Microwave enhanced chemical reduction process for nitrite-containing
wastewater treatment using sulfaminic acid |
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Authors: | Nan Li Peng Wang Qingsong Liu and Hailei Cao |
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Institution: | State Key Lab of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China |
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Abstract: | High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is difficult 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 (NO_2~-) could be removed within time as short as 4 min under 50 W microwave irradiation in pH range of 5-10 when molar ratio of SA to nitrite (SA/NO_2~-) was 0.8. Pilot-scale investigations demonstrated that MECRP was able to achieve nitrite and chemical oxygen demand (COD) removal with efficiency up to 80% and 20%, respectively under operating conditions of SA concentration 80 kg/m~3, SA/ NO_2~- ratio 0.8, microwave power 3.4 kW, and stirring time 3 min. Five-day biological oxygen demand (BOD_5)/COD value of treated effluent 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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Keywords: | microwave-enhanced chemical reduction process nitrite-containing wastewater sulfaminic acid |
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