Preparation of New Type of Coagulant by Fly Ash and Its Application for Slaughter Wastewater Treatment

Due to the enormous amount of fly ash and its pollution to environment, fly ash was investigated for preparation of coagulant. By measuring the Al₃₊ and Fe³⁺ solubility rate by changing the dosage of Na₂CO₃, it was concluded that the best ratio of Na₂CO₃ and fly ash was 0.8. At the condition of the best ratio, 805 and 1.5 h were recognized the best reaction temperature and reaction time. On the basis of these results, COD and SS removal efficiency of slaughter wastewater using fly-ash coagulant was measured at the condition of different pH, temperature and coagulant dosage, which was compared with the effectiveness of aluminum sulfate and PAC. For pH of 6-7, COD and SS removal efficiency of the three coagulants were the best. The highest SS removal efficiency of Al₂(SO₄)₃, PAC and fly-ash coagulants was 92.7%, 94.2%, 96.3%, respectively. The most COD removal efficiency of Al₂(SO₄)₃, PAC and fly-ash coagulants was 67.9%, 69.1%, 72.4% respectively. Within the temperature range of 12 to 29°C, the coagulation effect of PAC and fly-ash coagulants were found slightly affected by temperature, within 4%. The optimum dosage of all the three coagulants was about 1mmol/L. All of this explored a new way for the resource utilization of fly ash.