Study And Engineering Practice Of Carbonless Copy Paper Coating Wastewater Treatment Technology

In the production process of Carbonless Copy Paper,a variety of coatings（pigments,chromogenic reagents and adhesives）were used,and some coatings were washed into the coating wastewater and became the main pollutants in the coating wastewater.Coating wastewater has high concentration and color strength,and it is difficult to treat.It caused great pollution to the environment.In this paper,the effect of chemical coagulation,biological method and advanced treatment on the treatment of coating wastewater was studied.The practical application on the treatment of coating wastewater was discussed,which provided the theoretical basis and practical experience for the treatment process of coating wastewater.First of all,the effect and rule of a combination of chemical coagulation with biotreatment on degradation of pollutants in coating wastewater were systematically studied.It was found that,compared with the coagulation effect of anaerobic sludge,the dosage of PAC and CPAM decreased by 50%and 33%respectively in the process of enhanced coagulation of anaerobic sludge,and the treatment cost was greatly reduced.The flocculation produced by enhanced coagulation of sludge has better sedimentation performance.It was found that the combination of PAC with CPAM has good effect on the treatment of coating wastewater.Under the conditions of PAC dosage of 400 mg/L,CPAM dosage of 6 mg/L,pH value 5⁷,stirring for 6min and stirring strength 240 r/min,the removal rates of COD_Cr,Color and SS in coating wastewater were 69.52%,98.61%and 96.62%by the chemical coagulation method.The removal rate of COD_Cr in chemical coagulation effluent was 79%⁸5%by a combination of hydrolysis acidification with activated sludge process.After chemical coagulation and biological treatment,the COD_Cr of coating wastewater decreased from about 3400 mg/L to about 170 mg/L,and the total removal rate of COD_Cr reached about 95%.On the basis of the experimental study on the treatment of coating wastewater by a combination of chemical coagulation with biotreatment,the combined process of high efficiency coagulation and A/O（anoxia/aerobic）biotreatment was used to treat the coating wastewater of a certain enterprise.The coating wastewater was first entered into an integrated paper wastewater dynamic treatment device by high efficiency coagulation treatment,and then it was entered into the A/O system for biotreatment.The operation results showed that the COD_Cr of effluent in secondary sedimentation tank was less than 200 mg/L,and the total COD removal rate reached more than 90%after a combined treatment of high efficiency coagulation and A/O system on the coating wastewater,when the influent amount is 400 m3/d and the influent COD<5000 mg/L.It indicated that the combined process of high efficiency coagulation and A/O system is a highly effective treatment of coating wastewater in engineering application.In order to solve the problem that the sedimentation of the flocculation produced by the conventional chemical coagulation process is poor and the precipitation effect is not good,the experiment of strengthening the coagulation on the treatment of coating wastewater by adding anaerobic sludge was studied.It was found the dosage of PAC and CPAM decreased by 50%and 33%respectively in the process of enhanced coagulation,and the treatment cost was greatly reduced,but the treatment effect of coating wastewater don’t become worse,compared with the coagulation effect without anaerobic sludge.According to the precipitation effect produced by flocculation treatment,laser particle size analyzer and scanning electron microscope,the flocculating floc enhanced by anaerobic sludge had better sedimentation.Under the conditions of anoxic for 1 h,aeration for 5 h and HRT 9 h,the anaerobic sludge enhanced coagulation effluent was treated by SBBGR method,COD_Cr decreased from about 931.8 mg/L to about115.3 mg/L,and the COD_Cr removal rate was up to 87.6%.It showed that the process could effectively degrade the dissolved pollutants in the coating wastewater.It has the advantages of short process time,high efficiency and no precipitation process.Finally,an integrated process of ozonation-nanofiltration as advanced treatment was used to treat effluent treated by enhanced coagulation-SBBGR process.After advanced treatment,COD_Cr,BOD₅,Color and SS of effluent decreaced to 36 mg/L,6 mg/L,1 C.U.and 1 mg/L respectively.The effluent water quality meets the standard of industrial water quality,which shows that the process can be used for the recycling of coating wastewater.The structure of organic compounds in the effluent treated by ozonation-nanofiltration was analyzed by FTIR and UV-vis spectrum.The results showed that the hydroxyl and carbonyl content of the wastewater decreased to a certain extent after the treatment of the intergreated process of ozonation-nanofiltration,indicating that the more complex organic pollutants in the wastewater were degraded or removed.