Study On Improving The Effect Of Pesticide Wastewater Treatment By The Pretreatment Of Coagulation/Ferric-Carbon Micro-Electrolysis

The wastewater of a pesticide plant is divided into high concentrated pesticide wastewater and comprehensive wastewater. The former is from the reaction of amination and the process of cleaning while the latter is from sewage, plant cooling water, etc. The high concentrated pesticide wastewater mainly contains drug butralin, nitrobenzene chlorobenzene and other impurities. The initial concentration of CODcr, SS is32000-35000mg/L,120-170mg/L respectively; The value of pH, chroma multiples is13～14,15000-16500respectively. The CODCr of comprehensive wastewater is50～150mg/L; pH is6～7. The original process of wastewater treatment is "combined process of Fenton oxidation-air flotation-hydrolysis acidification-BIOFOR filter ". The high concentrated pesticide wastewater flows into biochemical treatment system after the treatment of Fenton oxidation-air flotation, mixing with the comprehensive wastewater. The quality of the high concentrated pesticide wastewater is changed for the improvement of this pesticide plant’s production process. Therefore, the effluent wastewater of original treatment process can’t meet the national standard. Taking the continuity into account, we suggest adding coagulation and ferric-carbon micro-electrolysis to the front of the original process.Coagulation of high concentrated pesticide wastewater shows that the initial value of pH is8, the optimum time is20min and the optimum dosage of PAC, PAM is600mg/L,12mg/L respectively. Under the condition of these optimum parameters, the removal rate of CODCr can reach21%. In actual debugging process of coagulation, the value of pH is8, the optimum dosage of PAC, PAM is800mg/L,15mg/L respectively. The removal rate of CODCr can reach18%after stirring20min and precipitating an hour.The best reaction conditions of ferric-carbon micro-electrolysis is found by single-factor analysis. It shows that, when the wastewater’s initial value of pH is2, the dosage of iron and graphite is2.5g/L,1.0mg/L respectively, the concentration of CODCr can be reduced from27000mg/L to17000mg/L after stirring6hours. The removal rate of CODCr can reach36%.The removal rate of CODCr can reach49%after the pretreatment of coagulation-ferric carbon micro electrolysis. It means that the effluent wastewater can meet the requirement of original process.We add reagents three times into Fenton oxidation. The pH is adjusted to7-8with lime after stirring for2hours, at last wastewater through the filter press. The influent concentration of CODCr is300-400mg/L in hydrolytic acidification. The removal rate of CODCr can reach50%after adding appropriate nutrients which can ensure the basic growth of microorganism. The influent concentration of CODCr is lower than200mg/L in BIOFOR filter generally. The CODCr, SS of effluent water can achieve Class A of Integrated Wastewater Discharge Standard (GB8978-1996). The results show that the effect of the original treatment process can be improved with the pretreatment of coagulation/ferric carbon micro electrolysis.