CONTRACT UNIDIRECTIONAL FLUSHING -A SURPRISINGLY COST EFFECTIVE ALTERNATIVE

摘要

Water utilities have traditionally practiced distribution main flushing for a variety of reasons including aesthetic, regulatory water quality issues and also to restore hydraulic performance. The aesthetic water quality problems amenable to control by flushing include color, turbidity, taste and odor. The primary regulatory compliance issues that flushing can help to correct include restoring disinfectant residual, reducing coliforms and reducing heterotrophic plate counts (HPCs). For example, flushing has been: 1. Identified as a "best technology and treatment technique" for Total Coliform Rule (TCR) compliance in accordance with the Virginia Department of Health Waterworks Regulations (12 VAC 5-590-370). 2. Recognized as an integral component of a total system optimization plan in accordance with USEPA Handbook, Optimizing Water Treatment Plant Performance Using the Composite Correction Program, 1998 Edition (EPA/625/6-91/027). Furthermore, utilities have flushed water mains in response to immediate water quality problems as reported through customer complaints. More recently, flushing has been implemented as a preventive measure to avoid regulatory-related water quality problems and customer complaints (Chadderton, et al., 1992, 1993).