Impacts of permanganate/bisulfite pre-oxidation on DBP formation during the post chlorine disinfection of ciprofloxacin-contaminated waters

Bisulfite-activated permanganate (PM/BS) oxidation process can oxidize ciprofloxacin in complex water matrices rapidly. However, effects of PM/BS pre-oxidation on the formation of disinfection byproducts (DBPs) during post-chlorination of ciprofloxacin-contaminated waters need to be addressed. This study investigated the formation of trihalomethanes (THMs), haloacetonitriles (HANs), haloketones and trichloronitromethane during chlorination of ciprofloxacin-contaminated humic acid (HA), bovine serum albumin (BSA) and alginate solutions, and revealed the effects of PM/BS pre-oxidation on ciprofloxacin degradation and DBP formation during post-chlorination, considering the presence of Br−. Only THMs and HANs were quantifiable. THMs were the most abundant. Ciprofloxacin-contaminated HA exhibited the highest formation potential of DBPs and integrated toxic risk value (ITRV). In the absence of Br−, PM/BS pre-oxidation reduced or hardly affected the toxicity risks derived from DBPs formed from the post-chlorination. However, the presence of Br− greatly reduced the degradation of ciprofloxacin (30–50%) in various waters. In the ciprofloxacin-contaminated waters containing Br−, the total ITRVs of DBPs formed from post-chlorination increased by 60%–800% with PM/BS pre-oxidation, attributing to the enhanced formation of DBPs especially bromochloroacetonitrile and dibromoacetonitrile. Overall, PM/BS is a potential pre-oxidation technology for the treatment of ciprofloxacin-contaminated waters without bromide. [Display omitted] •Ciprofloxacin-contaminated HA had the highest risks in terms of DBP formation.•Without Br−, PM/BS oxidation reduced or hardly affected subsequent DBP formation.•Br− significantly inhibited the degradation of ciprofloxacin in all samples.•In most waters containing Br−, PM/BS pre-oxidation enhanced the formation of DBPs.•With Br−, PM/BS oxidation increased toxic risks of DBPs formed in post-chlorination.