Study On The Treatment Of Cold Rolling Mill Watewater Containing Emulsion

A New kind of process: Coagulant/air floating—anaerobic treatment—oxidation treatment—discharge (or advanced treatment) is proposed to treat the cold rolling mill wastewater containing emulsion of WISCO. This thesis emphasizes on two points: the kind and the dosage of the best coagulants for physico-chemical treatment;COD removal rate,factors of bio-chemical treatment units. The experiment results are as followings:⑴When flocculants were applied to break the emulsion,it was found that the association of high-molecular weight inorganic flocculants PAC, PFS and organic flocculant CPAM was the best choice. When the dosage of PAC was 80mg/L,PFS was 800mg/L,CPAM was 15mg/L,and the pH was controlled at about 7, it could get a good effect of emulsion breaking. It was testified for half of the year that the effluent of air floating could get a steady state:COD was 1000～1500mg/L,oil was 15～20mg/L,SS was 0～5mg/L.⑵When the anaerobic process was applied to treat the effluent of air floating,digested sludge from the municipal treatment plant was inoculated to the anaerobic reactor.Glucose as inducer used in the sludge culture played a very important role,but when the biomass in the sludge adapting to the wastewater,the glucose should be reduced to 0.The anaerobic system operated in low VLR,and the best condition for anaerobic was HRT=48h, while the VLR was 0.5～0.6 kgCOD(/m3·d). Under this condition, the COD removal rate reached about 70% while the influent was 1000～1200mg/L.It also could be seen that anaerobic system had an ability to resist the load shock. Temperature was an important factor to anaerobic system. Sufficient alkalinity was demanded in the influent to keep pH as about 7.2. At the end of the experiment, the sludge of low and mid part in anaerobic reactor was searched by SEM, it inferred that organism in the inner part of the reactor layered clearly by height and got a diversification.⑶Internally circulating contact oxidation pond connects after anaerobic reactor, when the HRT (comaring to the anaerobic system) were 31h and 27h, the effluent could get a steady state: COD was less than 100mg/L;Oil was less than 10mg/L, which achieves the first class criteria specified in the Integrated Wastewater Discharge Standard (GB8978-1996). It was also found that DO was an important factor in the operation of contact oxidation pond, and the DO should be at 4mg/L or above 4mg/L.⑷UF was not fit for advanced treatment of the discharge of contact oxidation pond, because the COD removal rate was too low.