Control of chemical and microbial pollutants in liquid-solid phases of sewer pipes by Fe(II)-activated persulfate: Performance and mechanism of simultaneous removal

Most of the problems such as odor and corrosion in sewage systems originate from the biochemical reactions of liquid and solid phases in the pipes. Suppressing the activity of microorganisms and biofilms in the sewers is conducive to maintaining the proper operation of the sewer system. This study verified the removal of microorganisms and sulfides from wastewater and the inhibition of biofilm activity by peroxodisulfate (PDS) with the activation of ferrous ions (Fe(II)). Fe(II)/PDS can achieve efficient microbial inactivation within a reaction time of 20 min after a single dosing (Up to 95% removal of planktonic bacteria in the liquid phase), and the sulfide reduction can be maintained for more than 5 days, providing the possibility of intermittent dosing. The sulfide concentration can be maintained below 4 mg/L by intermittent dosing (average dosing interval is 10 days) during the long-term operation of the reactor. Dissolved organic matter (DOM) changes in sewage predict biofilm destruction. Changes in the biofilm microscopic morphology, extracellular polymer substances (EPS) fraction, biofilm functional groups, and microbial community revealed the effects of Fe(II)/PDS on the solid–liquid phase material fraction and biofilm structure of the sewage pipeline. The mechanism of biofilm disruption was analyzed based on the identification of strongly oxidizing active species in the Fe(II)/PDS system. This study shows that it is feasible to develop an efficient and cost-effective sulfide and microbial control strategy using Fe(II) with PDS in sewage systems.