Ferrous iron (Fe(II)) activated persulfate has been reported to be very effective for the oxidative removal of various organic pollutants, although an authoritative characterisation of the mechanistic details of this system is lacking. Studies of Fe(II)-activated persulfate oxidation of <sup>14</sup>C-formate as a function of pH, iron and persulfate dosage are described here with formate used as a surrogate organic substrate due to its simple structure and well-defined oxidation pathway. As expected, the oxidation rate increased with decreasing pH and increased with increasing persulfate and iron concentration. It was also found that Fe(II) was completely oxidised to Fe(III) within the first 2 minutes of the reaction. As the organic oxidation continued after this period, this led to the conclusion that the catalytic oxidation of formate was actually driven by the ferric iron/persulfate system (Fe(III)/PS) rather than Fe(II)/PS. The Fe(II)/Fe(III)/PS process was subsequently used for the treatment of the polymeric matter present in concentrate obtained from the nanofiltration of membrane bioreactor permeate. Humic acid, one of two classes of polymeric material present, was found to be the major component of the concentrate. More than 80% of total organic carbon (TOC) was completely oxidised after 7 days using Fe(II)/Fe(III)/PS with the contribution of adsorptive removal shown to be negligible. Biological oxygen demand (BOD<sub>5</sub>) increased 3.5 times while the chemical oxygen demand (COD) after 1 day of treatment was close to 0 mg/L, indicating significantly improved biodegradability and polymer breakup. The results from Liquid chromatography-Organic carbon detection (LC-OCD) also revealed a rapid degradation of humics to building blocks after 1 hour, followed by a slow decrease in the concentration of the building blocks. Less than 10 % of PS was consumed during 24 hours. As such, we conclude that Fe(II)/Fe(III)/PS appears to be a promising alternative for the treatment of polymeric organics present in wastewaters.

Degradation of polymeric organics in domestic wastewater using iron-activated persulfate

2019 Spring National Meeting

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