|Ask the Expert: August 2008
|Question: My customers are asking about their RO systems and if they will make their water safe. Edmonton, Alberta (Canada) has just experienced a leak of an industrial (presumably) solvent into the river that feeds the municipal water supply. Alberta Environment is currently sampling, but so far all theyre releasing is that it is a solvent of some sort.
Is this the sort of contamination RO is typically suited for removing or should we be advising people to purchase bottled water sourced elsewhere as a precaution?
Greg Douglas, Indoor Environmental Specialist
Douglas Environmental Solutions
There are a couple factors in play regarding this spill. First, the news article you provided for review states 'the location of the spill means Edmontons drinking water supply will not be affected' and 'the city will continue to monitor. If there is a need to send out a warning, well do that as soon as possible.' So it appears that the spill has not worked its way in to the drinking water.
Under the umbrella of Homeland Security, the EPA/ETV program-in conjunction with NSF International-tested RO units for removal of chemical contaminants in drinking water. The testing was conducted to evaluate point of use reverse osmosis units in the event of a short-term chemical contamination of drinking water. The test chemicals included aldicarb, benzene, cadmium, cesium, carbofuran, chloroform, dichlorvos, dicrotophos, fenamiphos, mercury, mevinphos, oxamyl, strontium and strychnine. The RO membrane was capable of reducing nearly all of the chemical challenges to 99 percent or better. The three challenges that did not perform well were benzene and chloroform, reduced to 84 percent and mercury, reduced to 44 percent. The test also included a chemical post filter after which all of the agents were reduced to over 99 percent. Further information is available at http://www.nsf.org/business/drinking_water_systems_center dws_ homeland_list.asp?program=Drinking WatSysCen.
One could state that certified RO systems are capable of providing a safety barrier, especially since the current status is that this spill has not entered into the drinking water system; however, if at any time the water district releases a formal statement to not drink the water, then this warning must be followed. For homeowners in the affected area that are on private wells, it would be advantageous to have bottled water in the house until additional information is released on what the contaminant is and if there is any underground contamination from the release. Once more information is available, groups of homeowners in the affected area should look into having their water tested for the chemical contaminant. I am sure they can work out a special group deal price for this testing.
Additionally, if a homeowner has a water filtration device and there is a formal statement from the water district regarding the drinking water being compromised, it is important to inform all of your callers and customers that the water filtration device needs to go through a filter change out and sanitization following the contamination incident.
Shannon Murphy, Watts Premier
Without knowing exactly what solvent it is, its difficult to recommend a treatment technology. My guess is that activated carbon or organoclayis more likely to do a better job. RO is best at removing salts (ionic constituents), not solvents. Of course, a residential RO will have activated carbon built in; however, a separate GAC cartridge or carbon block will have a greater adsorption capacity.
Again, I believe that its essential that the actual chemical be determined before recommending a solution.
Peter Cartwright, Cartwright Consulting Co.
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