Human Overpopulation and Water Pollution: Reduction of Microbial Pollution by Vertical Flow Constructed Wetland

Introduction

The water demand supply gap is increasing continuously due to population explosion and alternate source of water are being explored to fill this gap. Reuse of treated effluents for non-potable purposes could significantly reduce this gap, as huge volume of wastewater is being generated and treated in urban metros and class II cities, but the incomplete treatment in STPs is polluting the existing water resources and thus high level of coliforms were found during monitoring of various rivers’ water quality in India (Jamwal & Mittal, 2009; CPHEEO, 2013). Coliforms levels has been even reported in groundwater aquifers, considered generally safe which are being used directly for potable water in areas around Delhi (Mutiyar et al., 2013). In Rajasthan, where the study was performed, the general trend for treated wastewater disposal has been either for irrigation purposes or into recreational lakes as there are not many rivers around. Since, with both these reuse applications, public health is at risk due to presence of microbial contaminants, there is a need to find solution to mitigate this risk and the importance of studying microbial removal as tertiary treatment. Hence, this research was classified as “Applied research” that often comes from a practical need to know or find a possible solution to a real world problem with real world challenges.

The idea behind this research was to find an applicable solution for the reuse of treated wastewater within the existing semi-arid weather conditions to overcome the public health risk of abovementioned reuses. The wetlands have been reported to be efficient in terms of microbiological contaminants removal though no such study has been reported for investigating as well as comparing the survival of different plants, which were used for the study, in treated wastewater during tertiary treatment in semi-arid climatic conditions prevailing in Rajasthan with their performance vis-a-vis microbial reduction. Additionally, the cities are now expanding as a part of growing urbanization, the wastewater plants have now come within the city limits and high land demand for horizontal flow wetlands is becoming a constrain for application of wetlands in sewage treatment. To reduce the land requirement in wetlands, therefore the vertical flow constructed wetland system, which requires less land area, as a tertiary treatment step and to assess its suitability especially with a focus on microbiological contaminants was chosen for the study.