Evaluating organics removal performance from lagoon-pretreated swine wastewater in pilot-scale three-stage surface flow constructed wetlands

Abstract

Pilot-scale three-stage surface flow constructed wetlands (SFCWs) planted with Myriophyllum aquaticum were constructed to study the organics removal performance from lagoon-pretreated swine wastewater. The removal performance of organics in the SFCWs was evaluated using deterministic and probabilistic methods and the results were consistent. The SFCWs achieved a relatively high removal efficiency (79.0–82.7%) for a wide influent COD concentration range (456–1010 mg L−1). No significant difference (p > 0.05) of COD removal efficiency and first-order removal rate constant among the various strengths of influent suggested that the present loading rates (2.74–6.06 g m−2 d−1) have not yet reached the maximum removal capacity of the SFCWs. The mean emission fluxes of methane from the SFCW units fed with different strengths of wastewater were 25–1210 mg m−2 d−1. A significantly positive correlation (p < 0.01) between methane emission fluxes and COD loading rates indicated that the anaerobic digestion of organics was an important process for organics removal in the SFCWs. No significant organics accumulation in the sediment over time suggested that plant harvest could be in favor of reducing the organics accumulation in the substrate and should be considered important during management of constructed wetlands.