How to Treat Produced Water from the Oil and Gas Industry for Agricultural Use

Energy companies are searching to offer sustainable methods that can treat produced water from the oil and gas industry for agricultural use. Consequently, produced water management has become a priority for stakeholders working in the sector. To address the issue, the scientific community has come out with solutions. Here is a brief overview of such electrochemical techniques that can be used to make produced water acceptable for agricultural use.

 Membrane Filteration

Microfiltration and ultrafiltration are two extremely popular techniques that can be used to separate suspended particles and macromolecules in the water. A microfilter has a pore size between 0.1 and 3 µm, which is enough to remove suspended particles and reduce turbidity. Similarly, ultrafiltration is a related albeit more efficient method used in the pre-salination process. While both MF and UF techniques can remove suspended solids, hydrocarbons, and other particles, they cannot remove salt from water. To get rid of salt, polymeric and ceramic membranes are used. These membranes have a lifespan of approximately ten years. Oil and gas facilities equipped with pretreatment filtration technology can also use reverse osmosis or nanofiltration. During the process, hydraulic pressure is applied to dense, non-porous membranes that remove contaminants as small as 0.0001 µm. However, this method is prone to membrane scaling and fouling, which significantly reduces the lifespan of membranes and is very expensive. Water produced using various types of membrane filtration techniques is free of suspended solids and the water recovery can range between 75% and 100%. In most cases, both cross-flow and dead-end filtration modes can be used to treat the water. 

Thermal Treatment

Recent advances in thermal technology can result in more efficient operations particularly in those areas where the cost of energy is low. The technique is also preferred when treating highly contaminated water. Thermal treatment methods include multistage flash, multieffect distillation, vapor compression distillation, and hybrid versions involving multieffect distillation. Among these, multistage flash is perhaps the most widely used. It involves preheating the feedwater to a certain temperature and then converting it into steam. Water recovery from MSF distillation is up to 20% but the plant life expectancy is almost double the membrane filtration process. Some thermal treatment methods such as multieffect distillation, MED, can offer up to 67% water recovery; however, the process is based on old technology that requires consistent maintenance. The operating plant has a larger life span. Moreover, the thermal plant can withstand hard conditions and can be adapted to varying degrees of groundwater quality. 

Emerging Technologies

Membrane filtration and thermal treatment are the two most widely used technologies to treat produced water for agricultural use. This may change in the future as certain emerging technologies and methods are starting to show potential for better results and greater efficiency. Such methods involve a mix of thermal, physical, and chemical systems. Among these is the newly adapted Hybrid MED–VCD, Multieffect distillation–vapor compression hybrid method. New emerging chemical additives are showing promising results. 

Hybrid MED-VCD

Hybrid MED-VCD uses highly specialized water evaporators that work on the mechanical vapor compression technique. These evaporators are more efficient than traditional systems, which results in the reduction of chemicals used during the process. The system also helps decrease cost, storage needs, fouling severity, handling, and other factors. Such a plant can survive for more than 20 years but requires a highly skilled labor source.

 Forward Osmosis

FO, Forward Osmosis is another emerging method that has shown potential for enhanced recovery during brackish water desalination. The method is efficient for treating brackish water as recent research confirmed that FO membranes do not degrade as quickly as traditional membranes particularly when used with feed streams containing a high concentration of soluble salt. FO also consumes less energy because it doesn't require hydraulic pressure. Accordingly, industrial plants using Forward Osmosis can continue to operate for up to 30 years.

Capacitive Deionization

CDI, Capacitive Deionization, is yet another technique that shows great potential. Researchers at the University of California have studied this technique since 1980 under different conditions. Their detailed analysis suggests that CDI can be extremely efficient where the produced water contains less than 3,000 mg/L TDS, total dissolved solids. CDI uses a chemical process where the positive and negative electrode attracts corresponding opposite ions cleansing the water of unneeded particles. During the process, the negative electrode attracts positively charged ions such as calcium, sodium, and magnesium. Similarly, the positive electrode attracts negatively charged ions that include nitrate, silica, and chloride. Due to low infrastructure requirements, CDI has great potential for future use. Unlike a lot of other new techniques, the plant can be installed anywhere and doesn't require highly skilled labor or a high level of monitoring. Researchers have also suggested adding an electronic water purifier to improve the overall performance. When used with the water purifier, the plant can remove almost 90% of total dissolved solids. At this time, the only drawback is its inability to remove certain uncharged particles, boron, and organics. 

Other Alternatives

Besides these methods, there is a range of other techniques that are used to treat produced water. Media filtration, adsorption, electrodialysis reversal, gas floatation, and hydro cyclones are just to name a few. However, most of these methods are very expensive.

 Potential of Produced Water for Agricultural Use

There is no doubt that water shortage is increasingly becoming a common issue. As the need for water resources grow, we will need to figure out new ways to replenish the diminishing water supply. In such circumstances, produced water can benefit everyone, particularly communities in drought-prone regions.  In addition to the varying quality of water, the geographical location is another major factor that determines the suitability of a specific technique. Studies by the US Department of Agriculture suggest that there seems a geographical relationship between produced water generation and the potential for agricultural use in surrounding areas. Hopefully, this renewed emphasis on emerging technologies, better data collection techniques, and better research methods will help further improve existing methods of treating produced water for agricultural use.

At Magical Chemicals, we are working to solve these problems. To work with us visit our contact page.