Nutrient recovery from wastewater through pilot scale electrodialysis

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Resource Recovery

Background:

• Domestic wastewater treatment generates supernatant (centrate) rich in nutrients like ammonium-nitrogen (NH4-N) and potassium (K).
• Conventional methods for nutrient removal can be energy-intensive or less effective in concentrating nutrients for recovery.
• Electrodialysis (ED) presents a potential solution for nutrient recovery from wastewater streams.

Purpose of the Study:

• To quantify the nutrient recovery performance of an electrodialysis (ED) process using a pilot-scale reactor.
• To assess the economic viability and operational sustainability of ED for nutrient recovery from wastewater centrate.

Main Methods:

• A 30-cell pair pilot ED reactor with a 7.2 m² effective membrane area was used.
• Domestic anaerobic digester supernatant (centrate) served as the feed source.
• Nutrient concentrations (NH4-N, K) and process parameters (current efficiency, power consumption) were monitored over several days.

Main Results:

• The ED process successfully concentrated nutrients, achieving product streams with NH4-N at 7100 ± 300 mg/L and K at 2490 ± 40 mg/L.
• Average total current efficiency for major cations was 76% (40% NH4-N transport, 14% K transport).
• Electrode power consumption was 4.9 ± 1.5 kWh/kgN, significantly lower than competing technologies and previous lab-scale ED trials.

Conclusions:

• Electrodialysis is an economically promising technology for recovering nutrients from wastewater.
• Pilot-scale testing demonstrated the importance of scaling up ED for improved efficiency and cost-effectiveness.
• Effective cleaning procedures and operational sustainability were confirmed for multi-day treatment durations.