Microbial composition of wastewater

  

Wastewater contains huge numbers of living organisms ranging from too small to be visible except when viewed under a microscope, which is why they are called "microorganisms". Typically, wastewater prior to entering the treatment plant will contain from 100,000 to 1,000,000 microorganisms per milliliter. These microbes have their origin from two general sources: sanitary wastes and the soil. Both wastewaters and soils contain large numbers of microorganisms. Generally, the microorganisms can be considered as a natural living part of the organic matter found in wastewaters and their presence is most important because they serve a primary function in the treatment in biological wastewater treatment. In a sense the successful operation of a biological wastewater treatment plant is dependent upon knowledge of the activities of the microorganisms (Abdel, 2011).

Wastewater environment is an excellent media for a wide range of microorganisms specially bacteria, viruses and protozoa. The majority of microorganisms is harmless and can be used in biological sewage treatment, but sewage also contains harmful microorganisms, which are drained to wastewater by sick individuals and a symptomic carrier. Bacteria which cause typhoid, cholera and tuberculosis; viruses which cause infectious hepatitis; protozoa which cause dysentery and the eggs of parasitic worms are all found in sewage (Shaaban et al., 2004).