Dec
25

Removal of Chemicals PCB THM TCE from Drinking Water

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Background

It is always a wise decision to be vigilant concerning the odor and taste of your drinking water, whether from surface or groundwater, municipal or well. Should your water ever have an odor or taste problem, it should come as no shock given the volume of possible causes of it. There are at least 700 pollutants found in the drinking water, but the EPA is required to set standards for only about sixty of them, and these standards are routinely violated without consequence. Out of the 250,000 violations, the states took just over 2,600 enforcement actions, while the EPA took about 600. Municipalities struggle with outdated technology. Over 70,000 different chemical compounds are now in use by industry, agriculture, and private citizens, with 5,000 new and unproven chemical compounds being added into the environment each year. That amounts to 18 billion pounds of new pollutants every year.

There are a vast number of chemical contaminates which can affect a water supply. Included in this category are trihalomethanes THM, pesticides, industrial solvents, halogenated hydrocarbons, polychlorinated biphenyls PCBs, trichloroethylene TCE, and polycyclic aromatic hydrocarbons PAHs. THMs are a byproduct of the chlorination process that most public drinking water systems use for disinfection. Chloroform is the primary THM of concern.

Removal Treatment

The best technology available for removing these chemicals is activated carbon or AC. For the vast majority of the water contaminants listed by the EPA, filter carbon, often called charcoal, is the preferred treatment.

Carbon adsorption is probably the most widely sold method for home water treatment. This is because of its ability to improve water by removing many disagreeable tastes and odors including objectionable chlorine. Activated carbon (AC) is processed carbon. In this form it will remove far more contamination from water than will non-activated carbon. AC is made from a variety of carbon based materials such as coal, petroleum, nut shells, and fruit pits. These are heated to high temperatures with steam in the absence of oxygen (the activation process) leaving millions of microscopic pores and great surface area. One pound of activated carbon provides from 60 to 150 acres of surface area. The pores trap microscopic particles and large organic molecules while the activated surface areas cling on to or adsorb the smaller organic molecules. While AC theoretically has the ability to remove or reduce numerous organic chemicals like pesticides, THM’s, TCE, PCB, etc., its actual effectiveness is highly DEPENDENT on the following factors:

1. The type of carbon and the amount used (carbon block filters will remove chlorine and it’s by-products — GAC will only remove chlorine)

2. The design of the filter and how SLOWLY water flows through it (Contact Time).

3. How long the carbon has been in service and how many gallons it has treated.

4. The kinds of impurities it has removed.

5. The water conditions (e.g. turbidity, temperature, etc.)

Drinking water units, counter top filters, under sink filters, whole house filters and reverse osmosis units (which normally have at least two high quality carbon filters) for the most part rely upon carbon block filters for their effectiveness at chemical removal. For the whole house systems, activated carbon blocks are the most effective chemical removal filters. The choice of a single, dual or triple housing system depends upon the level of contaminants in your water, number of people in the house and the daily water usage.

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