Example 15.5 A domestic wastewater with a flow of 20,000 m /d is to be nitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. The concentration of nitrate nitrogen after nitrification is 30 mg/L. (a) Calculate the amount of bicarbonate alkalinity required for nitrification. (b) Determine if the primary treated sewage can produce enough alkalinity to satisfy nitrification requirement. Assume that 97% of the nitrate nitrogen is destroyed in denitrification.


The literature reports cell yields Ym for Nitrosomonas of 0.04—0.29 mg of the bacteria per mg of NH4—N destroyed and cell yields for Nitrobacter Yn of 0.02—0.084 mg of the bacteria per milligrams of NO2—N destroyed.

0.05/113 n

Therefore, r. , 0.186 + 0.0062(1-0.186n cn m . [ Amt ]mmoi = -r_0786-- (2.14) = 0.50 mmol/L Ans

mmol sewage


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