For many utilities waste management dictates treatment selection, as was the case for one Tribe
in Nevada faced with complying with the revised arsenic (As) maximum contaminant level (MCL) of 10 µg/L. For this Tribe, treatment
selection was not as simple as which process reliably removed arsenic below the MCL for the
least cost, but how to manage the residuals generated from the treatment process. The Tribe
explored multiple treatment processes through the Arsenic Removal Technology Pilot Plant
Study. The study included an assessment of coagulation/microfiltration, coagulation/direct
filtration, 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 and
coagulation/microfiltration (C/MF) process were capable of consistently removing arsenic below
the 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 would
potentially leave the Tribe with a hazardous waste management program for compliance with
federal regulations under 40 CFR and/or possibly be classified as a hazardous waste RCRA
facility. In addition to the liability associated with managing hazardous waste and a decrease in
public acceptance, the additional costs to dispose of the hazardous waste would increase the life
cycle cost of the Tribe's facility by 20 percent. So, while the water treatment process proved
uncomplicated and reliable, the waste treatment would potentially be costly and require
additional permits to operate the facility. On the other hand, research on C/MF sludge has
indicated that the dried sludge from the C/MF would pass the TCLP test and could be disposed
of in a municipal, non-hazardous landfill with fewer regulatory compliance issues and for a
significantly lower disposal cost. In the end, it was not the water treatment life cycle treatment
cost or reliability that dictated the appropriate technology, but the management of the As laden
waste. The Tribe selected C/MF to provide their people with affordable and safe water with an
easy to manage waste residual. Includes 4 references.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 300 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 06/17/2004 |
