Performance of hybrid constructed wetland systems for treating septic tank effluent.
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 BOD5 (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.
Cui
Li-hua
LH
Department of Environmental Science and Engineering, South China Agricultural University, Guangzhou, China. lihcui@scau.edu.cn
Liu
Wen
W
Zhu
Xi-zhen
XZ
Ma
Mei
M
Huang
Xi-hua
XH
Xia
Yan-yang
YY
D001673:Biodegradation, Environmental; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D012621:Seasons; D012722:Sewage; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D018508:Water Purification / Q000379:methods*
D012722:Sewage; D010758:Phosphorus; D009584:Nitrogen; D010100:Oxygen