Microbial mediated Phycoremediation of industrial effluents: A case study

Microbial mediated Phycoremediation of industrial effluents: A case study

Executive Summary

Industrial effluents are familiar sources of environmental degradation. Considering the efficient reuse and management of wastewater systems minimizes pollution. Conventional systems for treatment of wastewater have proven to be costly and less effective for complex treatment of wastewater. However, the cultivation of photoautotrophic microorganisms has the potential for remediation of wastewater since it utilizes carbon dioxide for growth. Photoautotrophs such as macroalgae, microalgae, and cyanobacteria assimilate excess wastewater pollutants photosynthetically. The case study examined conventional wastewater treatment systems and strategies adopted to mitigate waste management. The study also recommended optimal, efficient measures for the management of industrial waste. Conventional treatments for wastewater consist of biological, chemical, and physical methods. Physical methods utilize adsorbents such as silica gels, wood chips, peat, and activated carbon, which are costly. Chemical methods use chemical reactions such as dechlorination, ozonation, and disinfection. However, the use of physiochemical waste treatment methods present limitations in the disposal of large quantities of chemical sludge. The biological treatment process involves rotating biological contractors or trickling filters for anaerobic digestion of waste through the application of indigenous microbes. Trickling filters are energy efficient and convenient for maintenance since they do not need aeration. However, the continual use of trickling filters has decreased over time due to inefficiencies with the removal of high suspended solids in the wastewater. Therefore increased environmental pollution arising from conventional methods of water waste treatment necessitates the natural application of microbial communities. Photoautotrophic microbial cultivation systems offer viable methods for remediating wastewater.   However, the limited availability of organic carbon and light in the environment hampers the growth of heterotrophic microbes. Autotrophic microorganisms also thrive in dark conditions, which also limits their growth.

Additionally, mixotrophic microorganisms assimilate carbon dioxide and organic compounds independent of light and therefore, applicable in the phycoremediation of industrial effluents. Further investigations on local environmental conditions could inform on the possible ways for cultivating viable microbes important mediating remediation of industrial effluents. Wastewater systems should adopt the algae biomass production system useful in the commercial production of fertilizer feeds and fuel to maximize on benefits of effective pycoremediation. Designing cost-effective bioreactors, choosing species that grow efficiently without being affected by contaminants is a probable solution. Further research is required to establish optimal microbial nutrient uptake, algal culture productivity, and growth. Therefore industries should implement phycoremediation through large scale systems consisting of conventional, photoautotrophic, mixotrophic microorganisms.

Background

Microbes are useful in environmental remediation of industrial wastes based on their ability to produce enzymes with high substrate specificity (pollutants) and use under extreme environmental conditions. (Brar et al., 2017). Microbial enzymes are also highly effective against a wide range of pollutants and show high activity in the presence of microbial metabolic inhibitors. A variety of microbial enzymes degrade a broad range of inorganic and organic pollutants. Phycoremediation is the discharge of pollutants through the utilization of cyanobacteria, microalgae, and macroalgae. (Pathak et al., 2014).

Findings

Successful applications of photoautotrophic microorganism include the use of Chlorella Vulgaris in the treatment process of effluents from facilities that process leather. Effluent phycoremediation indicated a substantial decline in magnesium at 50% and calcium levels at 60 % (Thakur et al., 2019). Aerobic bacteria and Chlorella Sorokiniana showed an increased removal of COD at 68% when used in treating potato industry wastewater. However, the application of phycoremediation failed due to exposing sewage treatment facility to high temperatures hence a decline in algae growth (Sen  & Karn, 2019).

Discussion

Phycoremediation has proved to efficiently remediate industrial waste discharge in various wastewater treatment and manufacturing plants (Katuwal, 2017). Some of the facilities include municipal wastewater, agro-industrial wastes, dairy manure effluents, and textile effluents. However, varying local environmental conditions such as wastewater composition, optimum pH, and salinity limit the growth of photoautotrophic organisms (Rajendran, 2016).

Conclusions

Photoautotrophic microbes in phycoremediation reduce nutrient load and alter physicochemical parameters in wastewaters. Integrated large scale systems consisting of both conventional and agal system is useful in minimizing pollution and adverse effects of carbon dioxide. This study explored the potential application of photoautotrophs and mixotrophic organisms in wastewater phycoremediation.

Recommendations

The challenges of phycoremediation should be addressed through the adoption of integrated technologies that monitor optimized uptake of nutrients, efficient use of energy, and determine viability thresholds of microbes.

Implementation

Conventional methods of wastewater treatment could supplement existing biological methods with photoautotrophic microorganisms that address issues limited to extreme microbial conditions. Additional research on the propagation of mixotrophic microorganisms could help to increase the repertoire of microbes required in phycoremediation.

References

Brar, A., Kumar, M., Vivekanand, V., & Pareek, N. (2017). Photoautotrophic microorganisms and bioremediation of industrial effluents: current status and future prospects. 3 Biotech, 7(1), 18.

Katuwal, S. (2017). Designing and Development of a Photobioreactor for Optimizing the Growth of Micro Algae and Studying Its Growth Parameters.

Pathak, V. V., Singh, D. P., Kothari, R., & Chopra, A. K. (2014). Phycoremediation of textile wastewater by unicellular microalga Chlorella pyrenoidosa. Cell Mol Biol, 60(5), 35-40.

Rajendran, A. (2016). Behavior of Light in a Photobioreactor and Design of Light Guides.

Sen, S., & Karn, S. K. (2019). Cyanobacteria: The Eco-friendly Tool for the Treatment of Industrial Wastewater. In Environmental Contaminants: Ecological Implications and Management (pp. 163-183). Springer, Singapore.

Thakur, M., Medintz, I. L., & Walper, S. A. (2019). Enzymatic Bioremediation of Organophosphate Compounds-Progress and Remaining Challenges. Frontiers in bioengineering and biotechnology, 7, 289.