ANALYSIS OF BIOLOGICAL AND HYDROLOGICAL ASPECTS OF CONSTRUCTED WETLAND

Naturally occurring microorganisms in wetlands produce enzymes to reduce sulfate in the anaerobic condition. Three enzymes, ATP Sulfurylase, APS reductase and Sulfite reductase, are known to involved in reduction of sulfate to hydrogen sulfide. Therefore, electrophoresis of total protein will show a characteristic pattern created by the three enzymes. The amount of the three enzymes can be a good indicator for the rate of sulfate reduction in wetland. Protein finger printing using gel electrophoresis was carried out to confirm the presence of sulfate reducing bacteria and their role in sulfate reduction. Total proteins were extracted from sediments in wetland and analysed by gel electrophoresis. Samples taken from the lower part of the sediment of model wetland in laboratory showed consistent protein patterns. The protein patterns were not found in upper part of the sediment or other soil samples. Samples were collected from various constructed wetlands in Korea and their protein patterns were analysed using protein finger printing. Efficiency of the subsurface-flow wetlands drops with time, as the hydraulic conductivity of the wetland soil decreases significantly due to the chemical reactions with the wastewater, eventually leading to overland flow or flooding. The changes in the hydrological properties of the substrates in a constructed wetland were investigated by a constant-head permeability test, using 3-inch long 8-inch diameter columns at an abandoned mining site. Columns were installed near the tunnel entrance, and wastewater flowing out of the tunnel was used for the tests. It was observed that the flow rate through the column was substantially lowered with time. mainly due to significant amount of sludge within the media. Concrete gravels were used to reduce precipitation of iron oxides within substrates, and the pH and Eh of outflow from the column were also measured to monitor the efficiency of the substrates and concrete gravel on the water quality. Reduction in the hydraulic conductivities of substrate materials with time was taken into account in the design of the subsurface flow system, using a numerical analysis program incorporating finite element method.