Tertiary treatment of municipal wastewater using isolated algal strains: treatment efficiency and value-added products recovery

ABSTRACT

Two microalgal strains (Chlorella sorokiniana, A&B,) grown optimally at pH 9 (A) and 7 (B) were isolated from a municipal wastewater treatment plant. These strains were used to check their efficacy for nutrients and organic carbon removal capacities from the tertiary wastewater. The strains were characterised using 18S rDNA sequencing method and both the strains closely related to Chlorella sorokiniana. Different inoculum doses (IDs) of both the strains were tried to check their efficacy on wastewater treatment. Due to the increase in the IDs, hydraulic retention time decreased from 6 d to 1 d. On an average, 12–100% of total kjeldahl nitrogen, 53–96% NO₃–N, and 59–92% PO₄–P, were removed. Despite the same growth environment, strain A with the highest ID (700 mg/L) showed the best performance in terms of overall organic carbon removal, nutrient removal, and value-added products recovery. Strain A showed an increase in carbohydrate and protein content by 42% and 13%, respectively. Both the strains showed luxury phosphorus uptake and found suitable for advanced wastewater treatment.

KEYWORDS:

• Chlorella sorokiniana
• nutrient removal
• inoculum doses
• hydraulic retention time
• value-added products
• light/dark study

Acknowledgements

Special thanks to Eurofins Pvt. Ltd for the genome sequencing. Fellowship of the first author is also provided through the Ministry of Human Resources and Development (MHRD), Govt. of India. We are also thankful to Dr Victor Lo and Dr Mavinic (University of British Columbia) and to IIT, Roorkee for providing partial funding for this study (FIG: CED-100685).

Notes on contributors

Swati Rani is a PhD student working in Dr. Chowdhury's group.

Dr. Raja Chowdhury and his team are working on resource recovery from waste and its sustainability assessment. The researchpresented in the manuscript is the part of the greater goal of the team to develop an algae based wastewater treatment process. Thebiomass produced from wastewater treatment which is the main ingredient of algal biorefinery is one of the main thrust of the research.

Dr. Wendong Tao is an Associate Professor at SUNY- Syrascuse. His research expertise is on resource recovery from waste materials, and wastewater treatment.

Dr. Asha Srinivasan is a Postdoctoral fellow at UBC and her research expertise is on microwave assisted sludge digestion.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research work is a collaborative effort of the University of British Columbia, Canada. [Funding agency: IC-IMPACT] and Indian Institute of Technology, Roorkee, India. [Funding agency: Department of Biotechnology (DBT-893-CED)], Gov. of India. We are also thankful to IIT, Roorkee for providing partial funding for this study [FIG: CED-100685].