Correlation Among Soil Enzyme Activities, Root Enzyme Activities, and Contaminant Removal in Two-Stage In Situ Constructed Wetlands Purifying Domestic Wastewater

Abstract

Two-stage in situ wetlands (two vertical flow constructed wetlands in parallel and a horizontal flow constructed wetland) were constructed for studying domestic wastewater purification and the correlations between contaminant removal and plant and soil enzyme activities. Results indicated the removal efficiency of NH4 (+) and NO3 (-) were significantly correlated with both urease and protease activity, and the removal of total phosphorus was significantly correlated with phosphatase activity. Chemical oxygen demand removal was not correlated with enzyme activity in constructed wetlands. Plant root enzyme (urease, phosphatase, protease and cellulose) activity correlation was apparent with all contaminant removal in the two vertical flow constructed wetlands. However, the correlation between the plant root enzyme activity and contaminant removal was poor in horizontal flow constructed wetlands. Results indicated that plant roots clearly played a role in the removal of contaminants.

Nitrogen and organic matter removal and enzyme activities in constructed wetlands operated under different hydraulic operating regimes

“…As an N resource for nitrification (Dong & Reddy, 2010) as well as the end product of urea hydrolysis (Thorén, 2007), decreased NH 4 + concentration stimulates urease enzyme microbial production for urea hydrolyze. This also explains the higher UA in CW in a Batch operating regime: during the "resting" period, filter beds drain completely enhancing oxygen transfer to improve nitrification (Ni et al, 2016). This is in line with the better N removal performance in Batch operation evidenced by the higher PC1 scores.…”