The provisions of sections 443.26 to 443.35 shall be construed as an addition to existing charter or statutory powers of any city of the first class and not as an amendment to or repeal thereof, the purpose of these sections being to permit any city of the first class to engage in the activities hereinbefore authorized, to promote the public health, safety, welfare, convenience, and prosperity of the city. The activity herein authorized shall be considered a public utility and such activity may be merged and operated with any other city operated utility, if deemed necessary and economical. Accounting for the activity herein authorized shall be separate as hereinbefore directed.