Integrating wastewater treatment to bio-stimulant & biochar generation for plant growth promotion using microalgae

The elevated level of pollutants in water highlights the urgency of effective wastewater treatment. Hence, the concern about the potential of microalgae as an economically and environmentally sustainable for wastewater treatment is addressed. Wastewater treatment using microalgae resulted in significant reductions in micropollutants by 82 % for chemical oxygen demand (COD) and biological oxygen demand (BOD). Iron (Fe) concentration was reduced by 99 %, while calcium (Ca) decreased by 25 %. Algal biomass obtained from wastewater is executed for biochar production and bio-stimulant preparation. Bio-stimulant treatment significantly enhanced seed germination and increased shoot and root lengths in maize (Zea mays) and beans (Phaseolus vulgaris) compared to the control. Conversely, seed germination was completely suppressed in both maize and beans in the presence of biochar of bio-stimulant treatment. The GC-MS and NMR analysis study revealed the presence of key compounds in the microalgal extract that have a great contribution to plant growth. Hence, the study concludes the multifaceted and potential application of microalgae as a remediation and bio-stimulant in a sustainable way. © 2024 Elsevier Ltd