In sewage treatment plants, centrifugal blowers are replacing roots blowers. In other words, the steps in the process take place one after another in the same tank. Usually a multiple tank system is used, thus allowing the incoming flow to be switched to the empty tank while the other is in operation. In order to keep microorganisms to treat the influent, a SBR is never completely emptied and retains a portion of the settled solids to provide starter microorganisms for the next batch. A sedimentation chamber is any container in which the velocity is slowed to allow settling to occur.
Sedimentation results anytime flow is reduced by restriction of velocity or a change in aeration.
Seeding is the process of inoculating the influent with microorganisms for removal of contaminants. Septic pertains to anaerobic conditions and usually refers to septic tanks or holding areas where free oxygen is unavailable and anaerobic bacteria consume BOD and give off hydrogen sulfide gas and methane. In some collection systems, sewage in held in the lines for a long period of time and pre-aeration is required to strip the influent of toxic volatile gases caused by the anaerobic conditions. A septic tank is used to detain domestic waters to allow the settling of solids prior to distribution to a leech field for soil absorption. Septic tanks treat sewage by anaerobic means and are installed primarily for private homes and housing tracts.