Udo Heinss

Potentials of vertical-flow constructed wetlands for septage treatment in tropical regions

Publisher Summary This chapter presents an assessment of the potentials of vertical-flow constructed wetlands (CWs) for septage treatment in tropical regions where microbial reactions and plant growth rates are substantially high. CWs are proven to be an effective low-cost treatment system, which utilizes the interactions of emergent plants and microorganisms in the removal of pollutants. Three pilot-scale CW beds consist of 65-cm sand gravel substrata, supported by ventilated drainage system, and planting with narrow-leave cattails are taken. During the first year of operation, the CWs are operated at the solid loading rates (SLR) and the application frequencies of 80–500 kg total solid (TS)/m2.yr and 1–2 times weekly, respectively. The SLR of 250 kg TS/m2.yr is found to result in the optimum treatment performances with respect to the TS, total chemical oxygen demand (TCOD), and total Kjeldahl nitrogen (TKN) removal efficiencies of 80, 96, and 92%, respectively, as well as less adverse effect on plant growth. The operating conditions in the second year are rectified by retaining the percolate in the CW beds for the periods of two and six days prior to discharge, but maintain the SLR of 250 kg TS/m2.yr. This operating condition results in the percolate NO3 concentrations of 20–50 mg/L.