Renewable energy powered membrane technology: Salt and inorganic contaminant removal by nanofiltration/reverse osmosis
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Date
2011Author
Richards, Laura A.
Richards, Bryce S.
Schäfer, Andrea
Metadata
Abstract
The objective of this study was to evaluate the effects of fluctuating energy and pH on retention
of dissolved contaminants from real Australian groundwaters using a solar (photovoltaic)
powered ultrafiltration – nanofiltration/reverse osmosis (UF-NF/RO) system. Four NF/RO
membranes (BW30, ESPA4, NF90, and TFC-S) were used. Energy fluctuations affected pressure
and flow. Solar irradiance levels impacted retention of fluoride, magnesium, nitrate, potassium,
and sodium where convection/diffusion dominated retention. Retention of calcium, strontium,
and uranium was very high and independent of solar irradiance, which was attributed to a
combination of size and charge exclusion and for some solutes sorption and precipitation.
Groundwater characteristics affected retention and the solutes were categorized into two groups
according to retention as a function of pH: (1) pH independent retention (arsenic, calcium,
chloride, nitrate, potassium, selenium, sodium, strontium, and sulfate); and (2) pH dependent
retention (copper, magnesium, manganese, molybdenum, nickel, uranium, vanadium, and zinc).
The retention of Group 1 solutes was typically high and attributed to steric effects. Group 2
solutes had dominant, insoluble species under certain conditions which led to deposition on the
membrane surface (and thus varying apparent retention). The renewable energy membrane
system removed a large number of groundwater solutes reliably over a range of real energy and
pH conditions.