge under high potassium ion stress during high-ammonia nitrogen organic wastewater treatment

The recycling reverse osmosis(RO)membrane concentrate of some high-ammonia nitrogen(NH_(4)^(+)-N)organic wastewater to the biological unit could cause potassium ion(K^(+))accumulation,thereby affecting the removal of NH_(4)^(+)-N by activated sludge.Thus,the effects of high K^(+) stress on activated sludge nitrification performance was studied.The results showed that the high K^(+) stress promoted the floc sludge to produce more extracellular polymers(EPS),which accelerated the sludge sedimentation and enriched the biomass in sequential batch reactors(SBRs).The ammonia oxidation process and nitrite(NO_(2)^(-)-N)oxidation process were further analyzed in the nitrification process.High K^(+) stress enriched ammonia oxidizing bacteria(AOB),which ensured the efficient ammonia oxidation process in SBRs,and ensured the removal rate of NH_(4)^(+)-N was maintained above 93%.However,high K^(+) stress(15g/L KCl)inhibited the activity of NO_(2)^(-)-N oxidizing bacteria(NOB)and reduced the abundance of NOB,thus leading to the accumulation of NO_(2)^(-)-N,and finally worsened the nitrification performance of activated sludge.In short,the performance of activated sludge will not be inhibited when the K^(+) in the wastewater does not exceed 5.23 g/L.The results could provide a reference for the optimization of the biological performance in treating high-NH_(4)^(+)-N organic wastewater with activated sludge coupled RO membrane treatment process.