The effect of submerged filter and ozone on biological treatment of wastewater

Wastewater treatment is carried out with various techniques. The conventional techniques are used for treatment of wastewater containing biologically active materials. The limitations of active-sludge method are production of sludge and failure of removal of carbohydrate and organic containing pollutants. Combination techniques are used successfully for treatment of industrial effluents including petrochemical, textural and similar wastewater. The aim of this study was to perform a combined biological system including fixed media reactor (Biofilm system) and ozonation and to compare the results with those of the conventional techniques. This experimental-applicable study was performed to construct an experimental model using an aerated fixed film biological reactor with ozonation. At first, the imported and exported parameters of treatment plant of Shahrekord were tested. Then, following the set up of a pilot plant, the effluents of the plant using biological treatment with and without ozonation were measured. Our results showed that the mean of chemical oxygen demand (COD) in the pilot input was 541.2±171.3 mg/lit and in its output at the first and the second step was 226.6±194.4 and 64.1±26.6 mg/lit, respectively (p<0.05). The mean of biological oxygen demand (BOD) in the pilot input was 227.9±78.2 mg/lit and in its output at the first and second step was 106.6±64.5 and 55.8±30.4 mg/lit, respectively (p>0.05). The percentage of decolonization was 80 to 90 percent. The efficiency of ozone transfer to wastewater was 35 to 45 % and ozone consumption for each gram of COD removal was 0.35 to 0.75 milligram. The results indicated that the combination of ozonation and fixed media biological reactors are strong tools for treatment of pollutants in wastewater. Removal of organic pollutants was considerably higher than that of the conventional methods and the sludge production was the lowest.