Self-regulating mechanism of sludge on cross-factors of high mass concentration NO2--N denitrification
High mass concentration of nitrite nitrogen(NO2--N,＞100 mg·L-1)will inhibit or even kill microorganisms in the denitrification process,which will affect the denitrification effect of industrial wastewater,resulting in excessive total nitrogen in the effluent.In order to study the effect of high concentration of NO2-N on sludge,track the recovery ability of the affected sludge,batch experiments were used to treat wastewater with different pH(6.5～9.5)and different NO2--N mass concentration(10～400 mg·L-1).The results showed that free nitrite(FNA)was the main inhibitory factor of denitrification.When the concentration of FNA was higher than 0.03 mg·L-1,it could have a short-term irreversible effect on the normal denitrification of sludge,being the result of the combined action of concentration and duration.When FNA was lower than 0.01 mg·L-1,high nitrite concentration also inhibited denitrification.But the inhibition can be reversed by sludge washing,or even only by the domestication of sludge itself.During denitrification,microorganisms had an ability to spontaneously adjust the pH of the environment within a certain range.The alkalinity change in the system during denitrification was affected by the carbonate buffer system.The higher the pH,the better the water buffering ability.
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