A zero liquid discharge (ZLD) wastewater treatment plant for a power plant in Ciudad Juárez, Mexico, marks another success for GEA’s range of small ZLD systems. Abengoa S.A. will use the ZLD plant to convert a salt-laden wastewater into pure water for internal recycling and dry solids for disposal.
The ZLD plant will treat brine from a reverse osmosis (RO) plant used to purify different wastewater streams collected within the power plant. The RO plant yields a waste stream containing mainly sodium chloride and sodium sulphate, plus nitrates and carbonates. For this project GEA is supplying a forced-circulation crystallizer followed by a decanter centrifuge for final dewatering. To overcome the boiling point elevation created by the dissolved salts, the crystallizer will use three high speed fans in series as mechanical vapour recompression (MVR) which is heating the system by using electrical energy only.
The forced-circulation crystallizer is a relatively simple solution that is nevertheless flexible and robust enough to handle the varying flows and salt concentrations it is likely to meet in practice, says Robert Buchfink of GEA’s sales support team. Together with the decanter, it provides a reliable yet economical solution for facilities that wish to avoid discharging wastewater containing salts. Larger ZLD plants would normally add a pre-concentration stage upstream of the crystallizer. ZLD is increasingly attractive in areas where water is scarce and in environmentally sensitive regions where it is not possible to discharge contaminated water. GEA ZLD systems are based around the company’s proven track record in membrane separation, evaporation, crystallization, drying and energy recovery. GEA offers modular ZLD systems in capacities up to around 10 m3/h, plus custom-engineered ZLD plants in sizes up to and above 100 m3/h.
GEA offers both thermal and non-thermal technologies for ZLD applications, including centrifugal separators, membrane concentrators, evaporators, crystallizers and dryers. GEA’s plants are designed to handle variable waste streams with high energy efficiency and minimum labour requirements, enabled by the use of amongst others corrosion-resistant materials, advanced automation and designs resulting in limited cleaning requirements. Applications include power generation, minerals, water treatment plants, and general industrial processes.