Suspended growth treatment systems freely suspend microorganisms in water. They use biological treatment processes in which microorganisms are maintained in suspension within the liquid. In suspended growth treatment systems, microorganisms convert the organic matter or other constituents in the wastewater into gases and cell tissue. The most common type of aerobic system is the suspended growth treatment system. Suspended growth technologies are conventional activated sludge treatment systems that use various process modes, ranging from conventional, extended aeration, contact stabilization, sequencing batch, and single sludge, which are available for polishing anaerobically treated effluents.

A water treatment system used with suspended growth treatment systems can apply to industrial plants, heating and cooling systems, cooling tower systems, steam systems, and domestic water supplies and swimming pools. A wastewater treatment system is an essential component of effluent distribution systems. These suspended growth treatment systems deliver wastewater to soil infiltrative surfaces either by gravity or by pressure distribution. Residuals are the by-products of a wastewater treatment process, including sludge and septage. Polymers are used for industrial water treatment as scale inhibitors in stressed cooling water. They do not contain phosphorous, inhibit the deposition of calcium carbonate and other low soluble salts, and provide good activity over a wide pH range.

Suspended growth treatment systems, such as biological treatment of water, involve the use of naturally occurring microorganisms in the surface water to improve water quality. Under optimum conditions, the organisms break down material in the water and improve the water quality. Natural suspended growth treatment systems, such as wastewater biological treatment, can be used for organic wastewaters such as municipal sewage and tend to be lower in cost for operation and maintenance. Although such processes tend to be land-intensive when compared to conventional biological processes, they are often more effective in removing pathogens and do so reliably and continuously when properly designed. Wastewater treatment equipment can be categorized as screening and conveying equipment, clarification and suspended solids removal equipment, aeration and biological treatment equipment, and tertiary treatment and disinfection equipment.