Learning from the Ozone layer recovery to save the…


he recovery of the Ozone layer is an incredible history that interlaces scientific discovery with citizen action, diplomatic leadership, and technical innovation.

A visualization of the ozone hole over Antartica at its maximum extent in 2015. (NASA Goddard Space Flight Center) [1]

The early 20th century was a very profitable time for inventions. In history, inventions have often helped humans to survive, made tasks easier and led to a jump into the future. Although, there are inventions that at first seem to make tasks easier and solve problems, then they are found to be very unhealthy for humans and corrosive for the environment. [2]

Thomas Midgley in his life won multiple prestigious awards thanks to his inventions, leaded gasoline and chlorofluorocarbons (CFCs), which solved big problems of the early 20th century. It was only after his death, that his fortune declined. Now, Midgley has a different reputation and is considered one of history’s most dangerous inventors. In those days leaded gasoline was sold from the Ethyl Corporation as tetraethyl lead, only mentioned as TEL when marketing, as the dangers of lead poisoning were already well known. Leaded gasoline was invented to eliminate the “knock”, a common engine problem at that time, and it was found to also enhance the engine performance and speed. After many cases of lead poisoning and a string of health maladies, it was only at the beginning of the 70s that TEL was banned and almost completely phased out. The other problematic innovation was chlorofluorocarbons. Back in the 20s, there was a long-standing problem with refrigerators; they were extremely unsafe. In the beginning, ether and ammonia, both very flammable, were employed. Then, they were replaced by sulphur dioxide, not flammable but very toxic. In the first case, fires and eventually explosions were common, in the second case a tiny release of the gas killed families. In 1930, Midgley with a team of scientists found a solution: the world’s first CFC. With the knowledge of those days, CFCs were the perfect safe solution, they became ubiquitous in refrigerators and cooling units, and they were used extensively as a propellant in aerosol spray cans. [3]

In the late 60s, James Lovelock, an independent environmentalist and scientist, was the first to detect the widespread presence of CFCs in the atmosphere, finding it in all the air samples collected in the Antarctic.  Years later, two chemists, Rowland Sherwood and Mario Molina, interested in Lovelock’s results, found out that CFCs were able to rise into the stratosphere, kilometres above our heads. The sun’s harsh rays were able to split the CFCs apart, which were releasing chlorine and posing a threat to our ozone layer. The ozone layer absorbs most of the sun’s ultraviolet radiation. A lack of the ozone shield would have condemned millions of people worldwide to suffer from an immune system disease, go blind with cataracts, and die from skin cancer. [4,5]

Rowland Sherwood (left) and Mario Molina (right) in the lab at the University of California, January 1975. [2]

For more than a decade, the companies involved in producing CFCs reacted by denying the science and attacking the scientists, as it meant economic ruin for them. It was quite easy for them to negate these discoveries, Rowland and Molina were saying that an invisible gas was destroying an invisible layer, kilometres above our heads

It was the first time in history that the public got involved in the problem, and in the late 70s, the people demanded action and so the government responded

In the mid-80s, the discovery of the Antarctic ozone hole added new urgency, and in 1986, Susan Solomons, NASA scientist, proposed the idea of a 10-year global phaseout through market incentives to rapidly block CFCs commercialisations. In September of 1987, 46 states agreed to cut the use of CFCs and signed the Montreal Protocol. By 1990, this agreement had further support and became the first global phaseout agreement to completely phase out CFCs. Literally a disaster was avoided. Millions of lives saved from skin cancers, and agricultural disaster was avoided. Today the ozone hole is showing signs of recovery. 

An important change in political behaviour also occurred. Now, the environment is a constant political issue. In 2015, the General Assembly of the United Nations drew a plan for peace and prosperity for people and the planet. To achieve a better and more sustainable future for all, they designed 17 Sustainable Development Goals to be achieved by 2030. [6,7]

The Sustainable Development Goals address global challenges including poverty, inequality, climate change, environmental degradation, peace and justice. [8]

It takes time to see the effects of the chemicals. The ozone treaty is our lesson. It showed us what it is possible when citizens are involved in scientific discoveries and have the power to influence diplomatic decisions, and finally when the nations of the World come together with a shared goal. We need to learn from history. We cannot repeat the mistake of ignoring invisible threats because they are the most dangerous ones. All together we need to fight against climate change and worldwide pollution, starting from our everyday life habits.


[1]            When we saved the ozone layer, we saved ourselves from even worse climate change. https://www.cbc.ca/radio/quirks/dec-14-saving-the-ozone-helped-climate-change-extra-solar-comet-great-auk-extinction-and-more-1.5391393/when-we-saved-the-ozone-layer-we-saved-ourselves-from-even-worse-climate-change-1.5391408 (accessed January 7, 2021).

[2]            We Saved the Ozone Layer. We Can Save the Climate. https://www.nrdc.org/experts/david-doniger/we-saved-ozone-layer-we-can-save-climate (accessed January 7, 2021).

[3]            This 1920s Inventor Sped Up Climate Change With His Chemical Creations. https://www.history.com/news/cfcs-leaded-gasoline-inventions-thomas-midgley (accessed January 7, 2021).

[4]            M.J. Molina, F.S. Rowland, Stratospheric sink of chlorofluoromrthanes: Chlorine atom-catalyzed destruction of ozone, Nature. 249 (1974) 810. https://www.nature.com/articles/249810a0.pdf

[5]            F.S. Rowland, M.J. Molina, Chlorofluoromethanes in the environment, Reviews of Geophysics. 13 (1975) 1–35. https://doi.org/10.1029/RG013i001p00001

[6]            Transforming our world: the 2030 Agenda for Sustainable Development. https://sdgs.un.org/2030agenda (accessed January 7, 2021).

[7]            Achieving the Sustainable Development Goals – General Assembly of the United Nations. https://www.un.org/pga/70/events/sdgs/ (accessed January 7, 2021).

[8]            Take Action for the Sustainable Development Goals. https://www.un.org/sustainabledevelopment/sustainable-development-goals/ (accessed January 7, 2021).

From coffee to tea drinking: my PhD journey from…


t the beginning of 2019, I was close to obtain my Master’s Degree in Brazil in Chemical Engineering, so naturally I started to think about what I wanted to do next career wise. In fact, conducting research day to day was something that was very exciting for me: I used to spend my entire days at the lab doing experiments and the time just flew by, it just felt right. Also, having the autonomy to develop my own research interests was something that kept me motivated while I was developing my Master’s studies. By that moment, I knew I wanted to keep working as a researcher, and pursuing a PhD position felt like the right direction.

To give some context on why I decided to change coffee beans for tea bags, I should mention that I had studied previously in Scotland for 1 year during university, as I was awarded an international exchange scholarship. I had an amazing experience at the University of Strathclyde (I do not miss the windy weather though!), in which I felt I grew as much personally as I did professionally. This background gave me the confidence to start searching for PhD positions abroad. It did feel a bit overwhelming going after a PhD in Europe, as it would be 3 years living almost 10.000 Km away from home, but I was not ready to give it up without even trying. Regarding my research interests, I have always been interested in processes and development of materials that could minimize environmental hazards to increase sustainability, so when I came across the early-stage researcher position in the REWATERGY Marie Curie European Industrial Doctorate, I knew it was the perfect match: the project focused on the enhancement of  energy and nutrient recovery from wastewater streams inspired by the circular economy concept. Besides, the PhD position was at the prestigious University of Cambridge, with an additional inter-sectoral experience at Delft IMP, a Company located in the Netherlands. Needless to say that it felt like the perfect opportunity to gain experience in both academia and private R&D sectors.

Luckily, all the recruitment was being done online, so I could participate smoothly, as at the moment I had just got recruited for an Engineer position at a Brazilian company. I applied for the PhD position and a while later I got an email saying that my CV matched the position, and I got invited to do a round of interviews in order to be evaluated. The first one was with the entire consortium, there were around 15 people in the Skype call. I remember I was a little bit tense, since it is always a bit nerve wrecking trying to show your personality in a different language than your mother tongue, but I had confidence in myself and it went really well. They mainly asked questions about my background, and I was happy to be able to come across as my true self. After that, I was soon invited to do a second interview with  my future two advisors, Laura and David. The final interview lasted approximately 1 hour and it was focused on science related questions. This last interview was very formal and serious, and it was very hard for me to read the room. I knew I had prepared myself and that I was on my top game, but I could not anticipate the outcome, and I must admit it was a bit nerve wrecking. A few days later I received an e-mail where I was offered the PhD position, and I’ve never felt so happy! Coming from a small city in Brazil and heading to a PhD abroad always felt more like a dream than a reality.

After that, I started with all the bureaucratic formalities that involves moving to a different country. My visa processing was quite long and took more time than expected, but even so, Laura, as my academic advisor, was very understanding and helpful. I was able to delay the start of my PhD contract until I got everything in place. Arriving at Cambridge mid-October, was a big life change to be honest. I left Brazil in the spring, with lovely sunny and warm days, suddenly to arrive in the English fall with temperatures around 10 °C! I know that for most people living in Europe it is not even that cold, but I was freezing from day one. Later, I got to finally meet Laura in person and I have to say that I am very happy to have a woman as one of my advisors. In Brazil, having women in leadership positions is still scarce (especially in science), so it is definitely a motivation and an inspiration to have Laura’s guidance and mentorship along my career path. 

Now, fast forward to the end of 2020, I am happily surprised on how much my life has changed so far. Of course, the COVID-19 pandemic has disrupted everybody’s life in so many different ways, but still I believe I have grown so much during this period. I have been through my 3-month evaluation and 1st year viva, in which I was successfully approved in both of them. Additionally, I have been privileged to work at an international and collaborative environment with a powerful and stimulating female guidance. I even had the courage to cycle during the fall and winter seasons: I still freeze, but at least now I can cope! Most importantly, I feel that I have matured scientifically, and that becoming an independent researcher is indeed my cup of tea.

Sunset in Cambridge, Uk.

Covid-19: Potential Wastewater Risks


he coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread widely, becoming a global pandemic. COVID-19 symptoms include cough, fever, difficulty breathing, and diarrhoea. Genetic material from SARS-CoV-2 ribonucleic acid (RNA) has been detected in the faeces of both symptomatic and asymptomatic people who have been infected 1.

This pandemic has become one of the most significant international public health challenges of this century; globally, nearly 53 million cases and more than 1.3 million deaths have been counted to date 2. Tools for rapidly identifying, containing, and mitigating the spread of SARS-CoV-2 are crucial for managing community transmission, particularly until a vaccine or effective pharmaceutical intervention is developed and becomes widely available 3.

Considering recent epidemics that have emerged around the world, there has been increasing awareness regarding the risk of exposure to pathogens during wastewater collection and treatment. Emerging pathogens may enter wastewater systems through several pathways, including viral shedding in human waste, animal farming, hospital effluent, or surface water runoff following biological incidents. Sewage and wastewater systems transport water to wastewater treatment plants (WWTPs), and the water is then discharged into the environment. SARS-CoV-2 viral material poses a significant threat to human health, and their transmission in wastewater systems may lead to increased exposure, potentially causing serious health consequences. This virus is primarily transmitted through person-to-person and aerosol/droplet transmission via the respiratory system, with fomite and touch-based contamination comprising a lesser proportion of cases. Potential exposure and transmission through sanitation systems have not been sufficiently studied and require further evaluation 4 5.

Environmental surveillance has commonly been implanted in public health management, and methods such as testing wastewater for evidence of pathogens can indicate the severity and scope of pathogenic spread in communities. In the context of the ongoing COVID-19 pandemic, environmental surveillance methods are being used to evaluate SARS-CoV-2 shed in wastewater via human waste 6. Wastewater monitoring exhibits significant promise as an early detection approach. However, available data indicate that the role of wastewater as a potential source of pathogens and as a risk factor for public health must be further explored 4.

Further, genetic material from SARS-CoV-2 in untreated wastewater and/or sludge has been detected in many regions, such as Milan, Italy; Murcia, Spain; Brisbane, Australia; multiple locations in the Netherlands; New Haven and eastern Massachusetts, United States of America; Paris, France; and existing poliovirus surveillance sites across Pakistan. Researchers in the Netherlands, France, and United States of America have reported a correlation between wastewater SARS-CoV-2 RNA concentrations and COVID-19 clinical case reports; research from the latter two countries further suggests that wastewater virus RNA concentrations can provide a 4- to 7-day advanced indication of incoming COVID-19 confirmed case data 6.

Recently observations of viral material in wastewater have intensified the need for the acquisition of more information on the transmission pathways of SARS-CoV-2 through various environmental exposure pathways, including that of wastewater. Wastewater is known to be a major pathogen transmission pathway, and contaminated water should be treated carefully to reduce the risk of human exposure 7. Moreover, contamination risk is extremely high in densely populated regions with minimally developed sewage and wastewater treatment facilities. This is particularly critical for SARS-CoVs, as they can survive for several days in untreated sewage and longer in colder regions 8.

Conventional sewage treatment methods that include disinfection are expected to effectively eradicate SARS-CoV-2 8. Despite ongoing treatment strategies, recent studies have shown that SARS-CoV-2 RNA has been found in the outlet of WWTPs as well as in water bodies receiving treated wastewater, indicating a serious public health risk via the faecal–oral or faecal–aerosol infection routes 9. Covid-19 transmission through wastewater poses a major concern in areas without adequate sanitation and water treatment facilities, as discharge of wastewater without appropriate treatment would expose the public for infection 7. Globally, approximately 1.8 billion people access faecal-contaminated water sources as drinking water, which significantly increases the risk of COVID-19 transmission by several magnitudes when proper precautions are not taken8. Therefore, the risk of infection through various forms of contact with conventionally treated wastewater cannot be dismissed.

Owing to the lack of clean natural water resources in many countries, treated and untreated wastewater is increasingly used for irrigation. In addition, sludge from treated wastewater has been applied as fertilizer, and it is increasingly used as an agricultural amendment. The viruses contained in this wastewater and sludge are thus deposited on crops and soil where they are likely to survive for a short period. This can facilitate further spread into ground and agricultural water sources, further increasing the risk of exposure. It is therefore important to understand the survivability of and exposure risk to these viruses, specifically on crops and soil. Studies on viral survivability in such conditions can only be conducted with enteric viruses that can multiply in cell cultures. Complex methods are required as the presence of the viral genome alone does not indicate the presence of infectious viral particles 4.

Wastewater Use in Irrigation Higher Than Thought | Fluence

 Although the extent of infectivity associated with SARS-CoV-2 RNA in treated wastewater is not yet clear, the potential risk can be minimized by ensuring complete viral RNA removal in wastewater treatment plants 9. It may be beneficial to add an additional disinfection step, or ‘tertiary treatment’, to further reduce the risk posed by viral pathogens. Disinfection methods for wastewater effluents and water include physical and chemical techniques, such as ultraviolet light and heat treatments as well as chlorine and ozone treatments, respectively. Ozonation and UV irradiation are reported to be more effective than chlorine-induced reactive oxygen species formation; however, the latter induces residual disinfection, which ozonation and irradiation cannot facilitate 10. Moreover, chlorine addition to create a residue after ozonation can be performed to produce water free of toxic residues. Despite existing disinfection techniques, further investigation is required to determine dose and contact time for SARS-CoV-2 inactivation 4 8. In addition to conventional treatment methods, household disinfection techniques such as boiling, nanofiltration, UV irradiation, and bleaching powder addition in appropriate doses are also effective and should be evaluated for regions without safe piped water supplies and centralized water treatment facilities.


1.      Ahmed W, Angel N, Edson J, et al. First confirmed detection of SARS-CoV-2 in untreated wastewater in Australia: A proof of concept for the wastewater surveillance of COVID-19 in the community. Sci Total Environ. 2020. doi:10.1016/j.scitotenv.2020.138764

2.       WHO Coronavirus Disease (COVID-19) Dashboard. Covid19.who.int. https://covid19.who.int/. Published 2020. Accessed November 14, 2020.

3.      Hassard F, Lundy L, Singer AC, Grimsley J, Cesare M Di. Comment Innovation in wastewater near-source tracking for rapid identification of COVID-19 in schools. The Lancet Microbe. 2020;5247(20):19-20. doi:10.1016/S2666-5247(20)30193-2

4.      Lahrich S, Laghrib F, Farahi A, Bakasse M, Saqrane S, El Mhammedi MA. Review on the contamination of wastewater by COVID-19 virus: Impact and treatment. Sci Total Environ. 2021. doi:10.1016/j.scitotenv.2020.142325

5.      Mohapatra S, Menon NG, Mohapatra G, et al. The novel SARS-CoV-2 pandemic: Possible environmental transmission, detection, persistence and fate during wastewater and water treatment. Sci Total Environ. 2020. doi:10.1016/j.scitotenv.2020.142746

6.      WHO. Status of environmental surveillance for SARS-CoV-2 virus. 2020;(August):1-4.

7.      Kataki S, Chatterjee S, Vairale MG, Sharma S, Dwivedi SK. Concerns and strategies for wastewater treatment during COVID-19 pandemic to stop plausible transmission. Resour Conserv Recycl. 2021. doi:10.1016/j.resconrec.2020.105156

8.      Bhowmick GD, Dhar D, Nath D, et al. Coronavirus disease 2019 (COVID-19) outbreak: some serious consequences with urban and rural water cycle. npj Clean Water. 2020. doi:10.1038/s41545-020-0079-1

9.      Abu Ali H, Yaniv K, Bar-Zeev E, et al. Tracking SARS-CoV-2 RNA through the wastewater treatment process. medRxiv. 2020:2020.10.14.20212837.

10.    Zhang CM, Xu LM, Xu PC, Wang XC. Elimination of viruses from domestic wastewater: requirements and technologies. World J Microbiol Biotechnol. 2016. doi:10.1007/s11274-016-2018-3

07 moments from a year of the REWATERGY Project


n the anniversary of the REWATERGY-EID project, we look back at 07 moments from the initial 12 months of the project, a personal testimony of an early stage researcher (ESR). REWATERGY is an industrial-academic partnership within the water-energy nexus, a Marie Curie Industrial Doctorate training network. The project is funded by the European Commission within Horizon 2020.

The REWATERGY project partners three universities and three companies across Europe. The universities are the University of Cambridge, United Kingdom; Universidad Rey Juan Carlos, Spain; and Ulster University, Belfast Ireland. The industries include Delft IMP, Netherlands; ProPhotonix, Cork Ireland and FCC Aqualia, Spain.

REWATERGY provides ESRs a unique opportunity to conduct their research in an academic and industrial environment. Therefore, ESRs acquire wider exposure to the practical application of their research.

1.  The start of a new journey

We started a new journey with excitement, curiosity, and determination. REWATERGY brought together eight ESRs from seven different countries of the World. The ESRs came from Brazil, India, Italy, Ireland, Jordan, Pakistan and Spain. The ESRs bring with them diverse experiences and add diverse perspectives to the project.

Low number of women in science, technology, engineering, and mathematics (STEM) subjects and industrial doctoral training programs is a common subject of discussion and concern since decades. In the REWATERGY project, four among the eight ESRs are women. The equal participation of women in the project is notable and encourages the participation of women in science.  

2. The first meeting with ESRs

Here arrived the most exciting part, the meetup in a beautiful venue. The University of Cambridge hosted the meeting, attended by all members and the ESRs. It provided a chance to share ideas, plans, socialize, discuss, and know each other. Secondly, attendees gave presentations on their research background, role in the project and research plans. REWATERGY project focuses on two important fields of research; water and energy.

After the meeting, we spent a valuable day and spared few worthy hours exploring the Cambridge. The enchanting beauty and academic atmosphere of Cambridge was visible to the eyes, as well as the diversity among the University of Cambridge community.

3. Enrollment in a Ph.D. program

The value of the project exceeds its many benefactions as it provides ESRs the chance to fulfill their dreams to further their studies. As an industrial-academic partnership program, REWATERGY provides us the opportunity to work in academia and the industry. In the first month, we all enrolled in a Ph.D. program in our respective partner institutions.

4. Three days’ workshop in Belfast, Ireland

Our first workshop in Belfast proved memorable, learning, and spending more days together. We attended live demonstrations of laboratory techniques in the laboratory facilities of Ulster University, Belfast.

At Ulster University, we met researchers and research groups working on related research domains. We started expanding our research network.

In Belfast, we were welcomed by the crowded Christmas market. During the three days, we visited various exciting parts of the city and tasted some local Irish food.

5. New friends, a new language, and new places

By a few weeks, we become friends. The REWATERGY project encouraged and supported the integration of ESRs in a new environment and culture. ESRs placed in countries speaking languages other than English availed an opportunity to take up language courses. This is a moment of personal growth along with the study and research. We are learning and developing an understanding of the countries, the work environment, the culture, and the language.

6. Socially distant but remotely connected

By the mid of the first year, the Covid-19 Pandemic spread to countries across the Europe. REWATERGY senior project members encouraged the ESRs to observe the restrictions imposed on mobility. We stayed home during the lockdowns as per each country´s law while remaining remotely connected.

Learning continued during the Covid-19 pandemic in a new work environment. REWATERGY adopted the new remote working route and observed social distancing.

In the first research progress, all partners, ESRs, and the project manager connected online. The research progress meeting was successfully conducted. We presented our individual research progress and attended the discussions. The research progress remained highly fruitful and provided new ways forward.

By the fifth and sixth month in some cases, still keeping with the social distancing and precautionary measures, gradually we resumed our laboratory activities. Together we remained resilient in the face of the Pandemic.

During the prolonged travel restrictions and in continuation with the remote work environment, REWATERGY successfully conducted over eight online training. Each training, delivered by an expert in the field, expanded our knowledge and horizon.

7. Looking at the future with renewed hopes together!

As we enter the second year of the REWATERGY project, we move on with higher and renewed hopes for a smooth transition back to normality. We realize more than ever the potential of scientific research and innovation in sustainable development and in building resilient societies.

Now our aims are not only to achieve the project objectives, expand our scientific skills or, grow professionally, but also to contribute to some of the pressing needs of our society through research and innovation.

Water Reuse Practices


hroughout my childhood, I was lucky enough to spend most of my summers on the Costa Del Sol. Coming to the end of the school term and knowing that a month of swimming, sunbathing, and eating Spanish food with my family was an unrivalled holiday experience. As kids, we were always warned off drinking the tap water, instead buying, and drinking bottled water. We also told each other stories that if you so much as let a drop of water from the shower into your mouth you would also get very sick. At the other end of the scale, we learnt very young that the water in the swimming pool was so heavily chlorinated that opening your eyes under water would result in redness for the rest of the day. All of this was far removed from our experiences back home in Ireland, but we didn’t pay it much attention, its just how it was.

On one day of my holidays in a café in Fuengirola, I found myself next to a table of two men. One man, I think a local, spoke in perfect English to a man who I later learnt had just moved to the Costa Del Sol from England to join the nomadic community here on the Costa. Between them on the table were two coffees and a sheet of paper. The sheet consisted of a hand drawing of a sort of travelling home. The drawing showed an all in one bed, chair, dining table, with solar powered chargers and storage space positioned across the home for all their travelling needs. As these men chatted about the nomadic home, it became apparent that the most important and interesting aspect of the design revolved around how they used their water to maximize efficiency. The water they stored to drink was different to the water they used to shower, the shower water itself mounted on the roof of the nomadic home to stay warm. The runoff water from the shower was collected to use for washing the home or else to dispose of at the next drain. As I sat eavesdropping on their plans, I realized it sat in complete contrast to my own experiences on the Costa Del Sol, drinking only bottled water, showering morning and night and by the pool side – the pool itself a reservoir of water with only one purpose and certainly not a use these nomadic travelers would feel at all necessary or efficient. Coming from Ireland, and perhaps readers from Northern Europe or countries with a similar climate will empathize, I had never really considered the need to make use of water in this cascading fashion. I wash, drink, flush and swim in water from essentially the same source, all initially of drinkable quality. Now, I am not advocating the need for water reuse at the scale these men were doing, but it was certainly an eye opener for me and introduced me at an embarrassingly old age to the concept of water reuse and water quality for different applications.

Life of Pi: A Solar Still is Shown Floating Beside the Boat

Fresh water is also not our only option of accessing more water for use across the globe. Salt water can be purified through desalination to achieve potable water. There is a passage from the book, Life of Pi where Pi discovers twelve solar stills in a survival locker. He takes the solar stills, fills them with salt water and leaves them to evaporate and simultaneously collect condensate in a separate vessel, helping Pi to survive in this section of his adventure. This is one of the few instances in the book where Pi successfully makes use of a man-made survival tool. Although a solar still is shown in the film, I do not believe much attention is drawn to its operation, however the book has at least demonstrated this technology to a wide audience of readers. Our nomadic travelers may not have considered this yet, or at least did not discuss it during the brief excerpt of their conversation I overheard, but it would complete the water cycle for them and in turn make them entirely self-sufficient for their water needs. So, what can we learn about water reuse across the globe from Pi and our survival experts? Although these examples are small scale, they do cover many of the segments of technology available and in use today for water reuse.

When reusing water, some treatment may be required before the water is of a suitable standard depending on the next application. For example, there may be instances where water used to clean agricultural equipment could immediately be used in irrigation, but there wouldn’t be many instances where reused water could be provided without treatment as drinking water. The degree of treatment required between one application and another will dictate the equipment required. In wastewater treatment plants, there are three levels of treatment: Primary, which will remove large, insoluble contaminants through techniques such as screening, secondary which combines physical and biological techniques such as sedimentation and activated sludge treatment, and finally tertiary treatment which will typically consist of chemical and biological treatment techniques to disinfect the water stream, using techniques such as UV irradiation to damage organisms and the addition of free radicals such as chlorine to oxidize organic material. For water being returned to waterways or used in some water reuse applications, secondary treatment will be sufficient to ensure, once diluted, the effluent is safe for the environment. For instances where water will be used for sanitation or consumption (often referred to as potable water) tertiary treatment will be required.

The agricultural sector is one of the hardest hit sectors by water scarcity, as it withdraws 70% of freshwater reserves globally and consumes 90% of all available water supplies globally [1]. So, there is an obvious need to increase the efficiency of water used in agriculture by improving the reuse of water. At the same time, climate change and increasing global populations are putting more strain on water resources as the demand for food and water increase. There are thankfully many opportunities for water reuse across industries, but particularly in the agricultural sector. Effluent from primary treatment is suitable for irrigation on parklands and forests, whilst water that has undergone secondary water treatment can be used to irrigate crops indirectly, for example in the irrigation of olive trees- the rule here being that water should not come into direct contact with foodstuffs. In both cases, the environment the water is introduced to acts as an environmental buffer before flowing to waterways that are used as sources for drinking water supply. Tertiary treated water can be safely discharged from site or potted for a range of sanitary uses. On a farm, tertiary water can be used to directly irrigate crops or for consumption by livestock.

Indirect Olive Tree Irrigation by Buried Diffusers

Water reuse for agricultural purposes is particularly popular in regions suitable for crop growth but equally prone to drought. As climate change progresses, instances of drought become more common and more widespread. Thus, water reuse will need to be used in more regions. Parts of California, USA adopted indirect water reuse in the 1950’ and 60’s as a means of improving the efficiency of water use and securing their limited water supply. Orange County, California has a flagship water reuse facility which recently broke a world record for the amount of water cleaned and stored for potable water use, recycling more than 100 million gallons of water in a 24-hour period [2]. The water is of ‘near-distilled’ quality, with minerals added to improve taste. Even with such high-quality water supply, Orange County has faced issues with perception of water cleanliness given it has been cleaned from previous uses, rather than being withdrawn from a reservoir. This perception issue is often termed ‘the yuck factor’ and is a problem faced globally.

Orange County’s Water Reuse Scheme

The most famous example of a water reuse project facing resistance due to the yuck factor occurred in Toowoomba, Australia. In 2006, during the Millennium Drought, Toowoomba was forced to consider treating sewage and sending it to a dam for reuse as potable water. Resistance to the idea quickly gained momentum, with an opposition group forming and forcing the local council to send the decision to a referendum. The group opposed to the water reuse appealed strongly to the yuck factor concept, naming their group ‘Citizens against Drinking Sewage’ and labelling the region ‘Poowoomba’ [3]. The example of Toowoomba demonstrates that even though the technical capability exists to reuse water, even to the point that it is now cheaper to reuse water than to withdraw water in Orange County, perhaps the more challenging aspect of water reuse is overcoming the misconception that reusing water is somehow unsafe or unhygienic in countries used to high levels of sanitation.

The REWATERGY project’s core objectives are to (1) enhance the energy recovery from wastewater, (2) improve the energy efficiency of water disinfection, and (3) increase the resilience of distributed household safe drinking water systems. Objectives two and three are concerned with water reuse, with the project aiming to develop prototypes for each of these objectives. The prototypes for objective two use technology that has shown promise as chemical free, highly efficient alternative to conventional tertiary treatment techniques, namely UVA LED photoelectrocatalysis. A prototype for objective three will incorporate a membrane sufficiently sized to remove microplastics from water streams with UVC LED technology to disinfect pathogens present in the water. Although the intended market of each of these prototypes potentially straddle the spectrum of water treatment applications (objective two prototypes are likely suitable for industrial, agricultural, or pharmacological waste streams, whilst the objective three prototype will be suitable for point of use), they could both have a role to play in improving water reuse. The objective two prototype’s main strengths in the industries named above would be the minimal operator input in an organization not otherwise trained in wastewater treatment processes, the long lifetime of a UV LED based system and the potentially broad range of treatable contaminants make it a sound solution for water treatment and reuse. The objective three prototype is an ideal solution for countries with mains water supply that is not suitable for consumption. By using membrane technology to filter out microscopic contaminants first, then treating pathogens in suspension, water can be upgraded for drinking and other potable water applications.

Going forward, water use practices will need to become more focused on reuse and efficiency as prevalence of drought and demand for food and water increase. All industries, in particular the agricultural sector, must leverage water reuse. Technology that makes this simple and financially viable to the sector is of particular importance to drive water reuse as a practice. The first time Pi turned on a tap, he observed, “its noisy, wasteful, superabundant gush was such a shock that my legs collapsed beneath me and I fainted in the arms of a nurse”. To protect our water resources, we must not be wasteful.


[1] D. Norton-Brandao, S.M. Scherrenberg, J.B. van Lier, Reclamation of used urban waters for irrigation purposes – a review of treatment technologies, J. Environ. Manage., 122 (2013), pp. 85-98, 10.1016/j.jenvman.2013.03.012

[2] From waste to taste: Orange County sets Guinness record for recycled water, Orange County Register, https://www.ocregister.com/2018/02/18/from-waste-to-taste-orange-county-sets-guinness-record-for-recycled-water/ Accessed: 2020-10-07

[3] Toowoomba says no to recycled water, https://www.smh.com.au/national/toowoomba-says-no-to-recycled-water-20060731-gdo2hm.html Accessed: 2020-10-07

Students’ Blog


elcome to the blog of the students of the REWATERGY-ITN project. Our objective is to establish a forum for information and discussion in which we hope all of you who are interested in the water problem will participate from the different points of view: water management and uses, needs and conservation of water resources, water quality, treatment and recycling of wastewater, purification, etc. For this we will publish news, comments and news, as well as information about courses, conferences, seminars, calls and in general about any type of event that we consider, may be of interest to you.