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.
A protagonist (from Ancient Greek ÏÏÏÏÎ±Î³ÏÎ½Î¹ÏÏÎ®Ï (protagonistes), meaning 'player of the first part, (chief actor)' is the main character in any story, such as a literary work or drama. The protagonist is at the center of the story, makes the key decisions, and experiences the consequences of those decisions. The protagonist affects the main characters' circumstances as well, as they are often the primary actor propelling the story forward. If a story contains a subplot, or is a narrative made up of several stories, then the character who is interpreted as the protagonist of each subplot or individual story.