Activated Carbon Filter

Introduction

Activated carbon filtration may be selected to reduce unwanted tastes, odors, and organic chemicals (such as disinfection by-products, pesticides, and solvents) from drinking water. Activated carbon will also reduce radon gas and residual chlorine. Activated carbon filters will not remove or reduce major inorganic ions (such as sodium, calcium, chloride, nitrate, and fluoride). However, some can reduce lead, copper, and mercury. Activated carbon filters will not soften the water or disinfect it. If the water source is cloudy, this type of filter may be used after a particle filter to remove particles that may plug or reduce its efficiency.

Principles of Activated Carbon Filtration

Activated carbon filtration makes use of a specially manufactured charcoal material made up of porous carbon particles to which most organic contaminants are attracted and held (sorbed) on/in the porous surface. However, organic pollutants have large differences in affinity for activated carbon surfaces. Also, the characteristics of the carbon material (particle and pore size, surface area, surface chemistry, density, and particle hardness), the size of the filter, and the flow rate of the water through the filter have a considerable influence on the pollutant removal efficiency of these filters. Usually, smaller carbon particles and slower water flows improve contaminant removal.

Types of Units

Faucet-attached devices, or point-of-use (POU) devices, may be directly attached to the faucet, or the filter may be placed on the countertop and connected to the faucet with a hose. These units may be equipped with a by-pass feature to draw unfiltered water. Units that attach to the faucet are very small in size and offer short contact time, relatively short life, and limited contaminant removal. Despite these limitations, these devices improve water taste and reduce smells when used as directed.

Pour-through filters also generally are also small and portable. Some work merely with gravity filtration and tend to be slow; others contain a power-operated pump. These devices also improve water taste and reduce smells when used as directed.

Speciality filters are intended to treat water for appliances such as ice makers and water coolers. These also are small units, normally a combination particle and activated carbon filter, installed in the water supply pipe. When service is required, the entire unit is replaced.

Line by-pass and stationary filters are very similar. These are usually the largest units and they are connected directly into the house plumbing, requiring the services of a plumber.

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