Advanced treatment of domestic wastewater by a reed filter bed system using vartical-percolation

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The objectives of this study are (i) to make clear the effectiveness of reed and the loading formula of wastewater (i.e., continuos loading (CL) or intermittent loading (IL)) on nitrogen removal efficiency in a reed filter bed system (RFB) and (ii) to measure denitrification rates using ィイD115ィエD1N tracer method. The obtained results are as follows:1) It was found that the nitrogen removal rate in the RFB tank was higher than that in the sand tank (Control, i.e. without reeds) in both CL and IL. Although the nitrogen removal rate of the RFB with IL ranged from 47-97% (average 76%) during 19 months, that of RFB with CL exhibited seasonal variations with range of 4-95% (average 54%).2) The ィイD115ィエD1N tracer methods showed that the denitrification rates of the RFB and the sand tank ranged form 0 to 5.5, 0 to 3.4 [g-N/mィイD12ィエD1 /day] respectively. These indicate that about 60% of nitrogen loading to the RFB tank and about 80% of nitrogen loading to the sand tank were removed by denitrification. A part of remaining nitrogen loss in nitrogen balance of the RFB tank was considered to be caused by plant uptake. High denitrification rate in the RFB suggested that microbial activity in the reed rhizosphere played a important role in nitrogen removal efficiency.