Simultaneous nitrogen, phosphorous, and hardness removal from reverse osmosis concentrate by microalgae cultivation

Area of Science:

• Environmental biotechnology
• Aquatic ecology
• Biomass production

Background:

• Reverse osmosis (RO) concentrate (ROC) poses treatment and disposal challenges.
• Conventional methods for ROC treatment have limitations in nutrient and hardness removal.
• A sustainable biological solution for ROC management is needed.

Purpose of the Study:

• To develop a novel biological approach for simultaneous removal of nitrogen, phosphorus, and hardness (Ca2+, Mg2+) from ROC.
• To evaluate the efficacy of microalgal cultivation for ROC treatment and biomass production.
• To investigate the potential of using microalgal biomass for valuable products.

Main Methods:

• Batch cultivation of Chlorella sp. ZTY4 and Scenedesmus sp. LX1 in ROC.
• Monitoring of microalgal growth, biomass production, and lipid content.
• Analysis of nitrogen, phosphorus, calcium, and magnesium removal efficiencies.

Main Results:

• Both microalgae strains demonstrated robust growth in ROC, achieving biomass production up to 318.7 mg/L.
• High removal efficiencies were observed for nitrogen (up to 89.8%) and phosphorus (up to 92.7%).
• Significant removal of Ca2+ (55.9%-83.7%) and Mg2+ (up to 56.0%) was achieved, primarily driven by pH-induced chemical precipitation.

Conclusions:

• Microalgal cultivation offers a promising biological strategy for simultaneous nutrient and hardness removal from ROC.
• The process yields lipid-rich microalgal biomass, creating opportunities for resource recovery.
• This approach presents a sustainable and efficient method for ROC management in wastewater reclamation.