Study On Treatment Of CMC Wastewater By Microelectrolysis-UASB-Contact Oxidation Technology

Carborymethyl cellulose (CMC) sewage is a kind of organic and chemical wastewater produced by the manufacturing process from some ShongDong plant, which features high COD concentration ranging from 20000 to 25000mg/L as well as salty concentration about 4 percent. According to the research on CMC's characteristics, pretreatment is required specifically for its low biodegradability. Iron-carbon microelectrolysis proves its effectiveness after the comparison among kinds of pretreatment methods.Results showed iron-carbon microelectrolysis can remove 35% of COD while improve B/C from 0.12 to 0.35, far better than any other pretreatment method in terms of the biodegradability improvement, which helps to benefit the latter bio-process. Factors affecting the efficiency by iron-carbon microelectrolysis ranked influent pH>effluent pH>HRT>Fe/C. The optimal condition concluded that influent pH=3.0, HRT=75min, effluent pH=9 and Fe/C=3:1. Upon GC-MS analysis, the mechanism of iron-carbon microelectrolysis is based on an integrated process including galvanic reaction, oxidation-reduction reactions, electrochemical adsorption physical adsorption and coagulation.After the pretreatment, UASB is applied for further treatment, which initiates with high concentration influent and low removal ratio. It took about 60 days for the domestication of granular sludge from municipal sewage treatment system, which is faster than common anaerobe reactors. Results showed the optimal conditions of UASB system summarized HRT=44h, temperature=37℃, return effluent =1:15 and 82% of COD removal. Granular sludge began to increase when COD loading reached 0.3 kgCOD/(kgVSS·d) and to the amount of 0.6 kgCOD/(kgVSS·'d), granular sludge has occupied most of the reactor. Upon scanning electron microscope analysis, the diameter of granular sludge is approximately 1 mm. After the operation by 200 days, SMA test (the max specific production methane activity) was required to study the granular sludge on carbon sources comparison with formic acid, acetic acid and glucose. Results showed the SMA by glucose was maximized by contrast to CMC wastewater.The COD removal ratio by first aerobic stage differed at three HRTs, 80% of which at HRT=32 h. The second stage achieved the COD removal ratio of 70% when the HRT equaled 16 h. After the treatment, the effluent can meet the state discharge standard with the residual COD less than 100mg/L.