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By James J. Pardini P.E., CPE, MEL Chemicals, Inc.

Rosemont Water Company is a community water system in Rosemont NJ, a small town in rural Hunterdon County, New Jersey. It serves approximately 72 customers. The New Jersey Department of Environmental Protection (NJDEP) has established a state drinking water MCL for arsenic of 5 parts per billion (ppb). This is more stringent than the federal EPA standard of 10 ppb. With an arsenic level of typically 6-7 ppb, Rosemont was faced with finding an appropriate technology for arsenic removal.

Rosemont's well site is in the midst of a residential community. It has no access to a sewer to handle any backwash stream. The well operates at 40 gallons per minute, and is housed in a well house that is an 8 ft. by 8 ft. structure. Expansion of the well house was not an option, both for financial and aesthetic reasons. Further, NJDEP required that the arsenic treatment system be fully redundant. In other words, the overall system must comprise two complete units in series. The first or "lead" vessel removes all of the arsenic, while the second, or "lag" vessel serves as back-up. When the media in the first unit is exhausted the second unit protects customers until the media in the first unit can be replaced.

So the problem became finding an arsenic removal technology that could provide a 40 gallon per minute redundant system that did not require backwashing and that could fit in the available space.