The provisions of this chapter relating to water mains and waterworks apply only to districts that own or contemplate owning a system of waterworks and water mains. In the purchase of a waterworks system or of a sewage treatment or disposal plant or of a system of sewers, either by eminent domain in accordance with chapter 32-15, or otherwise, a district may create improvement districts, direct the preparation of plans and specifications, adopt a resolution declaring the purchase of the facilities necessary, and take all other proceedings prescribed by this chapter which would be taken in case of the construction of such facilities by the district itself for the purpose of defraying the cost by special assessment of the benefited property. The benefited property may be specially assessed for the purchase of such facilities, either separately or as a part of a new system, the same as if the facilities were constructed entirely anew.