Purified water for saturation / Olive Ferman

Purified wastewater can be used as an environmentally friendly source of safe drinking tap water - if only we can overcome the feeling of disgust

On a sunny day in December, I visited a sleek and sterile wastewater treatment facility nestled in the hills north of San Diego, California. Huddled under an ugly, cream-colored roof, in the wallless facility, the wintry sunlight shone in the warm interior of this oversized chemical laboratory. Rows upon rows of silver pipes, containers of various shapes and sizes, and large gray metallic boilers containing hidden liquids were visible from all sides. Towards the end of my visit to the small institute, a challenge was placed before me: I was asked to identify, by sight, the contents of three large glass bottles, full of clear liquids, which were placed in front of me on a table, at equal intervals from each other. The liquid in the first bottle appears to have a slightly yellowish tint. The liquid in the second bottle was colorless. while the third bottle had the luster of a polished diamond.

I completed the task easily, and identified the contents of the bottles, in order, as regular tap water, purified water originating from a conventional wastewater treatment facility [also known as reclaimed or settled water], and toilet water that underwent a special purification process at the on-site facility. To my astonishment, I felt a strong urge to taste the purified sewage, and was equally surprised when I was prevented from doing so. "We are forbidden to taste the water or allow visitors to taste it," explained Marcy A. Steyer, my tour guide, who serves as deputy director of the San Diego City Public Services Department, which operates the treatment plant, in all seriousness.

This policy is going to change soon. A pioneering project conducted at this advanced wastewater treatment institute for six years under Steyer's supervision, and completed in 2013, shows that purified wastewater originating from residential homes is not only cleaner than the drinking water we use today, but can also be produced at a lower cost than that required to produce water Amphibian in other ways, such as desalination of sea water. As far as San Diego is concerned, the process could be revolutionary, if and when state authorities grant it approval.

No less than 90% of San Diego's water is supplied to it from the Colorado River, which flows east of the city, and from the delta formed by the Sacramento and San Joaquin rivers to its north. But these two sources are dwindling, and in the next decade, the price of this water will double. Through wastewater treatment, San Diego could supply 40% of its daily water consumption. Moreover, this will put an end to the discharge of low-level treated sewage from the city's treatment facilities into the ocean.

But to be honest, not everyone is ready to drink purified sewage. It was the "disgust factor" that thwarted an attempt made in the late 90s to realize a similar project in San Diego, and in a survey conducted in 2004, it was found that 63% of the city's residents are still opposed to the idea. Many initiatives in this vein that have been put forward in Australia have also been rejected in the face of strong opposition from civil action groups. Lawrence Jones, who founded one of these groups in Australia, called "Citizens Against Drinking Wastewater," questions the very possibility of completely purifying wastewater originating from hospitals, industrial plants, residential homes, and slaughterhouses. "As far as we know, wastewater treated at a treatment plant is XNUMX% contaminated water," says Lawrence.

However, the worsening of the drought and the development of residential areas along the coast brought about a surprising turn in the attitude of the residents of San Diego. Today, about three-quarters of the city's residents support the reuse of purified toilet water, but on one condition: that after purification, the waste water will be flowed into a reservoir or water tank where it can be diluted with benign water, and then undergo further purification before being flowed into homes.

The whole process is known as "indirect drinking water reuse." The directors of the Advanced Wastewater Purification Institute, which is currently being used as an experimental site where this process will be tested, hope to perfect and advance it to a stage where they can purify wastewater to the highest degree of purity, and flow it directly into the taps. A process known as "direct reuse of drinking water." However, many San Diego residents believe that this option is going too far. "It just seems like the process would be more acceptable if the water was pumped back into the water reservoir," says Megan Burns, head of the Coast Guard of San Diego, a non-profit organization that played a key role in convincing city officials to launch the project.

The process that will win the support of the residents is the process that is expected to win a legal standard that will allow its implementation in San Diego and California as a whole. And if direct reuse is approved here in California, where environmental regulations are known to be especially strict, experts say the process will soon be adopted in other drought-stricken areas around the world. "California has a reputation for influencing environmental decisions around the world," says University of Arizona international water expert Shane Snyder, "and its wastewater treatment policies will have a similar impact."

Purified water will sweeten

All eyes are therefore on the pioneering facility in San Diego. Today, the institute produces about 3,700 cubic meters (mXNUMX) of purified water every day. And although the water is purified to the level of drinking water, it is pumped to irrigate the Torrey Pines golf course and the cemetery next to the facility. Steyer aims to increase output tenfold over the next five to ten years. At the moment the plan is to flow the purified water into the nearby San Vicente Reservoir for dilution, and the mixture of the purified water and the water from the reservoir will then undergo further disinfection before being fed to homes. According to a second plan, if the authorities approve it, the direct reuse will be realized.

However, laws and regulations are not enough to win overwhelming public support in any possibility. First of all, it must be ensured that the consumers will overcome the feeling of disgust, and for that, the public must be convinced that the water is indeed clean. More than 4,000 visitors thus toured the purification institute in San Diego, including mothers of children, members of the Boy Scout movement, doctors and elected officials. Many of them question the drinking safety of water derived from raw sewage. And their concern is not without foundation. Every year, 19 million Americans get sick, and 900 of them die, after being infected with viruses, bacteria or parasites found in water that has gone through the routine purification process common in most US municipal authorities.

One of the ways to reach the hearts and minds of the public, and to mobilize their support, is to ensure that the water produced is purer than the water they drink today. On a tour of the purification facility, visitors learn that the wastewater that is purified there today is, ironically, much cleaner than the tap water in their homes. The reason for this is that the water that most Americans drink is water that reaches them directly from the source, that is, from a river or a lake into which water is also pumped from regular purification plants. This water is not purified enough to be drinkable. "The water in the Mississippi River goes through five cycles of use before it reaches New Orleans," explains George Tchovangolos, an international water expert at the University of California, Davis. However, people expect sewage-derived water to be purified to a much higher level than the regular water they receive from municipal systems.

According to Steyer, the purified wastewater in San Diego is indeed "much cleaner" than the drinking water provided by conventional wastewater treatment plants. What's more, the storage of the water from the purification plants in surface water bodies or in groundwater quifers also involves risks, says David Sedlak, a professor of engineering at the University of California, Berkeley. Ducks and other animals, among others, pollute the surface water bodies, and at the same time, arsenic, for example, may seep from the rocks and contaminate the groundwater. "Some argue that in order to neutralize these risks, we must adopt the direct approach to wastewater treatment," says Sedlak.

The accepted process in the USA for treating drinking water includes two or three stages of filtering solids and an additional stage of disinfection with chlorine. But to turn wastewater from smelly faucets into tap water, a different process is required. The advanced institute in San Diego uses wastewater that has already undergone purification at another institute in the north of the city and passes it through additional cleaning and disinfection processes at a higher level.

The first step in the advanced institute is the filtering of microscopic particles, which is carried out in large tubes that resemble giant pasta containers [See illustrations on pages 72 and 73]. Shane Trussell, president of Trussell Technologies, who also serves as the director of engineering at the facility, tells me that each such tank contains 9,000 porous fibers. The diameter of the microscopic pores in these fibers is 300 times smaller than the diameter of a human hair. As the water is forced through the pipes, the fibers filter and remove viruses, bacteria, single-celled organisms and suspended solids.

In the next step, the water is pumped at high pressure through pipes containing even finer pores, in a process known as reverse osmosis. At this stage, other dissolved particles left in the water are removed, which are up to 10,000 times smaller than the smallest bacteria, including chemicals, viruses and drugs. In the final stage of water treatment at the advanced institute, the water undergoes an oxidation process during which the water is mixed in huge tanks with tiny amounts of hydrogen peroxide (hydrogen peroxide) at a very high concentration, and then exposed to ultraviolet light. At this stage, remnants of any pollutants left in the water are destroyed, even in small amounts down to the order of a few parts per trillion, a concentration equivalent to that of a single drop of water in the volume of hundreds of Olympic swimming pools.

Of the approximately 3,700 cubic meters of wastewater that is transferred to the institute for treatment every day, 80% reach the final approval stage, and are of a quality that does not fall short of that of bottled mineral water of the best brands. If the treatment plant had a permit for indirect reuse of water, it would be possible to flow it into the San Vicente Reservoir. As things currently stand, the water is channeled through California's purple pipe system, which can be seen alongside several roads, used to supply recycled water for irrigation and industry in the region. The rest, about 20%, is sent to the local sewage treatment plant for disposal. Among the substances that are frequently detected in purified water are caffeine, hand soap and artificial sweeteners, but their concentrations in water are too small to be harmful. According to Trussell, the concentration of salts in the final product is also extremely low - 20 parts per million (ppm), compared to 600 parts per million in the regular tap water in the city.

In April 2014, Trussell and his team of engineers added another step to the process with the goal of making the water even purer. At this stage, the purified water will be exposed to ozone, in a way that will remove an even higher proportion of pollutants: 99.9999% of the bacteria, for example. After that, the water will pass through dedicated filters, which will further reduce the content of organic substances in the water. If this experimental phase is crowned with success, it may be enough to convince the authorities that there is no need to flow the purified water into a mikva water. "We can never guarantee complete removal of every pathogen from the water," Trussell says. But the water quality will be considerably higher than that required by the American standards for drinking water. In fact, even the water produced today, even before the new step was added to the process, meets these standards, or even exceeds them.

The psychological advantage

However, facts alone are not enough to gain public trust. Advocates of direct reuse must overcome a psychological barrier. It seems that many are willing to consider indirect reuse of wastewater, in part, because transferring the water to a surface or underground reservoir creates an important psychological buffer between the wastewater and the drinking water.

Lessons can be drawn on the subject of psychological acceptance from several communities that have successfully implemented an indirect cycle of water. In the late 90s, Orange County, located approximately 145 kilometers north of San Diego, had to deal with dwindling water sources, rising prices for imported water, and a growing population. In 2008, the district proudly inaugurated the largest purification plant in the world that discharges purified wastewater into the groundwater. The institute processes about 250,000 cubic meters of wastewater every day, or about 20% of the daily consumption in the district. Several other local governments in California discharge tap water containing treated sewage, albeit at a lower rate. In July 2014, an advanced wastewater treatment institute was inaugurated, which was established with an investment of 68 million dollars in San Jose, with the aim of providing daily 30 thousand cubic meters of purified wastewater to Silicon Valley. The water is pure enough to drink, but for now, it will only be used to irrigate agricultural crops and golf courses as well as for the needs of local industry.

Just like San Diego residents, Orange County residents were skeptical at first about the idea and 70% of them opposed the plan. But until the facility was connected to the water network, it won the support of the entire local community, thanks to a highly effective public relations campaign conducted by its initiatives. Ron Wildermus, who led the trip, says that the water department team in the district collected data on water quality during seven whole years before presenting his plan to the residents of the district. In the following ten years, the team members approached all avenues of the public, from Rotary club members and gardening enthusiasts to local business owners, explained to them what the alternatives were for solving the water shortage, and invited them to sip from the water.

This advocacy campaign prepared the ground for what is happening today on the subject in San Diego. "The Orange County project showed that indirect water reuse is a safe and feasible process," Steyer says, "otherwise we wouldn't even be discussing the direct approach." San Diego has adopted much of the technology used by Orange County. However, the city's ambition is to implement the direct approach, in part because there are no natural groundwater basins in the city's vicinity into which it would be possible to flow the purified water. Many local authorities throughout the US and the entire world are in a similar situation, so San Diego is the testing ground.

Attempts made in this field in Australia show how אסור conduct a campaign to mobilize public support. Progress on the issue is "disappointing," says Stuart Khan, a water management expert at the University of New South Wales in Sydney. In the face of public opposition, a blanket ban was imposed on drinking treated water in several Australian states, and water reuse plans were thwarted in cities such as Brisbane and Melbourne, which every few years are prone to prolonged periods of drought. Khan believes that the Australian government was wrong when it urged the public to agree to the plan at the wrong time. "We learned the lesson from the folly of waiting for the last moment, when the situation becomes desperate," says Khan sadly. His intention is that people felt they had to agree, no matter what, to something that didn't seem right to them in the first place.

It would have been worthwhile to start talking to the public earlier, says Khan, adding that now may be the right time to try again in Australia, as the water sources have started to refill, allowing a time-out for a calm public discussion. One of the wastewater treatment facilities in Australia is ready to move. The Western Corridor Recycled Water purification project, launched in 2006, at the height of a drought, is a water recovery system developed at a $2.3 billion investment to provide recycled water for industry, agriculture and drinking. According to the original plan, the recycled water was supposed to be discharged into a lake that forms a dam and fills it, and serves as the main source of drinking water for the city of Brisbane and its surroundings. The system drains wastewater treated at six wastewater treatment facilities and transfers it to advanced treatment at three purification facilities.

However, when the facility was connected to the water network, between the years 2008 and 2010, the drought period ended, and plans to produce drinking water were shelved until the water supply reservoirs dwindled to less than 40% of their capacity. The recycled water is currently used only for the needs of the local industry. Khan and many other water experts in Australia argue that one of the most advanced wastewater treatment facilities should be converted into a facility for direct reuse of drinking water, which would be able to supply about 35% of Brisbane's water consumption.

If the Queensland government adopts the scheme, it will be the largest institute for direct reuse of drinking water in the southern hemisphere. It may be easier to convince the politicians and the public this time, but both will need not only time, but also enough information to consider the alternatives, just like in Orange County.

A study published in 2013 by the WateReuse Research Foundation operating in the USA can provide food for thought for government officials. In the study, the foundation's researchers presented four different scenarios for the production of tap water to a group of California residents and Australian citizens, men and women of different ages and with different educations. In the first scenario, the currently accepted process was described, where the drinking water is supplied from a river, which is also used as a site for the disposal of treated sewage. The second scenario described a process in which treated wastewater underwent an additional purification process and was then mixed in a water reservoir, before being discharged to a drinking water production facility for final treatment. In the third scenario, purified wastewater was directly discharged into the river, from which the water mixture was discharged to another treatment plant. In the last scenario, direct reuse, the purified water was flowed directly into the residents' homes, without first being flowed into a water mikvah or undergoing additional treatment at a wastewater treatment facility. The participants in the study, regardless of their gender or level of education, were unanimous that direct reuse is the safest of the alternatives, and that the currently accepted process is the least safe of them.

Innovation out of necessity

In the absence of any other water sources, it is easier to mobilize public support, as demonstrated by the successful experience of Namibia, the only place in the world where recycled water is supplied directly to consumers' homes on a large scale. In 1957, a severe drought drained all the groundwater reservoirs of the capital city of Windhoek in just eight weeks. The residents of the city, which is more than 300 kilometers from the coastline, and more than 800 kilometers from the nearest Eitan river, were left without stable water sources. In 1968, a water treatment plant with direct access was already operating in the city, at full capacity. Today, 25% of the tap water supplied to the residents of Windhoek is purified wastewater.

Unlike San Diego, the project in Windhoek did not arouse real public opposition. First, "in those days, social activism was not yet in vogue," says Petros Di Pisani, who oversees the institute. "The residents may have been afraid, but they accepted the inevitable decision." In the late 60s, says Di Pisani, "people had a lot of faith in science and the authorities." In any case, the local authority took the trouble to provide information to the residents and even invited them to taste the water. "Today," says Di Pisani, "drinking recycled water was a common practice for us."

However, Namibia's system currently has no chance of succeeding anywhere else. Although it includes multiple purification steps, it does not use reverse osmosis, a key step in the San Diego project and other projects, such as the one in Orange County. According to officials in Namibia, the water is safe to use and meets the standards set by the World Health Organization.

Due to its inland location, Windhoek cannot easily remove the large amounts of salt water produced by the reverse osmosis process. Moreover, in the 60s, "there were fewer man-made chemicals" in the wastewater, Di Pisani says. "What bothered us the most at the time was the soap residue and the foaming agents." One of the disadvantages of skipping this step in the process is the high concentration of dissolved salts remaining in the drinking water which gives it a salty taste.

Di Pisani says that probably by 2020, a small reverse osmosis facility will be added to the water recycling process in Windhoek to reduce salinity. According to him, drinking water quality standards are changing rapidly all over the world, even in Namibia, and the approach to the issue in Windhoek is no longer the most appropriate. Elsewhere, a process of directly reusing wastewater as drinking water including reverse osmosis may be too expensive, due to the large amount of salt water it produces and the large amount of energy it requires. At the same time, new purification processes are in the development stages, which have the purpose of reducing the amount of salt water, and the waste in general, that is created in the process. Reverse osmosis is also used in indirect wastewater reuse processes, as well as in water desalination. In any case, in many cases, direct reuse of wastewater consumes less energy than these alternative processes, since there is no need to install additional piping systems and to invest additional energy to flow the water through them.

As the drought spreads in the USA, several cities are forced to face a situation similar to that of Windhoek. For several years the amount of rain in the city of Big Spring in Texas has been decreasing. The small mountain whale town of Cloudcroft, New Mexico, whose population doubles or more on weekends and holidays when tourists flood it, used to import water from far away. In the last year, the two cities began to purify sewage and add the purified water to the drinking water. Neither of the two has a surface or underground water reservoir into which the purified wastewater can be flowed over time. Instead, in Cloudcroft, the purified wastewater is diluted with water from a nearby well or spring, and stored temporarily in emptying tanks, until it is transferred to further purification, after which it is discharged to the residents' homes. At Big Spring, the purified wastewater is diluted with water from a remote regional reservoir before further purification. These processes cannot be unambiguously classified; Some classify them as direct reuse, and some claim that it is indirect reuse.

A taste of success

The predicament in San Diego is not yet that severe and therefore, according to some of the experts, the city should consider alternative solutions. Although he describes himself as a "passionate supporter of the idea," water expert Peter Glick, who serves as president of the Pacific Research Institute, believes it will be decades before direct wastewater reuse is implemented in California. "There is no sense of urgency regarding the use of waste water," he says. According to him, California should instead focus on saving water, both in cities and even more so in the agricultural sector, which needs about 80% of the water supply in the country. On the other hand, Burns claims that the residents of San Diego are already aware of the need to save water: "We shorten our shower times, and make sure to water our gardens in the early morning hours or in the cool evening hours." But, according to Steyer, water conservation is a problematic issue, partly because it depends on free will, so it is difficult to rely on it in future planning.

Under these circumstances, advance development of wastewater treatment technologies may be the next step. Singapore inaugurated its first purification institute, NEWater, in 2000. Today, it operates four such institutes, the water they produce is known as the purest treated water in the world. Only less than about 5% of this water is used for drinking, and even then, only after it is diluted with benign water. The rest of the water is used for industrial purposes. But if the relationship with neighboring Malaysia, which supplies 40% of Singapore's water consumption, deteriorates, Singapore will be able to pump a larger portion of the output of the treatment plants into domestic taps.

The cost involved in wastewater treatment may deter some local authorities. Studies conducted in San Diego indicate that the cost of purifying wastewater in the indirect process at an institute that treats 60 cubic meters daily is approximately $1.6 per cubic meter of purified water. This is, more or less, the cost of the water currently imported into the city. On the other hand, according to studies that examined advanced institutes for the purification of wastewater in the direct process, which operate at the level of the advanced institute in San Diego, the cost of producing water in them is 0.6-1 dollars. The Poseidon Institute for Water Desalination, which is under construction in the city of Carlsbad near San Diego, is expected to produce, according to its operators, purified water at a cost of $1.52 to $2 per cubic meter, although independent sources estimate the cost of desalination of such a quantity of water in California at -1.6 2.4 dollars per cubic meter or even more.

If the state-of-the-art facility in San Diego receives a "green light" for direct or indirect reuse of wastewater, San Diego will gain a stable local supply of water, and will also be able to reduce the amount of wastewater discharged into the sea, saving billions of dollars needed to upgrade the wastewater treatment facility currently operating there . Until then, treated (but not purified) sewage will continue to flow in purple pipes along California roads, which will carry the water to the industrial plants in the area. These pipes are clearly marked with the warning "Not for drinking!"

San Diego now has an opportunity to be a world leader and revolutionize the way wastewater is recycled and used. "Water is a resource that can be recycled and not a source of waste," says Chovangolos. When this is understood, "local authorities will act as private entrepreneurs and try to restore the water." It may be another decade before the California authorities grant full legal approval for the direct reuse of wastewater as drinking water and before San Diego can flow purified water directly into consumers' homes. "We would be happy if we could sip from the water and allow people to taste it right now," says Steyer, who is waiting for the day when he can finally raise a glass of purified water.

on the notebook

Olive Heffernan is a freelance environmental reporter living in London. Previously served as editor-in-chief of Nature Climate Change.

in brief

In many regions around the world, drinking water is becoming scarcer as it becomes more expensive. New multi-step purification processes can help solve the problem by purifying wastewater into tap water.

San Diego has developed an innovative, advanced wastewater treatment system. If the authorities approve the flow of the purified water it produces directly into consumers' homes, the project could set the standard in many other cities and countries.

The biggest obstacle on the way to realizing the project is the need to convince the public to overcome the feeling of disgust and reluctance to drink purified water, even when it is proven that purified wastewater is cleaner and more beneficial than the water supplied today.

More on the subject

Direct Potable Reuse: A Path Forward. George Tchobanoglous et al. WaterReuse Research Foundation and WaterReuse California, 2011.

The article can be downloaded as a PDF file at the link

http://aim.prepared-fp7.eu/viewer/doc.aspx?id=39

Water Reuse: Potential for Expanding the Nation's Water Supply through Reuse of Municipal Wastewater. National Research Council et al. National Academies Press, 2012. www.nap.edu/catalog.php?record_id=13303

Potable Reuse: Developing a New Source of Water for San Diego. Marsi A. Steirer and Danielle Thorsen in Journal–American Water Works Association, Vol. 105, no. 9, pages 64-69; September 2013.

The most advanced water purification facility in San Diego

The article was published with the permission of Scientific American Israel