A3.10.2 Biological Technology


Biological Technology refers to any technological application that uses biological systems or living organisms.

Aerobic Treatment

Aerobic treatment is commonly used for the treatment of sewage. The process generally consists of the four phases:

  1. Pre-treatment stage – to remove large solids and other undesirable substances from the wastewater.
  2. Aeration stage – aerobic bacteria digest the biological wastes in the wastewater.
  3. Settling stage – undigested solids to settle to form a sludge which must be periodically removed from the system.
  4. Disinfecting stage – a disinfectant is mixed with the water, to produce an antiseptic output.



Microfiltration is a filtration process which removes contaminants from a fluid (liquid & gas) by passage through a microporous membrane. It is commonly used in water treatment.

Although the filter itself is physical, microfiltration is generally considered to be biological technology because it deals with biological entities.

It is often used with fluids containing bacteria that can be filtered to trap the microorganisms on the membrane surface for subsequent culture and analysis. Microfiltration can also be used in sample preparation to remove intact cells and some cell debris.

The filters can be in a submerged configuration or a pressure vessel configuration. These filters are porous and allow water, monovalent species (Na+, Cl-), dissolved organic matter through but do not allow particles, sediment, algae or large bacteria through.



Biological Scrubbers are often used for odour control in sewage plants. Specially selected bacteria colonize the substrate media within the biological filter housing and there digest the odour-causing compounds (which typically include H2S, organic sulphides and ammonia). The optimised environment for bacterial activity is maintained by controlled irrigation.

Activated Sludge

Activated sludge is a process dealing with the treatment of sewage and industrial wastewaters. Atmospheric air (or pure oxygen) is introduced to a mixture of primary treated or screened sewage (or industrial wastewater) combined with organisms to develop a biological flocculant which reduces the organic content of the sewage.