Aquatic environment

Microwave enhanced chemical reduction process for nitrite-containingwastewater treatment using sulfaminic acid


Nan Li , Peng Wang , Qingsong Liu , Hailei Cao

DOI:

Received March 09, 2009,Revised June 05, 2009, Accepted , Available online

Volume 22,2010,Pages 56-61

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High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is di cult to be treated using traditional biological process. In this study, a novel microwave-enhanced chemical reduction process (MECRP) using sulfaminic acid (SA) was proposed as a new manner to treat such type of wastewater. Based on lab-scale experiments, it was shown that 75%–80% nitrite (NO2??) could be removed within time as short as 4 min under 50 W microwave irradiation in pH range 5– 10 when molar ratio of SA to nitrite (SA/NO2??) was 0.8. Pilot-scale investigations demonstrated that MECRP was able to achieve nitrite and chemical oxygen demand (COD) removal with e ciency up to 80% and 20%, respectively under operating conditions of SA concentration 80 kg/m3, SA/ NO2?? ratio 0.8, microwave power 3.4 kW, and stirring time 3 min. Five-day biological oxygen demand (BOD5)/COD value of treated e uent after MECRP was increased from 0.05 to 0.36 (by 620%), which clearly suggested a considerable improvement of biodegradability for subsequent biological treatment. This study provided a demonstration of using microwave irradiation to enhance reaction between SA and nitrite in a short time, in which nitrite in wastewater was completely converted into nitrogen gas without leaving any sludge and secondary pollutants.

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