Ecological and Economic Aspects of Mining Water Treatment for District Heating System
Heat supply systems have a significant impact on the environment of residential areas as a result of gas emissions and discharges of saline wastewater into surface water sources. Along with a significant shortage of drinking water, there is an inefficient use of water in technical systems. Considered is the solution to the problem of deficit of drinking water through the use of alternative sources - mine water after purification to indicators that meet the requirements of consumers. To purify the make-up water of heating networks in domestic practice, the technology of water softening in sodium cationic filters is mainly used. A significant disadvantage of this technology is the need to use increased specific consumption of potable salts for filter regeneration, 2.3-3 g ∙ eq per g ∙ eq of absorbed hardness cations. This causes pollution of surface water sources. There are at least 11 alternative technologies for the preparation of make-up water for hot water boilers, which make it possible to reduce the discharge of saline effluents: water softening in sodium cation exchange filters with countercurrent regeneration, hydrogen cationization with «hungry» regeneration of medium acid cation exchangers, hydrogen cationation on carboxyl cation exchangers, water softening by liming, the use of sodium-chlorine ionization, water acidification, magnetic water treatment, reduction of the water residence time in the heating zone, double-circuit water heating, water heating with direct contact of fuel combustion products with heated water, the use of anti-scale additives and the use of evaporator concentrate (if any) for filter regeneration. Accounting for the cost of reagents in terms of their equivalent weight per ton of marketable product also significantly improves the economic performance of the water treatment process. Indicators of pollutant emission when using the most widely used water treatment technologies for different quality of source water are given. Indicators of the specific cost of reducing the carbonate index of treated water for the existing cost of reagents in the Russian Federation are given.