Cultivating photosynthetic microorganisms in cooling water waste and urban effluents as a strategy of water regeneration and valorization

ABSTRACT

Contaminants from cooling water waste (CWW) generated by industries represent an environmental hazard if discharged into aquatic bodies and soil without treatment. Most treatment strategies are energy-demanding and costly; hence, low-cost and sustainable treatment alternative technologies are needed. The present study proposed cyanobacteria culture as a low-cost biological method to treat cooling water waste (CWW) while simultaneously producing carbohydrates. For this purpose, CWW from a cooling tower was evaluated in different dilutions with domestic wastewater (DW) (DW25% -CWW75%, DW50% -CWW50%, DW25% -CWW75%, DW100%, and CWW100%) (v/v). The CWW provided a high content of inorganic carbon and low content of N and P, which resulted in a high C/N ratio promoting a fast carbohydrate accumulation but low biomass production. In contrast, cultures with higher DW concentrations achieved similar results in 14 days. The best results were obtained with DW25% -CWW75%, achieving up to 52 ± 18% carbohydrate content on day 8, with the highest biomass concentration of 1.7 ± 0.12 g L⁻¹ on day 14. This culture removed >94% of TAN, N-NO₃^- and P-PO₄^3-, and 84 ± 10.82% of COD. This strategy could be a promising approach to treating CWW and DW from the same industry and producing value-added products and bioenergy.

GRAPHICAL ABSTRACT

KEYWORDS:

• Carbohydrate-based biofuels
• cooling towers
• cyanobacteria
• photobioreactors
• microalgae

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are freely available from the corresponding author upon request.

Additional information

Funding

This work was supported by Dirección General de Asuntos del Personal Académico (DGAPA), Universidad Nacional Autónoma de México (UNAM), México under the PAPIIT Project [No. IA102821, IA102522].