In a UK research project that might revolutionise water and wastewater quality monitoring, the University of Hertfordshire's Water Engineering Research Group has developed a laser system which could make the tried and tested 100-year-old means of measuring 'five day' Biochemical Oxygen Demand (BOD) obsolete.
"Potential applications for this new technology are enormous and could push back the frontiers of detection, monitoring and control technologies well into the next millennium," said Dr. Darren Reynolds, part of the university's research group responsible for developing the system. "When perfected, this method could provide a major contribution to science, by enabling potential water pollution events to be detected before they become problems, benefiting both consumers and the environment."
The standard BOD test, designed to measure the oxygen demand of rivers and lakes receiving significant quantities of biodegradable organic material, usually takes five days, making it unsuitable for instant online monitoring.
In an attempt to combat the problem, a series of 'wet chemical' techniques to measure pollution levels have been developed and introduced. These include monitoring Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC). "Although these tests are faster than the traditional BOD one, they are unable to differentiate between biodegradable and non-biodegradable matter, making true online monitoring and control impossible," said Dr. Reynolds. His university's latest development could provide an extremely valuable additional contribution to improving the environment, he claims.
"Illumination of water by optical radiation causes light scattering and tests have indicated that there is a direct correlation between this phenomenon and water quality," he explained. "Recent research has demonstrated that using these unusual properties can improve the detection of both organic and inorganic pollutants in potable and waste waters. In our research 'normalised' fluorescence intensities have been successfully used to predict long and short-term variations in BOD from both industrial and domestic wastewater samples. As light scattering can be easily initiated and detected by lasers, the technique is also applicable for determining the nitrate levels in potable water by the use of differential absorption," said Dr. Reynolds.
Because of its 'real time' capabilities, use of the light scattering principle could save up to five days in identifying a potential problem through the use of non-invasive sensors located at key water supply points. Online monitoring of both water and wastewater quality in real time could be developed to implement an international network of remote 'star wars' type sensors designed to relay water quality back to a central collection point. Perhaps in the future it could be linked directly to the Internet system, providing instant access for both developed and developing countries.