Del. Code tit. 9 § 6514
The annual assessments, shall be collected by the county government as are other county taxes. The properties against which such assessments are levied shall be liable for the payment of the assessments in the same manner as they are liable for other county taxes. Such assessment charges shall, as near the county government deems practicable and equitable, be uniform throughout the area served by the sanitary sewer district, and may be based or computed either on the consumption of water or in connection with the real property, making due allowances for commercial use of water, or on the number and kind of water outlets on or in connection with the real property, or on the number and kind of plumbing fixtures or facilities on or in connection with the real property, or on the number of persons residing or working on or otherwise connected or identified with the real property, or on a front footage basis, or on other factors determining the type, class and amount of use or service of the sanitary sewer system, or on any combination of such factors. No assessment shall be made against any property which is not subject to taxation and assessment for county and municipal purposes.
9 Del. C. § 6514