Parameter optimization and performance analysis of nanofiltration membrane in treatment of compound-contaminated high-hardness water

Abstract

Increased pollution caused by socio-economic development has led to compound-contaminated high-hardness water pollution. In this study, laboratory-scale nanofiltration (NF) treatment of such water was investigated. Response-surface methodology was used to optimize the NF operating parameters, and a regression model with desalination rate and transmembrane pressure changes as response values was established. The NF membrane efficiencies in contaminant removal from groundwater and surface water with compound-contaminated high hardness and the membrane-fouling characteristics during long-term operation were investigated. The results show that the optimal operating parameters for the NF membrane in the removal of inorganic salts from groundwater are as follows: influent pH 8, influent pressure 1 MPa, and water yield 27.976%. The removal rates for groundwater total hardness, total alkalinity, total soluble solids, K+, Na+, Ca2+, Mg2+, , Cl−, , and were 99.4, 90.3, 84.7, 63.2, 56.8, 99.6, 95.2, 99.6, 68.3, 86.1, and 65.9%, respectively. Surface water contains more complex components; therefore, membrane fouling during surface water is more serious. The NF membrane was operated continuously for more than 35 days under the optimal operating conditions with no serious membrane fouling. HIGHLIGHTS Response-surface methodology was used to optimize the NF operating parameters.; NF membrane was operated continuously for more than 35 days under the optimal operating conditions with no serious membrane fouling.; The membrane fouling by hardness ion was analyzed by SEM-EDS.;

Keywords

• composite-contaminated
• high-hardness
• nanofiltration
• parameter optimization
• response-surface methodology