Sequencing Batch Reactor Design and Operational Considerations SBRs are used all over the
world and have been around since the 1920s. With their growing popularity in Europe and
China as well as the United States, they are being used successfully to treat both municipal
and industrial wastewaters, particularly in areas characterized by low or varying flow
patterns. Municipalities, resorts, casinos, and a number of industries, including dairy, pulp
and paper, tanneries and textiles, are using SBRs as practical wastewater treatment
alternatives. Improvements in equipment and technology, especially in aeration devices and
computer control systems, have made SBRs a viable choice over the conventional activatedsludge
system. These plants are very practical for a number of reasons: •In areas where there
is a limited amount of space, treatment takes place in a single basin instead of multiple
basins, allowing for a smaller footprint. Low total-suspended-solid values of less than 10
milligrams per liter (mg/L) can be achieved consistently through the use of effective
decanters that eliminate the need for a separate clarifier. •The treatment cycle can be adjusted
to undergo aerobic, anaerobic, and anoxic conditions in order to achieve biological nutrient
removal, including nitrification, de nitrification, and some phosphorus removal. Biochemical
oxygen demand (BOD) levels of less than 5 mg/L can be achieved consistently. Total
nitrogen limits of less than 5 mg/L can also be achieved by aerobic conversion of ammonia to
nitrates (nitrification) and anoxic conversion of nitrates to nitrogen gas (de nitrification)
within the same tank. Low phosphorus limits of less than 2 mg/L can be attained by using a
combination of biological treatment (anaerobic phosphorus-absorbing organisms) and
chemical agents (aluminium or iron salts) within the vessel and treatment cycle. Older
wastewater treatment facilities can be retrofitted to an SBR because the basins are already
present. Wastewater discharge permits are becoming more stringent and SBRs offer a costeffective
way to achieve lower effluent limits. Note that discharge limits that require a greater
degree of treatment may necessitate the addition of a tertiary filtration unit following the SBR
treatment phase. This consideration should be an important part of the design process.
Advantages:-
Equalization, primary clarification (in most cases), biological treatment, and
secondary clarification can be achieved in a single reactor vessel
Operating
