Wastewater treatment equipment is used to treat, remediate, and process effluent wastewater. By definition, wastewater carries a mixture of dissolved or suspended solids from residences, agriculture, and industries. Some wastewater is polluted, meaning that industrial wastes, chemicals, toxins, or other objectionable materials are present in sufficient quantities to cause a measurable degradation of water quality. Often, wastewater treatment equipment is used at sewage treatment plants, facilities that use a series of tanks, screens, filters, and other processes to remove dissolved and suspended solids from wastewater. Wastewater treatment equipment may also be used commercially, typically in conjunction with aboveground or sub-surface systems such sewers, disposal wells, and waste ponds.

Wastewater treatment equipment is used to achieve three levels of treatment. Primary wastewater treatment uses screening to remove large objects, grit chambers to remove smaller particles, and sedimentation tanks to separate solids from liquids. Secondary wastewater treatment uses biological methods such as activated sludge, trickling filters, and lagoons. Activated sludge is a bacteria-containing microorganism that breaks down organic materials. Typically, activated sludge is used in conjunction with aeration and agitation. Trickling filters are beds of coarse media that drain at the bottom. Lagoons or waste ponds rely upon the interaction of sunlight, algae, microorganisms, and oxygen. Once primary and secondary treatment is complete, wastewater may be disinfected with chlorine or other disinfecting compounds, or with ozone or ultraviolet light (UV).

There are many types of wastewater treatment equipment. Examples include biological wastewater treatment systems, aerobic wastewater treatment systems; products such as trash rakes; and various types of filters. Biological wastewater treatment systems cultivate microrganisms that consume disease-causing organisms and other pollutants from wastewater. Aerobic wastewater treatment systems settle out solids, but do little else to treat wastewater. Wastewater treatment equipment also includes trash rakes, clarifiers, filters, demineralizers, degasifiers, centrifuges, and sludge dryers. Many different types of filters are used. Examples include sand filters, neutralizing filters, oxidizing filters, activated carbon filters, and crossflow filtration systems.