Whenever the city shall deem it necessary, it may, by ordinance, provide for the construction of a septic tank or other sewage reduction device for the purpose of purifying the discharge from any district or joint district sewer. In such case the cost thereof shall be assessed against the lands in the district or joint district for which the same is provided in the same manner as is provided for the assessing of the cost of district sewers.
§ 88.767, RSMo