The Removal Of Oscillatoria By Per-Oxidation Of Potassium Permanganate And Co-Coagulation With Mineral And PAC

In the past few years, water safety has been seriously influenced by the bloom events in China. At present the main method for purifying water in water treatment plants is coagulation with inorganic polymer flocculants polyaluminum chloride (PAC). However, the formed floccules are too incompact to subside effectively to separate algae from water effectively. And excessive dosage of PAC will increase the concentration of residual aluminum, which will pollute the water. The flocculation effect could be improved by adding clay mineral, but the flocculating constituents may floating up, because of the oxygen that released by algae photosynthesis.The removal of Oscillatoria by using the potassium permanganate as the per-oxidant agent was studied in this work. The activity of Oscillatoria was inhibited. The floccules will not floating up after the settlement, because of oxygen that released through photosynthesis. Then, algae was removed by using PAC and kaolin as the co-coagulation agents.Algae toxin is extremely harmful to human body. How to prevent algae toxin from releasing into the water due to the destruction of algae cell walls during the oxidation process should also be paid attention.Dosage of potassium permanganate, kaolin and PAC, pre-oxidation time of potassium permanganate, particle size of kaolin, were determined by orthogonal experiments. The suitable removal results were: pH8.0, potassium permanganate concentration 0.5 mg/L, PAC concentration 2.5mg/L, kaolin dosage 50 mg/L, particle size 160 mesh, and pre-oxidation time 15 min. Under these conditions, removal rate of turbidity and chlorophyll (a) reached 96.9% and 98.3% respectively, which is better than the effect of removal of algae by flocculating with kaolin.The results showed that the hydrated manganese dioxide acting as the condensation nucleus promoted the flocculation process by forming the dense aggregates to settle the Oscillatoria.And cell walls of Oscillatoria were not destructed during the oxidation process and therefore the leak of poisonous substances was avoided. Water quality has been improved.