The exact timing of the construction of the plant depends on a number of factors, including the planning of the local government and environmental protection departments, capital investment, technical programs and so on. Generally speaking, the construction of a sewage treatment plant requires a series of planning and preparatory work, including site selection, land acquisition, design, bidding, construction and so on. In this process, many factors need to be taken into account, such as the size of the local population, the amount of sewage discharged, the geographical environment, traffic conditions and so on.
Therefore, the exact timing of the construction of the plant requires detailed planning and evaluation, and I suggest that you can consult with the local government or environmental protection department to learn about the latest plans and progress. Meanwhile, you can also pay attention to local news and announcements in order to keep abreast of the relevant construction progress.