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- Creators: Perreault, Francois
- Creators: School of Sustainability
- Status: Published
This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.
The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
The rise in urban populations is encouraging cities to pursue sustainable water treatment services implementing constructed treatment wetlands (CTW). This is especially important in arid climates where water resources are scarce; however, research regarding aridland CTWs is limited. The Tres Rios CTW in Phoenix, Arizona, USA, presents the tradeoff between greater water loss and enhanced nitrogen (N) removal. Previous research has suggested that water loss due to transpiration is replaced by a phenomenon termed the Biological Tide. This trend has been documented since 2011 by combining transpiration values with a nitrogen budget. Calculations were made at both the marsh and whole-system scale. The purpose of this paper is to demonstrate how the Biological Tide enhances N uptake throughout the CTW. Results indicate that about half of the nitrogen taken up by the vegetated marsh is associated with new water entering the marsh via the Biological Tide with even higher values during warmer months. Furthermore, it is this phenomenon that enhances N uptake throughout the year, on average, by 25.9% for nitrite, 9.54% for nitrate, and 4.84% for ammonium at the whole-system scale and 95.5%, 147%, and 118% within the marsh. This paper demonstrates the Biological Tide’s significant impact on enhanced N removal in an aridland CTW.