(a) Any water and wastewater treatment authority that is created by a county legislative body pursuant to part 6 of this chapter, subject to approval by the county legislative body, may enact a regulation that creates requirements for the installation and operation of advanced treatment systems (ATS) and the structures served by ATSs within the county; provided, that:
(1) The requirements are equal to or more stringent than the requirements imposed on the systems or structures by the department of environment and conservation pursuant to this part or title 69, chapter 3, part 1;(2) A copy of the regulation is filed with the department prior to its effective date;(3) Any modifications to the regulation requested by the department at any time are promptly adopted; and(4) Enforcement of the regulation shall be the responsibility of the county legislative body and shall not be the responsibility of the department.(b) Subsection (a) shall only apply in counties having a population, according to the 2000 federal census or any subsequent federal census, of:
