California Scientists Develop Water Monitoring System

Scientists at the Los Angeles Department of Water and Power (LADWP) and Biospherical Instruments, Inc., (BSI) have developed a state-of-the-art remote sensing device to monitor algal growth in Los Angeles area reservoirs. A third generation of the patented device, called a remote electro-optical sensor (REOS-3), has been operating in five LADWP reservoirs since 1997. Eight systems will be installed in LADWP reservoirs by the end of 1999.

Although an overabundance of planktonic algae in municipal water systems is not a health concern, it affects the taste of drinking water, produces an undesirable odor, and causes aesthetic problems that undermine the public's confidence in LADWP's ability to provide high quality water. In addition, an overgrowth of algae can cause the oxygen level in reservoir waters to become so low that fish and other aquatic species either migrate to other waters or suffocate. According to Brian White, a biologist at LADWP and codeveloper of REOS-3 with BSI senior scientists John Morrow, Los Angeles Reservoir was chosen as the test site for a REOS-3 algal control strategy because it produce algae at an extremely rapid rate, serves most of the people in Los Angeles, is a headwater for several downstream reservoirs, and has the staffing and facilities to support immediate action in response to an impending algal bloom.

REOS-3 is a state-of-the-art remote sensing device that monitors algal growth.

The REOS-3 system works by monitoring algal biomass with a pair of reflectance radiometers that are permanently submerged in the reservoir. The radiometers, which were developed by BSI to provide ground truth for NASA ocean color satellites, measure both the natural fluorescence of planktonic algae and the attenuation of ambient light passing through the water column. These independent measurements support estimates of the algal standing crop.

The radiometers transmit data every 2 second to an onsite controller that is polled once a day by a master domain controller located at LADWP headquarters. The master domain controller distributed daily REOS-3 reports to a team of treatment operators, biologists, and engineers at three different locations. The team then determines if the reservoir should be treated to alleviate the algae. This daily decision making process allows algal growth to be controlled with fewer chemicals before water quality is compromised. The result is higher water quality at less cost.

The on-year demonstration at Los Angeles Reservoir showed that the REOS-3 system allowed for 42 percent fewer chlorine treatment days and a 40 percent decline in tons of chlorine used, compared with previous years. The reduced chlorine treatments have saved the LADWP about $140,000 in yearly chlorine costs at Los Angeles Reservoir, which exceeds the REOS-3 purchase price by $40,000.

White and Morrow plan to simplify the approach so it can be used for smaller, less high-tech applications. They also plan to test additional sensors, including a probe that measures copper concentration since copper is another means of treating algae in reservoirs.

U.S. Patent No. 5,905,570.