Algae-Based Wastewater Treatment: Energy Savings, Nutrient Recovery, and Scaling Challenges

A new review in Blue Biotechnology highlights algae as a viable alternative for wastewater treatment, cutting energy use by more than 50% compared to conventional activated sludge systems. Algae absorb nitrogen and phosphorus from domestic, industrial, and aquaculture wastewater while producing oxygen naturally, reducing the need for aeration and chemicals. The biomass can be harvested for biofuels, fertilizers, or even animal feed, turning treatment plants into resource recovery facilities. The review reports pilot-scale systems achieving over 85% nitrogen and phosphorus removal, with high-rate algal ponds reaching 90% removal. Cost estimates suggest algae-based treatment can save aquaculture operations tens of thousands of dollars per hectare annually. However, scaling faces hurdles like unstable removal efficiency, high capital costs ($50,000-$100,000 per hectare), and the need for robust bioreactor designs. Machine learning is being used to optimize light, nutrients, and retention time, improving performance by up to 25%. While not yet mainstream, algae-based treatment is approaching cost parity for biodiesel and offers a path to decarbonize a critical infrastructure sector.