Treatment of pig manure liquid digestate in horizontal flow constructed wetlands: Effect of aeration |
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| Authors: | Shubiao Wu Ming Lei Qimin Lu Luchen Guo Renjie Dong |
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| Affiliation: | 1. Key Laboratory of Clean Utilization Technology for Renewable Energy, Ministry of Agriculture, College of Engineering, China Agricultural University, Beijing, P. R. China;2. Department of Biomass Engineering College of Agriculture and Biotechnology, China Agricultural University, Beijing, P. R. China |
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| Abstract: | With the rapid development of scaled anaerobic digestion of pig manure, the generation of liquid anaerobic digestate exceeds the farmland loading capacity, causing serious environmental pollution. Three laboratory‐scale horizontal subsurface flow constructed wetlands (CWs; planted + aeration, planted, and unplanted) were set up to investigate the feasibility of liquid digestate treatment in wetlands. Treatment capacity in different wetlands was evaluated under different influent concentrations (chemical oxygen demand COD], 5 days biochemical oxygen demand BOD5], and nitrogen forms). The effect of aeration and effluent recirculation on organic matter and total nitrogen removal was investigated. Results showed that integrating intermittent aeration in CWs significantly improved the oxygen condition (p < 0.01) in the wetland bed and promoted BOD5 removal to 90% in aerated CWs as compared with <15% in the unaerated CWs. Meanwhile, COD removal between these three wetlands did not show any difference and varied from 52 to 72% under influent concentration of 200–820 mg/L because of the high content of hard‐degradable organic matter in the liquid digestate. Intermittent aeration resulted in high ammonium removal (>98%) although the influent loading varied from 65 to 350 mg/L. However, intermittent aeration caused nitrate accumulation of 300 mg/L and limited total nitrogen (TN) removal of 33%. To intensify the TN removal, we verified effluent recirculation to increase the removal efficiency of TN to 78%. These results not only show the potential application of CWs for treatment of high‐strength liquid anaerobic digested slurry, but also indicate the significance of intermittent aeration on the enhanced removal of organic matter and ammonium. |
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| Keywords: | Anaerobic digestion Effluent recirculation Farmland loading capacity Horizontal flow constructed wetland Intermittent aeration |
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