In December 2006, Pure Aqua, Inc., Irvine, Calif., successfully supplied a water treatment package consisting of twin multimedia filters (model MLF-48A-F-twin), a pretreatment system, a double-pass reverse osmosis (RO) unit, an electrodeionization (EDI) system, a storage system and an RO cleaning system to a major power plant in Hawaii.
Pretreatment of the feedwater included filtration using twin multimedia filters to remove sediment down to the 10 to 20 micron range, thus providing service feedwater with a flow rate of 126 gpm at a maximum operational pressure of 100 psi.
Filtration using activated carbon filters with carbon block cartridges removed chlorine, salt, taste, odor and sediments from the water. The use of antiscalant dosing helped to minimize the precipitation of sparingly soluble sulfate salts such as calcium and barium sulfate as well as silica oxide.
The double-pass RO unit came with a high-pressure pump to boost the feed pressure of 5-micron cartridge filters. This removed the last traces of suspended solids and reduced the feedwater silt density index to less than three.
The unit came equipped with an advanced Allen Bradley programmable logic controller and 14-in. color touch screen control panel. The system also had an air conditioner because of the surrounding tropical weather conditions.
EDI removes ions from aqueous streams to achieve a water quality of 18.6 mega ohms. The product pumps then take the product water from the EDI system to a product storage tank. The RO cleaning system is used to clean membranes in three pressure vessels simultaneously.
From a feed total dissolved solids of about 300 mg/L at a temperature of 27°C, the power plant now produces 60 gpm of ultra pure water at 18.6 mega ohms. Since the time of its startup in March 2007, the plant has been running smoothly with minimal troubleshooting.
Article contributed by Pure Aqua, Inc. Additional information is available at 949.305.9996, or at www.pure-aqua.com.