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The City of McAllen, Texas, with the assistance of CH2M HILL and theco-sponsorship of the United States Bureau of Reclamation (BOR), Electric PowerResearch Institute, and the Texas Water Development Board, has pilot tested anintegrated membrane bioreactor (MBR)/reverse osmosis (RO) treatment train toreclaim municipal wastewater to a quality suitable for use as a new drinkingwater supply in the process called indirect potable reuse. Previous testing bythe City (Phase 1) demonstrated the applicability and cost of microfiltration(Memcor and ZeeWeed systems) to enhance the quality of secondary effluent forsubsequent treatment by RO and the feasibility of a membrane bioreactor system(ZenoGem) to produce RO feedwater directly from minimally processed sewage. Phase2 testing, reported on in this paper, is designed to demonstrate, when treatingscreened, degritted sewage, reliable operation of both the MBR and RO processesand that the effluent from such a train can meet all federal primary and statesecondary drinking water regulations and comply with state requirements forindirect potable reuse. Results show the ZenoGem process to be reliable, requireminimal operator attention and maintenance, produce an effluent that can beprocessed by RO with little fouling and that easily exceeds the City's currenteffluent discharge requirements relative to biological oxygen demand (BOD), totalsuspended solids (TSS), and ammonia. The ZenoGem permeate quality exceeds ROfeedwater criteria for turbidity and silt density index and the RO systemperformance confirms minimal membrane fouling by particles. However, the highcalcium hardness and phosphate levels in the City's wastewater (and ZenoGempermeate) caused mineral precipitation within the RO system when operated athigher recoveries. Precipitation can be controlled, however, by increasedacidification of the RO feedwater. Includes 2 references, tables, figures.

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Edition: Vol. - No. Published: 01/01/2000 Number of Pages: 18File Size: 1 file , 330 KB