'ALTERNATIVE UV DISINFECTION TECHNOLOGY DEMONSTRATION STUDY ON LOW-GRADE WASTEWATERS AT THE ROCKLAND COUNTY SEWER DISTRICT NO. 1 WWTP'

摘要

The application of alternative ultraviolet lamp technology configurations to low-gradernwastewaters was evaluated at the Rockland County Sewer District (RCSD) No1.rnWWTP. After studying five different configurations on the plant's final effluent, twornconfigurations were then applied to the primary effluent: a low-pressure, high-intensityrn(low/hi) open-channel system and a medium-pressure lamp system. Maximumrnhydraulic loadings were found to be 1.1 Lpm/UV Watt and 1.0 Lpm/UV Watt,rnrespectively, to achieve a target fecal coliform level of 1000 cfu/100mL, or a 3-logrnreduction. Both secondary and primary effluent data were used to calibrate thernUSEPA UV Disinfection Design model, and to then determine sizing requirements forrna sample application. The low-grade, primary effluent application favored the use ofrnhigher output lamps; the design example presents sizing estimates for five differentrnUV technology configurations.rnLaboratory-scale, collimated-beam, dose-response studies on primary influent andrneffluent samples were used to evaluate the impacts of particulate size and solidsrnmaceration. When treating the primary influent, a higher dose was required tornaccomplish a desired coliform reduction in a macerated, or blended sample, asrncompared to an unblended sample. Removing particles greater than 50-祄 producedrna substantial change in the sensitivity to UV. At the 1-祄 filtration level, the doseresponsernresults also showed a greater sensitivity to UV, indicating that after havingrnremoved particles greater than 1祄, the residual coliforms are primarily nonaggregated.rnWith respect to primary effluent dose-response results, there was littlerndifference between the blended and unblended samples, likely because the largerrnsolids, particularly those greater than 50 micron which would be macerated by thernblending, were removed through the primary clarifiers. The results further indicate thatrnthe dominant fraction of fecal coliform-related solids in the primary effluent are of submicronrnsize. Particle size reductions below the level of approximately 50-祄 will notrnnecessarily result in improvements to the sizing and/or performance of UVrndisinfection systems, unless the treatment removes particles greater than 1 micron.