Residential users may be considered to be one class of user and an equitable service charge may be determined for each user based on an estimate of the total wastewater contribution of this class of user. The city council may classify industrial, commercial, and other nonresidential establishments as a residential user, provided that the wastes from these establishments are equivalent to the wastes from the average residential user with respect to volume, total suspended solids, and BOD. (Ord. 414 § 5, 1982)