Full Description

The Central Shoshone County Water District (District) serves potable water in ruralNorthern Idaho near the City of Kellogg. The State of Idaho has designated the watersource as groundwater under the direct influence of surface water (GWUDI).Consequently, the District is implementing a treatment facility to comply with the LongTerm 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). Membrane filtrationwas selected as the core treatment process and three suppliers participated in acompetitive procurement pre-qualification pilot study.Several factors related to the pilot study created a ripple effect that influencedprocurement specification of the membrane system and facility design. Each supplierstarted their pilot work at different times resulting in a limited window of data where allthree pilot units were operated at the same time. The pilot study duration was also lessthan typical, and repeatability of the efficacy of cleaning cycles could not be verified. Anattempt was made to simulate a high turbidity event during the pilot study similar to theevent that led to state designation of the water source as a GWUDI. The short durationof the pilot study also limited observation of the impact of seasonal temperature extremeson membrane performance.Process definition from the pilot study shaped the design. The backwash, chemicallyenhanced backwash or maintenance clean and recovery protocols used in the pilotstudy also played a significant role in the design of the facility. The selected site is notserved by a sanitary sewer and the climate, topography and soils are not compatible withevaporation or percolation beds for wastewater disposal. Consequently, recovery ordisposal of backwash and cleaning wastes were critical design factors. For this reason,backwash water is recovered to minimize the quantity of residuals requiringdisposal. The broad range of water demands and seasonal water temperatures led todevelopment of multiple criteria for design flux rates and redundancy requirements. Includes tables, figures.

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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 15File Size: 1 file , 1.7 MB