Water Conditioning & Purification Magazine

Looking for an Arsenic Antidote: POU RO Finds a Warm Reception in the Desert

By Shannon Murphy

Summary: With the advent of a new federal arsenic limit set to go into effect in two years, some water treatment companies across the nation are conducting their own pilot tests. One company in Arizona pitted centralized water vs. point-of-use reverse osmosis in two communities and came away with definitive results.


For many small water systems, finding a cost efficient method to meet the approaching deadline for the new arsenic standard has more questions than answers. There are a few different technologies available to the water systems. Making the decision on which one is best for the user, however, can appear to be a complex one. Several factors need to be addressed—cost, engineering, training, installation, operation and maintenance, and reassurance that the technology works.

To provide some of these answers, one company started pilot testing point-of-use (POU) reverse osmosis (RO) units with a few different communities in the Phoenix area. The first public water system is a relatively large community consisting of 2,000 residents and 700 service connections. What makes this community a candidate for POU approach over a centralized system is the fact that the water district has three separate non-mixing well heads, each requiring a separate arsenic treatment system if they were to proceed with a centralized approach. As a result, this triples the cost of such an approach. The second community is a smaller water system, consisting of 40 residents and 20 service connections with 20 to 30 additional connections planned in the coming year.

Town meetings
In both cases, initial meetings were set up with the community where the company provided background information about the Safe Drinking Water Act, the new arsenic ruling, timelines on compliance, and an overview of the role POU RO can play in cost efficiently meeting these requirements. Community meetings are invaluable as many participants have several questions, which are easily addressed up front in this type of forum. Following the meetings, both community water boards agreed to proceed with a POU RO study, with one water system deciding to pursue complete community installation.

In brief, these case studies included 20 NSF-certified RO units with total dissolved solids (TDS) monitoring faucets installed into volunteer dwellings where specific water and operational parameters will be evaluated over an eight-month period. Water characteristics to be monitored included: arsenic, alkalinity, bacteria, total chlorine, free chlorine, fluoride, hardness, inlet pressure, iron, manganese, pH, TDS and temperature. The testing matrix will evaluate pre- and post-filtration concentrations as well as any difference between the Arizona Department of Environmental Quality (ADEQ) wet lab test results and on-site quick test kits supplied by Hach Co. Water parameters will be evaluated every other month over an eight-month period and charted. During the study, the homeowners will be provided three surveys to complete regarding the project.

Installation of POU RO
The installation of RO units was completed through use of a local water dealer. In one case, the water dealer was bonded to the water system. For many of these water systems, the use of a local bonded plumber or water dealer will prove to be an easier, more economical route to take. This is due to the fact that many water systems do not have the expertise or time needed to install, maintain, sample and document for a POU approach. By relying on the local plumber or water dealer to manage the installation, operation and maintenance, testing and result documentation, water systems can quickly review these maintenance records and results submitted to ensure efficient operation of the POU program within their own office.

During the installation process, there were a few participants already equipped with a home filtration device. All of these, however, were simple carbon systems not certified for the reduction of arsenic. These systems were removed and replaced with an RO system. The installations took an average of 45 minutes as many of the homeowners wanted to discuss the purpose of the project as well as background of the arsenic regulations. In the end, units were installed ahead of schedule.

Public education
Another aspect to a successful installation is education of the public. The company in this instance developed a manual for all participants that provided information regarding the U.S. Environmental Protection Agency (USEPA), where regulations originate, why arsenic regulations changed, and information about the RO unit and expectations of the project. These booklets were reviewed and left with each homeowner participating in the case study. Additionally, an initial survey was left with the homeowner at the time of installation.

Water sampling and testing
One week following the installation of the units, water samples were obtained from the houses, one from the RO and one from the outside hose bib. These initial water tests results show the RO unit reduces the concentration of arsenic to below detection levels. In addition, the RO provided an average of 81 percent reduction in alkalinity, 94 percent reduction in hardness, and a 92 percent reduction of TDS when compared to the raw incoming water (see Figure 1).

Pricing out the program
Several different cost estimates regarding the use of POU RO have been published by the USEPA and other agencies. Many of these estimates for a POU RO installation are substantially higher due to initial cost estimates of the RO unit (the USEPA has used numbers between $300 and $600 per RO). A cost comparison of POU vs. centralized treatment using an NSF-certified, five-stage RO unit and based on realistic assumptions regarding initial cost of the RO, installation, replacement elements and periodic service costs over a 10-year period was put together. With these calculations, the cost to implement a POU project using the RO mentioned above averages under $14 a month per service connection. Compare this 10-year cost against centralized treatment provided by an independent regulatory body, and the break-even point for centralized treatment cost comes in between 300 and 350 service connections (see Figure 2).

Financial assistance
There are currently a number of financial assistance programs that are available to small drinking water systems working to comply with the arsenic rule. Many state departments of commerce have infrastructure grant and loan programs. The drinking water agency with primacy in each state can also help small water utilities identify state funding opportunities.

Two federal programs set up to assist small water systems are the USEPA Drinking Water State Revolving Fund (DWSRF) and the U.S. Department of Agriculture Rural Utilities Service (RUS) grant and loan program. The DWSRF provides capitalization grants and loans to states for implementation of these drinking water projects. Many small systems have already been inquiring about and benefiting from the funding from DWSRF. The RUS program provides loans and grants for drinking water projects, which have totaled on average $750 million annually. Assistance from the RUS program is targeted for small systems serving fewer than 10,000 people.

Conclusion
The new arsenic rule goes into effect in January 2006 and, for many small water systems, there are many time-consuming factors which need to be completed before then in order to implement a successful water treatment program. Small water systems may have the greatest at stake with this upcoming rule, as many of these systems currently do not treat their water, and thus have the greatest learning curve ahead of them. Small water systems also need to be aware of proposed regulations for several different water contaminants and other coming disinfection rules. POU RO provides a single cost efficient way for many water districts to meet the needs of today’s regulated contaminants and tomorrow’s discoveries. Where there has been success in providing education, there are still questions regarding the use of POU ROs for compliance. Many of these issues are expected to be answered this year through pilot studies that are being conducted. With these answers, millions of dollars can be saved by small water communities and homeowners for today’s concerns as well as future ones.

About the author
Shannon Murphy is vice president of municipal sales for Watts Premier Inc., of Phoenix, whose RO units were used in the above study. Before that, he was operations manager for NSF International’s DWTU Program. For updates regarding the progress and survey results of these and other projects with which Watts Premier is involved, go to: www.wattspremier.com/adwa/. A member of the WC&P Technical Review Committee, Murphy can be reached at (623) 505-1514 or email: murphysp@wattsind.com

 

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