Rugaika Anita M, Kajunguri Damian, Van Deun Rob, Van der Bruggen Bart, Njau Karoli N
Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium E-mail:
Department of Mathematics, Kabale University, P. O. Box 317, Kabale, Uganda.
Water Sci Technol. 2018 Dec;78(12):2639-2646. doi: 10.2166/wst.2019.031.
Pilot-scale constructed wetlands (CWs) that allowed wastewater to flow with high interstitial velocities in a controlled environment were used to evaluate the possibility of using mass transfer approach to design horizontal subsurface flow constructed wetlands (HSSF-CWs) treating waste stabilisation ponds (WSPs) effluent. Since CW design considers temperature which is irrelevant in tropics, mass transfer approach could improve the design. HSSF-CWs were operated in batch recycle mode as continuous stirred tank reactors (CSTR) at different interstitial velocities. The overall removal rate constants of chemical oxygen demand (COD) at various interstitial velocities were evaluated in mesocosms that received pretreated domestic wastewater. The mean overall removal rate constants were 0.43, 0.69, 0.74 and 0.73 d corresponding to interstitial velocities of 15.43, 36, 56.57 and 72 md, respectively. Results showed that the interstitial velocities up to 36 md represented a range where mass transfer effect was significant and, above it, insignificant to the COD removal process. Since WSPs effluent has high flow rates and low organic load, it is possible to induce high interstitial velocities in a HSSF-CW treating this effluent, without clogging and overflow. The performance of these HSSF for tertiary treatment in tropical areas could be improved by considering flow velocity when designing.
中试规模的人工湿地（CWs）可使废水在可控环境中以较高的间隙流速流动，被用于评估采用传质方法设计水平潜流人工湿地（HSSF-CWs）处理稳定塘（WSPs）出水的可能性。由于传统人工湿地设计时考虑了温度因素，而这在热带地区并不相关，因此传质方法可改进设计。HSSF-CWs以间歇循环模式运行，类似连续搅拌釜式反应器（CSTR），具有不同的间隙流速。在接收预处理生活污水的中试系统中，评估了不同间隙流速下化学需氧量（COD）的总去除速率常数。平均总去除速率常数分别为0.43、0.69、0.74和0.73 d，对应的间隙流速分别为15.43、36、56.57和72 m/d。结果表明，间隙流速高达36 m/d时，传质效果显著，高于此值时，对COD去除过程影响不显著。由于稳定塘出水流量大且有机负荷低，在处理该出水的HSSF-CW中有可能诱导出较高的间隙流速，而不会造成堵塞和溢流。在热带地区设计时考虑流速，可提高这些HSSF用于三级处理的性能。
