Study Of Alums On Sewage Purifying Effect In Intensive Pig Farm

To improve the sewage treatment effect in intensive pig farm and optimize the treatment process, this study adopted coagulating sedimentation with the combination of alums and sodium silicate for coagulation to test the sewage treatment effect. The sewage from solid-liquid separation and biogas slurry through anaerobic fermentation were separately collected. Different doses of coagulant of alums(1 mg/kg, 2 mg/kg, 3 mg/kg)and coagulant aid of sodium silicate(40 mg/kg, 60 mg/kg, 80 mg/kg) were added. Then the p H value, turbidity(SS, suspended solids), ammonia nitrogen(NH3-N), COD(chemical oxygen demand), total N( TN) value and total P(TP) value in different time period during purification were determined. The content of metallic elements of Cu, Fe, Zn, Mn, Cd, Cr+6and change of fluoride and salinity were also measured to observe the purifying effect of the combination of alums and sodium silicate to sewage in intensive pig farm. The results showed that the treatment effect of biogas slurry through anaerobic fermentation in biogas digester was better than that of the sewage from solid-liquid separation. 24 hours later, the p H value of biogas slurry and sewage decreased 45.58 % and 49.94 %, respectively. Their decreasing range of turbidity reached 52.45 % and 74.26 %. The ammonia nitrogen content of biogas slurry and sewage was not obvious. 24 hours later, the COD of biogas slurry and sewage reduced 19.22 % and 7.86 %, respectively. Their total N value reduced 23.38 %and 14.67 %, and total P value reduced 29.20 % and 21.74 %. 24 hours later, the content of Cu, Fe, Zn, Mn, As, Cr+6 and Cd in biogas slurry and sewage reduced significantly. Their content of Cu reduced 62.99 % and 55.46 %. That of Fe reduced 34.04 % and 31.33 %,that of Zn reduced 38.62 % and 18.78 %, that of Mn reduced 37.93 % and 22.45 %, that of As both reduced 50.0%, that of Cr+6 reduced 44.44 % and 58.33 %, that of Cd reduced45.45 % and 42.86 %. 24 hours later, the content of fluoride and salinity reduced to a certain extent. the fluoride concentration of biogas slurry and sewage reduced 9.4 %and 16.48 %, respectively. Their purity content of salinity reduced 10 % and 18.18 %. It is observed from above results that the coagulating sedimentation effect of sewage from biogas digester is better than sewage from solid-liquid separation. After the processing of coagulating sedimentation, the p H value and turbidity decreased in a large degree during degradation of contaminants, and other indicators are not obvious. The concentration of metallic elements of Cu, Fe, Zn, Mn, Cd, Cr+6 and As decreased in a large degree, and the content of fluoride decreased to some extent. And the addition of 80 mg/kg alums and 3mg/kg sodium silicate in biogas slurry and sewage has better purification effect.