Abstract
In rural country like India, low cost and decentralized treatment unit like vertical subsurface flow constructed wetland (VSSF CW) can be reflected as a novel wastewater system. In this concern a pilot-scale VSSF CW unit of size 0.92 m × 0.92 m × 0.85 m bed planted with a Typha latifolia and Phragmites australis was operated for a 12-month duration to treat the simulated rural wastewater. During the operation, a constant head arrangement was done to maintain a continuous flow to achieve 5 different Hydraulic Retention Time (HRT) of 2, 4, 6, 8 and 10 days in each seasons such as winter, summer and rainy to investigate the performance of unit under different retention time. Reactor showed optimum removal efficiency at 6 days HRT at 12.5 cm/day Hydraulic Loading Rate (HLR) for organic matter removal. Both macrophytes and microbial biomass of filter media were effectively treated the rural wastewater. Average removal efficiency of the reactor during entire study were 64.73%–88.80% for Chemical Oxygen Demand, 74.96%–95.34% for Biochemical Oxygen Demand, 40.13%–79.45% for Ammonia Nitrogen, 25.36%–65.65% for Total Kjeldahl Nitrogen, 22.86%–58.48% for Phosphate phosphorus, 23.50%–55.45% for Total phosphorous, 74.91%–98.59% for Faecal Coliforms and 71.14%–95.31% for Total Coliforms respectively. Two-way ANOVA followed by post hoc Tukey's test showed that HRT had a significant impact on removal efficiency but not the season. Overall performance of the unit was good and study suggested that VSSF CW can be an smart alternative technology to treat rural wastewater before the final disposal.
Effect of hydraulic retention time on chemical oxygen demand and total nitrogen removal in intermittently aerated constructed wetlands
