Influence Of Oil On The Water Quality Stabilizers And Removal Of Oil From Oily Sewage Using Enzyme

Oily sewage is a kind of organic wastewater with toxic and hazardous, moreover it might affect the normal function of the water quality stabilizer. At present, the combination craft of oil separation-flotation-aeration to process oily wastewater is adopted by most factories in domestic, but its oil removal efficiency is difficult to reach the national discharge standard. Therefore, it is a urgent task for the water-operators to develop high-efficient, environmental-friendly and economical wastewater treatment technology. There are advantages of high catalysis efficiency, mild processing condition, short reaction time and wide applicability for enzymatic technology. So that enzymatic technology has become a quite important and applying potentiality new technology in wastewater treatment in recent years.Firstly, the influences of oil on the performances of scale inhibitors, corrosion inhibitors, dispersers and bactericides in synthetic oily containing wastewater were investigated in this paper. Secondly, the optimum technique conditions of catalysis reaction of oil with HRP, Laccase and Fenton reagent had been studied. The enzymatic reaction mechanisms and reaction kinetics characteristics were also researched. In addition, the impacts and variation rules of metal ions and reaction assistants on the enzyme catalytic oxidation were discussed. Finally, the oil removal efficiencies were compared synthetic oily wastewater with actual oily wastewater. The results are as follows:1. The oil in the industrial circulating water had great influence on the performances of water stabilizing agents at temperature 25℃. All the efficacies of scale inhibitors, corrosion inhibitors, bactericides and dispersers were decreased. The oily containing water made the relative supersaturation of calcium carbonate declined under scale inhibitors (HEDP and PBTCA). The function of corrosion inhibitor (HEDP) was weakened by diesel oil with low concentration, with the increase of corrosion inhibitor concentration the corrosion rate of carbon steels was controlled at a certain extent. However, when the concentration of diesel oil was up to 200 mg/L, it was conducive to protect carbon steels. The diesel oil in water had slight influence on germicidal efficacies of sodium dichloroisocyanate and isothiozolone when the concentration of bactericides were low, and had no influence on efficiencies as the concentration of bactericides are high. With the increase of diesel oil the dispersing power on ferric oxide of dispersants (T-225 and YSW-301) was decreased when the oil concentration was lower than 60mg/L.2. Fenton process was used to treat oily wastewater. The conditions of Fe²⁺ dosage 4 mM, H₂O₂ dosage 40 mM, pH 3.0 and temperature 30℃over 2h of reaction period were determined for the initial oil concentration of 120mg/L in the water sample, 48.4% of oil removal efficiency was obtained under these conditions.3. The optimum conditions to remove diesel oil from the synthetic-water sample by catalyzed oxidation with horseradish peroxidase and H₂O₂ were 0.8U/mL of HRP, 250 mg/L of H₂O₂, 160 mg/L of PEG, 7.4 of pH, 27℃of temperature, 3 hours of reaction time for the initial oil concentration of 120mg/L, and the oil removal efficiency was as high as 75.82 %. The oil removal efficiency was up to 82.25 % for the actual oily wastewater under the same conditions. Cu²⁺ and Mn²⁺. inhibited the enzymatic activity, but Fe²⁺, Mg²⁺ and Ca²⁺ enhanced the catalytic reaction of HRP. The reaction mechanism of oxidation of oil catalyzed by HRP could be considered as ping-pong kinetics. There were no obvious differences in ratio of K_m/V_max of kinetics parameter catalyzed diesel oil by HRP at different concentrations of H₂O₂, and it was close of V_max of kinetics parameter catalyzed H₂O₂ by HRP at different concentrations of diesel oil. H₂O₂ was a kind of inhibitive substrate and had great influence on the enzymatic reaction.4. The removal of oil from synthetic oily containing wastewater by catalyzed oxidation with laccase was investigated. The removal efficiency of oil was as high as 83.15% at the optimum technique conditions of 3U/mL of laccase, 120 mg/L of chitosan, 6.0 of pH, 30℃of temperature, 6 hours of reaction time for the initial oil concentration of 120mg/L in the water sample. The oil removal efficiency of actual oily wastewater was over 93 % under the same conditions. The catalytic efficiency of Laccase is affected by high concentration of Cu²⁺ and Fe²⁺. There was no remarkable difference in K_m catalyzed diesel oil by Laccase. Compared with HRP, Laccase was more suitable for the degradation of diesel oil in water because of better affinity between Laccase and diesel oil.These results were illustrated that it was totally feasible to treat oily sewage with HRP and Laccase. The residual concentration of diesel oil is under 10 mg/L when the actual oily water is treated with the two enzymes, and the handled wastewater can meet the national sewage discharge standard. These may provide feasibility basis for industrialized application catalyzed oil by enzymes in the treatment of oily containing wastewater, and also give necessary technical conditions and data for industrialzation design in the future.