By Paula Rice

Summary: It's clear not all carbon filters are alike in terms of contaminant reduction performance. Rigorous product development, quality control and experimentation have shown solid carbon block products to be far more efficient at removing contaminants of aesthetic and health concern.

Drinking water pollution comes from many sources. Surface water becomes contaminated from agricultural runoff, community landfills, polluted runoff (the nation's leading cause of water pollution), and hazardous waste produced as byproducts of manufacturing. Groundwater is contaminated by leaks of pollutants such as gasoline and MTBE from underground storage tanks and injection of hazardous waste into deep wells (which is being phased out). The drinking water treatment industry is experiencing significant growth due to consumer demand for products that could protect them from these potentially harmful contaminants which may be found in drinking water supplies as well as aesthetically improve their water.

Highly Regarded

The effectiveness of any drinking water treatment device is measured by the performance of its filter. A close review of drinking water treatment unit certifications shows that solid carbon block filters are the most effective for reducing a wide range of contaminants, including those that may be found in groundwater. Certain drinking water treatment units (DWTU) that use solid carbon block filters have been tested and certified to reduce as many as 65 contaminants.

In the early 1970s, the solid carbon block filter technology was developed for the purpose of treating contaminants for health reasons as well as aesthetically improving water quality.

The technology combines mechanical filtration, chemical reaction and physical adsorption into a single device to reduce a broad spectrum of harmful contaminants.

Importance of Raw Materials

Activated carbon is the primary raw material used in solid carbon block filters. Multi-Pure determines the characterization of activated carbons to use for its filters. Carbons specified are especially effective in reducing inorganics such as lead and mercury as well as organic compounds - disinfection by-products (DBPs), volatile organic compounds (VOCs), PCBs, MTBE, etc.

Many carbons are selected with a high surface area and high retentivity characteristics. Years of research, development and manufacturing experience have helped Multi-Pure develop specifications for carbon and other media that give its compacted carbon block filters distinctive performance advantages over other treatment alternatives. Quality assurance procedures are carefully developed and maintained to assure that raw materials meet our high standards.

Technological Advantages

As evidenced by independent laboratory testing and certification of solid carbon block filters, Multi-Pure has been successful in developing the technology to produce filters that provide greater chemical adsorption and mechanical filtration. Materials are formed into a carbon block, which is densely compacted. Compression enhances the kinetics of the filter and provides performance that cannot be achieved with extruded or granular activated carbon (GAC) filters. Compacted solid carbon block filters have a large surface area for chemical/physical adsorption to take place. With a solid carbon block, the water contact time is longer and provides for greater adsorption of many different chemicals, pesticides, herbicides and certain heavy metals. A close review of product listings confirms that Multi-Pure's Drinking Water Systems are among the few that have been certified to reduce PCBs -a difficult contaminant to treat. Only a handful of products have been tested and certified to reduce a wide range of contaminants that are more difficult to treat.

In addition, the densely compacted carbon block mechanically filters particles down to 0.5 micron, including Giardia and Cryptosporidium, asbestos, turbidity and particulates. Our filter design incorporates an outer prefiltration medium to remove large particles and prevent premature clogging of the filter. Multi-Pure's solid carbon block filters are exceptionally uniform and don't channel or allow bypass.

Filter Capacity

Filter capacity varies depending on the density and size of the filter. The characterization of activated carbons used by Multi-Pure determines the capacity of the water filters. Capacity ratings apply to the chemical adsorption capabilities of the carbon and specialized media. Carbons with a high surface area allow for long life and high adsorption capacity. Capacity ratings for Multi-Pure Drinking Water Systems range from 600 gallons to 1,200 gallons, depending on model.

Claims of capacity aren't applicable to contaminants reduced by mechanical filtration because of broad variations in the quality and quantity of physical matter in the drinking water. The solid carbon block filter is engineered so that contaminants removed by mechanical filtration will cause the flow rate to decrease and the water filters to clog, thus offering protection to the consumer from Giardia, Cryptosporidium and other contaminants with a specific physical size.

Applications

Solid carbon block filters are used in point-of-use drinking water treatment devices designed for countertop, undersink and inline applications.

Conclusion

Solid carbon block filters effectively treat the age-old contaminants of yesteryear, such as lead, TCE, chlorine, benzene and "new" contaminants found in the nation's drinking water supplies today like MTBE, chloramines and PCBs. They also likely will be proven capable of significantly reducing contaminants that may be found in drinking water supplies in the future such as antibiotics and other drugs. The effectiveness of solid carbon block filters in treating a broad spectrum of contaminants of aesthetic as well as health concern makes it the technology of choice by distributors and more importantly, consumers throughout the country.

Re-edited version of article published in Water Conditioning & Purification Magazine