Evaluation of separate urine collection and treatment to augment existing wastewater treatment works

Simultaneous increases in wastewater loads and effluent quality demand improved nutrient removal techniques. A simple technique for nitrogen removal is post-denitrification with methanol. The tradeoff between better effluent vs. methanol consumption is debatable. Methanol dosing is not only un-sustainable in the long term, but the cost of methanol is also becoming increasingly important. Urine contains 80% of the total nitrogen (N) and 50% of the phosphate in wastewater. Separate collection and treatment of urine could improve existing treatment works and diminish the need for post-denitrification. In this paper, a nitritation-denitrification process is proposed where 20-30% of the N in urine is removed with the COD available in urine. The treated urine consists of ammonium-nitrite, which is to be introduced to the anoxic zone of a conventional treatment plant. Optimal denitrification via nitrite is possible with COD from other wastewater sources. The case study presented here shows that 40-50% urine separation and improvement of the flow scheme would improve effluent quality from 19 to 10 g N/m3, which would eliminate the need for post-denitrification.