Performance of Filter Beds and Macrophytes in a Vertically Constructed Wetland for Treating Domestic Sewage Effluents

An experiment with different filter beds and macrophytes was carried out to study their phytoremediation capacity on the efficiency of domestic wastewater treatment through constructed wetland (CW) from November to March 2017-18 at the University of Agricultural Sciences, Dharwad campus, Karnataka. Twenty treatment combinations involving five types of filter beds (FB-1: gravel, FB-2: gravel-sand-gravel, FB-3: gavel-sand-brick-gravel, FB-4: gravel-sand-charcoal-gravel and FB-5: gravel-sand-(charcoal+brick)-gravel) and four macrophytes (MP-1: Typha latifolia, MP-2: Brachiaria mutica, MP-3: Canna indica and MP-4: Phragmites sp.) were evaluated for treating domestic waste water. After 120 days from start, across treatment combinations, water electrical conductivity (EC), total dissolved and suspended solids (TDS-TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), sodium, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), bicarbonates, total nitrogen-phosphorus-potassium (N-P-K) and boron (B) were reduced by more than 40 percent due to wetland treatment. The system enhanced the mineralization of organic nitrogen to ammoniacal nitrogen (NH4+-N) and nitrate-nitrogen (NO3-N) fractions. Among filter beds, Type-5 caused a higher reduction in pH, EC, BOD, COD, and Organic-N, while Type-4 proved efficient in removing total solids and lowering pH in the sewage effluent. The Type-3 filter bed removed more suspended solids, potassium, and ammoniacal nitrogen. Among the macrophytes, Brachiaria (Paragrass) removed more nitrogen and potassium, while Phragmites removed more nitrogen, phosphorus and boron. The flexibility of implementation allows the CW to be adapted to different sites with different configurations, being suitable as the main, secondary, or tertiary treatment stage.