Impact of Effluent Treatment Plant Sludge on Growth, Physiology, and Biodegradation Potential of Cyanobacteria: Anabaena variabilis, Nostoc muscorum, and Nostoc sp.

Organic compounds and pollutants from industries like oil refineries, such as total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbons (PAHs) are known to pose toxic effects to the environment by degrading the soil and water quality along with the deposition of heavy metals thereby causing a threat to the life forms existing in them. This pose of imbalance in the ecosystem calls for an exigent notice and effort regarding controlling it. Hydrocarbon sludge from Effluent Treatment Plant (ETP) is one such toxic effluent eluted from oil refineries, and that is yet to be reported for a biodegradation study. Among a huge number of physical and chemical techniques, bioremediation has been a much talked about measure but is not in the required scale of practice yet. The reason could be a lack of efficient standardization for environmental applications. Cyanobacteria being well-known for their ability to survive difficult environmental conditions efficiently and to adapt to a mixotrophic nature, makes them ideal for performing bioremediation at a large scale in the open environment. The study aimed to quantify this ability of cyanobacteria by assessing the TPH content of the treatment sample, Effluent Treatment plant (ETP) hydrocarbon sludge pre- and post-treatment using GC-FID. The study was designed to treat the sludge by cyanobacterial strains in a pre-determined lethal dose concentration and monitor the activity of enzymes vital for a basic degradation metabolism, in addition to the growth rates of the cultures. The figures obtained from the enzyme assays and the growth rates appeared to be collateral in the direction of it being a highly promising bioremediation approach that could be efficiently performed by increasing the scale of application. The chromatograms obtained from the GC-FID depicted significant reductions in the TPH content of the treated samples that strongly indicated the potential of the cyanobacterial cultures to bioremediate an oil- contaminated site or treat toxic effluents from oil refineries.