Mass Balance Study on Domestic Wastewater Treatment Using Constructed Wetlands

Mass Balance is the application of conservation of mass to the analysis of physical systems by accounting for material entering and leaving the system. For this analysis mass can be flows and identified which might have been known through this technique. A mass balance study was conducted to know about the soil, plant and water relationship in the CW unit. The mass balance calculations comprised water and nutrient budget calculations to show the percentage distribution of water and nutrients such as N, P and K in constructed wetland. The distribution of water from the constructed wetland unit was observed to be contributed by evapotranspiration, outflow from the wetland and storage in soil with 1.78; 62.61 and 35.61% respectively. The reduction percentage of nutrient content (macro elements like nitrogen, phosphorous and potassium) present in domestic wastewater after treatment using constructed wetlands was observed to be 53% (total nitrogen) and out of this, 32% reduction is due to plant uptake (Phragmites australis) and 6% absorption is contributed by soil. For phosphorous, the results obtained from the analysis showed 52.6% soil accumulation and 49% plant uptake. For potassium 4% plant uptake and 46.9% soil accumulation was observed respectively. The pH in the range around 7.1 to 7.8 and so the contribution of ammonia volatilization low is observed. The water distribution in the CW unit was contributed by Input and output. Input in the unit comprised precipitation and wastewater inflow which contributes 2.6 and 97.39% respectively and the output comprised evapotranspiration and outflow of treated water from the wetland unit which contributes 1.78 and 62.61% respectively. 35.61% of water was observed to be stored in the soil of the constructed wetland unit.