UK celebrates reservoir management success
The UK's first reservoir management system, designed by US-based Severn Trent Services (STS), marked its second year of successful operation in September 2005. Matthew Sears, STS's business development manager for disinfection solutions, reports on a system that eliminates reservoir water quality problems associated with thermal stratification, stagnation and blending of different water qualities within water storage systems.
Stored bodies of water are subject to thermal stratification, stagnation and the blending of different water qualities. It is notoriously difficult to ensure thorough mixing of free chlorine or chloramines disinfectant in order to maintain a constant residual level.
The RMS system enables water utilities to maintain uniform chlorine-related water quality and temperature uniformity within large water storage bodies through a self-regulated process that detects chlorine levels in real-time water quality samples. The precise amount of disinfectant is then dosed to maintain a constant predetermined level.
The desired disinfectant residual level at Diamond Avenue was 0.3mg/L. Two 9ML reservoirs are used to store water before it is distributed to the Nottinghamshire area. Previously, chlorine tablets were added at the reservoir inlet to increase disinfectant levels, but this resulted in poor control, with residuals dropping to 0.1mg/L.
Neither inlet nor outlet dosing was considered appropriate due to the fluctuating 16ML/day flow rates. Both reservoirs were exhibiting reversed flow with changing pressures in the distribution system.
The powerful RMS system was initially trialled for a period of six days, during which 70 samples were taken from 10 locations across the reservoir to give the overall picture of the chlorine distribution. A six-day trial of the RMS system, using fixed-rate dosing, indicated that the distribution of chlorine across the reservoir was even and responded in a linear manner.
After the trial, the RMS was put into permanent operation and has retained control of the residual regardless of water level or flow pattern. The innovative RMS technology has delivered a data set which compares favorably with a reservoir in which the disinfectant has been calculated to be perfectly mixed.
Stuart Crymble, senior process engineer for technology and development at STW, said, "The RMS system is attaining residual control which was never achievable with previous dosing methods."
"We are delighted with the results of our first UK installation," said Julian Routh, technical manager for STS. "The RMS technology is delivering unrivalled disinfection control and management. And other Severn Trent Services' equipment can be integrated with the RMS system to provide a complete water storage management solution, including the ClorTec on-site sodium hypochlorite generator and the CL1000B bufferless chlorine analyser."
Severn Trent's success in marketing ClorTec in the United Arab Emirates recently won the company a US Department of Commerce Export Achievement Award.