The Extended Aeration (EA) system is one of common Biological system used to treat domestic wastewater due to its functionality and simplicity.
The treatment plant provides the proper environment, sufficient oxygen and other elements which allow the bacteria to consume the organic matter and to live and multiply within the treatment plant. In this way the aerobic bacteria and microbes decompose the sewage and waste to a stable form – odor and nuisance free.
The Extended Aeration Process, a modification of the Activated Sludge Process, effectively treats the contaminants in wastewater. The standard basis of design includes an aeration system, providing a 24-hour detention time and a final settling tank, with an effective 4-hour detention time. Diffused air is introduced into the aeration tank, this provides the proper environment for the development of aerobic bacteria. These bacteria thrive on the materials contained in the wastewater. The prolonged period of aeration, in addition, oxidizes a portion of the solids in the system. Oxygenation by diffused aeration provides operating flexibility and standby reserve to meet the demanding requirements of varied package plant applications. Separation of the solids from the mixed liquor developed in the aeration tank takes place in the settling compartment. The clarified effluent is withdrawn for reuse or discharged into a receiving stream from the top of the settling tank. The settled solids are rapidly pumped from the bottom of the settling tank back to the aeration system. These Extended Aeration Plants are proven workhorses, providing excellent Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) removal efficiency. Only minimal routine housekeeping and operational tasks are required of the plant operator.
Raw domestic wastewater from last manhole is channeled into the primary screen where mechanical coarse screen was installed to remove coarse solid materials. The screened sewage inside wet well will then be lifted up to the secondary screen by a set of raw sewage pumps. A duty mechanical fine screen was also installed at the secondary screen chamber to remove finer solid materials in the sewage. Two aerated grit chambers are proposed subsequent to fine screen chamber for removing inert materials such as fine sand, gravel etc. Last but not least for the pre-treatment system, a grease/oil removal system is used to remove the potential oil in sewage to ensure good performance of the extended aeration system.
Advantages of Extended Aeration System:
- Easily maintained mechanical work.
- Extended aeration processes are often better at handling organic loading and flow fluctuations, as there is a greater detention time for the nutrients to be assimilated by microbes.
- Systems are odor free, can be installed in most locations, have a relatively small footprint, and can be landscaped to match the surrounding area.
- Extended aeration systems have a relatively low sludge yield due to long sludge ages, can be designed to provide nitrification, and do not require a primary clarifier.
Aeration Tank is the main component in this system, where in this section the decomposition of pollutant substances (Organic Compounds) occurs. In this Aeration Tank, wastewater is blown with air, so that the existing “aerobic” micro-organisms will decompose organic substances in wastewater. The energy obtained from the decomposition results will be used by micro-organisms for the growth process. Thus the biomass will grow and develop in large quantities, which will decompose the pollutant compounds present in the wastewater.
The addition of air in the water uses an air blower which functions to supply air, so as to create aerobic conditions. In addition, this aeration tank is equipped with a diffuser (air seal diffuser), which functions to create air bubbles (bubbles) so that the process of oxygen absorption by micro-organisms can be optimized.