Fuzhou Hongmiaoling Leachate Salt-Recovery Project (Fujian's first evaporative salt-separation line; about 12.5 t of industrial salt a month)

The Hongmiaoling circular-economy eco-industrial park in Fuzhou handles the city's landfill disposal, waste incineration and leachate treatment. Landfill leachate is a high-strength organic wastewater with a complex, saline composition, often called the hardest wastewater in the industry. The Hongmiaoling leachate plant had long relied on a full membrane process. Effluent met standards, but salts and refractory organics could not be destroyed by membranes; they stayed in the membrane concentrate, recirculating and accumulating in the system until equipment struggled and costs kept climbing. From 2024 a task force at the plant, part of Fujian Haitai Environmental Group under Fuzhou Water Group, spent more than two years comparing advanced oxidation, material membranes and evaporative salt separation. They settled on evaporative salt separation, which treats the concentrate outright instead of letting it circle inside the plant. After fine pre-treatment for the high-salinity, high-hardness concentrate, MVR mechanical vapour recompression crystallisation separates the salts, linking biological treatment, multiple membrane filtration, evaporative crystallisation and water reuse, and producing both sodium and potassium salts. The combination of membrane and thermal processes is described as a first in China. By the first half of 2026 the line, the first of its kind for leachate in Fujian, had run smoothly for more than five months. Plant general manager Lin Wei said the site now produces about 12 tonnes of sodium chloride and 0.5 tonnes of potassium chloride a month, both meeting national standards; by June 2026, 60 tonnes of sodium chloride had been shipped for use in leather manufacturing. After the upgrade, capacity rose to 2,600 t/d of leachate and 550 t/d of membrane concentrate, with residues handled separately as resources. Reuse runs in parallel. The plant supplies 200 tonnes of reclaimed water a day, meeting the urban miscellaneous water standard (GB/T 18920-2020) for greening, street washing, firefighting and construction, and used in the park for irrigation, road cleaning, fire emergency supply and process cooling. For a plant that has operated for three decades, the line means more than an extra product. Leachate has moved from compliant discharge to resource recovery, the park no longer has to find an outlet for membrane concentrate, and salt sales plus water reuse turn treatment from a pure cost into a circular, value-adding operation. Sources: Fuzhou Municipal SASAC, "From king of wastewater to urban treasure" (27 May 2026, https://gzw.fuzhou.gov.cn/zwgk/gqfc/202605/t20260527_5327127.htm); Fuzhou Municipal People's Government, "Black water into white salt" (5 June 2026, https://www.fuzhou.gov.cn/gzdt/rcyw/202606/t20260605_5330701.htm). Image: MVR evaporative crystallisation unit in the salt-recovery workshop of the Hongmiaoling leachate project, pipe labels reading salt thickener to mother-liquor tank and centrifuge exhaust to deodorising header (source: Fuzhou SASAC / Haitai Environmental).