BP Solar high-purity water system saves chemical costs
BP Solar upgraded a deionised water system to produce high-purity water with less than 100 ppb total organic carbon (TOC), while saving on chemical and maintenance costs.
By Trude Witham
BP Solar Building
BP Solar's Frederick, Maryland plant was undergoing rapid expansion and needed to upgrade their reverse osmosis (RO)/service deionised (DI) water system to handle their higher production needs. They were using approximately 20 DI tanks a week to keep up with the demand for water. In addition, the system, which ran 24 hours a day, seven days a week, required considerable maintenance, and acid and caustic chemicals. Their specification for a new water system called for a 200-gallon-per-minute (gpm) loop providing 15 megohm water with less than 100 parts-per-billion (ppb) total organic carbon (TOC).
USFilter recommended that BP Solar replace the mixed-bed deionisers with CDI-LX™ systems as a way to meet their water quality specification, while eliminating acid and caustic chemicals and reducing maintenance costs. In Spring 2001, BP Solar installed a USFilter high-purity water system with multi-media filters, softeners, carbon filters and two FlowMAX® RO systems feeding two 75-gpm CDI-LX systems.
The CDI-LX product water supplies a 6,400-gallon storage tank, and that water is pumped through two ultraviolet (UV) sterilisers in parallel, four 30 FT3 mixed-bed service DI polishers, four 0.2 micron cartridge filters in parallel, and then out to a polypropylene distribution loop. The loop returns through a backpressure-regulating valve into the tank.
USFilter recommended that BP Solar purchase a central DI system rather than simply add on to their existing system. According to Plant Engineer Bruce Pickett, "We had two separate distribution loops, but needed another one. So, USFilter designed a main header loop and tied it into the existing ones, saving us money on installation costs and eliminating storage tanks and other equipment."
Started up in May 2001, the system has exceeded BP Solar's specification for water quality. Pickett, explained, "Our spec is for electronics-grade water. We're getting 18 megohm quality from the DI polishers and less than 10 ppb TOC."
System flow diagram
BP Solar also purchased a maintenance contract from USFilter so they would not have to worry about routine system maintenance. Brian Davidson, maintenance manager at BP Solar explained: "With our old RO/DI system, we required three to four people to maintain it. Now we use zero resources to maintain the system, and can use these people for other areas of the plant."
Because the plant uses 100,000 gallons of water a day and operates 24 hours a day, seven days a week, the water system must be reliable with no downtime. With two identical treatment trains installed in parallel, one system can be placed online while the other is taken off-line for regularly scheduled maintenance, such as service DI polisher tank exchanges.
BP Solar reported that the system has performed reliably since it began operating and continues to do so. Davidson said: "What I like about the system, and the CDI-LX in particular, is that it's out of sight, out of mind. It's maintenance-free. If I don't go into the room where the system is but once a week, I don't feel guilty. With the old system, I had to check on it two or three times a day." Eventually, both treatment trains will run continuously to meet the plants' increased production needs.
BP Solar is the largest provider of integrated photovoltaic systems, or solar cells, in the world with operations in Australia, India, Spain and the USA.
Trude Witham is a senior technical writer for USFilter at the company's Lowell, Massachusetts, USA facility.