Study On The Treatment Of Concentrated Wastewater From Wiping Forme

The main kind of wastewater produced during the production of banknote printing isthe concentrated wastewater from wiping forme, which has a large amount of emission. Itcontains quantities of pollutants such as alkali, ink, surface active agent, organic matter andso on, and with the characteristics of high concentration, dark colority, high salinity, strongalkalinity, poor biodegradibility, high emulsifying ability and strong hydrophilicity. It ishard to treat the wastewater, the cost and operating expense is also expensive, and thedischarged wastewater will do harm to the environment and waters if it is not treated well.This study indicates that, the value of the effulent chemical oxygen demand, COD, could beno more than150mg/L after wastewater treatment through the combined method ofphysical, chemical and biochemical, thus meets the requirements of discharged water inenterprises. Furthermore, the process parameters have been optimized through differenttests, which provides a theoretical basis for the engineering design and commissioning ofthe concentrated waste wiping solution treatment.In this study, tests were made firstly to ultrafilter the waste wiping solution, thendemulsify it with Carbon dioxide, and finally determine the process conditions of Carbondioxide demulsification. The dimulsified wastewater will be treated with several processtests, including hydrolytic acidification, biological contact oxidation, biological carbon andtwo-stage biological contact oxidation, etc. Based on the test statistics, it suggests that thehighest removal efficiency was recorded by the combinated process of “deepeninghydrolytic acidification+biological contact oxidation”. Research shows that with thetemperature remained above14℃, the total hydraulic retention time6d, the influent COD2000mg/L and the effluent COD140mg/L, the removal efficiency will be greatly improvedto93%after processing the dimulsified waste wiping solution by the combined treatment of“deepening hydrolytic acidification+biological contact oxidation”. In addition, the effectof applying “CO2+CaCl2” method for the ultrafiltered concentrated waste wiping solutionwill be more stable than that of “CO2+PAM”. The results of both small-scale andmedium-scale test of “deepening hydrolytic acidification+biological contact oxidation”are correspondingly the same, which achieves the expected requirements. So far, theprocess has been demonstrated as the technology in the newly-built comprehensive wastewater treatment plant in Banknote Printing Corporation.