Biological Treatment Units And Processes

Biological unit processes are used to convert the finely separated and dissolved organic matter within wastewater into flocculent settleable organic and inorganic solids. In this procedure, micro-organisms, particularly bacteria, convert the colloidal and dissolved carbonaceous organic matter within several gases and into cell tissue that is then removed in sedimentation tanks. Biological processes are commonly used in conjunction with physical and chemical processes, along with the major objective of reducing the organic content (measured as BOD, TOC or COD) and nutrient content (notably nitrogen and phosphorus) of wastewater.

Biological processes used for wastewater treatment might be categorized under five main headings:

(a)        Aerobic processes.

(b)       Anoxic processes.

(c)        Anaerobic processes.

(d)       Combined processes.

(e)        Pond processes.

These processes are additionally subdivided, depending on whether the treatment takes place within a suspended growth system and an attached-growth system or a combination of both. Here we will be concerned along  with the most generally used biological processes, involving trickling filters, the activated sludge procedure, aerated lagoons, stabilization ponds and rotating biological contactors.