5. Sludge treatment, reuse and disposal. Sludge is produced from the treatment of wastewater in on-site (e.g. septic tank) and off-site (e.g. activated sludge) systems. This is inherently so because a primary aim of wastewater treatment is removing solids from the wastewater.
Definition of central. 1  1 : containing or constituting a center. 2  2 : of primary importance : essential, principal the central character of the novel. 3  3a : situated at, in, or near the center the central part of the stateb : easily accessible from outlying districts a central location for the new theater.
Character (arts) A character (sometimes known as a fictional character) is a person or other being in a narrative work of art (such as a novel, play, television series, video game, and film). The character may be entirely fictional or based on a real-life person, in which case the distinction of a fictional versus real character may be made.