Study On Treatment Of Wastewater From Printed Circuit Board By Return Sludge Flocculation Sedimentation Process

It is found that a large fluctuation of water quality can be sawn in Printed circuit board wastewater, while the buffer ability of traditional flocculation processes is poorer, the water quality of fluctuated strongly during actual wastewater treatment, and the water quality even does not meet the compliance. Aiming at the problems of traditional flocculation process, the experiment is performed by return sludge as load dose to deal with PCB heavy metal wastewater.This experiment using loading process and conventional proces the contrast test as the main method,which is mainly to investigate the loading process and traditional process of treatment effect and the optimum experimental parameters, the main research content are:comparison of different coagulants, pH, coagulant dosage, flocculant dosage, return sludge flow, depositing time, hydraulic condition on the loading process and traditional process effect. Finally, based on two technology under the condition of optimum technological parameters of stable operation, two effluent effect can be compared,and relative analysis can be used.There are four affecting Factors of the test:aluminum sulfate, PAC, PFS and ferric chloride, the most suitable treatment for experimental wastewater is ferric chloride; two optimal pH value of two treatments are all ranged in8～9; the optimum coagulant dosage of loading process is0.125mmol/L, only50%of traditional technology; the best dosing volume of loading process on PAM is lmg/L and traditional process on PAM is0.5mg/L; sludge recycle flow rate has obvious effect on the process, sludge recycle flow ranged in3～4g/L which is relatively good and stable; optimal hydraulic condition:velocity gradient of loading process are100.6G-1,54.8G-1,29.8G-1respectively;HRT are4min,4min,4min respectively; traditi-onal process velocity gradient are76.5G-1,40G-1,20.1G-1respectively; HRT are4min,6min,8min respectively.The settling time of Loading process is far less than that of traditional process, that arelOmin and30min respectively; in stabilization stage, there is a lower turbidity,heavy metal concentration and water quality fluctuation, sludge production,meanwhile there is a higher floc density in loading process.It can be sawn that Loading process can not only solve effectively problem in the traditional process,that is weak resistant capability, high water quality fluctuation and other issues.but also improve the quality of the effluent, reduce the total amount of heavy metals emission; improve the flocculation rate effectively, saving the flocculation time; improve the floc strength, improve the settling performance reduce the settling time; it can also save the dosage of coagulant process etc. Compared with the traditional technology, the return system should be in the loading flocculation technology wich increased the chance of heavy metals in the sludge reflux to the water,so pH conditions must be ensured no less than a certain value in the flocculant process.