Evaluation of Contaminant Mixing in Rainwater Harvesting First Flush Diverters

摘要

As the world population increases, the demand increases for quality drinkingwater. The harvesting of rainwater has the potential to assist in alleviating pressures oncurrent water supplies and storm water drainage systems. Diversion of a portion of thecollected water away from storage is a technique used to improve harvested rainwaterwater quality prior to storage. Six configurations of a downspout first flush diverterwere constructed and tested in the laboratory. The configurations of diverters wereevaluated for their affinity to allow diverted water in the diverter chamber to interactwith the flow of water to storage. Experiments were conducted at flow rates rangingfrom 0.76 L/min to 113.56 L/min. This range of flow rates adequately represents a widerange of common storm intensity patterns across the United States to which downspoutfirst flush diverters are subjected.The diverter chamber to downspout transition fittings tested on a 10.16 cmdiameter diverter chamber, upward and downward oriented sanitary and straight tee, donot have a significant impact on the mean difference in initial and final total dissolvedsolids concentrations observed at multiple sample ports. No statistical difference was observed when comparing upward and downward oriented sanitary tees used as diverterchambers to downspout transition fittings on 10.16 and 15.24 cm diverter chambers.Utilizing a straight tee as a transition fitting with a floating ball, acting as a barrierbetween water collected in the diverter chamber of a downspout first flush diverter andthe flow passing through the transition fitting, limited diverted water from interactingwith the subsequent flow of harvested rainwater. There is not a significant differencebetween the use of a downspout first flush diverter with diverter chamber diameters of10.16 and 15.24 cm utilizing upward and downward oriented sanitary tees as downspoutto diverter chamber transition fittings. Tests at flow rates less than or equal to 12.11L/min exhibited limited changes in total dissolved solids concentrations in thedownspout first flush diverters with 15.24 cm diameter diverter chambers. Tests at flowrates less than or equal to 1.51 L/min exhibited limited changes in total dissolved solidsconcentrations in the downspout first flush diverters with 10.16 cm diameter diverterchambers. The diverter chamber drain flow rate and volume impacts the observeddifferences in initial and final TDS concentrations at all sample ports on the diverterchamber of a downspout first flush diverter regardless of flow rate. The diverterchamber drain flow rate impacts the flow rate of water entering the diverter chamberthrough the transition fitting.