Study On Strengthened Pretreatment For Landfill Leachate By Using Serial Coagulation-precipitation

Garbage is a potential resource. But if not be treated properly, it will be a serious pollution. Now, the main method is hyginene landfill.Treatment of the landfill leachate is the key link of hyginene landfill.The concentration of color, CODcr and ammonia-nitrogen are high, so treatment of the landfill leachate is difficult and the result is not ideal. Generally, the treatment schedule is physical-chemistry combined together with biotechnology. The treatment form is pretreatment-incorporate treatment.The purpose of this thesis is studying on the strengthened pretreatment of the landfill leachate by serial coagulation-precipitation and chemical precipitation, eagering that the effective removal of color, CODcr and ammonia-nitrogen could be obtained. Then the feasible treatment method of landfill leachate can be introduced, and it can be reference for the treatment of other high concentration organism wastewater. The mam content of experiment is described as followes: (1)Selecting the programme. High concentrition of color, CODcr act as collid, so they can be removed by coagulation-precipitation according the quality of collid.To enhance the result, serial coagulation-precipitation was adopted. The water after coagulation-precipitation was treated by coagulation-precipitation again. For amonia-nitrogen, small part of it can be abluted in coagulation-precipitation, and then it can be removed further in the chemical precipitation by making the precipitate.(2)Studying on the performance. pH, dosage, temperature and precipitation time were observed, then the best effect factors were defined. (3) Analyzing the mechanism of the experiment.The result of the test showed that the removal of color and CODcr is high. For ammonia-nitrogen, the removal is lower. Whh the optimal pH for first coagulation-precipitation about 5, by using PFS as coagulant, PFS dosage of 350mg/L, temperature of 20D, precipitation time of 50 min , 42.1% of color, 35.4% of CODcr and 4.4% of ammonia-nitrogen were achieved. With-the optimal pH for scond coagulation-precipitation about 5, by adding PAM as coagulant, PFS dosage of 250mg/L, PAM dosage of 4mg/L, temperature of 20D, precipitation time of 30 min , 52.8% of color, 45.2% of CODcr and 5.1% of ammonia-nitrogen were achieved. The total removal is 72.7% of color, 64.6% of CODcr and 9.27% of ammonia-nitrogen. Cost of serial coagulation-precipitation is 1.68 yuan/m3. So, for color and CODcr, precipitation time is short, the volume of the equipment is small, the cost is cheap ,the removal is effective .The serial method is feasible.With the optimal pH for chemical precipitation about 7 and the ration of Mg2+:NH4+:PO43" was controlled at 1: 1: 1, by using MgSO4-7H2O and Na2HPO4'12H2O as chemicals, MgSO4-7H2O dosage of 11275 mg/L, Na2HPO4-12H2O dosage of 4140mg/L, temperature of 20D , precipitation time of 30 min, 18.4% of ammonia-nitrogen was achieved. The total removal is 25.96%. The effect factors are pH and the dosage of the chemical. Cost of chemical precipitation is expensive.