Aquatech International Corporation (www.aquatech.com) won a ZLD (zero liquid discharge) contract from AES (www.aes.com) for its 800 MW coal-fired power plant in the Commonwealth of Puerto Rico. The power plant operates on treated sewage as feedwater and thus faces a combination of makeup water treatment and discharge challenges.

Prior to obtaining the order, Aquatech worked with the project site to pilot test equipment to solve the challenges faced by the customer. This order includes an ultrafiltration unit as pretreatment for an existing demineralization reverse-osmosis unit and brine concentrator followed by a forced circulation crystallizer for a ZLD system to evaporate the demineralization reverse-osmosis reject plus cooling tower blowdown.

Aquatech’s ultrafiltration system will use hollow-fiber membranes configured in two trains of 300 GPM each. The ultrafiltration system will treat cooling tower blowdown that utilizes treated sewage water for makeup to improve the quality of the feedwater to the demineralization reverse-osmosis unit.

The brine concentrator and crystallizer system will utilize seeded slurry technology and is expected to be capable of continuous operation, 24 hours per day, producing distillate for reuse in the process. As specified, the system is configured as 1 x 100 percent brine concentrators and 1 x 100 percent crystallizer, processing 100 GPM of wastewater stream. The crystallizer unit, specially designed to handle organic-laden waste stream, will be integrated with the brine concentrator to produce semi-solid sludge to be disposed off site.