Evaluation on the nutrient concentration changes along the flow path of a free surface flow constructed wetland in agricultural area

Abstract

In this study, the nutrient concentration changes along the hydrologic flow path of a free water surface flow constructed wetland (CW) treating agricultural stream runoff was investigated. Dry sampling was performed from April 2009 to November 2011 at five locations representing each treatment units of the CW. Grab water samples were analyzed for nitrogen forms such as total nitrogen (TN), total Kjeldahl nitrogen, nitrate, and ammonium; and phosphorus forms including total phosphorus (TP) and phosphate. Findings revealed that the physical properties such as temperature, dissolved oxygen and pH affected the TP retention in the CW. High nutrient reduction was observed after passing the first sedimentation zone indicating the importance of settling process in the retention of nutrients. However, it was until the 85% of the length of the CW where nutrient retention was greatest indicating the deposition of nutrients at the alternating shallow and deep marshes. TN and TP concentration seemed to increase at the final sedimentation zone (FSZ) suggesting a possible nutrient source in this segment of the CW. It was therefore recommended to reduce or possibly remove the FSZ in the CW for an optimum performance, smaller spatial allocation and lesser construction expenses for similar systems.

Status of Constructed Wetlands in Nepal: Recent Developments and Future Concerns

“…CW technology has been widely used due to its ease of operation, cost-effectiveness and low operation and maintenance cost (Mercado, 2013). In Nepal, CW was used This was because the construction of long sewer line for centralized wastewater treatment was economically impossible in most part of Nepal due to diverse topography.…”