Wastewater Sludge Aeration Tanks

Wastewater Aeration Tanks are usually built using reinforced concrete with the top open area exposed to the environment. Usually the whole design is rectangular in shape so that partitions can be created to come up with multiple tank setup. Basically the purpose for the construction is to contain wastewater for activated sludge process to take place using different types of aeration system like blowers, diffusers, mechanical aerators and high purity oxygen introduction.

Sizing for the aeration tank capacity is usually determined by the amount of wastewater the system is designed to take in per day. For a small-sized standard package plant that can treat wastewater volume of 400 cubic meters per day, the holding capacity that the individual tanks should total up to at least 2400 cubic meters, roughly about six times the treatment volume. A four-aeration tank setup is also preferred because this allows better control and flexibility and if a tank encounters operational problem, the wastewater can be diverted to the remaining ones. In all, it is also a fact that construction of more tanks should be advantageous but the setback is that, doing this will incur more investment to purchase aeration systems and higher cost of maintenance later part.

Design on the depth of a typical activated sludge aeration tank should not be an issue unless the system is operated using diffused air. In this case, one must ensure that the depth should be at least measure from 5 to 7 meters in total in order for the whole process to function efficiently. For spiral-flow mixer, width of the tank should be taken into consideration and usually the width to depth ratio can be anywhere between 1 to 1 and 2 to 1 ratio. Other considerations involving the design of aeration tank, whereby in the case of mechanical aerators being used, the most efficient arrangement should have a dedicated aerator to serve every single tank.

Other provisions for the construction and setup must also involve having a freeboard platform located at least 1 meter above the overflow water line. The concrete walls at all sides must be thick enough to withstand calculated hydrostatic pressure. Other than that, the flow distribution to the next step of treatment process before going to sedimentation tanks must be equally balanced and with presence of control valves at the outlet point.

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