Shortcut Biological Nitrogen Removal from Coal Gasification Wastewater in Three-Stage MBBRs.

Abstract

A lab-scale aerobic-anoxic-aerobic (AE1-AN-AE2) MBBR system was tested for the removal of COD, <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm01.gif"/>, SCN-, phenols, and nitrogen from coal gasification wastewater, using a shortcut biological nitrogen removal process. Dissolved oxygen concentration in AE1 was maintained at 1.0 to 2.0 mg/L to ensure stable <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm12.gif"/> accumulation. Adding methanol wastewater to AN guaranteed denitrification efficiency. AE2 ensured high removal rates of <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm23.gif"/>, SCN-, and phenols. The effects of influent pollutant concentration and hydraulic retention time (HRT) on nitrogen removal were studied. Improving the dissolved oxygen concentration in AE1 eliminated the negative effect of increased organic loading on nitrification, but it affected the stability of nitrosation. Shortening the HRT had negative effects on the performance of the system and performance recovered after it was extended. The average total nitrogen removal rate was 82.6% with a CODmethanol/<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="01977-ilm34.gif"/> ratio of 3.5. Biomass and activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria were measured to understand the evolution of nitrification.