These secondary systems have additional screens, clarifiers and digesters. These act as filtration to improve the water quality before it enters the outfall. Today, a tertiary process of sanitary waste treatment is now available. This process adds additional filtration devices to the waste system. The process discharges an effluent that is nearly drinkable and is utilized when the water quality near the discharge site needs to be maintained to the highest standards.
Industrial waste is separated from residential waste.
Inspection, repair and installation of sanitary waste treatment facilities are the three areas that provide work opportunities for the underwater contractor. External inspections of the diffuser section are common jobs that are performed. The length of the diffuser section can vary from one pipe section to several thousand feet, depending upon the rate and concentration of diffusion that is required. External inspections can be performed by divers or ROVs, and may involve the use of closed circuit video, flow meter, visual survey and hydrographic survey. The external inspection is looking for damage to the pipe and to confirm that the diffuser ports are not buried or plugged.