Affiliation:
1. Henan International Joint Laboratory of Watershed Ecological Security in the Water Source Area of the Middle Route of South-to-North Water Diversion Project, College of Water Resource and Modern Agriculture, Nanyang Normal University, Nanyang 473061, China
2. School of Environmental Engineering, Henan University of Technology, Zhengzhou 450001, China
3. College of Water Resource and Modern Agriculture, Nanyang Normal University, Nanyang 473061, China
4. Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
Abstract
The quartz sand-enhanced coagulation (QSEC) is an improved coagulation method for treating water, which uses quartz sand as a heavy medium to accelerate the sedimentation rate of flocs and reduce the sedimentation time. The factors that influence the QSEC effect and can be controlled manually include the quartz sand dosage, coagulant dosage, sewage pH, stirring time, settling time, etc., and their reasonable setting is critical to the result of water treatment. This paper aimed to study the optimal conditions of QSEC; first, single-factor tests were conducted to explore the optimal range of influencing factors, followed by response surface methodology (RSM) tests to accurately determine the optimum values of significant factors. The results show that the addition of quartz sand did not improve the water quality of the coagulation treatment, it took only 140 s for the floc to sink to the bottom, and the sediment volume only accounted for 12.2% of the total sewage. The quartz sand dosage, the coagulant dosage, and sewage pH all had a significant impact on the coagulation effect, and resulted in inflection points. A QSEC-guiding model was derived through RSM tests, and subsequent model optimization and experimental validation revealed the optimal conditions for treating domestic sewage as follows: the polyaluminum chloride (PAC) dosage, cationic polyacrylamide (CPAM) dosage, the sewage pH, quartz sand dosage, stirring time, and settling time were 0.97 g/L, 2.25 mg/L, 7.22, 2 g/L, 5 min, and 30 min, respectively, and the turbidity of the treated sewage was reduced to 1.15 NTU.
Funder
Henan Provincial Department of Science and Technology Research Project
Ph.D. Special Project of Nanyang Normal University
National Natural Science Foundation of China
Major Science and Technology Projects of Henan Province
Key Research and Development Projects of Henan Province
Overseas expertise introduction center for discipline innovation of watershed ecological security in the water source area of the Middle Route of South-to-North Water Diversion Project