The Physi-Chemical Treatment for Wastewaters from Disc Recovery Process

• Main Authors: Chiu Yi-Chieh, 邱羿傑
• Other Authors: Sheng-Kun Chen
• Format: Others
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/81204834764631521642

碩士 === 崑山科技大學 === 環境工程研究所 === 94 === In the disc-recovery plant, the pre-broken disc was first immersed with the alkaline liquid containing hypochlorite to solve the UV lacquer, dye and the metal reflex layer from the poly-carbonate-ester resin, the waste-liquid originated from this step containing high COD concentration and pH was named waste liquid A. The other wastewater defined as wastewater B was produced from the next step of washing the poly-carbonate-ester resin treated at the first step. This study treated both the waste liquid with coagulation and the oxidation process in order to search the operation parameters, which would be applied to design and operate the wastewater treatment process in the plant in order that the effluent quality would meet the criteria standard regulated by the industrial park. After about 10 times of investigation, it was found that the waste liquid A in a sample plastic barrel contained 49,000 ± 1,500 mg/L COD, pH of 13 ± 0.5 , and some metals of Ag, Zn, Cd and Cu contents of 2.57, 2.62, 0.02 and 0.007 mg/L individually, while the waste water B having lower pH of 9.8 and COD of 900 mg/L. The opposite alkaline pH was hypothesized to be able to re-congeal some material that solved in the liquid at the first step for treating the waste liquid. After being soured with hydrogen chloride in the waste liquid A, it was approved that the lower pH from 13 to 2 the much more grey glue material precipitated with the COD removal percentage up to 69 % in the supernatant. It was also found that that the COD removal efficient was increased with the decreasing of the pH value and the increasing addition of coagulant in the jar test with agent of aluminum sulfate, ferric sulfate and ferric chloride individually. The economical suggestion for coagulant addition were 1200, 2000 and 2000 mg/L for aluminum sulfate, ferric sulfate and ferric chloride with the COD removal of 92, 71 and 92 % respectively in the initial liquid pH of 4. After the coagulation and sedimentation in the jar test with ferric chloride, the residual COD in the supernatant was 9000 mg/L which was further oxidized by chloric acid or with Fenton method. The COD removal efficient increased with the increasing of the dosage of chloric acid from 0.5 ~ 100 g/L or the H2O2/Fe2+ from 5/2.5 ~ 50/25 g/L, and the economical dosage were suggested as chloric acid 50 g/L or the H2O2/Fe2+ 50/25 g/L which resulted in the residual COD of 400 and 3300 mg/L individually for 95 and 63 % COD removal percentages. Oxidation test showed that only 5 minutes was needed for 92 % COD removal in the case of chloric acid dosage 50 g/L. It was suggested that the raw waste liquid A was conditioned with hydrogen chloride to pH 4, then dosage of ferric chloride as 1200 mg/L for the rapid mixing 1 minute and slow mixing for 30 minutes, then after further settled in the clarifier for at least 1 ~ 2 hours, the effluent was treated by the oxidation with chloric acid for no more than 10 minuts in the dosage of 50 g/L or the correspond ORP value of 334 mV.