Upon the completion of plans for the proper purification, filtration, and distribution of water or proper collection and treatment of sewerage, the board of county commissioners, the regional planning commission, the county planning commission, or any regional water and sewer district which has prepared such plans shall file a copy thereof with the environmental protection agency, which may approve or reject any provisions thereof. In deciding whether to approve or reject the plan, the agency shall consider, among other factors, the protection of the public health, and compliance with air and water quality standards and regulations and solid waste disposal requirements. If such agency rejects such plans or refers them back for amendment, other or amended plans shall be prepared. If the agency approves such plans, it shall certify a copy of its action and thereafter any district may proceed to carry such plans into effect.