The life of a sewage treatment plant is determined by
1. Quality of construction material used for tank
2. Quality of components and machines used for treatment
a. Blowers
b. Filtration units
c. Pumps
d. Diffusers, etc.
3. Achievable treatment values presently and in the future if there is a change to stricter treatment norm
4. Flexibility in operation to changing conditions of inflow and pollutant load
5. Ability to accommodate higher inflows that can happen due to future expansion, etc
With all these factors in place, one can expect a sewage treatment plant to have a trouble-free operation. Globally best-in-market components and machinery used would ensure the long life of the plant. This also has to be complimented with good maintenance of the plant by timely service and maintenance of the machine. Wear and tear parts should be replaced as per the recommendation of the manufacturer too. With this STP can work trouble-free for up to 10 years.
Beyond this period, you have to plan for a revamp or you may face frequent breakdowns that would be more expensive to manage with interruption to operations. Blowers and pumps may need overhauling of electrical parts, bearings, etc, while fine bubble diffusers may have reached their full lifetime. In the case of the usage of stainless steel fittings, the replacement cost of fittings may be minimised.