In‐Stream Wetland Mitigation of Nitrogen Contamination in a USA Coastal Plain Stream

Abstract

Nonpoint source N from riverine origin is a major water quality problem throughout the world. Nitrogen removal from a contaminated (6.6 mg L−1, NO3‐N) stream was evaluated in this study using an instream wetland (ISW). The ISW was established at the exit of a 425‐ha USDA Water Quality Demonstration watershed in the Coastal Plain of North Carolina. It ranged in depth from about 0.2 to 2 m, and it was <1% (3.3 ha) the size of the watershed. The ISW dramatically lowered mean stream NO3‐N from 6.6 to 2.0 mg L−1. Nitrate‐N mass removal was highly correlated to inflow NO3‐N (r = 0.93) in the warmer months when biological processes were more active. Ammonia‐N mass removal was opposite that of NO3‐N. It was highly correlated to inflow NH3‐N (r = 0.81) during the cooler months. Removal of both NO3‐N and total‐N (NO3‐N + TKN) were positively correlated to temperature with r values of 0.77 and 0.62, respectively. Total annual N removal for the ISW was approximately 3 kg ha−1 d−1, which was about 37% of the inflow N. The ISWs appear to be very good landscape features for mitigating excess nonpoint source N in the southeastern Coastal Plain of the USA. As such, they are a good complement to other best management practices for improved water quality.

Characteristic Analysis of Plants for the Removal of Nutrients from a Constructed Wetland using Reclaimed Water

“…They are also a good choice for the ER of the SNWTP because this project is not only a major water transfer project from south to north in China, but also an ecological project with high landscape requirements. To date, FWS wetlands have been mainly used for treating domestic sewage [6,7] and livestock wastewater [8,9], controlling non-point pollution [10,11], rehabilitating and re-establishing rivers and wetlands [12], and improving river quality [13].…”

Denitrification of agricultural drainage line water via immobilized denitrification sludge

“…[21,[24][25][26]36,39] Relative to carbon and nitrogen concentration, all 3 of the methanol:nitrate concentrations (2:1, 10:1, and 20:1) seemed to function adequately. However, pushing the ratio lower could result in either lower denitrification or potentially incomplete denitrification.…”

“…Thus, a bioreactor of 1 m 3 would be required to treat 1 m 3 of drainage water in 1 h. This HRT would likely be very useful for much of the base and storm flow. For instance, Jaynes and Colvin [41] [21,24,26] As such, the IDS bioreactors offer the potential for requiring small bioreactor footprints, treating nitrate concentration hot spots, and treating moderate storm flows. Furthermore, the reaction rate is conservative relative to the potential for IDS reactors.…”

“…This is similar to 37% reduction in nitrogen export from an agricultural watershed in the southeastern Coastal Plain by an in-stream wetland which constituted 8% of the watershed. [24] However, these portions of watersheds may often not be available for created wetlands. To decrease the amount of land required for nitrate removal, various types of bioreactors have been successfully used to treat drainage waters.…”

Dissolved Phosphorus Transport During Storm and Base Flow Conditions From an Agriculturally Intensive Southeastern Coastal Plain Watershed

“…They reported that prior animal operations within SW2 applied high amounts of manure to soils. Additionally, stream water hydrology at the SW2 outlet was drastically altered in April 1993 when beavers (Castor canadensis) created a 3.3 ha pond that temporarily impounded water (Hunt et al, 1999). We hypothesized that P from animal manure and inorganic P fertilizer from past cropping activity was transported into the stream and later deposited into the pond.…”