The first step in wastewater treatment is the preliminary treatment units, which remove large solid objects. They also protect pipes and pumps. A second stage of the process is called the aeration tank. Aeration introduces air into the wastewater to provide an oxygen source for naturally occurring microorganisms. This will allow the microorganisms to consume the contaminants present in the wastewater. This part of the process has been shown to improve efficiency. Lastly, there are a variety of different types of biological processes used to treat waste. Some of these are chemical precipitation, ion exchange, adsorption, and neutralization. Each type of process has its own unique advantages and disadvantages. As far as the best aeration system is concerned, the Extended Aeration Activated Sludge System (EAAS) has been demonstrated to be the most effective at removing nitrogen. It is a well-known technology with lower capital and operational costs. The Extended Aeration sludge processing system has been shown to reduce phosphates considerably. A good civil engineering can reduce the area required to install an ETP.