SURFACTANTS The major components of cleaning products are surfactants. In a septic tank system, the surfactants are adsorbed onto soils and digested by the microorganisms in the drain field. They break down into water, carbon dioxide and minerals. This is known as biodegradation. The Soap and Detergent Association undertook a field study where the concentrations of major surfactants were measured in the soil beneath a household septic system drain field. The study found that in a properly sited and maintained septic tank system, there will be no surfactant residues in groundwater, indicating that surfactants are completely removed before they reach groundwater. BUILDERS The other major ingredients in cleaning products are builders. The most commonly used builders are inorganic compounds, including carbonate and phosphate compounds and zeolites (aluminosilicates). Builders either break down in

the drain field into minerals common in nature, such as carbonate, phosphate and silicate; or they settle out in the septic tank and are disposed with the sludge; or they are captured by the soils below the drain field and remain in the soil. BLEACHES Sodium hypochlorite, sodium perborate, or hydrogen peroxide are bleaches commonly used in cleaning products. They react in the wash water or during the cleaning of hard surfaces and convert to sodium, chloride and borate salts _ minerals commonly found in the environment. OTHER INGREDIENTS Other ingredients, such as fabric softening agents, antimicrobial agents and fluorescent whitening agents, biodegrade and adsorb to solids in the tank and soil. continued...

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Illustrations: [The Septic Tank System] [Biodegradation] [Adsorption]