Study On The Treatment Method Of Seed Coating Wastewater

Seed coating is more and more popular as high efficiency,safety and environmentally friendly pesticide.During seed coating's production and purification process,a large amount of high COD concentration,high chroma,salinity and bio-inhibitory waste-water are discharged.According to the properties of such waste-water,and to meet the first discharge standard(GB8978-1996),we used cogulation-anaerobic-aerobic-deep oxidation combined process to treat the seed coating wastewater(SCW).Take COD,chroma as the key indicators to the treatment effect on processing unit and combined process.During the coagulation,the effects and the dosage of coagulants were investigated.It was found that the coagulation had obvious effect.These results showed that the effect of PAC/PAM was favorable,he removal efficiencies of COD and chroma were 81.7%and 56.3%,respectively.And BOD5/COD ratio was improved from 0.28 to 0.43,implying the higher biodegradability of SCW.Pretreated waste-water by coagulation was pumped into biochemical unit.During the anaerobic,when inffluent COD was 900.0 mg/L,and the COD volume loading was 0.8 kgCOD/m3 d,the effluent COD and chroma from anaerobic reactor was about 605.3 mg/L and 150 times,and the removal rates was about 33%and 80%.with HRT for 24 h.As for contact oxidation ponds,activated sludge inoculation method was made for starting and culturing for several days.Experimental study shows that the effluent COD stable at the average on 203.7 mg/L for contact oxidation with HRT=24 h,DO was between 4.0 and 6.0 mg/L.Fe(?)/NaC10 oxidation technology was used as the deep treatment,the effects of dosages of NaCIO and FeSO4,and reaction conditions were investigated.Through several single factor experiments,it was identified that the COD removal of 55.2%at optimal conditions:NaClO dosage 5.0 ml/L,FeSO4 dosage 0.4 g/L,stir rapidly at 200 r/min for 1 hours.The final effluent COD was from 203.7 mg/L to 94.5 mg/L.After the treatment,the COD decreased from 4400 mg/L to 94.5 mg/L,and the effluent was colorless.