Researchers Use Minitab to Demonstrate Effectiveness of Constructed Wetlands for Water Treatment

Minitab helped researchers in Ireland demonstrate the effectiveness of removing excess nitrogen from a local water supply with artificial wetlands.

Most of us take clean, fresh water for granted. We rarely think about the processes required to remove harmful contaminants before we use water for drinking, cooking or cleaning. The health and safety of the people who use a water supply depends on the effectiveness of its treatment method. The success of a treatment method needs to be demonstrated with sound data analysis.

When researchers from the University College in Dublin, Ireland sought to demonstrate the effectiveness of removing excess nitrogen from a local water supply with artificial wetlands, they relied on Minitab Statistical Software.

The local water supply of Glaslough village, located just outside of Belfast, Ireland, had excess nitrogen levels. While nitrogen is a natural and essential macronutrient found in all ecosystems, high doses of nitrogen in water-based ecosystems can be deadly for aquatic life. Excess nitrogen fuels algae growth in open waters, depleting oxygen levels and causing many fish and aquatic plants to die off.  In a municipal water supply, excess nitrogen can be toxic— especially to infants.

The researchers implemented a water treatment plan using Constructed Treatment Wetlands (CTWs) to rid Glaslough’s waters of dangerous nitrogen pollution. CTWs are marshes built to treat contaminated waters. Although they are man-made, they are constructed to utilize natural processes that involve actual wetland vegetation and soils. Like natural wetlands, CTWs provide food and habitat for wildlife. They are known for being a low-cost, environmentally-friendly option for treating waters affected by nitrogen pollution.

With the CTW in place, researchers measured nitrogen levels in the water supply each week for two years. Custom-designed measurement tools were installed and helped researchers record nitrogen levels for all flows into, within, and out of the wetland system.

They used Minitab’s powerful Regression and Analysis of Variance (ANOVA) tools to uncover the relationships between nitrogen removal and outside factors such as seasonality. Their goal: to see how these factors affected nitrogen removal efficiency, and if any outside factors helped to optimize its removal.

Before performing an ANOVA, researchers entered their data into Minitab and compared data means with a simple paired t-test. This helped them determine if there was a statistically significant difference between nitrogen levels recorded before and after the CTW implementation. The data revealed statistical significance, and researchers concluded that nitrogen had been effectively removed from Glaslough’s water supply.

Now, with Minitab’s help, researchers performed regression analysis to produce a model that revealed the optimal conditions for nitrogen removal. Minitab’s graphical representations of their analysis made it easier for them to pinpoint the factors that contributed to optimal nitrogen removal.

They concluded that nitrogen removal efficiency consistently exceeded 90% over the two-year period of study. They also found that removal rates in the warmer months were slightly higher than in the cooler months, with the lowest rates being observed during the winter months.

With Minitab, the researchers from the University College in Dublin showed that man-made wetlands could be a viable solution for combatting worldwide water pollution concerns.

Research discussed in this article was originally published in “Nitrogen Removal in Integrated Constructed Wetland Treating Domestic Wastewater,” 2nd Irish International Conference on Constructed Wetlands for Wastewater Treatment and Environmental Pollution Control, October 2010.


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