Comparison of Comparison of Comparison of Comparison of Treatment Performance between Treatment Performance between Treatment Performance between Treatment Performance between Constructed Constructed Wetlands with Different Substrates Wetlands with Different Substrates Wetlands with Different Substrates Wetlands with Different Substrates

Constructed wetlands are manmade systems that mimic the functions of natural wetlands. The aim of the present study is to examine effect of substrate on organic and nutrient removal in constructed wetlands. With this in mind, we have designed, constructed and operated two pilot-scale horizontal subsurface flow constructed wetlands having two different substrates, gravel and pebble, in our open-air laboratory receiving pre-treated domestic wastewater. The removal efficiency of COD, BOD, TN, and TP was increased from 39 to 69%, 29 to 56%, 23 to 45%, 25 to 75% and 35 to 74%, 33 to 50%, 16 to 31% and 15 to 58% when there was an increase in hydraulic residence time from 2 days to 8 days in the first and second units respectively. It was found that substrate type influenced concentration reduction.