Sequential batch reactors

Sequential batch reactors (SBRs) are used in a traditional process of municipal or industrial wastewater treatment. They are particularly effective in treating lowly concentrated wastewater which are to be discharged to the river, or as one of the methods of polishing after other solutions.

There are several configurations of SBRs, but the basic process is the same for all of them. The installation consists of one or more biological reactors (PPEKO’s preferred configuration consists of two reactors). There is one inlet, common to both tanks, through which the wastewater is fed automatically to the suitable reactor.

 


Principle of operation:

The SBR process can be divided into five stages: fill, react (aeration), settle, decant, idle. During the aeration stage the air is fed through mechanical aerating system (floating, submerged aerators) or by means of fine bubble aeration. Using two or more reactors fosters the effective and continuous wastewater treatment.

  • Filling and aeration: aeration time is typically 60-90 minutes. Addition of oxygen allows for the multiplication of aerobic bacteria, which consume the organic compounds. As a result the amount of nitrogen compounds increases, as well as the bacterial population. PPEKO performs also the process of phosphorus reduction.
  • Settling: usually it takes as much time as aeration. During this stage the excess sludge is formed and settles at the bottom of the reactor. The aerobic bacteria multiply until the oxygen dissolved in the activated sludge is completely consumed. At the same time the bottom part of the reactor becomes more suitable for the anaerobic bacteria to grow. They convert the nitrogen present in the wastewater by consuming the nitrogen compounds produced during the aeration stage. This is the de-nitrification process.
  • As bacteria multiply and die in the reactor, the excess sludge is formed. It is removed during the decant stage – it undergoes further treatment (concentration or dehydration). The effluent (the water from above the sludge, pollutant-free) flows to the collector.

Advantages:

  • Simple design;
  • Zarządzanie w funkcji czasu;
  • Efficient management of the excess sludge.

Disadvantages:

  • Intervals – filling and emptying required;
  • Various levels depending on the working cycle;
  • Drawbacks of the classic activated slugde;
  • Low sludge concentration.

Examples of application:

  • Boryszew S.A. – wastewater from chemical industry.
  • Jahnckepol – wastewater from fruit industry.