Making waves: How to clean surface water with photogranules

Area of Science:

• Environmental Science
• Microbiology
• Water Treatment Engineering

Background:

• Global surface waters face severe ecological and chemical degradation, necessitating effective pollution control strategies.
• Photogranules, microbial aggregates of algae and bacteria, show promise for wastewater treatment with reduced aeration and CO2 capture.
• Previous studies focused on high-strength wastewater, leaving potential for surface water treatment unexplored.

Purpose of the Study:

• To evaluate the efficacy of photogranules in removing nutrients from polluted surface water.
• To assess photogranule performance under low nutrient concentrations and short hydraulic retention times.
• To investigate morphological changes in photogranules during surface water treatment.

Main Methods:

• Photogranules were applied to treat polluted surface water with low nutrient levels (3.2 mg/L N, 0.12 mg/L P) and a hydraulic retention time of 1.5 hours.
• Sequencing batch operations were employed without pH control to monitor nutrient removal.
• Photogranule morphology was analyzed under surface water treatment conditions.

Main Results:

• Photogranules achieved significant nitrogen removal (<0.6 mg/L, ~80%) and phosphorus removal (<0.01 mg/L, 90-95%).
• Photogranules adapted to surface water conditions by developing a finger-like morphology, increasing surface area.
• Despite morphological changes, photogranules maintained excellent settling properties.

Conclusions:

• Photogranules are effective for nutrient removal from polluted surface water, even at low concentrations and short hydraulic retention times.
• The adaptability of photogranule morphology enhances their suitability for diverse water treatment applications.
• Photogranular technology presents a viable and sustainable approach for surface water remediation.