AWWA ACE59976

For many utilities waste management dictates treatment selection, as was the case for one Tribein Nevada faced with complying with the revised arsenic (As) maximum contaminant level (MCL) of 10 µg/L. For this Tribe, treatmentselection was not as simple as which process reliably removed arsenic below the MCL for theleast cost, but how to manage the residuals generated from the treatment process. The Tribeexplored multiple treatment processes through the Arsenic Removal Technology Pilot PlantStudy. The study included an assessment of coagulation/microfiltration, coagulation/directfiltration, ion exchange (IX), and three adsorptive medias at both ambient and depressed pH.Due to challenging water quality characteristics including high arsenic levels (70 and 110 µg/L),significant levels of silica (55 mg/L) and an elevated pH, only the IX andcoagulation/microfiltration (C/MF) process were capable of consistently removing arsenic belowthe MCL. Additionally, these technologies were estimated to have similar life cycle costs, +/-10%, assuming all waste generated would be classified as non-hazardous.With As concentrations as high as 10,000 µg/L in the waste brine, the IX process wouldpotentially leave the Tribe with a hazardous waste management program for compliance withfederal regulations under 40 CFR and/or possibly be classified as a hazardous waste RCRAfacility. In addition to the liability associated with managing hazardous waste and a decrease inpublic acceptance, the additional costs to dispose of the hazardous waste would increase the lifecycle cost of the Tribe's facility by 20 percent. So, while the water treatment process proveduncomplicated and reliable, the waste treatment would potentially be costly and requireadditional permits to operate the facility. On the other hand, research on C/MF sludge hasindicated that the dried sludge from the C/MF would pass the TCLP test and could be disposedof in a municipal, non-hazardous landfill with fewer regulatory compliance issues and for asignificantly lower disposal cost. In the end, it was not the water treatment life cycle treatmentcost or reliability that dictated the appropriate technology, but the management of the As ladenwaste. The Tribe selected C/MF to provide their people with affordable and safe water with aneasy to manage waste residual. Includes 4 references.

Product Details

Edition:

Vol. - No.

Published:

06/17/2004

Number of Pages:

6

File Size:

1 file , 300 KB