New Harquahala Generating Project - Tonopah, AZ USA
Design-Build Zero Liquid Discharge (ZLD) System
Treatment of the water for upstream plant use, primarily as cooling tower makeup, as well as the subsequent waste generation from the process was critical to facility operations. Protection of the environment was another equally important consideration when designing this system. Harquahala is a Zero Liquid Discharge facility where no aqueous waste is permitted.
The Client's NeedsThe project at Harquahala required generation of high-quality water for reuse by the power plant and process remaining solid waste based on the
chemistry of feed water to the plant. Zero Liquid Discharge regulations mandate that the resulting solid waste, in the form of wetcake, was to be generated with a nominal content of 10% moisture for proper landfill disposal.
Veolia Water Technologies was selected to supply the entire plant on a Design-Build project basis.
Project & Technology Solutions
- Precipitation softening system to remove calcium, silica and other scale forming materials from the cooling water circuit. The system includes two 50% solids contact clarifiers, a sludge thickener/storage tank, twin sludge presses and chemical storage/feed systems for softening.
- RO Pre-concentration system to recover a majority of water in the softened tower blowdown prior to evaporation and concentration in the ZLD system.
- Zero Liquid Discharge (ZLD) system consisting of two MVR (Mechanical Vapor Recompression) driven, 50% HPD falling film evaporators and HPD brine crystallizer trains for reclamation of waste water and concentration of plant effluents in the form of wetcake for landfill disposal.
Entire infrastructure including site preparation, foundation
- Entire infrastructure including site preparation, foundation with chemical, electrical and control buildings.
The RO system design recovers ~65% of the softened blowdown. The remainder is sent to the evaporation set at a rate of 260 gpm where further concentration takes place to minimize the load to the crystallizer. In turn, the brine crystallizer system, designed at a flow rate of 26 gpm, further concentrates the stream. The resulting slurry is sent to a centrifuge for de-watering where the wetcake is collected and the centrate is returned to the incoming crystallizer feed.