Industry k slowly moving beyond the concept of zero liquid discharge toward the ideal of “zero waste discharge”. While zero liquid discharge means no liquids are discharged off site, the tons of dry solids removed from treated wastewater are often hauled to landfills off site if they cannot be stored at the plant. In recent years, some plants have opted to recover valuable salts and them icals from wastewater to reduce the cost of hauling away useless mixed salts. Some plants even recover some of the cost of wastewater treatment by selling recovered salt. This paper will discuss three industrial sites where all wastewater is treated and recycled and most salts removed from the wastewater are turned into saleable products. The case studies will be a coal mine in Poland, where distilled water and sodium chloride are recovered from mine drainage; a uranium mine in the Czech Republic, where distilled water and ammonium alum are recovered from acid waste; and a power plant in New York, where distilled water and calcium chloride are recovered from scrubber blowdown.
Keywords: zero liquid discharge, zero waste, evaporator, crystallizer, wastewater, salt recovery.