The HERO process consists of several tried and proven pretreatment steps in combination with reverse osmosis operating at high pH. The resulting process has several features that make it particularly well suited for the treatment of cooling tower blowdown for recovery of waste water or as a preconcentrator for zero liquid discharge. Attractive features include robust self-cleaning operation, the ability to concentrate dissolved silica to 1600 mg/l and higher, feedwater recovery of 90 percent and greater, and the suitability for start-stop operation. HERO has been successfully pilot tested in a number of installations. It has the potential for significant cost savings when used for treatment of cooling tower blowdown. The anticipated benefits of the process will be tested when the first full-scale ZLD installation becomes operational later this year. The primary cost advantage of HERO based ZLD systems when compared to brine concentrator based systems is improved energy efficiency. A net present value analysis shows an economic advantage of about 7 million dollars for a typical 500 MW combined cycle power station over a period of 15 years.
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