Reducing operating costs through modernization of reverse osmosis facilities used to produce drinking water

Abstract

Introduction. The authors address problems of operation of reverse osmosis facilities, used to treat ground water and produce drinking water; they also focus on operating cost reduction strategies. Nanofiltration membranes may reduce operating costs, concentrate consumption, and sedimentation. A smaller antiscalant dosage can also reduce the cost of chemicals. The purpose of this research is to evaluate the ecological and economic efficiency of the new technique. Materials and methods. The authors conducted groundwater treatment experiments to reduce groundwater hardness and ammonia content. Scaling rates and the composition of water, produced by each membrane module, were determined in each membrane module depending on coefficient K values. Results. The relationships, identified in the course of experiments, enabled the authors to calculate the number of membranes required to reach the designed efficiency value. The design of a membrane facility, tailored to a certain groundwater composition, is presented; membrane models and treatment efficiency values are identified. The use of nanofiltration membranes reduces the operating costs by 40 percent due to the lower consumption of antiscalants, power, and concentrate. Conclusions. The research has proven that the replacement of reverse osmosis membranes by nanofiltration membranes at the water treatment facilities in operation ensures a 40–50 percent increase in their production capacity. The water quality remains the same and meets the WHO standards. Also, the concentrate consumption rate goes down 10–20-fold. The authors have also found out that the use of nanofiltration membranes reduces the water hardness and ammonia content at lower pressure values and scaling rates, although the safe operation and higher efficiency are in place. The proposed modernization strategy reduces operating costs by 40–50 percent through membrane replacement without any changes in the membrane design.