5:15 PM - 7:15 PM
[AGE34-P09] Evaluation of the Impact of Artificial Macropore Introduction on Water Purification Characteristics
Keywords:Artificial macropore, water purification, column experiment, tidal flow
As part of its climate change mitigation efforts, Japan declared its goal of achieving carbon neutrality by 2050 in 2020, necessitating various decarbonization initiatives. Artificial wetlands (AW) have gained attention as a wastewater treatment method and have been increasingly adopted worldwide. However, in Japan, their application has been largely limited to dairy wastewater treatment, with only a few cases of implementation in sewage treatment facilities. One of the major obstacles to their widespread adoption is the large area required, as observed in case studies from Western countries. To address this issue, Tidal flow AW have been proposed, demonstrating high purification efficiency within a compact area. Tidal flow AW achieve both anaerobic and aerobic treatment by varying water levels, making them more efficient than conventional AWs. However, challenges such as clogging due to wastewater inflow and performance deterioration over time remain unresolved. In this study, artificial macropores were introduced into soil columns, and the purification performance of two flow modes -vertical flow (VF) and tidal flow (TF)- was compared using synthetic wastewater. This approach aimed to evaluate improvements in permeability and clogging mitigation while examining the impact of different flow modes on the water purification characteristics of organic matter and nitrogen in the presence of macropores.
To compare the removal efficiency of organic matter and nitrogen, AW columns were utilized. Cylindrical columns with an inner diameter of 8cm were filled with 10cm-thick sandy soil (<2mm grain size) containing 2.5% bentonite. Four experimental setups were prepared :C (control, sandy soil only), M0 (no macropores), M1 (one macropore), and M4 (four macropores).The synthetic wastewater was formulated to achieve target concentrations of CODcr:1500mg/L, T-N:100mg-N/L, and T-P:10mg-P/L. In the VF, 1,500mL of synthetic wastewater was introduced daily for 10days, and treated water was collected once/day to measure T-C and T-N concentrations. In the TF, an electromagnetic valve was installed at the drainage outlet of the column to simulate tidal conditions. 265mL of synthetic wastewater was introduced every two days for 20days, and treated water was collected every two days.
Throughout the experiment, the average T-C removal rates in the VF were C:67%, M0:16%, M1:33%, and M4:18%, whereas in the TF, they were C:64%, M0:76%, M1:78%, and M4:74%. In particular, in the M series, the removal rate was significantly higher in TF compared to VF. In TF, the water level drop during drainage induces a pressure reduction, which acts as a driving force for atmospheric air to be forcibly drawn into the filter bed. This mechanism enhances aerobic treatment efficiency. Additionally, in both VF and TF, the columns with macropores exhibited higher removal rates, suggesting that the introduction of macropores improved permeability and facilitated oxygen supply, which played a beneficial role in organic matter degradation that requires aerobic conditions. The average T-N removal rates during the experimental period were C:66%, M0:76%, M1:90%, and M4:88% in the VF, and C:83%, M0:88%, M1:92%, and M4:85% in the TF. In VF, the removal rates for C and M0 showed a decreasing trend over time, whereas M1 and M4 maintained consistently high removal efficiency. In TF, M1 exhibited stable and high efficiency, similar to VF. Furthermore, the ORP values were measured at proximal and distal points of the macropores in M1 and M4. During flooded conditions, the proximal point exhibited a significantly more reducing state than the distal point, whereas during drained conditions, the ORP values at both points were similar. These findings suggest that the presence of macropores contributed to the formation of anaerobic conditions during flooded phases, thereby promoting denitrification and enhancing nitrogen removal performance.
The experimental results using synthetic wastewater demonstrated that TF was more effective than VF for water purification. Furthermore, in both VF and TF, the introduction of artificial macropores significantly improved purification efficiency, highlighting their potential to enhance the performance of AWs.
To compare the removal efficiency of organic matter and nitrogen, AW columns were utilized. Cylindrical columns with an inner diameter of 8cm were filled with 10cm-thick sandy soil (<2mm grain size) containing 2.5% bentonite. Four experimental setups were prepared :C (control, sandy soil only), M0 (no macropores), M1 (one macropore), and M4 (four macropores).The synthetic wastewater was formulated to achieve target concentrations of CODcr:1500mg/L, T-N:100mg-N/L, and T-P:10mg-P/L. In the VF, 1,500mL of synthetic wastewater was introduced daily for 10days, and treated water was collected once/day to measure T-C and T-N concentrations. In the TF, an electromagnetic valve was installed at the drainage outlet of the column to simulate tidal conditions. 265mL of synthetic wastewater was introduced every two days for 20days, and treated water was collected every two days.
Throughout the experiment, the average T-C removal rates in the VF were C:67%, M0:16%, M1:33%, and M4:18%, whereas in the TF, they were C:64%, M0:76%, M1:78%, and M4:74%. In particular, in the M series, the removal rate was significantly higher in TF compared to VF. In TF, the water level drop during drainage induces a pressure reduction, which acts as a driving force for atmospheric air to be forcibly drawn into the filter bed. This mechanism enhances aerobic treatment efficiency. Additionally, in both VF and TF, the columns with macropores exhibited higher removal rates, suggesting that the introduction of macropores improved permeability and facilitated oxygen supply, which played a beneficial role in organic matter degradation that requires aerobic conditions. The average T-N removal rates during the experimental period were C:66%, M0:76%, M1:90%, and M4:88% in the VF, and C:83%, M0:88%, M1:92%, and M4:85% in the TF. In VF, the removal rates for C and M0 showed a decreasing trend over time, whereas M1 and M4 maintained consistently high removal efficiency. In TF, M1 exhibited stable and high efficiency, similar to VF. Furthermore, the ORP values were measured at proximal and distal points of the macropores in M1 and M4. During flooded conditions, the proximal point exhibited a significantly more reducing state than the distal point, whereas during drained conditions, the ORP values at both points were similar. These findings suggest that the presence of macropores contributed to the formation of anaerobic conditions during flooded phases, thereby promoting denitrification and enhancing nitrogen removal performance.
The experimental results using synthetic wastewater demonstrated that TF was more effective than VF for water purification. Furthermore, in both VF and TF, the introduction of artificial macropores significantly improved purification efficiency, highlighting their potential to enhance the performance of AWs.