The Study Of Dewatered Sludge Volume Reduction Using Potassium Ferrate

With the development of urbanization, the capacity of wastewater treatment is increasing. Because the wastewater treatment plants are increasing, more and more active sludges are produced. The safe treatment and disposal of these sludges have become one of the major social problems, which lead to a technical bottleneck for the wastewater treatment in the environmental fields. The harmless reduction, stabilization and reusing of the sludge from the wastewater treatment plant are technically restricted by its high moisture content. Because the treatment and disposal of the sludges have become a serious problem, it’s deep dewatering becomes to be very necessary.Potassium ferrate is an environmental friendly agent for the water and wastewater treatments. It has such excellent properties as oxidation, coagulation, disinfection etc. The domestic and international research progress of the sludge reduction technology is reviewed. The hypothesis of application of potassium ferrate to the sludge reduction technology is proposed. The feasibility and mechanism were investigated by the way of the detailed designed experiments.With comparing and analyzing the potassium ferrate production and analysis methods, the calcium hypochlorite oxidation method to produce potassium ferrate was studied. The potassium ferrate of80%purity was prepared in the laboratory. A method based on spectrophotometry of measuring the ferrate concentration was used.In order to study the best dosage and reaction conditions of potassium ferrate, we design series of the single factor experiments. The study shows that the sludge treated by potassium ferrate could be reduced96%with the dosage of45g/Kg of potassium ferrate. It showed sludge dewatering ability had been improved. Meanwhile, the sludge’s treatment conditioning could reduce CST effectively. The results also illustrated the sludge dewatering ability could be improved by increasing the dosage of potassium ferrate. Besides, the study also shown the treatment affectivity of the MLVSS/MLSS and COD was increasing with the dosage increasing. The optimum dosage of potassium ferrate was between60g/Kg TDS and90g/Kg TDS.Under the conditioning of dosage60g/Kg TDS of potassium ferrate, when80ppm cationic polyacrylamide was added, the results shown that63.13%moisture content of sludge cake was obtained, which indicated the combining of potassium ferrate with cationic polyacrylamide could have better treatment result than that of only using potassium ferrate.Potassium ferrate, as a strong oxidizing agent, was shown it could effectively oxidize activated sludge cells. Therefore, the activated sludge microorganisms in the cell lysate could release intracellular substances. The cell lysate produces organic compounds could be metabolized by the activated sludge. Thus, a part of the total carbon would be transferred to CO2. So that the total amount of sludge would be decreased. In addition, the strong oxidization of potassium ferrate would kill many bacteria to achieve the effect of deodorant and improve the working environment.