DISTRIBUTION OF DO, SUBSTRATE ENZYME ACTIVITIES AND OPERATING PERFORMANCE OF CONSTRUCTED WETLANDS FOR WASTEWATER TREATMENT.

Substrate enzyme plays an important role in the transformation and the degradation processes of nutrients in constructed wetlands. The spatial distribution of the substrate enzymes, including urease, dehydrogenase and phosphatase, was monitored systematically. Meanwhile, the spatial distribution of dissolved oxygen and the spatial degradation rule of nutrients were investigated. The relationship between the enzyme activities and wetland operation characteristics was analyzed. Results showed that there was a close relationship between the spatial distribution of dissolved oxygen, the spatial degradation regularity of nutrients, and the enzyme activities. The activity of urease, dehydrogenase and phosphatase in the upper layer of soil was generally higher than that in the lower layer. The distribution regularity of the urease activity was similar with that of dissolved oxygen. The activity of dehydrogenase and phosphatase declined gradually along the flow in the wetland. The urease activity influenced the nitrification intensity significantly, showing a remarkable positive correlation with the nitrification intensity in the wetland. The dehydrogenase activity had no significant correlation with the nutrient removal, but was associated with the accumulation of organic matters in the substrates. The phosphatase activity was closely related to degradation of organophosphorus. [ABSTRACT FROM AUTHOR]