Sewage treatment plant functions with air supply in a given time in a certain volume and flow to remove certain quantity of pollutants. When there is a new regulation the newly applicable standards should be applied to the design and the respective volume, time of retention and the air supplied should be adjusted to achieve the new treatment standards. Tertiary treatment is only to polish the treated water to give improved aesthetic appearance, while secondary treatment is where the real treatment happens. There are lots of vendors, consultants and companies that are recommending ultra filtration to have better quality of water, which is nothing but a white elephant for the customer.