Denitrification in constructed wetlands receiving municipal solid waste landfill leachate.

摘要

Constructed wetland systems have the potential of providing a low cost and low maintenance wastewater treatment alternative for nitrogen removal. The focus of this research was to investigate denitrification in constructed wetlands and to the use the knowledge gained to improve the nitrogen treatment capabilities of these systems. The constructed wetlands used for this research were located at the New Hanover County Municipal Solid Waste Management Facility and nitrogen removal was investigated in two of the pilot scale constructed wetlands including free water surface and subsurface horizontal flow. Both wetlands received pretreated leachate with total nitrogen primarily in the form of nitrate.; Field water sampling in conjunction with a laboratory acetylene block method were used to quantify nitrogen removals in the wetlands. Monthly or semi-monthly water samples were taken from the influent and effluent of the constructed wetlands in 1996 and 1997. Average nitrate nitrogen removal rates in the constructed wetlands during 1996 and 1997 were 2.5 {dollar}pm{dollar} 2.3 and 4.5 {dollar}pm{dollar} 2.2 g N/m{dollar}sp3{dollar}/d for free water and 1.1 {dollar}pm{dollar} 1.1 and 0.62 {dollar}pm{dollar} 2.6 g N/m{dollar}sp3{dollar}/d for subsurface flow, respectively. Complete removal of nitrate nitrogen was not achieved in either wetland system during this time period.; A modified acetylene block method was used in the laboratory to investigate rate limiting factors in denitrification. Background denitrification rates as well as potential denitrification rates using sodium acetate and sodium phosphate were measured. A significant increase in the denitrification rates for samples with the addition of sodium acetate occurred over the denitrification rates of controls with no additions. Denitrification in the free water wetland was limited in the availability of an easily degradable source of organic carbon. Background denitrification rates measured using the acetylene block method compared well to the nitrate nitrogen removal rates measured by field water sampling. The laboratory method provided information on rate limiting factors in denitrification that could be used to improve nitrogen treatment in the free water wetland in the field.