Evaluating the impact of dispersed particles in the water of a power plant recirculating cooling system on the discharge of suspended solids into a natural water body

Abstract

The object of this study is the processes of formation and changes of dispersed particles in fresh, make-up, cooling, and return water in open recirculating cooling systems (RCS) with an assessment of the influence of suspended substances in discharge waters on the aquatic ecosystem. The study was carried out on the example of the Rivne Nuclear Power Plant (RNPP) and the Styr River. Dispersed particles (DPs) pose technological obstacles in the RCS of power plants, and their content in discharge waters determines the ecological quality of water bodies. This paper describes the results of studying the formation and changes of DP in raw, make-up, cooling, and return waters of RNPP RCS with an assessment of the impact of suspended substances in discharge waters on the aquatic ecosystem of the Styr River. It was found that the formed dispersed particles after water treatment by liming contain DP consisting of calcium carbonate and have a size of 10–30 μm. As a result of agglomeration of DP in RCS, they aggregate to 120–150 μm, and due to low sedimentation resistance (sedimentation time 0.97 h), they settle in RCS. As a result of the deposition of DP in RCS, their significant decrease in return water (min–max=7.31–16.12 mg/dm3) is observed, despite the increase in their content in make-up water after water treatment (min–max=10.22–49.46 mg/dm3). According to the ecological classification, according to the content of suspended substances, the water of the Styr River in the zone of influence of RNPP discharges belongs to the II class, category 2, which characterizes the quality of the water as "very good" in terms of its state, and "clean" in terms of its degree of purity. It was concluded that the content of suspended solids does not exceed the established maximum permissible concentration (25 mg/dm3), the increase in the concentration of suspended solids does not exceed the established ecological standard of 0.25 mg/dm3 and does not have a negative impact on surface water. The results of the research could be used for other power plants equipped with an open RCS