Treatment of high-strength wastewater by Fe(2+)-activated persulphate and hydrogen peroxide.

Ferrous ion-activated persulphate and hydrogen peroxide were studied for the treatment of real high-strength industrial effluent. The Fenton process demonstrated greater organic load removal, biodegradability improvement and toxicity reduction as well as lower treatment cost than the activated persulphate system. However, the use of an activated persulphate process was more favourable due to the exothermic effect intrinsic to the Fenton reaction, which resulted in a rapid increase in the temperature of the high-strength wastewater along with excessive foam formation. Overall, for the H2O2/Fe(2+) and [Formula: see text] processes, the application of a chemical oxygen demand (COD)/oxidant/Fe(2+) weight ratio of 1/0.4/0.075 resulted in a COD removal of 58 and 50%, a 7-day biochemical oxygen demand/COD ratio increase from 0.14 to 0.3 and 0.23, and an increase in the EC50 (Daphnia magna) by 6.5-fold and 2.9-fold, respectively. The stepwise addition of the oxidant and activator was favourable for the Fenton process and resulted in negligible improvement in the wastewater treatment efficacy in the activated persulphate system.

Column experiment on activation aids and biosurfactant application to the persulphate treatment of chlorophene-contaminated soil.

An innovative strategy integrating the use of biosurfactant (BS) and persulphate activated by chelated iron for the decontamination of soil from an emerging pollutant chlorophene was studied in laboratory down-flow columns along with other persulphate activation aids including combined application of persulphate and hydrogen peroxide, and persulphate activation with sodium hydroxide. Although BS addition improved chlorophene removal by the persulphate treatment, the addition of chelated iron did not have a significant influence. Combined application of persulphate with hydrogen peroxide resulted in a significant (p≤.05) overall improvement of chlorophene removal compared with treatment with persulphate only. The highest removal rate (71%) of chlorophene was achieved with the base-activated persulphate, but only in the upper part (of 0.0-3.5 cm in depth) of the column. The chemicals at the applied dosages did not substantially influence the Daphnia magna toxicity of the effluent. Dehydrogenase activity (DHA) measurements indicated no substantial changes in the microbial activity during the persulphate treatment. The highest oxygen consumption and a slight increase in DHA were observed with the BS addition. The combined application of persulphate and BS at natural soil pH is a promising method for chlorophene-contaminated soil remediation. Hydroquinone was identified among the by-products of chlorophene degradation.