Nitrogen resource recovery from mature leachate via heat extraction technology: An engineering project application

A large pool of ammonia in mature leachate is challenging to treat with a membrane bioreactor system to meet the discharge Standard for Pollution Control on the Landfill Site of Municipal Solid Waste in China (GB 16889-2008) without external carbon source addition. In this study, an engineering leachate treatment project with a scale of 2,000 m³/d was operated to evaluate the ammonia heat extraction system (AHES), which contains preheat, decomposition, steam-stripping, ammonia recovery, and centrifuge dewatering. The operation results showed that NH₃-N concentrations of raw leachate and treated effluent from an ammonia heat extraction system (AHES) were 1,305-2,485 mg/L and 207-541 mg/L, respectively. The ratio of COD/NH₃-N increased from 1.40-1.84 to 7.69-28.00. Nitrogen was recovered in the form of NH₄HCO₃ by the ammonia recovery tower with the introduction of CO₂, wherein the mature leachate can offer 37% CO₂ consumption. The unit consumptions of steam and power were 8.0% and 2.66 kWh/m³ respectively, and the total operation cost of AHES was 2.06 USD per cubic metre of leachate. These results confirm that heat extraction is an efficient and cost-effective technology for the recovery of nitrogen resource from mature leachate.