Water | Sequential batch reactor (SBR)

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Biological treatment: sequential batch reactor (SBR)

Purpose

  • Removal of organic substances (TOC, COD, BOD, ...)
  • Breakdown of biodegradable detergents, oils and fats, ...
  • Nitrogen removal (ammonification, nitrification, denitrification)
  • Phosphate removal

Principle

A possible configuration for a biological wastewater treatment plant is a batch reactor. In certain cases the aeration process and the settling process take place in the same basin to avoid the cost of a clarifier. In this case, the different steps of the treatment process are performed after each other. This type of wastewater treatment plant is called a sequencing (or sequential) batch reactor (SBR).

The water treatment process in a SBR consists of at least four steps:

  1. Feeding with wastewater

  2. Aeration

  3. Settling

  4. Discharge of the purified effluent

In case of biological nitrogen removal, an anoxic step has to be added to the treatment program. In this step the reactor is mixed but not aerated.

Scheme

Applications

SBR wastewater treatment is interesting for wastewaters with a relatively high concentration of organic pollutants. In the case of continuously produced wastewaters a buffer is needed to store the wastewater during the settling and release phases. In certain cases multiple SBR reactors are used simultaneously and at least one reactor is fed at each moment.

Configuration

Biological wastewater treatment plants exist in several variations. The most important differences are found in the sludge/water separation process. In a continuous activated sludge system the flocks settle in a clarifier. In a sequencing batch reactor (SBR) the aeration and settling processes take place in the same reactor. In a membrane bioreactor (MBR) the separation is done by means of membrane filtration.

Operational costs

Besides the water treatment infrastructure there are also operational costs associated with water treatment. The most important among these are the energy cost for aeration and the handling of the produced biological waste sludge.

Approach Trevi

In the design of an SBR wastewater treatment plant, Trevi uses a very energy-efficient fine bubble aeration system. Besides savings in the energy cost, this systems also allows for compact wastewater treatment plants with a low sludge production. To ensure the desired treatment results, the dimensioning of a new treatment plant is always supported by pilot tests.