Papers by Author: Wei Zhao

Abstract: A pilot study was carried out for direct filtration assisted with low-dose coagulation to treat low temperature and low turbidity reservoir water for drinking water. The impacts of filtration rate, gap between coagulation and filtration, coagulant dosage and filtering material were examined. The tested ranges were as following: filtration rate 4-10 m/h, gap between coagulation and filtration 1-5 min, coagulant dosage 4- 20 mg/L. The results show that direct filtration with low-dose coagulation was very effective in treating the low temperature and low turbidity source water. The optimal conditions were as following: PAC dose of 12 mg/L, filtration rate of 6 m/h, gap between coagulation and filtration of 3 min. The effluent turbidity was 0.5 NTU, COD was 2.4 mg/L, and the filtration cycle was 9 h. The coagulant dose was only 40% of that of conventional treatment.

Abstract: Photosynthetic bacteria (PSB) have various applications but the culture cost is very expensive. To find an efficient and economic culture medium the effects of yeast extract, C/N ratio, and trace elements on the growth of PSB were studied. The results showed that the optimal condition for PSB growth was: yeast extract of 100mg/l, C/N of 12:1, and trace elements (in mol/L): Mn2 + (0.009), Fe3+ (0.0025), Co2+ (0.0024), Cu2 + (0.0024), and Zn2 + (0.0033). Trace element lack could affect the growth of PSB. The order was Mn2 +> Fe3 +> Co2+> Cu2 +> Zn2 +. The improved medium was named HCH, and the optimum medium components were (in g/l) DL-malic acid: (4), MgSO4: (0.12), (NH4)2 SO4: (1), CaCl2: (0.075), KH2PO4: (0.5), K2HPO4: (0.3), Na2EDTA: (0.02), yeast extract : (0.1), trace elements 1ml (in mol/l ): Fe3+: (0.0025), Mn2+: (0.009), Zn2+: (0.0033), Co2+: (0.0024), pH:6.8. Comparing with the traditional RCVBN medium, in HCH medium yield of PSB increased 1.2 times and the cost decreased 19.8 times.