Affiliations: Department of Environmental Science and Engineering,
South China Agricultural University, Guangzhou 510642, China | Coast to Coast Analytical Specialists, Garland, TX
75081, USA
Abstract: The integrated wetland systems were constructed by combining
horizontal-flow and vertical-flow bed, and their purification efficiencies for
septic tank effluent were detected when the hydraulic retention time (HRT) was
1 d, 3 d, 5 d under different seasons. The results showed that the removal
efficiencies of the organics, phosphorus were steady in the hybrid systems, but
the removal efficiency of total nitrogen was not steady due to high total
nitrogen concentration in the septic tank effluent. The average removal rates
of COD (chemical oxygen demand) were 89%, 87%, 83%, and 86% in summer, autumn,
winter and spring, respectively, and it was up to 88%, 85%, 73%, and 74% for
BOD_5 (5 d biochemical oxygen demand) removal rate in four
seasons. The average removal rates of TP (total phosphorous) could reach up to
97%, 98%, 95%, 98% in four seasons, but the removal rate of TN (total nitrogen)
was very low. The results of this study also indicated that the capability of
purification was the worst in winter. Cultivating with plants could improve the
treated effluent quality from the hybrid systems. The results of the operation
of the horizontal-flow and vertical-flow cells (hybrid systems) showed that the
removal efficiencies of the organics, TP and TN in horizontal-flow and
vertical-flow cells were improved significantly with the extension of HRT under
the same season. The removal rate of 3 d HRT was obviously higher than that of
1 d HRT, and the removal rate of 5 d HRT was better than that of 3 d HRT, but
the removal efficiency was not very obvious with the increment of HRT.
Therefore, 3 d HRT might be recommended in the actual operation of the hybrid
systems for economic and technical reasons.
