Q
Can public water systems use POU/POE decentralized water treatment for compliance with drinking water standards? If so, why aren’t more of them doing it? – U.S.
A
Public water systems (PWS) are defined as providing piped water for human consumption for 25 persons or 15 service connections. There are about 160,000 PWS in the U.S., including communities and non-communities, and the vast majority of them are small systems. Almost all of these water systems are central systems with water treated and piped from one or a few producing sources to the consumers’ taps. However, the Safe Drinking Water Act (SDWA) specifically allows use of POU or POE for PWS compliance with SDWA requirements in small systems defined in three categories ranging from 10,000 to 3,300; 3,300 to 500; and 500 to 25 persons. When EPA lists compliance technologies for Maximum Contaminant Levels or Treatment Techniques that are affordable in small systems, they are required to include packaged or modular systems and POU and POE treatment units. This requirement was an amendment to the SDWA in 1986 that resulted from active lobbying by the POU/POE industry.
The law
According to Section 1412(b)(4)(E)(ii) of the SDWA, POU and POE treatment units in a decentralized system, shall be owned, controlled and maintained by the public water system or by a person under contract with the public water system to ensure proper operation and maintenance and compliance, and equipped with mechanical warnings to ensure that customers are automatically notified of operational problems. POE, but not POU, devices are acceptable to achieve compliance with microbial contaminants or indicators of microbial contaminants. In addition, if the American National Standards Institute (ANSI) has issued product standards applicable to a specific type of POU or POE treatment unit, individual units of that type shall not be accepted for compliance with a maximum contaminant level or treatment technique requirement unless they are independently certified in accordance with those ANSI standards.
POU, POE or bottled water may be required by states as part of a Variance or Exemption (40 CFR Section 142.62)(f) from a regulation to avoid an unreasonable risk to health during the time that the compliance delay is allowed. Bottled water is not allowed for compliance. POE cannot be required for an exemption from corrosion control treatment requirements under the Lead and Copper Rule. POE, POU or bottled water can be required as a condition for an exemption from the source water or lead service line replacement.
The regulations
Subsequently, EPA produced regulations (40 CFR 141.100) that provided additional restrictions for POE devices summarized as follows:
- The PWS has the responsibility to operate and maintain the POE treatment system. This can be contracted.
- The PWS must obtain state approval of a monitoring plan before installation. The device and plan must provide public health protection equivalent to central water treatment. Monitoring must include physical measurements such as total flow and mechanical condition of the equipment.
- Effective technology must be properly applied according to the plan including microbial safety, performance certification, field testing and a “rigorous” engineering design review, if not part of the certification process. Backwashing, post contactor disinfection and HPC management “may be necessary.”
- All consumers must be protected. Every building must have a POE device and be subject to the plan requirements, i.e. 100 percent community participation, and the responsibilities for the POE device must convey with the property.
EPA has identified several applicable POE technologies including activated alumina, anion and cation exchange and other media for inorganic contaminants. However, RO devices are not listed by ANSI/NSF 58 because of reject water volume and copper pipe corrosion. POE could be required for microbial regulation compliance, and also for volatile contaminants like radon or volatile synthetic organic chemicals because of inhalation exposures. The likely principal reason for these rigid restrictions for POE devices is because they are eligible for control of microbial non-compliance, which would include acute risks. The requirement to consider post treatment for HPC management might be desirable for possible taste and odor control, but HPCs are not regulated as a health risk, per se, except as part of the Surface Water Treatment Rule, at 500 colony counts per ml. On the other hand, bottled water guidance values are much higher, and HPC control is not required for individual POE water softeners. In 2004, the World Health Organization concluded that there was not a connection between HPC and gastrointestinal infections in the general population.
Some of these are onerous requirements and make it unlikely that many small public water suppliers would opt for a decentralized POE system except under extreme circumstances. In addition, I would suspect that the cost of decentralized POE is often probably greater than for a central treatment system. I know of a few decentralized POE examples that might be special cases in very small communities: North Pole, Alaska (sulfolane); and several small communities in Northern Illinois (esp. radium) and nearby.
POU guidance and implementation experience
POU requirements are similar to those listed for POE, but they are not permitted as compliance treatments for microbials or volatiles like radon and nitrate. They are especially applicable and cost effective in small systems for inorganics like arsenic.
State regulatory status
Most states have had limited or no activity for implementation of POU or POE for compliance in small systems, and most do not have rules or policies in place. The general impression is that many of the state drinking water regulators have limited familiarity as well as limited interest in allowing these approaches, even though there are many successful examples and published studies that demonstrate the implementation methodologies and safety. They probably feel that central treatment is the ideal and that decentralized systems are too complicated and require too much oversight, even though there are streamlined approaches that have been employed in some states, e.g. arsenic in Arizona that would be possible and actually desirable and cost effective.
There are numerous examples in the published literature on experiences with decentralized compliance. About 60 arsenic POU systems are in operation with a concentration in Arizona. Watts Water Co. has been aggressively marketing the approach. One example of a full scale demonstration was an EPA funded demonstration project for arsenic removal in Grimes, Calif. (EPA X82952301).
Grimes, Calif. has a population of about 300. The water supply was centrally chlorinated and contained about 25 ppb arsenic. POU devices were installed in 122 locations, 105 were residences and 17 were community buildings or businesses; one residence included a daycare. Each POU unit had an automatic shutoff device based upon volume of use. The POU iron modified activated alumina (AA) units were equipped with two AA media cartridges and a GAC post-filter. After one year, 90 percent of the POU AA cartridges did not need replacement. The POU iron media units used one iron media cartridge, one pre-sediment filter and a GAC post-filter. Installation of each AA device took about one hour due to the age and diversity of the plumbing; the time was about 15 minutes in more modern homes. The POU devices, installation and maintenance were donated to the community by Kinetico and installed and managed by their local distributor.
Every POU device was sampled for arsenic after installation with inexpensive test kits ($1 or $2 each). A portion of the POU devices was sampled quarterly with each device sampled at least once during the study period. Only two samples exceeded the MCL of 10 ppb during the study. Microbiological samples were also collected; the geometric mean for HPC was 320 cfu/ml. No samples tested positive for fecal coliforms. The units were rated at 500 gallons capacity. The iron media cartridges actually treated 800 to 1,100 gallons before breakthrough; the AA media cartridges treated up to 1,600 gallons before needing replacement. At the end of the study, the community attitude toward the use of the POU devices was positive. Depending on the frequency of sampling and filter cartridge change-out, this decentralized approach could cost less than half the estimated cost of central treatment. Generally, the crossover between annualized costs of decentralized and centralized systems is probably in the range of several hundred installed units.
Conclusions
Even though the regulations and guidelines are more complicated than necessary, and often unnecessarily have a chilling effect, there are significant opportunities especially for POU and sometimes POE to meet drinking water regulations or for variances or exemptions. Costs of decentralized approaches can be much lower than central treatment, which in very small systems is ultimately subsidized by U.S. taxpayers. Distributors and providers should be more actively promoting the decentralized approach and especially providing complete contractual services to the community water supplies that include sales, installation, O&M and problem-solving sampling and monitoring. It might be appropriate for states to certify those providers so they can feel more comfortable relying upon them to help assure that the water system is in compliance with all drinking water standards. It would also be appropriate for the industry as well as the Rural Water Association and related assistance organizations to try to encourage the EPA and state regulators to have more reasonable and cost effective requirements that would assure safety and do not penalize communities that could benefit from these proven and cost effective technologies and implementation approaches. A minor amendment to monitoring regulations would probably suffice to optimize and clarify the implementation requirements.
Additional information:
http://water.epa.gov/type/drink/pws/smallsystems/compliancehelp.cfm.
Feasibility of an Economically Sustainable Point-of-Use/Point-of-Entry Decentralized Public.
Water System. EPA Report X 82952301.
Point-of-use or Point-of-entry Treatment Options for Small Drinking Water Systems, http://www.epa.gov/ogwdw/smallsystems/pdfs/guide_smallsystems_pou-poe_june6-2006.pdf. EPA 815-R-06-010, April 2006.
Cotruvo, JA. Two Tier Systems; Non-traditional compliance strategies and preliminary cost estimates, Journal American Water Works Association, Vol. 95, No. 4, April 2003.
Dr. Cotruvo is president of Joseph Cotruvo and Associates, LLC, Water, Environment and Public Health Consultants. He is a former director of the U.S. EPA Drinking Water Standards Division.
