| Electronics industry wastewater wastewater has been produced, which includes hypophosphite, at the same time. As the wastewater is discharged into water body, it will cause great threat to the environment. Fenton process is widely used to remove hypophosphite in the wastewater. However, it has been noted that Fenton process requires long oxidation time and produces much chemical sludge. In addition, its cost of p H adjustment is high and its treatment efficiency is unstable. Ozone and hydrogen peroxide have strong oxidizability and they are more useful to the oxidation of hypophosphite. Therefore, the combination, which contained ozone, hydrogen peroxide and ferrous sulfate, was conducted to realize the cost-effectiveness of hypophosphite oxidation and TP removal. At a condition of organic matter and heavey metals, the correlated influential factors of ozone/hydrogen peroxide/ferrous process were investigated on the hypophosphite oxidation and TP removal, by which the process was optimized. Finally, the real wastewater of advanced manufacturing industry was selected to examine and verify the TP removal performance in a pilot scale experiment.First of all, different processes were researched, which contained O3, O3+H2O2, O3/H2O2/Fe2+, O3+Fe2+, O3/Fe2+/H2O2, O3+H2O2+Fe2+ and Fenton process. The experimental results revealed that O3/H2O2+Fe2+ process performanced well in the hypophosphite oxidation and TP removal. O3 and H2O2 were added into the wastewater firstly and ·OH was produced to oxidize hypophosphorus. Then ferrous was brought into the system, which catalyzed O3 and remove phosphorus. The optimized p H of O3/H2O2+Fe2+ process is 7.0, whose hypophosphorus oxidation rate and TP removal rate reached 74% and 65%. The appropriate concentration of hydrogen peroxide had positive effect on process efficiency and it should be added continuously.Co-existing metallic ions and organic matters in bulk solution was also researched. High concentration of Ni2+, Cu2+, citric acid and humic acid showed apparently negitive effect on hypophosphite oxidation and influence on TP remova in the O3/H2O2+Fe2+ process. However, EDTA decreased the efficiency of hypophosphite oxidation and TP remova in all concentration. The process got certain removal rate of metallic ions and organic matter.Considering the bench scale experiments, ozone/hydrogen peroxide/ferrous process showed higher hypophosphite oxidation and TP removal rate than Fenton process. The results revealed that after 60mins’ treatment, hypophosphite was oxidized completely and TP concentration was below 0.5 mg/L, which satisfied the discharge standard, in the ozone/hydrogen peroxide/ferrous process. However, in the treatment of Fenton process, it needed 100 mins to realize the effect above. The addition of Ca(OH)2 enhanced TP removal and guarantee the p H of effluent after the treatment of ozone/hydrogen peroxide/ferrous process. And, the chemical sludge in the ozone/hydrogen peroxide/ferrous process process was just 50~65% of that in the Fneton process, which saved the cost of sludge treatment. ozone/hydrogen peroxide/ferrous process made TP removal more stable than that in the Fenton process.Finally, the pilot scale research comparison between ozone/hydrogen peroxide/ferrous process and Fenton process was carried out. When the concentration of TP increased, the dosage of ozone, hydrogen peroxide and ferrous sulfate needed to be raised at the same time, which promised the qualified effluent. Compared with Fenton process, the cost of ozone/hydrogen peroxide/ferrous process saved more than 2.5~4.2 yuan/t in the treatment of different hypophosphite concentration wastewater. The chemical sludge production and hydraulic retention time of ozone/hydrogen peroxide/ferrous process was just 60% and 1/2~2/3 of Fenton process. In the continuous experiment, the removal of TP in the ozone/hydrogen peroxide/ferrous process was more stable than that in the Fenton process. |
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