Biological treatment processes: suspended growth vs attached growth

Abstract

Microorganisms play important role in biological treatment processes. Complete removal of the biodegradable organic constituents in wastewaters can be achieved with proper microbial consortia. The mixed culture is either essentially present in the wastewater, or is introduced to the target wastewater by blending it with domestic sewage or biological sludge. However, pure cultures of organisms may be utilized in certain cases for the removal of specific contaminants. In favorable environmental condition, microorganisms are capable of presenting high efficiency in destruction of pollutants. Thus, organisms can produce an acceptable effluent. If the environmental conditions are suitable for the growth; including sufficient nutrition, proper pH, optimal temperature, adequate presence or complete absence of dissolved oxygen for respective aerobic and anaerobic systems; absence of toxic and inhibition and desired hydraulic and sludge retention time to allow the microorganisms to grow and remove organic pollutants through biochemical activities. Several pilot scale of advanced and hybrid systems are developed. Combination of fluidized and fixed film has created active biogranules which were quite efficient in treatment of industrial wastewater. The mechanism of anaerobic process is discussed. Growth kinetics and COD removal of effluents were investigated.