SEQUENCING BATCH REACTOR or SBR Wastewater treatment plants


The sequencing batch reactor wastewater treatment plants in France (SBR), are a fill up and treat wastewater system. In this system, wastewater is added to a single “batch” reactor, treated to remove undesirable components, and then discharged. Equalization, aeration, and clarification can all be achieved using a single batch reactor. To optimize the performance of the system, two or more batch reactors are used in a predetermined sequence of operations. SBR systems have been successfully used to treat both municipal and industrial wastewater. However, they are best suited for wastewater treatment applications characterized by low or no flow variations – not conditions usually found in single domestic and holiday properties.


Influent wastewater generally passes through screens and grit removal prior to entry into the sequencing batch reactor wastewater treatment plant. The waste water then enters a partially filled reactor, containing biomass, which is self adjusting to the wastewater contents during preceding cycles. Once the reactor is full, it behaves like a conventional activated sludge system, but without a continuous influent or effluent flow. The aeration and mixing is discontinued after the biological reactions are complete, the biomass settles, and the treated fluid is pumped out. Excess biomass is wasted at any time during the cycle. Frequent wasting results in holding the mass ratio of influent substrate to biomass nearly constant from cycle to cycle. Continuous flow systems hold the mass ratio of influent substrate to biomass constant by adjusting return activated sludge flow rates continually as influent flow rates, characteristics, and settling tank underflow concentrations vary. After SBR wastewater treatment plants, the “batch” of wastewater may flow to an equalization basin where the wastewater flow rate to additional process units can be controlled at a determined rate.

Service/ Maintenance

The suppliers typically recommendations and observations:

  • Quarterly checking of pumps to pre-empt potential system failure
  • Annual checking and servicing of pumps inside the tank
  • Bi annual de-sludging of SBR WWTP’s

Environmental Benefits

Correctly performing sequencing batch reactor wastewater treatment plants in France (SBRs) with sophisticated control systems can bring significant environmental benefits and clean results compared to traditional anaerobic treatment methods such as fosse septiques and sand filter configurations. Whether the often complicated arrangement of pumps and electronics, which require reasonably frequent attention, can be considered ecologically defendable, remains to be decided.


Whilst equalization, primary clarification (in most cases), biological treatment, and secondary clarification can be achieved in a single all be it large, reactor vessel there is a potential need for a balancing tank, depending on the discharge arrangement. Whilst sequencing batch reactor wastewater treatment plants (SBRs) can be highly efficient in industrial/municipal application, with low flow variation and with minimal footprint in domestic applications they can be problematic and expensive. They are often complicated, meaning a higher level of maintenance, potential failure and cost (compared to conventional domestic wastewater treatment systems) associated with more sophisticated controls, automated switches and valves. There are inevitable silting problems in the variable organic loading corresponding to domestic and holiday properties and it can be difficult to control discharge quality due to varying loads causing premature ejection of untreated material. There is also a potential of discharging floating or settled sludge during the DRAW or decant phase with some SBR wastewater treatment plants configurations. Be certain to scrutinise the EN 12566-3 CE certification and the terms and conditions in the warranty, linked to the cost of spares, as with an SBR type wastewater treatment plant it is probable that you will need them.

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