Water softening technologies for small and medium capacity systems

The current state of water resources is largely determined by human activities. The discharge of polluted waters into surface water bodies significantly reduces their quality and complicates direct usage. One of the main sources of increasing mineralization and hardness of surface waters is the discharge of spent regeneration solutions after ion-exchange softening, which creates a closed cycle of sodium, calcium, and magnesium chlorides. The need to reduce the intensity of this cycle and decrease environmental pollution has arisen long ago. Studying the standard soda-sodium softening method has shown its low suitability for systems with small and medium productivity due to the need for water heating and subsequent pH correction. Using phosphate anions as precipitants proved to be more effective, successfully removing calcium and magnesium ions over a wide range of temperatures and pH levels. Research has revealed that the formed solid phase in such treatment is poorly separated from the liquid. As one of the solutions to this problem, the use of anionic flocculants is proposed, which provide effective separation of the formed solid particles from the water. A technological scheme has been developed, which involves usage at the stage of preliminary water treatment for reverse osmosis systems with small and medium productivity.