Potential Uses of Immobilized Bacteria, Fungi, Algae, and Their Aggregates for Treatment of Organic and Inorganic Pollutants in Wastewater

Bioremediation of wastewater using microorganisms and their aggregates is recognized to be an efficient green treatment (biological origin) mean with a relatively low cost compared to conventional physical and chemical treatment processes. Microorganisms such as bacteria, fungi and often algae are used for removal of targeted pollutants from wastewater. Microorganism can be used in following two ways (1) Direct mixing of free microorganisms with waste water, and there is no separation between microorganisms and treated water (2) Microorganism immobilized in bedding materials or encapsulated within a matrix, and there is a distinct separation between microorganisms and the treated water. However, use of immobilized or encapsulated cells is considered more effective than free cells as it leads to higher biomass loading, easier operation of solid-liquid separation, higher biodegradation rates, better operation stability, greater protection from toxic substances, increased plasmid stability of immobilized cells. Lignocellulosic biomasses, ceramics, polymers from both natural and synthetic origin are commonly used as bedding materials or for entrapment of microorganisms within it. These immobilized cells show immense potential to clean up a wide range of pollutants including phenolic compounds, hydrocarbons, propionitrile, organic and inorganic dyes, N,N-dimethylformamide, pyridine, benzene, toluene and xylene (BTX), heavy metals and also unwanted amount of nutrients such as nitrogen and phosphorus from wastewater streams. Integrated process of assimilation, adsorption and biodegradation is the sole responsible mechanism behind wastewater remediation by immobilized microorganisms. However, much more multifaceted investigations are still required in this field to develop more systematically integrated technologies and increase treatment efficiencies.