A pilot-scale MBR plant, manufactured by Zenon Environmental Inc., was operated at the Whittier Narrows Water Reclamation Plant (WNWRP) for twenty-one months. The objective of this study was to compare the long-term performance of the system, with respect to effluent water quality, to that of the WNWRP. Water quality parameters of particular interest were COD, suspended solids, turbidity, nitrogen, priority pollutants, microbial indicator organisms, and emerging micropollutants (NDMA and selected hormones). Primary effluent from the plant was used as influent to the MBR. Average COD, total suspended solids (TSS), and ammonia concentrations in the primary effluent were 330, 100, and 24 mg/L, respectively. Key findings from the study include (1) the MBR plant achieved excellent COD (96%), TSS (> 99%), and turbidity (typically <0.2 NTU) removals; (2) the MBR plant was able to achieve excellent nitrogen removal with an average effluent nitrate nitrogen concentration of 6.4 mg N/L and an ammonia nitrogen concentration typically <1 mg N/L; (3) all priority pollutants detected in the primary effluent were removed by the MBR to levels below the detection limits or to levels equivalent to that of the WNWRP effluent; (4) the MBR typically achieved >6-log removal of total coliform and fecal coliform as well as indigenous coliphage; (5) the MBR process removed approximately 80% of the NDMA and most of the selected hormones. The performance with respect to NDMA and hormone removals was comparable to that of the WNWRP despite the fact that the MBR was operated at a longer solids retention time and higher mixed liquor suspended solids concentration than the WNWRP; (6) membrane production capacity and cleaning requirements have met or exceeded manufacturer's recommendations.
The unprecedented demand for gallium arsenide integrated circuits presents manufacturers with a significant challenge, to maintain compliance with wastewater discharge limits for arsenic. Violating this limit can result in fines, interruption of operations, and even criminal liability. Recent action in the US regulatory arena suggests that this limit is likely to decrease dramatically in the near future. Consequently, management of this aspect of gallium arsenide manufacturing could have a significant impact on sustaining fab operations. The characteristics of typical arsenic-contributing wastewater streams are described as well as the processes and associated chemistry employed in conventional arsenic treatment . A brief overview of advanced and emerging technologies is presented as well as some of the results of recent evaluations in the Motorola "CS 1" wastewater treatment operations.
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