Application of Bioaugmentation in Biological Wastewater Treatment and Sludge Utilization

Bioaugmentation method is an attractive solution to problems associated with exposure of many wastewater treatment plants to high load of wastewater pollutants. This strategy involves introduction to activated sludge an additional pool of bacteria or microscopic fungi of desired properties, capable of aggregation and adhesion, production of polysaccharide substances, biofilm formation, synthesis of bioflocculants and synergistic interactions with indigenous microorganisms, insensitive to changes in environmental parameters and of high tolerance to toxic substances. Not only may inoculation of activated sludge with such microorganisms lead to the increased biodiversity and biomass of microorganisms living in a biological reactor, accelerate the decomposrtion of organic pollutants, improve the process of biogenic compounds removal, but also prevent excessive growth of filamentous bacteria, improve sedimentation properties of sludge, counteract sludge foaming and support the process of its regeneration. Currently, great promise is held out for the development of new methods of cell delivery to the activated sludge that employ nanomaterials, prospects of using carbon nanotubes as adsorbents of toxic compounds and use of knowledge in the field of modulation of bacterial quorum sensing leading to biofilm formation. Since bioaugmentation could be employed at various stages of biological wastewater treatment, it may significantly improve the operation of wastewater treatment plants. However, this method has some limitations, related to the poor survival rates of inoculants and disappearance of their activity after being introduced into the new environment. In order to broaden our understanding of this area, it is necessary to monitor the fate and activity of inoculants using modern molecular techniques and to develop new methods of cell delivery to the active sludge ecosystem. Yet, implementation of the practices tested in the laboratory environment directly into the wastewater treatment plants remains a challenge for the future.