Enhancing biological removal of nitrogen from wastewater in activated sludge process

Abstract

The removal of total nitrogen from wastewater has become a worldwide emerging concern because the compounds of nitrogen, ammonium, nitrite, also nitrate are toxic to aquatic species and causes eutrophication in natural water environments; although activated sludge technology is old, but until now it is effective in the removal of nitrogen compounds. To enhance the removal of nitrogen compounds, a modified process including the usage of internal mixed liquor recycling pump (IMLR), with variable rates starting gradually from one to fifth of influent flow. A Pilot plant consists of three tanks, the first and the second tanks are rectangular, and the third is circular with a conical bottom which acts as a final sedimentation tank. The experiments divided into four phases; phase (1) consists of (A.T), anoxic T. and finally, sedimentation tank with using (IMLLR) rates from (1-4) influent flow, phase (2) as phase (1) but without using (IMLR), phase (3) consists of anoxic tank, (A.T) and final sedimentation tank with using (IMLLR) rates from (1-5) influent flow, finally phase (4) as phase (3) but without using (IMLLR), the average DO in (A.T) about 2.5mg/l, the temperature ranged from (18–21), PH ranged from (6.5–8). Total nitrogen removal was 61.5% in phase one, 27% in phase two, 64.5% in phase three, and 27% in phase four. The most effective removal of nitrogen in phase (3), with rateQIMLR = 2QINFachieve 64.5% of total nitrogen removal, then in phase (1) with rate QIMLR=3QINF. Achieve 62.39% of total nitrogen removal.