Hybrid System of Fenton Process and Sequencing Batch Reactor for Coking Wastewater Treatment

The aim of the work was to investigate the treatment efficiency of coking wastewater in a hybrid system combining the Fenton process with an SBR reactor. The Fenton reaction was optimised using variable reagent doses of 0.75, 1.0, 1.25 and 1.5 g/L for iron ions and 750, 1000, 1250, and 1500 mg/L for H2O2. The effects of Fe2+ and H2O2 concentration on BOD, COD, TOC, TN N-NH4+ and BOD/COD ratio were studied in detail to optimise the pretreatment performance. The selection of the most favourable parameters for the Fenton reaction was based on the frequency of occurrence of a different combination of the chemical reagents. The most beneficial doses were found to be 0.75 g/L of iron (II) ion and 1000 mg/L of hydrogen peroxide, at which the COD reduction rate was about 40% and a high increase in the BOD5/COD ratio from 0.1 to 0.31 was observed. Moreover, the obtained results showed that the efficiency of removing organic pollutants and nitrogen compounds was higher in the SBR reactor fed with pretreated wastewater. However, the relatively low efficiency of removing TKN (25%) and NH4+ (21%) indicates the presence of toxic substances in them that may inhibit the removal of nitrogen compounds.