The provisions of this chapter relating to water mains and waterworks apply only to municipalities that own or contemplate owning a system of waterworks and water mains. In case of the purchase of a waterworks system or of a sewage treatment or disposal plant or of a system of sewers, either by eminent domain proceedings subject to chapter 32-15, or otherwise, a municipality may create improvement districts, direct the preparation of plans and specifications, adopt a resolution declaring the purchase of such 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 municipality itself for the purpose of defraying the cost thereof by special assessment of the property benefited thereby. The property benefited may be specially assessed for the purchase of such facilities, either separately or as a part of a new system, the same as if said facilities were constructed entirely anew.