The researchers determined one pass through the membrane would clean contaminated water enough for reuse at a well, significantly cutting the amount of risk from carrying out the process.
The filters keep emulsified hydrocarbons from passing through the material's ionically charged pores, which are about one-fifth of a micron wide, small enough that other contaminants cannot pass through. The charge attracts a thin layer of water that adheres to the entire surface of the filter to repel globules of oil and other hydrocarbons and keep it from clogging.
A hydraulically fractured well uses more than 5 million gallons of water on average, of which only 10 to 15% is recovered during the flow back stage
'Frac water' represent a significant challenge. If a membrane with pores small enough to separate is used, it fouls, and this renders the membrane useless. However, the superhydrophilic treatment results in an increased flux (flow) of water through the membrane as well as inhibiting any hydrophobic material – such as oil – from passing through. The difference in solubility of the contaminants therefore works to allow for separation of molecules that should in theory pass through the membrane.
“Fracking has proved highly controversial in the UK in part as a result of the pollution generated from produced waters”, co-author Darren Oatley-Radcliffe, an associate professor, at Swansea University, said, “However, with this new super-hydrophilic membrane we can clean up this waste produced water to a very high standard and recycle all of the materials, significantly improving the environmental performance of the fracking process.”