Seawater reverse osmosis plant in Xiao Qingdao, China, which was fitted with an Energy Recovery, Inc.’s PX-25 in January, 2001 has been producing water below 2.2 kwh/m3, according to Mr. Tan Yongwen, Vice Director of Development Center of Water Treatment Technology (DCWTT) in Hangzhou, China. The plant employs a positive displacement pump and operates on a lower pressure cycle of 750-800 psi.
One of the benefits of the new PX technology is that the main highpressure pump flow is approximately equal to the product water flow. This allows systems in the 50-500 m3/day size range to easily use 90% efficient PD pumps. The result is that these smaller systems can be as much as 25% more efficient than even the largest plants.
Two other SWRO plants (one in Changdao County, Shangdong Province, one in Shengsi County, Zhejiang Province) that also use the PX units are both producing 1,000 m3/day of permeate water operating at less than 2.7 kwh/m3 consistently. These plants are using centrifugal main high-pressure pumps.
Mr. Tan said that all three plants performed excellently during start-up, and have shown excellent performance since that time without maintenance or downtime.