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Removal of Inorganic, Microbial, and Particulate Contaminants from Secondary Treated Wastewater - Village Marine Tec. Expeditionary Unit Water Purifier, Generation 1 at Gallup, NM
Citation:
NSF International, M. Blumenstein, B. Bartley, AND J. Q. ADAMS. Removal of Inorganic, Microbial, and Particulate Contaminants from Secondary Treated Wastewater - Village Marine Tec. Expeditionary Unit Water Purifier, Generation 1 at Gallup, NM. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/151, 2011.
Impact/Purpose:
To inform the public.
Description:
The EUWP was developed to treat challenging water sources with variable turbidity, chemical contamination, and very high total dissolved solids (TDS) including seawater, during emergency situations when other water treatment facilities are incapacitated. The EUWP components are designed to operate with a generator and include feed pumps, a UF pretreatment system, a one or two pass RO desalination system with an energy recovery device, storage tanks, and product pumps. The first pass part of the RO system has two arrays. One of the arrays is driven by the normal RO feed pump and the other array is driven by the energy saving device. There is only one array in the second pass part of the RO system. The EUWP has chemical feed systems for optional pretreatment coagulation and post treatment chlorination. Clean-in-place systems are included with the UF and RO skids. During this verification test, coagulation pretreatment was employed, but not post-treatment chlorination. The test was performed at the City of Gallup WWTP at 800 Sweetwater Place, Gallup, New Mexico. The WWTP treats an average of 3 million gallons per day (MGD) of wastewater with a peak of 5.5 MGD in the summer. The source water for testing was secondary wastewater effluent prior to chlorination. The UF system reduced turbidity from a mean of 11.1 Nephelometric Turbidity Units (NTU) in the feed water to a mean of 0.74 NTU in the UF filtrate as measured by the daily grab samples. The RO permeate had a mean turbidity of 0.15 NTU based on the handheld meter readings. The 95% confidence interval for the handheld meter results showed an expected range of 0.13 to 0.17 NTU for the RO permeate. The RO permeate turbidity, as manually recorded from the in-line analyzer, had a mean value of 0.016 NTU. The UF system was found to have faulty seals, which is discussed in the verification report. This may explain why the turbidity reductions by the UF system did not meet the NPDWR of <0.3 NTU 95% of the time. While the UF system did not achieve the results expected, the RO system handled the increased loading and did serve as the ultimate barrier to ensure low turbidity product water was produced. The RO permeate turbidity levels based on the manually recorded in-line meter results show that the system did meet the NPDWR of <0.3 NTU 95% of the time and all values below 1.0 NTU. Dye-marker direct integrity tests were performed on the RO system at the start and end of the test period. The RO membranes rejected the dye at a rate higher than 99%. The rejection rate actually improved at the end of the test. These results, supported by the high rejection rate for conductivity, the low turbidity in the permeate, and the 3 LRV for coliform samples, indicate that the RO membranes maintained integrity throughout the verification test.