https://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/16678/New-Water-Treatments-Address-Biological-and-Synthetic-Contaminants.aspx
[How applicable are these relatively simple approaches to small
community water sytems?
images and links in on-line article]
New Water Treatments Address Biological and Synthetic Contaminants
Rachel Maya Gallagher posted on March 28, 2018
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.
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.
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?
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.
