New Water Treatments Address Biological and Synthetic Contaminants
Rachel Maya Gallagher posted on March 28, 2018 |
Using principles of water flow and chemical adsorption, researchers created a cheap, efficient filtr...

Most of the world does not enjoy access to clear, running water that is free of bacteria and pollutants. Factors impacting water quality vary based on geography, infrastructure, industry and even climate, making water treatment a constantly evolving practice that faces new demands every day. A new system that combines targeted circulation of standing water with a novel technique for removing pollutants just might have the versatility needed to address water contamination in a rapidly changing world.

Simple PVC Sprinkler Reduces Bacterial Infections

In the municipal water tanks used to supply drinking water to communities throughout the United States and Canada, the layer of water above the tanks’ intake and outtake pipes is stagnant. Chlorine treatment can prevent the layer of still water from becoming infected with bacteria, but in hotter climates especially, the chlorine is used up quickly.

Until now, the primary method for preventing infection has been avoiding the upper water layer by drawing the drinking supply from the bottom of the water tank. Unfortunately, this means that when the municipal water supply is quickly consumed while fighting a major forest fire, a community that has already suffered devastating property damages also faces a higher risk of bacterial infection from stagnant water that has been drawn rapidly down into the bottom of the tank.

Brian Barkdoll and Mohammad Alizadeh Fard developed a simple mechanism for ensuring circulation throughout a municipal water tank. (Image courtesy of Sarah Bird and Michigan Tech.)
Brian Barkdoll and Mohammad Alizadeh Fard developed a simple mechanism for ensuring circulation throughout a municipal water tank. (Image courtesy of Sarah Bird and Michigan Tech.)

The solution to this problem, as proposed by researchers at Michigan Technological University, is installing two cheap PVC sprinklers in the top and bottom of a municipal water tank. Using this mechanism, incoming water was sprinkled evenly across the surface of water contained in a cylindrical tank, and the reverse sprinkler at the bottom of the tank drew out water from more than one location. The parallel downward streamlines generated by this sprinkler system eliminated the majority of the stagnation zones within the tank.

PVC sprinkler installed in the top of the tank. Its action is complemented by a reverse sprinkler of similar design installed at the bottom of the tank. (Image courtesy of Sarah Bird and Michigan Tech.)

PVC sprinkler installed in the top of the tank. Its action is complemented by a reverse sprinkler of similar design installed at the bottom of the tank. (Image courtesy of Sarah Bird and Michigan Tech.)

Blue dye added to the water illustrates increased circulation in a model tank fitted with the PVC sprinkler system. (Image courtesy of Sarah Bird and Michigan Tech.)
Blue dye added to the water illustrates increased circulation in a model tank fitted with the PVC sprinkler system. (Image courtesy of Sarah Bird and Michigan Tech.)

Magnetic Removal of Adsorbed Molecules Addresses Wide Range of Synthetic Contaminants

No circulation system is going to prevent contamination by micropollutants, which can enter the water supply through discarded or excreted medication, recycled laundry water or industrial runoff. Municipal water treatment plants are generally fitted with filters for specific pollutants, and adapting them for novel contaminants is prohibitively expensive. How can new threats to water safety be addressed in a timely manner?

Illustration of the process for adding polymer-coated magnetic nanoparticles to contaminated water, magnetically removing them after adsorption occurs, and rinsing with methanol so that the adsorbent can be reused. (Image courtesy of Mohamed Alizadeh Fard et. al, Elsevier and Colloids and Surfaces A: Physicochemical and Engineering Aspects.)
Illustration of the process for adding polymer-coated magnetic nanoparticles to contaminated water, magnetically removing them after adsorption occurs, and rinsing with methanol so that the adsorbent can be reused. (Image courtesy of Mohamed Alizadeh Fard et. al, Elsevier and Colloids and Surfaces A: Physicochemical and Engineering Aspects.)

When researchers introduced only 0.1 milligrams of polyvinylpyrrolidone (PVP)-coated magnetite nanoparticles into a contaminated model water tank, 98 percent of Bisphenol-A (BPA) and 95 percent of Ketoprofen micropollutants were adsorbed within 15 minutes. The PVP-coated nanoparticles were then removed from the water with a magnet and rinsed with methanol so they could be reused. A system that relies on adsorption by magnetic nanoparticles to remove micropollutants requires minimal infrastructure changes when adopted by a water treatment plant.

The Future of Water Treatment

The newly developed PVC sprinklers and magnetite nanoparticles have only been tested in small-scale laboratory water tanks. To bring them into real-life water treatment plants, the systems would have to be scaled up, but the adaptability makes them well-suited to widespread testing throughout North America.

To learn more, check out our sections on engineering solutions for water quality.


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