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<p>This study was conducted to assess the treatment performance of vertical subsurface flow constructed wetlands (VSSF CWs), either operated alone or coupled with slow sand filter (SF) for the treatment of urban wastewater in semi-arid regions. In this context, two VSSF filters were established and investigated at Tlemcen city, in the North-West of Algeria, for seven months. One unit was planted with <i>Phragmites australis</i> while the other has remained unplanted. The system followed an 11-day cycle (3 days of feeding / 8 days of rest) with a hydraulic loading rate (HLR) of 0.30 m/d applied via pulse loading. An additional treatment was provided by a slow sand filter receiving effluent from the planted bed. Physicochemical parameters (temperature, pH, dissolved oxygen DO, electrical conductivity EC, biochemical oxygen demand BOD<sub>5</sub>, chemical oxygen demand COD and total suspended solids TSS, TN and TP) and microbial indicators (<i>E. coli</i>, Salmonella) were analyzed during the experience in both influent and effluent using standard ISO and HACH methods. Obtained results showed that the planted bed proved to be more efficient than the unplanted one confirming the positive role of plants in the treatment processes. It achieved a good removal rate of 75%, 74%, 72% for TSS, COD and BOD<sub>5</sub> respectively, while the unplanted bed achieved moderate removal rates of 65%, 55% and 56% for TSS, COD and BOD<sub>5</sub> respectively. Nutrient analysis showed, also, that the planted bed nearly doubled the nitrogen removal capacity of the unplanted control (31% vs. 16%) and achieved a phosphorus removal rate of 49% compared to 23%. Moreover, microbiological results demonstrated that when the unplanted bed achieved a 3-log reduction of <i>E. coli</i>, the planted bed reached a 5-log reduction. The integration of the sand filter ensures high stability of the planted system, yielding a cumulative COD removal of 91% and maintaining effluent TSS below 15.00 ± 5.00 mg/L. The sand filter reached high nutrient polishing capacity, with phosphorus removal at 90% and nitrate concentrations rising to 17.0 ± 4.0 mg/L and attained a final 6-log removal for <i>E. coli</i>, reducing concentrations from 10<sup>6</sup> to 10<sup>1</sup> CFU/100mL. These results confirm that while planted wetlands provide effective treatment and significant pathogen reduction, the addition of a secondary treatment is essential for achieving the high-standard pollutants removal required and the slow sand filter can be a good solution.</p>

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Performance of Phragmites Australis and Slow Sand Filtration in a Multi-Stage Vertical Constructed Wetland for Enhanced Domestic Sewage Treatment

  • 期刊论文

  • 发表日期：

    2026年5月22日

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  • Meriem Benyagoub,
  • Abdelghani Chiboub Fellah,
  • Racha Medjda Bouchenak Khelladi,
  • Lamia Cherif,
  • Fatima Zohra Chiboub Fellah,
  • Soumia Boulefred,
  • Lotfi Benadda

摘要

This study was conducted to assess the treatment performance of vertical subsurface flow constructed wetlands (VSSF CWs), either operated alone or coupled with slow sand filter (SF) for the treatment of urban wastewater in semi-arid regions. In this context, two VSSF filters were established and investigated at Tlemcen city, in the North-West of Algeria, for seven months. One unit was planted with Phragmites australis while the other has remained unplanted. The system followed an 11-day cycle (3 days of feeding / 8 days of rest) with a hydraulic loading rate (HLR) of 0.30 m/d applied via pulse loading. An additional treatment was provided by a slow sand filter receiving effluent from the planted bed. Physicochemical parameters (temperature, pH, dissolved oxygen DO, electrical conductivity EC, biochemical oxygen demand BOD5, chemical oxygen demand COD and total suspended solids TSS, TN and TP) and microbial indicators (E. coli, Salmonella) were analyzed during the experience in both influent and effluent using standard ISO and HACH methods. Obtained results showed that the planted bed proved to be more efficient than the unplanted one confirming the positive role of plants in the treatment processes. It achieved a good removal rate of 75%, 74%, 72% for TSS, COD and BOD5 respectively, while the unplanted bed achieved moderate removal rates of 65%, 55% and 56% for TSS, COD and BOD5 respectively. Nutrient analysis showed, also, that the planted bed nearly doubled the nitrogen removal capacity of the unplanted control (31% vs. 16%) and achieved a phosphorus removal rate of 49% compared to 23%. Moreover, microbiological results demonstrated that when the unplanted bed achieved a 3-log reduction of E. coli, the planted bed reached a 5-log reduction. The integration of the sand filter ensures high stability of the planted system, yielding a cumulative COD removal of 91% and maintaining effluent TSS below 15.00 ± 5.00 mg/L. The sand filter reached high nutrient polishing capacity, with phosphorus removal at 90% and nitrate concentrations rising to 17.0 ± 4.0 mg/L and attained a final 6-log removal for E. coli, reducing concentrations from 106 to 101 CFU/100mL. These results confirm that while planted wetlands provide effective treatment and significant pathogen reduction, the addition of a secondary treatment is essential for achieving the high-standard pollutants removal required and the slow sand filter can be a good solution.