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.