The purpose of this chapter is to enable the collection of the costs of operation and maintenance of the sewage treatment works in the City from all customers in proportion to the contribution of each to the total sewage loading of the treatment works; to recover sufficient revenue to equal the cost of all treatment works operation and maintenance, including replacement; and to enable collection of revenue at least sufficient to provide for amortization of and payment of interest on indebtedness incurred in the construction of the sewage treatment works.