The study of denitrification in a “sequential fill and drain technique subsurface-flow constructed wetland” is the focus of this thesis. The constructed wetland is located at the botanical gardens in Huntsville, Alabama and treats a flow of one hundred fifty gallons of domestic wastewater per day. Data collected from the wetlands is analyzed for nitrates, ammonia, nitrites, biochemical oxygen demand, turbidity, pH and coliform bacteria. As per the design requirements of the wetland, the treatment was to effect a reduction in the effluent nitrate levels, a definite indication of denitrification. On the contrary, the effluent nitrate levels did not reduce following complete treatment with a two-hour recycling time. The time interval between consecutive fill and drain cycles was then increased from two hours to four hours providing additional time for the anaerobic denitrification to further reduce the effluent nitrate levels. Increase in the time interval brought about a reduction in effluent nitrate values with an increase in the pH. The reduction in nitrate values and increase in pH confirmed effective denitrification process.
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