Energy-efficient wastewater treatment technologies in constructed wetlands
2011
Tilgalis, E., Latvia Univ. of Agriculture, Jelgava (Latvia). Dept. of Architecture and Building | Grinberga, L., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Rural Engineering. Dept. of Environmental Engineering and Water Management
Usually in wastewater treatment plants the removal of organic matter is ensured in aerotanks in biochemical reactions where activated sludge in presence of oxygen transforms the organic matter. The quantity of organic matter in water can be determined as the biochemical oxygen demand in five days (BOD). BOD in village municipal sewage is around 250 mg lE-1 or 65 g per day from each resident. It means that 1.7 kg of oxygen is needed for mineralizing one kg of organic matter. Therefore, it can be concluded that high oxygen demand is required to mineralize organic matter using aerotanks. With a compressor and aeration discs or tubes the oxygen in the form of air is provided to aerotank. To reduce electricity consumption in wastewater treatment, we present to adapt natural conditions. Mineralization of organic matter in constructed wetlands performs basing on bacteria activity in presence of oxygen. The main difference is the method for oxygen supply. In constructed wetlands oxygen demand provides the plants growing above the filter material and it consumes no electricity. Constructed wetlands can be designed with different water flow in filter material – horizontal flow wetlands, vertical flow wetlands and shallow ponds with plants.
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