Pathogen Treatment in Single and Two-Stage Vertical Flow Wetland as a Potential Sanitation Technology for Rural India

Abstract

Vertical flow-constructed wetlands (VFCW) are well-established, cost-effective, and sustainable options for wastewater treatment. Along with organic matter removal, wetlands are helpful in the removal of microbial pathogens. This study focuses on understanding the bacterial pathogen removal efficacy of three different design types of VFCWs and understands the best designs for the efficient removal of pathogens in a tropical climate. The three wetlands studied for removal efficiency were (a) two-stage vertical flow constructed wetland (TSVFCW), (b) Single-stage vertical flow constructed wetland (SSVFCW), and (c) single-stage saturated vertical flow constructed wetland (SSSVFCW). Results revealed that all three types of wetlands were effective in removing pathogenic bacteria. Still, TSVFCW was found to be more efficient in pathogen removal (Total Coliforms, Shigella spp., Salmonella spp., Pseudomonas spp., Vibrio spp., Enterococcus faecalis) 7.04 ± 0.17, 6.53 ± 0.08, 4.0 ± 0.42, 7.67 ± 0.08, 5.73 ± 0.70 and10 5.23 ± 0.96 Log10 reductions respectively compared to SSVFCW (5.28 ± 0.18, 5.18 ± 0.09, 3.74 ± 0.74, 6.98 ± 0.01, 3.97 ±0.32, 4.74 ± 1.08 Log10 reductions respectively) and SSSVFCW (4.48 ± 0.46, 4.83 ± 0.15, 2.74 ± 0.44, 6.71 ± 0.03, 4.31 ± 0.49, 5.03 ± 1.20 Log10 decreases respectively). For abiotic factors (Chemical oxygen demand, total Kjeldahl nitrogen, and phosphorus) also TSVFW shows better efficiency (45 ± 8.7, 24.7±4.5 and 3.1, ± 0.2 g.m-2, respectively) than SSVFCW (12 ± 1.3, 7.6 ± 0.4 and 1.8 ± 0.2 g.m-2 respectively) and SSVFCW (6.3 ± 1.1, 7.7 ± 0.1 and 1.2 ± 0.1 g.m-2 respectively). However, the removal efficiency of both single-stage wetlands was comparable.