Reuse, Desalination Emerge as Global Force to Combat Drought, Sustain Water Supply
By Lior Eshed
The success of Orange County’s Groundwater Replenishment System has resulted in greater public trust of water reuse and has placed a spotlight on the potential advanced water purification technology has for solving serious water shortages.
Water scarcity is a worldwide problem, with more than half a billion people today lacking access to clean water. Climate change, water pollution, population growth and movement to another place increases the pressure on limited water supplies, and calls for new water sources. This prompted the United Nations to launch the Sustainable Development Goals (SDGs) program in 2015, with the aim of ensuring everyone has access to safe water by 2030.
In the United States, the water scarcity problems are most pronounced in the dry, heavily populated and industrialized states of California, Texas and Florida. The well-communicated drought conditions have raised public awareness of water conservation and increased public acceptance of new technologies, such as seawater desalination and wastewater reuse. California has taken the lead in the legislative aspect (the famous title 22), as well as actual implementation of water reuse facilities (such as the groundwater replenishing facility in Orange County and the planned Pure Water San Diego Program), see above.
Recent years have seen a major shift in the perception of wastewater. The understanding that the local wastewater treatment plants could become a source of safe and cost-effective fresh water changed the perception of the authorities from wastewater as a burden to wastewater as a resource. This shift of mindset toward water reuse was accompanied by major investments in public education and outreach (visitor centers in water reuse facilities, educational programs and public relation efforts), which proved very successful and opened the door to more and more water reuse projects. These facilities produce water mainly for irrigation (69 percent), industrial uses (16 percent) and augmentation of depleting aquifers through Indirect Potable Reuse (IPR) projects (15 percent) according to Bluefield Research’s “U.S. Municipal Wastewater and Reuse: Market Trends, Opportunities and Forecasts.”
This change in public acceptance, together with shorter construction time, environmental limitations on developing new seawater desalination facilities, and higher costs of seawater desalination (i.e., $0.55$/m³ for reuse in GWRS vs.$1-1.5/m³ in typical SWRO according to the Global Water Intelligence’s Global Water Market in 2018 report) and accumulated experience from existing reuse facilities, has made water reuse the main infrastructure response to drought. The same is true for other places around the world – such as Australia, Singapore, Taiwan and India – which have promoted major growth in the water reuse production capacity (see Figure 1). This trend appears to be here to stay.
In the United States, California accounts for 48 percent of water reuse (municipal and industrial) projects, currently with 363 of 763 reuse projects being planned. Published investment in these planned reuse projects totals more than $18.6 billion according to Bluefield Research’s “U.S. Municipal Wastewater Reuse: Project Pipeline and Segmentation Analysis, 2017-2030.”
Figure 1 – Incremental contracted desalination and reuse capacity,
1990–2022 (Source: GWI).
There is a growing demand for reused water in the industrial sector. Major industrial consumers of water around the world such as BASF, Coca-Cola, Diageo, Novozymes and Unilever are integrating water reuse goals into their sustainability plans. For example, Diageo – manufacturer of Guinness beer and the world’s largest alcoholic beverage producer – released an ambitious plan that includes a 50 percent improvement in its water use efficiency and 100 percent recycling of wastewater.
Current Trends
When referring to water reuse projects, one has to distinguish between simple tertiary reuse (as can be achieved by sand filtration or Membrane Bio Reactor, for example) that are mainly for irrigation or cooling tower makeup and the more advanced triple-barrier reuse scheme (also known as FAT-Full Advanced Treatment) that normally includes MF/UF, followed by reverse osmosis (RO) and a final advanced oxidation phase (such as UV/AOP) that produces drinking-quality water that may also be used for boiler feed makeup or process water in industrial applications. This article addresses the latter.
Higher Recovery (brine minimization)
Normally FATs that contain two RO stages operate at recovery of about 75 to 80 percent. Facilities that want to increase its productivity add a third stage of RO to further boost the recovery to about 85 percent (such as GWRS in CA). At this recovery, issues such as scaling and fouling are more significant, and require careful operation and maintenance. Even higher recoveries can be reached by implementing techniques that manage the scaling issue in a different way, such as Desalitech’s Closed Circuit Reverse Osmosis (CCRO) process, which works in a batch operation by gradual increase of the feed pressure to overcome the increasing osmotic pressure and maintain the required cross flow velocity. Another approach is the MaxH2O (developed by IDE Technologies), which enables scale-free operation by using an integrated pellet-reactor to remove the scale-forming minerals from the feed water between the second and third stages. IDE Technologies also develops Pulse Flow RO technology, which enables operation at very high recoveries in a single RO stage by operating in short intervals of reverse osmosis in dead-end mode.
Zero Liquid Discharge (ZLD)
In applications that do not have available access to brine disposal, or have stringent legislation on its brine discharge (usually in industrial applications), the brine has to be minimized to very high concentrations or even solids, and then transported to a permitted disposal site. This usually involves reaching maximum recovery (as explained above) and then further treating the brine by natural or enhanced evaporation using a thermal process. As this is a very energy intensive process (40-50kWh/m3), currently it is used mostly for niche industrial applications.
Figure 2 – Total water reuse capacity segmented to states (source: Bluefield Research).
Contaminants of (Emerging) Concern (CECs)
Contaminants of (Emerging) Concern (CECs) are organic contaminants from various sources. These sources include human consumption of pharmaceuticals and personal care products (PPCPs), residual concentrations of organic contaminants from industrial sources and organic contaminants that might be formed during the FAT reuse process itself (i.e., NDMA as a byproduct of chloramine dosing to the RO. NDMA is a toxic compound and a suspected human carcinogen). These CECs are increasingly being detected at low levels in surface water and wastewater effluent. In water instanced for potable use, it is these compounds that are removed to below the permitted levels, as many CECs and PPCPs act as so-called endocrine disruptors (EDCs). EDCs are compounds that alter the normal functions of hormones, resulting in a variety of health effects. These compounds are normally removed during the RO and advanced oxidation processes. However, it is beneficial to reduce their levels at an earlier stage. For example, NDMA formation can be avoided by not dosing chloramines to the RO. IDE applies frequent RO membrane cleaning using forward osmosis, thus enabling RO operation without dosing chloramines, and providing a system that is safer and cheaper to operate.
Construction on San Diego’s now-complete Carlsbad Desalination Plant.
Direct Potable Reuse (DPR)
Direct Potable Reuse (DPR) is the introduction of advanced-treated reclaimed water either directly into the potable water system or into the raw water supply entering a water treatment plant. This is as opposed to Indirect potable reuse (IPR) facilities that discharge treated water to a natural receiving body (such as an aquifer or lake), in which there is significant retention time and blending with other water sources. Due to the lack of retention time, which allows the operators to take action in case of any kind of failure in the treatment process, the DPR process must be tightly controlled (even more than IPR) and is generally not preferred by the water authorities. This obstacle can be overcome by installing a constructed storage facility that, of course, has its price.
However, the successful implementation of the first DPR facilities in Texas (Big Spring and Wichita Falls, which is no longer active) opened the door for planning other facilities – mostly in Texas (i.e., El Paso, San Angelo and others), but also in California (i.e., San Mateo DPR).
Decentralized Water Reuse
As conveying wastewater to the WWTP and then conveying the reclaimed water to its discharge points might be difficult and expensive in some cases, it might be beneficial to treat the water on a community level, as well as in a commercial/industrial facility, to reuse this water resource optimally.
Such treatment units are usually prefabricated containerized units that can be installed on site in a short time and can also be upgraded in a modular fashion in response to growing demand.
Global Perspective
The United States is currently the world leader in water reuse for IPR and DPR. Rules and practices that are implemented in the United States are soon adopted in other projects around the world, and many U.S.-based companies are involved in global projects.
Other countries have been implementing water reuse for years before the U.S., but usually not in a sophisticated treatment train (such as the FAT process), but using tertiary effluent with limited post treatment. This limits the uses of the produced water. Israel is by far the country that reuses the highest percentage of its water, with more than 75 percent of its municipal wastewater treated in 135 plants, almost exclusively for reuse in irrigation. This accounts for 31 percent of the total water supplied for irrigation, and 20 percent of the total water supplied.
In the EU, unplanned IPR has been practiced for years, as effluent from WWTPs flows to natural streams and rivers and is used again downstream, sometimes more than 10 times along the same water body. The issue of micro pollutants and endocrine disruptors (as mentioned above) that accumulate along the water streams led to the understanding that these should be removed prior to their discharge. As a result, Switzerland recently decided to upgrade its WWTPs to include means (ozone or powdered activated carbon) to remove 80 percent of preselected micro pollutants. The same trend will likely be adopted in other west-European countries.
To conclude, water reuse facilities have become more abundant and more sophisticated as the demand for fresh water increases. The transition from relying on natural water sources to the development of new water sources through water reuse facilities is inevitable, and these will continue to become a major source of safe, dependable and sustainable fresh water.
Lior Eshed
Product Manager | IDE Technologies
Lior Eshed leads the water reuse process team and is a product manager at IDE Technologies. As a process engineer, he has expertise in the field of membrane technology and has a broad range of knowledge of technologies such as membrane bioreactors, sludge treatment, log removal and more.
