Advantages of continuous Fenton reaction over the traditional batch process in wastewater treatment in a single and two-step mode

The article presents results of laboratory studies on the oxidation processes, by using Fenton's reagent for treatment of colourful and odour-emitting industrial wastewater characterized by high CODCr - 66 g O-2/L and TOC - 18 g/L values and pH below 1. Analyses were conducted for a continuous and cyclic process, divided into single- and two-step modes. Tests were performed for different initial mass ratios between CODCr:H2O2:Fe(II). It was found that the highest reduction of COD(Cr )and TOC parameters, corresponding with a mass reduction efficiency equal to 75% and 65%, respectively, occurs for the two steps continuous Fenton process, at a mass ratio of CODCr:H2O2:Fe(II) equal to 1.0:2.5:1.25. The advantage of conducting the process in a continuous (flow) mode over a cyclic (batch) has been demonstrated and proven mostly by the stabilization of temperature and pH value of the reaction mixture, foaming limitation and decrease of the reaction time. It was also found that during a two-step continuous process CODCr removal efficiency increased even by 40% compared with the single-step process using the same amount of the reagents. Moreover, generation of solid wastes was reduced at 18.8% and other advantages such as increase of arsenic removal were also obtained in a two-step continuous Fenton reaction.