title: Coagulation efficiency and flocs characteristics of recycling sludge during treatment of low temperature and micro-polluted water.
abstract: Drinking water treatment sludge, characterized as accumulated suspended solids and organic and inorganic matter, is produced in large quantities during the coagulation process. The proper disposal, regeneration or reuse of sludge is, therefore, a significant environmental issue. Reused sludge at low temperatures is an alternative method to enhance traditional coagulation efficiency. In the present study, the recycling mass of mixed sludge and properties of raw water (such as pH and turbidity) were systematically investigated to optimize coagulation efficiency. We determined that the appropriate dosage of mixed sludge was 60 mL/L, effective initial turbidity ranges were below 45.0 NTU, and optimal pH for DOMs and turbidity removal was 6.5-7.0 and 8.0, respectively. Furthermore, by comparing the flocs characteristics with and without recycling sludge, we found that floc structures with sludge were more irregular with average size growth to 64.7 microm from 48.1 microm. Recycling sludge was a feasible and successful method for enhancing pollutants removal, and the more irregular flocs structure after recycling might be caused by breakage of reused flocs and incorporation of powdered activated carbon into larger flocs structure. Applied during the coagulation process, recycling sludge could be significant for the treatment of low temperature and micro-polluted source water.
authors.affiliation: College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124, China. hubeizhouzhiwei@163.com
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yanling
authors.initials: Y
authors.lastname: Yang
authors.forename: Xing
authors.initials: X
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.forename: Heng
authors.initials: H
authors.lastname: Liang
authors.forename: Guibai
authors.initials: G
authors.lastname: Li
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D009391:Nephelometry and Turbidimetry; D059027:Recycling; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; D000536:Aluminum Hydroxide