Study and engineering and economic comparison of chemical methods of softening the Bolshoi Kinel River water

Summary

Softening water for domestic water supply can be carried out by different methods including the addition of alkaline agents into water. Experimental studies of the use of lime-soda and caustic soda methods for softening the Bolshoi Kinel River water that is the source of drinking water supply for the city of Otradny, Samara Region, have been carried out by the employees of EKOFES SPE LLC in the laboratory and working environment. A diagram of a laboratory setup has been developed consisting of a mixer with aeration and an air separator, a vertical sedimentation tank with laminar modules, and a rapid filter. Experimental studies on the effect of chemical doses on the values of residual water hardness and total dissolved solids have been carried out. It has been established that the caustic soda method provides for efficient water softening, however results in an increase in the total dissolved solids, thus limiting the area of application. The results obtained in the study of the lime-soda method allow to conclude that the technology is advantageous owing to the elimination of extra water salinization and to recommend it for softening the water of the Bolshoi Kinel River. The engineering and economic calculation of the cost of 1 m³ of processed water depending on the softening method is presented.

Key words

drinking water supply , chemical softening , water hardness , lime-soda softening method , caustic soda softening method

Study of the eco-economic efficiency of electrochemical pH correction for reducing hardness salts

Summary

In industry, water recycling systems or units have been widely used to cool equipment and other industrial processes. One of the main problems associated with operating these systems is scale formation owing to the presence of hardness salts, such as calcium and magnesium compounds. Traditional addressing water hardness problems involves the use of chemicals such as phosphates and polyphosphates to bind calcium and magnesium ions, preventing their precipitation. Electrochemical pH correction provides for a more environmentally friendly solution. Changing water pH by electrolysis enhances the precipitation of hardness salts as insoluble compounds, that can be further removed from the system. The theoretical foundations and mechanism of water softening by electrochemical treatment are examined. It is noted, however, that direct reduction of hardness salts using electrochemical pH correction alone is not possible. It is expected that electrochemical methods can significantly enhance water softening processes and improve the efficiency. The eco-economic efficiency of the electrochemical pH correction method for the side stream filtration system of an industrial water recycling unit is estimated.

Key words

softening , electrolyzer , electrochemical treatment , water hardness , water recycling facilities , eco-economic efficiency