Total Chlorides and Bromines in Sewage Sludge and Variation of Total Bromines in Hydrolysis and Acidification Processes

Abstract:

The combined method of automatic quick furnace and ion chromatography was applied to investigating total chlorides and bromines in sewage sludge from eight wastewater treatment plants as well as total bromines in the degraded samples collected from hydrolysis and acidification processes.The results show that the content of total chlorides (0.63~3.6 mg·g-1) in sewage sludge is about one order of magnitude higher than that of total bromines (0.04~0.20 mg·g-1).Meanwhile,the content of total chlorides in this study is 2~4 orders of magnitude higher than that of organic chlorides in literature (0.08~6.9 mg·g-1).As for the hydrolysis and acidification processes,total bromines of sludge flocs are significantly degraded at pH 10.0 when compared with pH 5.5.However,the superiority of thermophilic condition on the degradation of total bromines of sludge flocs is uncertain when compared with mesophilic condition.This study reveals for the first time that the hydrolysis and acidification processes at pH 10.0 could reduce the total bromines of sludge flocs and thereby reduce the risk of sludge disposal (i.e.,land application,incineration).However,the volatile fatty acids (VFA) produced in the fermentation process at pH 10.0 may increase the risk as the carbon sources of tertiary treatment in WWTP,owing to the total bromines transferring from the solid state to the liquid state.