QF’s research project explores energy generation from industrial wastewater
IN an innovative project funded by Qatar Foundation’s (QF’s) Qatar National Research Fund, scientists from Global Water Sustainability Center (GWSC), Texas A M University at Qatar (TAMUQ) – a QF partner university – and University of Technology Sydney (UTS) have been working together to use PW to generate what is called ‘blue energy’, sometimes also called osmotic power or salinity gradient power.
It is based on the phenomenon of osmosis, which is the movement of water molecules from a region of low solute concentration to a region of high solute concentration, through a semi-permeable membrane.
The technology being pursued by the group is called Pressure Retarded Osmosis (PRO). In simpler words, imagine you have two solutions of water, one with high salt content and the other with little or no salt. If these two solutions were placed side by side, with only a thin semi-permeable membrane between them – which means it only allows water molecules to pass through and not salt ions – water molecules will move from the side with low salinity to the side with high salinity. This movement of water molecules across the membrane will build up pressure which can eventually be used to drive turbines and generate power.
The oil industry handles more water than oil. It goes by the name of produced water – a term used to describe water that is generated as a byproduct during the extraction of oil and natural gas. An average of three to five barrels of water is produced per barrel of oil, this number increases as oil wells age and can reach up to 10.
“Since aging is inevitable, the amount of produced water (PW) generated is only expected to increase. With that in mind, we are trying a different approach wherein instead of trying to find new ways to dispose PW, we are looking at it as a resource rather than a nuisance. For the past two to three years, we have been exploring the possibility of generating energy using PW,” said Dr Samer Adham, head of the ConocoPhillips GWSC at the Qatar Science and Technology Park, part of Qatar Foundation Research, Development, and Innovation.
“The challenge with PW is its complex composition, in addition to being hypersaline, it also consists of dispersed oil, hydrocarbons and suspended solids. Its complex composition means it does not make economic sense to treat this water for use in irrigation or such. It is typically reinjected into disposal wells so it can help maintain reservoir pressure and enhance oil recovery via water ooding,” added Dr Adham
While its high salinity is perhaps what hinders its reuse the most, it is also what gives it potential in blue energy generation. Since the amount of energy generated is dependent on the salinity difference – a greater salinity difference will mean more energy produced. This is exactly what the group is trying to do.
Dr Adham said, “In most of the previous studies of power production using PRO, low salinity waters such as freshwater or treated wastewater have been used as feed solution, with seawater or rejected brine from seawater desalination plants used as draw solution. Our project aims at adopting seawater or brine from desalination plants as feed solution, and the hypersaline produced water as draw solution. Hypersaline produced water can have salinities up to eight times higher than seawater and this greatly increases the osmotic pressure differential and can be the key to better efficiency.”