Designing Constructed Wetlands for Nitrogen Removal

Abstract

Many constructed wetlands adequately treat BOD5, TSS, and bacteria. However, a review of nitrogen (N) data from 52 constructed and natural wetlands in the North American data base confirmed that N removal was variable. Nitrification and denitrification require aerobic and anaerobic conditions. This paper presents case histories of systems that use alternating shallow and deep water zones to create both environments. Regression analysis of N removal and N loadings in 18 shallow-deep water systems suggested that NH4+ loading (kg N/ha/day) could be used to predict effluent NH4+ values. Combinations of shallow water-emergent vegetation and deep water-submergent vegetation with low NH4+ (and TKN) loading rates can produce very low levels of discharged NH4+.

Efficiency of small constructed wetlands for subsurface treatment of single-family domestic effluent

“…The low ammonia removal efficiency of these systems individually and collectively is expected based on other treatment wetland studies (Gersberg et al, 1983;Hammer and Knight, 1994;Koottatep and Polprasert, 1997). The upper limit of the ammonia reduction confidence interval for these data (87%) falls within the 80-95% removal rate cited for conventional systems employing tertiary treatment (Kadlec and Knight, 1996).…”

Roles of substrate microorganisms and urease activities in wastewater purification in a constructed wetland system

“…Substrate enzyme might play a vital role in the processes of many important biochemical reactions, such as formation and decomposition of humus, hydrolysis and transformation of resides of organic compounds, plants, and microorganisms, and oxidation-reduction reactions (Douglas and Bremner, 1971). Many reports from previous research suggested that the removal of nitrogen in the constructed wetland system is a complicated process (Koottatep and Polprasert, 1997;Hammer and Knight, 1994). In the present study, significant relationship between TKN removal efficiencies and substrate urease activities was achieved; indicating urease activities played an important role for TKN removal during wastewater treatment in constructed wetlands.…”

Effects of vegetation management in constructed wetland treatment cells on water quality and mosquito production

“…The combination of the aerobic and anaerobic zones within a wetland system is thus required for effective N removal (Mitsch and Gosselink, 2000;Kadlec and Knight, 1996;USEPA, 2000). Hammer and Knight (1994) stated that open water areas totaling 10-20% of a wetland system, arranged intermittently along its length, appeared to be beneficial for N treatment. However, the 50% open water ratio in the pondmarsh -pond -marsh control and thinned cells alone was not open enough to maintain the treatment benefits in this Californian coastal scrub climate (Pase and Brown, 1994) This interspersion effect appears to mimic an early successional plant growth stage, such as the first growing season of a typical free water surface wetland.…”