Wastewater Sequencing Batch Reactor SBR

A Sequencing Batch Reactor (SBR) is often used in wastewater treatment plant whereby space availability is a constraint and cost of construction and setup is a major issue to keep the budget low. Unlike conventional continuous flow system, which has several separate process tanks, SBR only has one single reactor for all the working processes. Although the unit of operations between both setups is basically the same, more control and attention can be given to sequencing batch reactor because only one process can be operating at any time.

Running an SBR can be rather straightforward because there are only 4 steps of operation that is carried out from start until completion. First step involves filling the reactor with the wastewater influent pump in to the tank and during the filling period, heavy turbulence is generated and this in turns encourage oxygen to dissolve in the water. Unlike conventional unit, which uses diffusers to force air to dissolve in the wastewater, basically SBR has an upper hand in this area as no additional energy consumption and extra moving mechanical setup is required. Usually the loading period can vary depending on the pump capacity and it is normal for the cycle time to constitute close to 25% of overall time needed.

Next step is the reaction period whereby a certain amount of time is given for biological reaction to take place. For better efficiency, use of diffusers in necessary or for cost saving measures a simple mechanical stirrer can be fixed into the tank. What follows next is the sedimentation period. Just like any conventional clarifier or sedimentation tank in continuous system, water is allowed to stay idle so that heavy sludge solid will settle to the bottom of the tank. Once this is done, use of a decanting unit such as adjustable level submersible pump can be employed so that only clean water layer floating on top can be pumped out. To achieve better quality and safer wastewater discharge, additional polishing step such as ozone disinfection can be carried out later part.

One major disadvantage associated with using Sequencing Batch Reactor is that only small volume of wastewater can be treated at any time and this means that it is only suitable to be employed in certain industries where generation of wastewater is rather minimal. Since it is a batch process, longer hours are needed and there is no guarantee that each batch will require the same number of hours to achieve the same target COD and BOD reduction because incoming wastewater load may be different. Therefore, consideration and overall long-term impact has to be taken into account before setting up SBR for treatment use.

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