Treatment of pig manure liquid digestate in horizontal flow constructed wetlands: Effect of aeration

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.

Intensification of constructed wetlands for land area reduction: a review

“…Biochemical oxygen demand (BOD) values were approximated using the ratio COD/BOD = 2 in the studies where BOD was not reported (Ouellet-Plamondon et al 2006 ; Fan et al 2013c ; Zhong et al 2015 ; Zapater-Pereyra et al 2015 ; Uggetti et al 2016 ). (1) Ouellet-Plamondon et al ( 2006 ), (2) Nivala et al ( 2007 ), (3) Zhang et al ( 2010 ), (4) Fan et al ( 2013c ), (5) Butterworth et al ( 2013 ), (6) Zapater-Pereyra et al ( 2014 ), (7) Li et al ( 2014 ), (8) Zhong et al ( 2015 ), (9) Uggetti et al ( 2016 ), (10) S. Wu et al ( 2016b ), (11) Ye and Li ( 2009 ), (12) Zapater-Pereyra et al ( 2014 ), (13) Zapater-Pereyra et al ( 2015 ) AA artificial aeration, HFCW horizontal flow constructed wetland, HCW hybrid constructed wetland, WT wastewater type, FF fish farm, LL landfill leachate, D domestic, S synthetic, P piggery, HLR hydraulic loading rate, OLR organic loading rate, AM aeration mode, CA continuous aeration, IA intermittent aeration, AP aeration position, B bottom, M middle, S surface, F front, R rear, AFR airflow rate, DO dissolved oxygen, TSSs total suspended solids, COD chemical oxygen demand, NH 4 + -N ammonium-nitrogen, TN total nitrogen, TP total phosphorus, NA not available, H + F + H HFCW free water surface flow CW and HFCW in a stack design, H + H HFCW and horizontal flow filter connected in series, V + H VFCW over horizontal flow filter…”

“…Biochemical oxygen demand (BOD) values were approximated using the ratio COD/BOD = 2 in the studies where BOD was not reported (Ouellet-Plamondon et al 2006 ; Fan et al 2013c ; Zhong et al 2015 ; Zapater-Pereyra et al 2015 ; Uggetti et al 2016 ). (1) Ouellet-Plamondon et al ( 2006 ), (2) Nivala et al ( 2007 ), (3) Zhang et al ( 2010 ), (4) Fan et al ( 2013c ), (5) Butterworth et al ( 2013 ), (6) Zapater-Pereyra et al ( 2014 ), (7) Li et al ( 2014 ), (8) Zhong et al ( 2015 ), (9) Uggetti et al ( 2016 ), (10) S. Wu et al ( 2016b ), (11) Ye and Li ( 2009 ), (12) Zapater-Pereyra et al ( 2014 ), (13) Zapater-Pereyra et al ( 2015 )…”

Digestate Liquid Fraction Treatment with Filters Filled with Recovery Materials

“…Additionally, the high NH 4 + -N and salinity content may compromise the plant survival in CWs [26]. In several papers, the digestate liquid fraction (DLF) was diluted (from 1:2 to 1:20 DLF:water) before CW treatment, and in some cases it was additionally subjected to a residence time in a sediment tank [13,19,20,31] with the aim to reduce the suspended solids and NH 4 + -N concentration. However, dilution may not be considered a suitable solution in practical conditions because it implies higher volumes to store and manage.…”

Synergy between anaerobic digestion and a post‐treatment based on Thermophilic Aerobic Membrane Reactor (TAMR)

“…Among all energy sources, the use of energy from biogas produced by anaerobic digestion (AD) plants is encouraged both by their availability and by the strong economic subsidies . Therefore, AD of manure from stables, crop residues, wastes from food industry, municipal wastes, and dedicated energy crops is becoming increasingly popular worldwide . Thus, the increasing number of AD plants (i.e.…”

“…As concerns the biological methods, available processes for liquid digestate treatments are conventional process with nitrification/denitrification and advanced biological processes such as nitritation‐denitritation process and completely autotrophic process (partial nitritation and Anammox process) . Recently, interesting results were obtained by the application of constructed wetlands with intermittent aeration on the enhanced removal of organic matter and nitrogen .…”