(a) "Combined sewage disposal system" means an approved sewage disposal system which provides for the combined collection and disposal of sewage from a group of residential, commercial or industrial buildings.
(b) "On-site sewage disposal system" means a septic tank installation on an individual lot which utilizes an anerobic bacteriological process for the elimination of solid wastes and provides for the proper and safe disposal of the effluent, subject to the approval of health and sanitation officials having jurisdiction.