Ohio Rev. Code § 6109.15
After the hearing provided for in section 6109.14 of the Revised Code, if the director of environmental protection determines that improvements or changes are necessary and should be made, the director shall order the mayor or managing officer or officers of the municipal corporation, county, or public institution or other person owning or operating a public water system to make improvements, corrections, and changes in the location, protection, construction, operation, or maintenance of the system satisfactory to the director, so as to prevent the contamination of the water or to provide a system not subject to the danger of contamination, or to provide a system adequate to avoid endangering the public health or to provide required quantities of fluoride. Notice of the director's order shall be made by personal service upon or by certified mail to the mayor or managing officer or officers of the municipal corporation, county, or public institution or to the officials, corporation, partnership, or person to whom the order applies.
R.C. § 6109.15