Volume No. 13 Issue No.: 04 Page No.: 292-299 April-June 2019

 

NITROGEN REMOVAL IN SUB-SURFACE FLOW CONSTRUCTED WETLANDS: INFLUENCE OF MIXED VEGETATION

 

AththanayakeA. M. N. D., DasanayakaD. A. I A. And Weerakoon G. M. P. R.

Department of Civil Engineering, Faculty of Engineering, University of Peradeniya, Peradeniya, (SRI LANKA)

 

Received on : December 29, 2018

 

ABSTRACT

 

Excessive nitrogenous compounds entering into water environment due to improper wastewater dischargers, can lead to ecological changes in natural water bodies and various public health issues to water consumers. Constructed wetlands (CWs) are gaining popularity in many parts of the world for treating an array of wastewater pollutants, including nitrogenous compounds, due to their lower investment and operation costs while providing higher treatment efficiency with ecological benefits, over the conventional technologies. This study evaluated the influence of mixed vegetation on removal of nitrogenous compounds from wastewater, using laboratory scale sub-surface batch flow CWs, using two plant species; narrow-leaf cattail (Typhaangustifolia) and umbrella palms (Cuperusalternifolius). Twelve wetland units of size 0.5 m x 0.66 m (Diameter x Height) were prepared using 10-20 mm gravel as the wetland media and planted with two plants in each unit; four units with narrow-leaf cattail, four units with umbrella palms and the remaining four units with both plant species. Wastewater feeding was carried out batch wise at seven-day interval for three months. Wastewater samples were collected from the influent and effluents of each wetland unit at every seven-day interval and chemical oxygen demand (COD), Total nitrogen (TN), Nitrate nitrogen (NO3--N), Ammonia nitrogen (NH3-N), pH, Electrical conductivity (EC) and temperature (T) were measured. Results showed that NH3-N and TN removal in umbrella palm wetland units was higher (p < 0.05) than Cattail and mixed vegetation wetland units. Also, results revealed that mixed vegetation had no effect on nitrogen removal in sub-surface batch flow constructed wetlands.

 

Keywords : Constructed wetlands, Nitrogen removal, Mixed vegetation, Sub-surface flow, Synthetic wastewater

 

 

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