Using hydrogen peroxide to supplement oxygen for nitrogen removal in constructed wetlands

Nitrification is often the main mechanism to remove ammonium in constructed wetlands. An important factor hindering this biochemical process in constructed wetlands is the availability of dissolved oxygen. This study introduced hydrogen peroxide-based chemical oxygenation to saturated vertical flow constructed wetlands for removal of nitrogen. Hydrogen peroxide is decomposed into water and oxygen in the presence of catalase. Three hydrogen peroxide concentrations, 0.6%, 1% and 2% (w/v), were applied over three operating periods at the same dosage to test the effects of hydrogen peroxide concentration on nitrogen removal and growth of wetland plants in secondary effluent. More than 92% ammonia was removed in all the three periods. Ammonia removal via nitrification was not adversely affected by hydrogen peroxide at the tested concentrations. As hydrogen peroxide dosing concentration was increased, concentration of nitrate in the effluent decreased substantially due to stimulated plant growth and plant uptake of nitrate instead of ammonia. Dosing hydrogen peroxide to constructed wetlands extended ammonia removal via nitrification to total inorganic nitrogen removal by nitrification and stimulated plant uptake of nitrate. The optimum dosing solution appeared to be 1-2% hydrogen peroxide.