Towards energy self-sufficiency: biogas production in wastewater treatment plants


ater is a vital resource in our society, not only for human consumption but for any kind of activity (food production, industrial processes…). During human activity, we contaminate water streams, so, before they can be returned to water bodies, such as lakes or rivers, they must be decontaminated. There is where wastewater treatment plants (WWTP) come into play. WWTP are the facilities where all the wastewater that we produce is treated to remove organic matter, solids and nutrients before it is returned to the environment [1]. During their operation , WWTP become important energy consumers. In the U.S., wastewater treatment accounts for 3 – 4% of national electrical demand, being the electric power consumption the highest operation cost in these plants (more than 30%) [2].

During their operation, WWTP generate a big volume of sewage sludge, around 250 grams of dry solids per m3 of treated wastewater. Sewage sludge is produced during the primary and secondary settling (Figure 1) and it is mainly composed of the organic matter and solids removed from wastewater, being usually rich in nutrients [3]. Furthermore, sewage sludge cannot be directly disposed, but it requires prior treatment and its management accounts for 30% of WWTP operating costs [2]. Therefore, it is crucial to apply strategies that enables a sustainable management of the sludge, allowing to get the most of it.

Figure 1. Schematic of a wastewater treatement plant with biogas production by anaerobic digestion of sewage sludge.

Anaerobic digestion is a widespread technology that allows generation of renewable energy in the form of biogas during sewage sludge treatment. During this process, microorganisms break down the organic matter present in the sludge into smaller molecules, producing biogas. Biogas is formed by a mixture of mainly methane and carbon dioxide and it can be used as a fuel for heat and electricity generation [3].

However, sewage sludge cannot be directly used from primary and secondary settling for anaerobic digestion. The generated sludge goes through a series of process in the WWTP (Figure 2) [3]. First, the sludge is sieved and thickened to reduce the content of water and hence the energy consumed during its digestion. The thickened sludge is then pumped into the digesters and continuously stirred in anaerobic conditions at mesophilic temperatures (35 – 42 °C) during a retention time of around 20 days. About a third part of the solid matter from the sludge is transformed into biogas during digestion, so the digested sludge becomes again very liquid and needs to be dewatered before its final disposal. Dewatering of the sludge is normally achieved by mechanical pressure or centrifugation, although sometimes it can be heat dried to remove even more water. The dewatered sludge can then be used for agriculture, disposed in a landfill or sent to an incineration plant [3]. Finally, as a result of the dewatering process, a liquid stream with a high concentration of contaminants is produced and recirculated to the entrance of the WWTP [4].

Figure 2. Sewage sludge treatment processes in a wastewater treatment plant with biogas production by anaerobic digestion [3].

During the anaerobic digestion, biogas is produced by biological breakdown of the biomass. Typical composition of biogas from sewage sludge consists of 60 – 67% methane, 33 – 40% carbon dioxide and traces of other compounds such as hydrogen, nitrogen, siloxanes and hydrogen sulphide [5]. Due to its high methane content, this biogas is a source of energy that is commonly used in WWTP to cover some of their energy demand. Biogas can be used to produce heat directly in a boiler, just as we all do at home. However, the most common application for the biogas produced in wastewater treatment plants is its use in Combined Heat and Power (CHP) units (systems that produce both, electricity and heat, from a single fuel source) [6]. Combustion engines and micro turbines are the most widely used CHP technologies, although some alternatives such as fuel cells are attracting attention due to their higher electrical efficiency [7], [8]. The heat and electricity produced through these CHP units is used in the WWTP to reduce the energy demand. Heat autonomy is generally achieved with the biogas, and the electrical consumption can be reduced from 30 to 70%, depending on the WWTP size [3]. Furthermore, some technologies aim to go even further to maximize the biogas production by co-digestion of other organic wastes from the WWTP itself (such as the grease removed in the pre-treatment) [9] or from other sources (such as food wastes or municipal solid wastes) [10]. Lastly, the biogas produced can be upgraded (i.e. increasing its methane content) so it can be used as a vehicle fuel or even injected to the natural gas grid [2].

Summarising, water and energy are vital and inseparably connected resources. Wastewater treatment processes consume a large amount of energy, which is translated into environmental, social and economic impacts. Anaerobic digestion at WWTP is a technology that produce biogas, a green energy source that can help reducing the footprint of the water cycle and supposes a step-forward towards a more sustainable society.


[1]         J. Palatsi, F. Ripoll, A. Benzal, M. Pijuan, and M. S. Romero-güiza, “Enhancement of biological nutrient removal process with advanced process control tools in full-scale wastewater treatment plant,” Water Res., vol. 200, p. 117212, 2021, doi: 10.1016/j.watres.2021.117212.

[2]         Y. Shen, J. L. Linville, M. Urgun-Demirtas, M. M. Mintz, and S. W. Snyder, “An overview of biogas production and utilization at full-scale wastewater treatment plants (WWTPs) in the United States: Challenges and opportunities towards energy-neutral WWTPs,” Renew. Sustain. Energy Rev., vol. 50, pp. 346–362, 2015, doi: 10.1016/j.rser.2015.04.129.

[3]         N. Bachmann, J. la C. Jansen, D. Baxter, G. Bochmann, and N. Montpart, “Sustainable biogas production in municipal wastewater treatment plants,” IEA Bioenergy, 2015.

[4]         A. Thornton, P. Pearce, and S. A. Parsons, “Ammonium removal from digested sludge liquors using ion exchange,” Water Res., vol. 41, no. 2, pp. 433–439, 2007, doi: 10.1016/j.watres.2006.10.021.

[5]         A. Kiselev, E. Magaril, R. Magaril, D. Panepinto, M. Ravina, and M. C. Zanetti, “Towards Circular Economy: Evaluation of Sewage Sludge Biogas Solutions,” Resources, vol. 9, no. 91, pp. 1–19, 2019.

[6]         M. MosayebNezhad, A. S. Mehr, M. Gandiglio, A. Lanzini, and M. Santarelli, “Techno-economic assessment of biogas-fed CHP hybrid systems in a real wastewater treatment plant,” Appl. Therm. Eng., vol. 129, pp. 1263–1280, 2018, doi: 10.1016/j.applthermaleng.2017.10.115.

[7]         D. M. Riley, J. Tian, G. Güngör-Demirci, P. Phelan, J. Rene Villalobos, and R. J. Milcarek, “Techno-economic assessment of CHP systems in wastewater treatment plants,” Environ. – MDPI, vol. 7, no. 10, pp. 1–32, 2020, doi: 10.3390/environments7100074.

[8]         M. Gandiglio, F. De Sario, A. Lanzini, S. Bobba, M. Santarelli, and G. A. Blengini, “Life cycle assessment of a biogas-fed solid oxide fuel cell (SOFC) integrated in awastewater treatment plant,” Energies, vol. 12, no. 9, 2019, doi: 10.3390/en12091611.

[9]         M. S. Romero-Güiza, J. Palatsi, X. Tomas, P. Icaran, F. Rogalla, and V. M. Monsalvo, “Anaerobic co-digestion of alkaline pre-treated grease trap waste: Laboratory-scale research to full-scale implementation,” Process Saf. Environ. Prot., vol. 149, pp. 958–966, 2021, doi: 10.1016/j.psep.2021.03.043.

[10]      S. Vinardell, S. Astals, K. Koch, J. Mata-Alvarez, and J. Dosta, “Co-digestion of sewage sludge and food waste in a wastewater treatment plant based on mainstream anaerobic membrane bioreactor technology: A techno-economic evaluation,” Bioresour. Technol., vol. 330, no. January, p. 124978, 2021, doi: 10.1016/j.biortech.2021.124978.

Ammonia Pollution


eleased data from the European Environment Agency shows how the emissions of most air pollutants are decreasing in the European Union, in contrast to the increasing ammonia (NH3) emissions from the agricultural section, which challenges the EU Member states to meet their air pollution limits.1

Ammonia is one of the most produced inorganic chemicals in the world, with an estimated annual global production of up to 200 million tons.2 Approximately 80% of the global ammonia production is used in the fertiliser industry,2 playing a key role in sustaining the exponential growth in human population in the last 50 years, as seen in Figure 1.3

Figure 1 – Portion of the global population supported by synthetic NH3 (in red), from 1900 to 2015.4

Despite our dependency on ammonia fertiliser, NH3 is a highly toxic chemical and undesirable NH3 emissions into the natural environment are responsible for damaging the biodiversity in aquatic and terrestrial ecosystems, as well as the human health. Exposure to high levels of gaseous NH3 has been associated to adverse health conditions in humans skin, lungs and eyes, and concentrations of about 3000 ppm can be fatal in roughly 30 minutes.5 Gaseous ammonia is colourless and it can combine with other contaminants present in the atmosphere, such as sulfuric dioxide, volatile organic compounds and nitrogen oxides, to form harmful small sized particulate matter, known as PM2.5.6 These PM2.5 can travel long distances (up to 1000 km).7 NH3-derived PM2.5 is responsible for causing adverse health conditions, as cardiovascular disease, asthma, lung cancer and premature death.7

In the past years, the increase in NH3 levels has been widely attributed to farming intensification. In this sector only, NH3 emissions increased by 90% between 1970 and 2005.8 It is estimated that more than 60% of the applied nitrogen-based fertiliser is not used by crops to grow.9 Nutrient loss is a major source of pollution and it is, in different extent, globally widespread. Another major source of ammonia emissions is produced by livestock manure.

In Europe, sixteen out of twenty-eight members had surpassed in 2016  their 2020 ammonia emission limits.10 Among which the most NH3-pollutant countries were in Latvia, Germany and United Kingdom.10

In UK, Northern Ireland (NI) alone is responsible for 12% of the total NH3 emission.11 The majority (94%) of these emissions originates from the agriculture sector, and in particular from cattle, which accounts for the largest portion (69%).12 Most of NI including priority habitats have a nitrogen concentration that causes significant and irreparable ecological damage. Northern Ireland Environment Link (NIEL) reported in 2019 that 90% of NI’s protected habitats, 98% of Special Areas of Conservation and 83% of special protected areas have exceeded critical loads of nitrogen deposition. Moreover, data released by Department of Agriculture, Environment and Rural Affairs (DAERA) shows significantly deteriorating water quality standards, with 95% of lakes not meeting the Water Framework Directive quality standards and nitrogen levels in both river and marine bodies rising in the past years.13

Some of the strategies that have shown to reduce emissions include: reducing food waste, changing crop allocation to maximise the gain in crop yield, investing in agriculture technology, supporting agricultural modernization, and using chemical nitrogen fertilisers effectively and efficiently.9, 10, 12 Ammonia pollution can be as well reduced by improving confined animal buildings and livestock raising techniques, with better design to sequestrate NH3, reducing the hazard for workers and the NH3 emissions to the atmosphere.11 Moreover, a careful slurry management, including artificial floating crust or a fixed cover, can also reduce ammonia emission up to 60%, during the storage.12

Ammonia emissions are a threat for humans and the natural ecosystems. There is an urgent need to reduce the impact of the agriculture sector, which represents the major source of NH3 emission in the natural environment. Further actions need to be implemented to prevent further biodiversity loss, prevent public health, and at the same time enable sustainable development.


1.           Air quality in Europe – 2020 report; European Environment Agency: 2020.

2.           Garagounis, I.;  Vourros, A.;  Stoukides, D.;  Dasopoulos, D.; Stoukides, M., Electrochemical Synthesis of Ammonia: Recent Efforts and Future Outlook. Membranes (Basel) 2019, 9 (9), 112.

3.           Smil, V., Detonator of the population explosion. Nature 1999, 400 (6743), 415-415.

4.           Erisman, J. W.;  Sutton, M. A.;  Galloway, J.;  Klimont, Z.; Winiwarter, W., How a century of ammonia synthesis changed the world. Nature Geoscience 2008, 1, 636.

5.           Birken, G. A.;  Fabri, P. J.; Carey, L. C., Acute ammonia intoxication complicating multiple trauma. J Trauma 1981, 21 (9), 820-2.

6.           Gu, B.;  Sutton, M. A.;  Chang, S. X.;  Ge, Y.; Chang, J., Agricultural ammonia emissions contribute to China’s urban air pollution. Frontiers in Ecology and the Environment 2014, 12 (5), 265-266.

7.           Asman, W.;  Sutton, M. A.; Schjørring, J. K., Ammonia: emission, atmospheric transport and deposition. New Phytologist 1998, 139, 27-48.

8.           Sommer, S. G.;  Webb, J.; Hutchings, N. D., New Emission Factors for Calculation of Ammonia Volatilization From European Livestock Manure Management Systems. Frontiers in Sustainable Food Systems 2019, 3 (101).

9.           West, P. C.;  Gerber, J. S.;  Engstrom, P. M.;  Mueller, N. D.;  Brauman, K. A.;  Carlson, K. M.;  Cassidy, E. S.;  Johnston, M.;  MacDonald, G. K.;  Ray, D. K.; Siebert, S., Leverage points for improving global food security and the environment. Science 2014, 345 (6194), 325-328.

10.         Giannakis, E.;  Kushta, J.;  Bruggeman, A.; Lelieveld, J., Costs and benefits of agricultural ammonia emission abatement options for compliance with European air quality regulations. Environmental Sciences Europe 2019, 31 (1), 93.

11.         Luke, J.;  Lucy, G.;  Courtney, S.; King, K. Air Pollution Inventories for England, Scotland, Wales, and Northern Ireland: 2005-2019; Department for environment Food and Rural Affairs: 2021.

12.         Code of Good Agricultural Practice for the Reduction of Ammonia Emissions; Department of Agriculture, Environment and Rural Affairs: 2019.

13.         Ciara, B.;  Laura, N.;  James, O.; Ekaterina, G. EJNI Briefing Paper Series Northern Ireland Assembly – Ammonia Pollution in Northern Ireland; Environmental Justice Network Ireland (EJNI): 2020.

Brine entering the Mediterranean, 300 metres off the coast of Israel. (Image: Hagai Nativ / Alamy)

Environmental Impacts of brine discharge from Desalination plant on…


owadays, the lack of freshwater is expanding with increasing the world population, urbanization, contamination, and environmental change. To keep up the equilibrium between water supply and demand; some strategies should be implemented. The best system to treat saline water is desalination. Desalination is a process of removing dissolved minerals and pollutants from seawater, brackish water, and treated wastewater Different desalination technology has been developed based on evaporation and membrane technology Table 1. 1 2


       Table 1 Desalination technology and mechanism 2

Most of the desalination plants are built on the coastline, where seawater is used to produce fresh water. The brine water (BW) is the byproduct of the desalination process and is discharged into the sea again by channels or pipelines. It has a high concentration of dissolved minerals, salts, and temperature compared to seawater. The brine characteristic depends usually on the type of feed water and desalination process, recovery percentage, and chemical used in the desalination process 2 3.

The BW has two different behaviors when it is dumped into seawater. The first behavior is near the discharge point, and it is called the near field region behavior. The second behavior is far from the discharge point, and it’s called the far-field region behavior. The Near-field region depends on the design of the brine discharge system, which is intended to increase the dilution rate at this region. The Far-field region is located far from the discharge point, where the brine is flowing down the seabed due to gravity current. In far regions, the brine mixing with seawater depends on ambient conditions and density differences between the Hypersaline brine and the receiving seawaters.

Figure 1 shows the near and far-field region 1.

BW discharge to seawater can cause a change to seawater salinity, alkalinity averages temperature, and can cause a change in the marine environment. The BW characteristic usually depends on the type of feed water, desalination process, recovery percentage, and chemicals used in the desalination process. Also, Brine discharge into seawater has several environmental impacts on marine life.4

The List of the environmental Impacts of a desalination plant on the seawater environment includes salinity, Temperature, Dissolved Oxygen, Chlorine Concentration, unionized ammonia, and Seawater Intake.

BW Salinity can lead to an increase in the seawater salinity level near the discharge point.  The negative effect of brine discharge occurs with the sensitive marine ecosystems 3 4. According to the Medeazza study, changes in the salinity of seawater have a potential to heavily affect marine biota. Changes in Seawater salinity affect the propagation activity of the marine species, their development, and growth rate. “Larval stages are very crucial transition periods for marine species and increasing salinity disrupts that period significantly”  5 6.

Also, some of the desalination plants are combined with power plants. Power plants produce water effluent at high temperatures. These water effluents are mixed with BW from the desalination plant and discharged into seawater causing an increasing the seawater temperature between 7 °C to 8 °C. The raises in the seawater temperature leading to a change in species composition and abundance in the discharge region. 4 6

Seawater dissolved oxygen level is a very important factor and depends on the temperature. By increasing the temperature of the seawater near the discharge point, the amount of dissolved oxygen will decrease. That causes Hypoxia, which is resulting from the low level of dissolved oxygen concentration in water, and it can cause serious damage for the marine life 6 4

Moreover, the presence of high chlorine concentration in BW can lead to the formation of hypochlorite and hypobromite in seawater, which affect seawater quality and the ecological system. Chlorine affects the fish and marine invertebrates can cause burns in both of them and resulting in serious damage to the marine organisms (Boumis). 4

Ammonia substances and un-ionized ammonia are very toxic to marine life. The ratio of ammonia substance and un-ionized ammonia are PH dependence. With increasing the PH, the concentration of both ammonia substance and un-ionized ammonia increases. The concentration of both ammonia substance and un-ionized ammonia in the discharge region depends on the size of the plant and the ambient seawater conditions. Usually, the concentration of ammonia substance and un-ionized ammonia should meet the water quality standard because they are very toxic and harmful for marine life 4 (Mohamed 2009).

Seawater Intake has the most impact on marine life.  Substantial Seawater intake can be very harmful to marine life, by causing Entrainment & impingement. Impingement happens when large organisms such as fish are pulled into the water intake pipe and looked in intake pipe mesh, causing death or injury of these organisms. Entrainment happens when small organisms pulled into the water intake pipe and pass the intake pipe mesh to feed the water tank, causing the death of these organisms in a pre-Chlorination process 6

Nowadays, the continuous increase of water desalination plant numbers led to the development of methods and processes to minimize the negative impact of BW discharge. There are many strategies for decreasing the negative impact of brine discharge. The main strategies include BW treatment before discharge and redesigning the desalination plant.6

Desalination plant brine can be treated before discharging into seawater to reduce the impact on the marine environments. In brine discharge into the seawater surface, outfall diffusion devices such as diffusion nozzles can be used to dilute the brine with the surface seawater. Also, the brine can be diluted with treated wastewater before the discharge into seawater. Further, the brine can be evaporated naturally by spreading it in pools and reused the solids lefts. These strategies are suitable for small and medium-sized desalination plants. It reduces the salinity of the brine and decreases the negative impact on the marine environment 6 7 8

The environmental impact for desalination plants can also decrease by designing them in a sustainable way and by installation mechanisms reduces their negative impact. Beach wells or infiltration galleries are one of the mechanisms that are used to reduce the negative impact. Beach wells or infiltration galleries work as a natural filter for feed seawater. It keeps out the marine organism, increases the quality of feed water, reduces the cost of pretreatment and Impingement, and entrainment. Jet brine release is another mechanism that can be added, where the brine released at an angle of 30-45⁰ can enhance brine mixing and offshore transport in coastal water. This leads to a decrease in the intensity of brine plumes resulting in a decrease in the salinity level 8 9.

However, BW management is on from the biggest challenge economically and environmentally. But Still, BW monitoring and quality standards should be applied in the desalination plant. More research and development in the field of brine impact on the environment and processes to reduce this impact should be further investigated. Research and comprehensive studies to minimize the negative impact of desalination plants should be carried out in water research centers and water authorities.


1.      Palomar P, J. I. Impacts of Brine Discharge on the Marine Environment. Modelling as a Predictive Tool. In: Desalination, Trends and Technologies. ; 2011. doi:10.5772/14880

2.      Danoun R. Desalination Plants: Potential impacts of brine discharge on marine life. Final Proj Ocean Technol Gr. 2007.

3.      Panagopoulos A, Haralambous KJ. Environmental impacts of desalination and brine treatment – Challenges and mitigation measures. Mar Pollut Bull. 2020. doi:10.1016/j.marpolbul.2020.111773

4.      Dawoud MA. Environmental Impacts of Seawater Desalination: Arabian Gulf Case Study. Int J Environ Sustain. 2012. doi:10.24102/ijes.v1i3.96

5.      Meerganz von Medeazza GL. “Direct” and socially-induced environmental impacts of desalination. Desalination. 2005. doi:10.1016/j.desal.2005.03.071

6.      Ahmed M, Anwar R. An Assesment of the Environmental Impact of Brine Disposal in Marine Envirnmento. Int J Mod Eng Res. 2012;2(4):2756-2761.

7.      Castillo RS, Maria J, Sanchez S, Castillo NS. Brine Discharge Procedures to Minimize the Environmental Impact and Energy Consumption. October.

8.      Salt HITS. Desalination: is it worth its salt? A Primer on Brackish and Seawater Desalination. 2013;(November).

9.      Laspidou C, Hadjibiros K, Gialis S. Minimizing the environmental impact of sea brine disposal by coupling desalination plants with solar saltworks: A case study for Greece. Water (Switzerland). 2010. doi:10.3390/w2010075

The leading-role in food production: phosphorus rocks



t is undeniable that phosphorus is vital for life – literally. It is an essential nutrient for all living forms since it plays an important role in DNA/RNA molecules, and is also related to cellular energy transport via ATP (i.e. the P in ATP – the molecule that carries energy around cells) [1]. Phosphorus is not found free in nature, due to its reactivity to air and many other oxygen-containing substances, but it is widely available in different minerals. Phosphorus rocks are a non-renewable resource originated from igneous rocks and marine sedimentary deposits. The widely used approach to obtain these rocks which contain a high content of phosphorus is by mining [2, 3].

Phosphorus rocks are used worldwide for many industrial applications such as detergents, food and drinks, metallurgy. However, the most important use of phosphorus rocks is for the production of phosphate fertilizers [4]. Agriculture is by large the main user of phosphorus globally, accounting for between 80-90% of the total world demand [5]. Phosphorus is one of the three macro-nutrients needed by plants to develop and grow. Together with nitrogen (N) and potassium (K) nutrients, phosphate (P) plays a leading-role in NPK fertilizers which are essential for optimal growth of crops [6]. Unfortunately, a shortfall of phosphorus in soils will result in a reduction of crop yield and can affect food production worldwide.

Phosphorus rocks reserves are being mined at growing rates due to increasing demand. According to the United Nations Food and Agriculture Organisation (FAO), the world demand for fertilisers was estimated to increase around 3 million tonnes every year [7]. The potential threat of phosphorus global limitation has been discussed since the quality of the existing rocks is declining, making the extraction more expensive. Indeed, in 2014, the European Commission declared phosphorus rock as one of the 20 critical resources from the European Union [8]. Estimation of the remaining time phosphate reserves will last are variable and contested, ranging between 100 to 600 years at current production rates [9]. Some researchers have applied Hubbert’s concept of “peak oil” to phosphorus rock mining and named as “peak phosphorus” [10, 11]. Peak phosphorus refers to the moment when production of phosphorus from mining reaches a maximum (its peak); followed by the decrease in quality of the remaining reserves, making it harder to access. Then, mining and processing will be more expensive, which will result in the supply decline and rapidly increase of the prices [5]. Additionally, phosphorus rocks reserves come from a limited number of countries, with large parts of the world, including Europe, being almost totally dependent on imports. As shown in Figure 1, Morocco holds the vast majority of global supplies of this resource, approximately 73%. China is currently in second place with only 4% [10]. This is geopolitically sensitive as Morocco currently occupies Western Sahara and controls its phosphate rock reserves, which could present significant food security risks.

Figure 1: Estimated global phosphorus reserve distribution (USGS, 2017).

In order to ensure phosphorus remains available for food production to future generations, the development of novel phosphorus recovery and reutilization initiatives through more sustainable wastewater systems is needed. In particular, human waste from households contributes largely to the amount of nutrients found in waste streams. Approximately, ~50% of the phosphate mass load in municipal wastewater treatment plants comes from human urine. Therefore, urine could play the new leading-role in food production worldwide and help current global demand for phosphorus. Thus, a new perspective that re-evaluates human urine as a reusable and eco-friendly resource should be established. Phosphorus recovery from human urine represents a new promising avenue, since the recaptured phosphorus from waste streams can be utilized for fertilizer production. Additionally, the development of new wastewater systems can offer a sustainable form of sanitation for 2.5 billion people in developing countries that still have no access to proper sanitation [12]. From the extraction and reuse of phosphate from wastewaters, it promotes a circular and sustainable closed-loop of nutrients. And, at the same time, it could increase phosphate availability for fertilizer production worldwide.


[1] Oelkers, E. H., & Valsami-Jones, E. (2008). Phosphate mineral reactivity and global sustainability. Elements, 4(2), 83-87. 79.

[2] Hosni, K., & Srasra, E. (2010). Evaluation of phosphate removal from water by calcined-LDH synthesized from the dolomite. Colloid Journal, 72(3), 423–431. 80.

[3] Phosphate rock, 2021. (accessed 30/06/21).

[4] Cordell, D., Drangert, J. O., & White, S. (2009). The story of phosphorus: Global food security and food for thought. Global Environmental Change, 19(2), 292–305.

[5] Tirado, R., & Allsopp, M. (2012). Phosphorus in agriculture: problems and solutions. Greenpeace Research Laboratories Technical Report (Review), 2.

[6] NPK: What is it and why is it so important?, 2021. (accessed 30/06/21).

[7] FAO, 2017. World Fertilizer Trends and Outlook to 2020. Food and Agriculture Organization of the United Nations (FAO), p. 66. (accessed 30/06/21)

[8] European Commission (2014). Press Release: 20 Critical Raw Materials – Major Challenge for EU Industry. (accessed 30/06/21)

[9] Van Kauwenbergh, S. J (2010). World Phosphate Rock Reserves and Resources. Technical Bulletin IFDC-T-75.

[10] Cordell, D., & White, S. (2013). Sustainable phosphorus measures: strategies and technologies for achieving phosphorus security. Agronomy, 3(1), 86-116.

[11] Ashley, K., Cordell, D., & Mavinic, D. (2011). A brief history of phosphorus: from the philosopher’s stone to nutrient recovery and reuse. Chemosphere, 84(6), 737-746.

[12] Rollinson, A. N., Jones, J., Dupont, V., & Twigg, M. V. (2011). Urea as a hydrogen carrier: A perspective on its potential for safe, sustainable and long-term energy supply. Energy and Environmental Science, 4(4), 1216–1224.

Mountain ecosystem restoration for disaster mitigation in Pakistan


xtreme events associated with the universe are older than human origin on earth and they have coexisted with old civilizations (Khan & Khan, 2008), while during the first half-decade of the twenty-first century, great human influences in incidents of disasters have been observed. Irrespective of location, hazards of multitude nature threaten mankind (Pinkowski, 2008). Climate change today is a serious issue all around the world and a biggest challenge posing threat to the people and economies. IPCC (Inter-governmental panel on climate change) assessment report shows that crop yield rates are declining in most parts of the world, due to the consequences of rising temperatures, while prevalence of climate induced diseases has been observed too. Fresh water availability is at risk, especially in large river basins and it is anticipated that, it may impact billions of people by 2050s (Ashraf, 2014).

Pakistan holds a complex and remarkable physiographical features that include the Northern high mountain ranges (Karakurum, Himalayas, Hindukush), the snow covered peaks, western bordering highlands in the north, the salt range and Potohar plateau, Indus plain and the Baluchistan plateau (Earthquake Review, 2011). Pakistan, despite contributing less to natural disaster driving phenomenon, such as greenhouse gases, has been among the top ten most affected countries worldwide. Events like the phenomenal floods (2010) that submerged one fifth of the country, displacing millions of people and changing monsoon pattern is just a single example of natural disasters in Pakistan.  Climate change is expected particularly to affect the agriculture sector in Pakistan (Ashraf, 2014).

Figure: A problem tree indicating some of the causes and impacts of natural disasters in mountain areas.

The mountain regions of the world pose special challenges to sustainable development. They tend to be ecologically fragile; highly variable in terms of precipitation, temperature, and other factors; and prone to landslides and other natural disasters. Local communities are often dispersed, situated in remote locations, and economically and socially marginalized from national development processes (IUCN, 2003), but there are huge benefits associated with these regions. They are the protector of water catchments, and they have unique cultural as well as biodiversity assets. These areas are rich in natural resources. Managing the problems of hazards in these areas and enhancing capacities in the communities has become crucial.

Some 25 percent of the earth’s surface is mountainous, inhabited by 26 per cent of world’s population, and are source of fresh water for more than half of humankind. The crisis is due to cultural, ecological, social and economic changes at faster rates. Moreover, population growth, infrastructure development, deforestation, over-grazing, agricultural expansion, climate change and violent human conflicts all threaten this fragile environment. In 1992, the special needs of mountain regions were taken into account in the form of the Agenda 21, “Managing Fragile Ecosystems: Sustainable Mountain Development.” In 2002, the year was declared as the International Year of the Mountains. The year culminated in the Global Mountain Summit and adopted at the Bishkek Mountain Platform (IUCN, 2003). Reports by IUCN in the mountain areas of Pakistan situated in the Northern areas show that these areas are confronted by a wide array of problems and threats. Natural resources such as forests and biodiversity are being degraded; food security is diminishing; women’s workloads, poverty and vulnerability are on the rise; energy supplies are insufficient to meet demand; drinking water supplies are inadequate and frequently contaminated; and access to health and education services remains constrained by many factors. Although the report was drafted more than a decade back, the current situation indicates little improvement and needs further actions. This area remained unrepresented in national political forums.

This year, Pakistan hosting the World Environment Day 2021 is a great opportunity to recognize the importance of a healthy mountain ecosystem for sustainable development in Pakistan. The theme of World Environment Day 2021 is Ecosystem Restoration, and in the context of Pakistan, the mountain areas, housing diverse biodiversity and the fresh water sources require special attention. The slogan: “Recreate, Reimagine, Restore”, further calls for resource allocation and involvement of local communities in the environmental protection. Managing the human impacts on the mountain ecosystem also holds greater promises in mitigating the natural disasters. Because, the mountain areas of Pakistan are predicted to receive greater climate change impacts, one reason being the presence of high number of glaciers in the area. Furthermore, the local communities’ access to alternative economic sources will decrease the human dependence on natural resources and degradation of the environment.


Khan, H., & Khan, A. (2008). Natural hazards and disaster management in Pakistan.

Pinkowski, J. (Ed.). (2008). Disaster management handbook. CRC Press.

Ashraf, A. (2014).  The changing climate. Pakistan Today Magazine, 4, 286.

Government of Pakistan & IUCN. (2003). Northern Areas State of Environment and Development. IUCN Pakistan, Karachi, 301.

Earthquake Reconstruction and Rehabilitation Authority.(2011). Earthquake Review.

The REWATERGY experience (part 1)

Rubén Asiaín Mira


rowing up in Spain includes a life full of good food and great people. Besides that, I did my undergraduate in Chemical and Energy Engineering in Madrid. After I obtained my degree, I started working as an energy consultant, which gave me valuable experience in the industrial sector. After working for one year, I still wanted to stay in touch with the industrial world, but I was missing the “lab life” that research development had to offer. When I discovered REWATERGY, I realised that it was the project I was looking for! An industrial doctorate in the University of Cambridge with half of the project carried out in Aqualia, a Spanish water company. It would allow me to study abroad and then come back to Spain to continue with the development of my project in an industrial environment – what a perfect match! Now, fast-forward to the middle of the project, my period in the United Kingdom is about to end. When I look back on my time here, all I can recall are all these amazing new experiences I have been through. Everything happened in a flash: the beginning of the project, moving to a different country, finding accommodation and meeting a lot of new people. There are moments that will always be highlighted in my mind: the first project meeting in Cambridge, when we met the other ESRs and the rest of the beneficiaries; the first time in the lab, so excited about all the “toys” available to play with; the first training course of the project when we all went to Belfast for three days and get to know each other much better. And of course, every journey has a downside: the lockdown caused by COVID-19, when we had to stop our activity in the lab, and which was probably the part of all this adventure. Fortunately, after 4 months we were able to resume our activities in the “new normal” situation and zoom became our best ally for social interactions. It has been a beautiful ride to this point, with its ups and downs. Now it is the moment to pack up things again and get ready to move to a new destination. I’m looking forward to this new part of the project in Aqualia, knowing that it will be full of new incredible moments.

Conor Redick


oining the REWATERGY programme offered something old and something new to me- I have lived in Cork before, the location of my first secondment at Prophotonix and I have also lived in Spain before, albeit in Malaga and not Madrid. This is also my second stab at a PhD. It’s not often you get second chances, especially in programmes as competitive as MSCA. For me, it took the perspective of time away from scientific research to realise it was right for me. between my first attempt at a PhD and joining the REWATERGY programme, I spent time working for a spin-out company in Belfast which was perhaps the most exciting and valuable job I have had to date and also worked with a government innovation lab. In both cases, after the initial honeymoon period subsided, it was obvious that I wouldn’t be involved in the type of work that excites me without returning to complete a PhD. Whilst remaining on the island of Ireland, Cork and Belfast (my home city) are culturally very different places. Both cities have long strived to step out of the shadow of Dublin and fight for unique identities. This is my second time living in Cork, having spent a year in the seaside town of Kinsale during placement in University. It has been a very different experience second time round, with the pandemic making it difficult to set roots and make connections in the city. Unfortunately, my initial ambitions to get involved in drama groups and sports clubs in Cork gradually dwindled to just coping with the pandemic and progressing with the PhD. Nonetheless, I have been fortunate enough to have a small group of friends to share some experiences with in Cork, as well as supportive colleagues in Prophotonix to help me progress with PhD work.

Towards Smart and Resilient Cities


he World’s inhabitants moving from rural areas to cities are in continuous increase. Cities with high inefficient transportation systems and poorly designed buildings, and with high consumption of quantities of fossil fuels and high levels of greenhouse gases emission, are headed to an inevitable collapse. In response, smart cities can replace today’s carbon-consuming urbanism with a new sustainable one. Thanks to the integration of information and communication technology (ICT) and various physical devices connected to the IoT (Internet of things) network, transportation systems, and buildings can be developed towards greater sustainability and resilience [1].

Smart cities aim to improve efficiency, equity, and quality of life by using collected data from different types of electronic methods and sensor with the purpose of improving and optimizing the operations and the management across the city, such as traffic congestion, energy usage, water supply networks, waste, and air quality. In the smart city concept, the community interacts directly with the city infrastructures and services, giving a contribution to the data collected and develop a real-time response which also prepares the city to respond quickly to challenges. Thanks to the use of ICT, the empowerment of citizens is largely emphasized to create a widespread sense of social cohesion, awareness of the relevant issues, and active support of the citizens.

Climate change, water scarcity, and growing waste are three of the main environmental issues challenging in contemporary cities. The resilient city concept aims to increase the quality of life by absorbing and adapting any heterogeneous stress factor and guaranteeing citizens’ safety. Consequently, the integration of the two concepts, as shown in Figure 1, improves simultaneously and synergically the whole city concept. Mitigation strategies combined with adaptation strategies are key to counterbalance possible catastrophic impacts and to absorb the effects of hazards through adaptation and transformation.

Figure 1. Smart and resilient city value chain [2].

To achieve the goals of smart and resilient cities, electrical infrastructures, called smart grid, have a key role in the energy transition. Important objectives of smart grids are the implementation of renewable energy technologies to power entire urban areas, achieving net-zero carbon dioxide emissions, decentralizing power, water, and waste in small-scale systems, endorsing green infrastructure, moving from liner to circular systems, increasing communication among cities and regions in a bidirectional way, and finally achieving “electrification” which refers to transportation supplemented by electric vehicles. Figure 2 shows the expected structural changes from a traditional to a smart system in energy management, made possible by the increased use of digital tools.

Figure 2. Characteristics of a traditional system versus a smart system [3].

To promote the smart and resilient concept, the European Commission has launched the European Innovation Partnership for Smart Cities and Communities (EIP-SCC), with the aim to support the energy production, distribution, transportation, and digital technologies and to improve services while reducing energy, as well as greenhouse gas emissions and resource waste [4,5].

In smart cities, circular economy is a key concept. Our global consumption is exceeding the capacity of the planet to regenerate, and because of this, it is important to shift from a linear to a closed-loop system. The main idea is to minimise the use of resource inputs and the creation of waste by reusing, repairing, and recycling. Waste materials and energy are input for other processes. The circular model has to be employed in every industrial sector, in the economic, social, and environmental production and consumption. An example of the circular economy application is the recovery of nutrients and the production of bioplastics from daily processed wastewater streams. Also, the scarcity of water is already a serious problem and many territories have been affected by water shortages, which are destined to worsen as a result of climate change [6]. Therefore, the need to encourage the use of alternative sources of water and the reuse of wastewater. Furthermore, the need to focus on the sustainable use of natural resources, the fostering of environmental remediation, the improvement and enhancement of ecosystems, the management and protection of water and air quality, the monitoring of the response to environmental threats for human health.

In the face of climate change, it is important to develop solutions, technologies, and financial response to possible impacts. A key asset of smart and resilient cities is the dynamic interplay of learning capacity, persistence, adaptability, and transformability across multiple scales, as shown in Figure 3 [7,8]. The model is structured as a cyclical process characterized by three different stages connected through a feedback loop: strategies’ definition, implementation, and management. Along the process, there are different periods: short, medium, and long term. In the short term, strategies are orientated to improve cities’ capacities to climate-related impacts by increasing systems’ persistence. In the medium term, cities enhance their capacity to deal with unexpected impacts by improving systems’ adaptability. In the long term, strategies should drive the urban transition towards the prevention of future climate-related impacts by improving cities’ transformability.

Figure 3. The conceptual model for building up smart and resilient cities in the face of climate-related challenges [9].

The capacity of continuous and dynamic learning is crucial for the smart and resilient city concept. Learning capacity can be improved using several approaches such as networking, the ability to connect people and devices for exchanging data and information, monitoring, to detect conditions of urban system, knowledge, to elaborate the information, memory, to learn from past events and predict possible future scenarios, and collaboration and participation, to involve people in the decision-making process [9].

To conclude, it is important to move towards smart and resilient cities for both our safety and the one of our Planet. The aim is to live in a city capable to optimize and interconnect the components that characterize the urban systems by taking advantages of the modern technologies and the big data available. A creative city able to reinvent a new equilibrium against destabilizing external stresses and to adapt to new circumstances.


[1]        R. Chapman, Resilient Cities: Responding to Peak Oil and Climate Change, Journal of Urban Design. 17 (2012) 301–303.

[2]        A. Visvizi, C. Mazzucelli, M. Lytras, Towards an ICTs’ enabled integrated framework for resilient urban systems, Journal of Science and Technology Policy Management. 8 (2017) 227–242.

[3]        Bartz/Stockmar, Smart Grid – Staying big or getting smaller, (2018). (accessed April 2, 2021).

[4]        European Commission, Energy and smart cities, (2020). (accessed April 2, 2021).

[5]        European Commission, Analysing the potential for wide scale roll out of integrated Smart Cities and Communities solutions, (2016). Solution 80 Best Practice Examples.pdf (accessed April 5, 2021).

[6]        ENEA, Circular management of water resources, (2021). (accessed April 3, 2021).

[7]        C. Folke, S.R. Carpenter, B. Walker, M. Scheffer, T. Chapin, J. Rockström, Resilience thinking: Integrating resilience, adaptability and transformability, Ecology and Society. 15 (2010).

[8]        S. Davoudi, E. Brooks, A. Mehmood, Evolutionary Resilience and Strategies for Climate Adaptation, Planning Practice and Research. 28 (2013) 307–322.

[9]        R. Papa, A. Galderisi, M.C.. Vigo Majello, E. Saretta, Smart and Resilient Cities. A Systemic Approach for Developing cross-sectoral strategies in the face of climate change, TeMA Journal of Land Use, Mobility and Environment. 1 (2015) 1–49.

Advanced oxidation processes for the removal of contaminants of…


ater quality can be affected by contamination due to microorganisms, trace metals, toxic chemical compounds, changes in salinity, temperature or acidity. All this contamination is removed in water treatment plants, ensuring the required quality of the water for each purpose following the correspondent legislation. However, in recent years, there has been an increase in global concern about water pollution and especially about the rise of contaminants of emerging concern (CECs) [1]. Contaminants of emerging concern can be defined as organic micropollutants, natural or synthetic, that present potential risks to health and the environment and are not, or are just beginning to be, regulated by current legislation [2]. Within this group of contaminants, we can find everyday products such as pharmaceuticals and personal care products, surfactants, plasticizers or industrial additives. These pollutants can be found in urban water and effluents from wastewater treatment plants mainly originated in industries, hospitals, pharmaceutical factories and processes related to livestock and agriculture [3].

The main problem associated with emerging pollutants is that they are refractory compounds whose removal is not completely guaranteed with biological treatments in wastewater treatment plants. Once these pollutants and their metabolites reach aquatic ecosystems, they present toxic effects and bioaccumulation. Furthermore, the effect of some of these contaminants on human health is not fully understood, presenting a risk if they reach the human body [4]. As a consequence of their refractory behaviour, it is necessary to use alternative methods, capable of producing changes in their structure and degrade them, such as Advanced Oxidation Processes (AOPs) [1].

Figure 1. The pathways of the Contaminants of Emerging Concern [5].

The concept of advanced oxidation processes was first defined by Glaze et al. in 1987 as processes involving the production and utilization of highly reactive transient species, especially the hydroxyl radical [6]. This species presents a great oxidizing power as a consequence of its high redox potential (2.80 V). The hydroxyl radicals generated by the process are responsible for oxidizing the contaminants of emerging concern present in the water by different pathways, in many cases achieving total mineralization (i.e., full degradation into carbon dioxide and water). There are many different advanced oxidation processes that can generate hydroxyl radicals by the action of light and/or chemical agents [7].

Figure 2. Classification of advanced oxidation processes [7].

Recently, heterogeneous photocatalysis has become one of the most studied AOPs. This process is based on the use of a solid semiconductor that is activated by the action of light. When the catalyst is irradiated it absorbs light so electrons “jump” from the valence band to the conduction band, creating an electron-hole pair (e/h+). Of these two formed species, the hole can react with water, oxidising it to produce the desired hydroxyl radicals. One key factor of photocatalysis is the wavelength of the light used. The energy of the light has to be enough to overcome the energy bandgap of the photocatalyst. Although several semiconductors can be used as photocatalysts, titanium dioxide is the most widely employed [7]. However, with a bandgap of 3.2 eV, it requires ultraviolet light for its activation, which requires a lot of energy. Hence there is a lot of research working for being able to carry out photocatalysis with solar radiation, aiming for a more sustainable process [8].

Figure 3. Reaction mechanism of radical generation through irradiation of a photocatalyst [7].

AOPs are usually limited by the rate of radical production and not so much by the degradation reaction of contaminants. An important role in the rate is played by the presence of radical scavengers, mainly dissolved organic matter, that can have a much higher concentration than CECs, blocking their degradation. Therefore, this process must be placed at the end of the water treatment, when other contaminants that can inhibit the degradation have already been removed.

Summing up, CECs present a risk to the environment and human health so they are starting to be regulated and need to be removed in WWTPs. Advanced oxidation processes can be the solution to this problem, in which photocatalysis can play an important role, especially if it can be achieved using solar light. This process could be installed in the tertiary treatment of wastewater treatment to ensure the removal of these pollutants.


[1] M. Salimi et al., “Contaminants of emerging concern: a review of new approach in AOP technologies,” Environ. Monit. Assess., vol. 189, no. 8, 2017.
[2] T. Deblonde, C. Cossu-Leguille, and P. Hartemann, “Emerging pollutants in wastewater: A review of the literature,” Int. J. Hyg. Environ. Health, vol. 214, no. 6, pp. 442–448, 2011.
[3] A. Pal, K. Y. H. Gin, A. Y. C. Lin, and M. Reinhard, “Impacts of emerging organic contaminants on freshwater resources: Review of recent occurrences, sources, fate and effects,” Sci. Total Environ., vol. 408, no. 24, pp. 6062–6069, 2010.
[4] S. A. Fast, V. G. Gude, D. D. Truax, J. Martin, and B. S. Magbanua, “A Critical Evaluation of Advanced Oxidation Processes for Emerging Contaminants Removal,” Environ. Process., vol. 4, no. 1, pp. 283–302, 2017.
[6] Quiroz, M. A.; Bandala, E. R.; Martínez-Huitle, C.A. Advanced Oxidation Processes (AOPs) for removal of pesticides from aqueous media. In: Pesticides- Formulations, Effects, Fate. Editor: Margarita Stoytcheva. InTech, 2011.
[7] G. Divyapriya, I. M. Nambi, and J. Senthilnathan, “Nanocatalysts in fenton based advanced oxidation process for water and wastewater treatment,” J. Bionanoscience, vol. 10, no. 5, pp. 356–368, 2016.
[8] C. Sordo, R. Van Grieken, J. Marugán, and P. Fernández-Ibáñez, “Solar photocatalytic disinfection with immobilised TiO2 at pilot-plant scale,” Water Sci. Technol., vol. 61, no. 2, pp. 507–512, 2010.

Taking a look underwater


hen we think at the sea and the thousands of varied animals living in them, certainly an image pops up in our head: the coral reef. Besides being spectacular and colourful ecosystems, home to very diverse organisms, coral reefs are also source of food, medicine, income and provide coastal defence to more than 500 million people [1]. This outstanding underwater ecosystem, comparable to an underwater rainforest, is today being threaten. This complex system, which can take thousands of years to form, risks to disappear in mass, resulting in an inestimable environmental catastrophe.

Coral reefs are large underwater structures composed of colonies of individual organisms, named polyps. The backbone structure is a robust protective exoskeleton derived by calcium carbonate. The polyps host inside them the zooxanthellae algae, which is responsible for their colours. In this symbiotic relationship, the algae produce oxygen and organic products (main source of nutrients for the coral itself) through photosynthesis from the CO2 and waste provided by the coral. This beneficial cooperation is highly affected by environmental conditions, such as water purity and water temperature.

Different species of coral reefs are found in more than hundred countries all over the planet. They are mostly found in tropical regions, where the right combination of sunlight, water temperature and nutrients allow them to healthily grow at a speed that can range between 0.5 and 10 cm per year. Some of these enormous coral atolls are considered one of the oldest inhabitants of the oceans. One example, the coral triangle, located in the Pacific Ocean around the waters of Philippines, Malaysia and Indonesia, which is recognized as one of the most diverse marine ecosystems on the Earth.

In the past years, thanks to a collaboration between Google Maps and The Catlin Seaview Survey, it was made possible to admire these marvellous ecosystems and to dive into the ocean comfortably from your couch (which can be a real turning point in “Corona-time”, when real life adventures are rarely possible!). For this peculiar project a special underwater camera, Seaview SVII, was designed to acquire unique, stunning imagines in “street-view” mode; now available on Google Maps ( The broadcasting of these ecosystems has great impact in moving the social awareness to an urgent environmental problem, at global scale.

Underwater “street-view” of the coral reef in The Great Barrier Reef available on Google Maps.

When coral reefs are under stress, they expel the zooxanthellae algae, turning white and losing their inner source of nutrients; this is event is referred as coral bleaching. Most of the big scale bleaching events are linked to the increased temperature in the water. The Intergovernmental Panel on Climate Change (IPCC) declared that with an increase of water temperature of just 1-to-2-degrees, the coral reefs would suffer from high mortality rates. In some circumstances, some corals might be able to recover after a coral bleaching event, but this regeneration can take up to 10-15 years. However, repetitive bleaching events over a short period of time result lethal, as corals do not have enough time to recover. The longest bleaching event was reported from 2014 to 2017, were 70% of earth coral reef were damaged [2]. A recent study has stated that heat stress has caused the Great Barrier to lose significant coral population and that the possibility for the recovery of these corals is uncertain due to increasing intensity and frequency of the disturbance events [3].  A different study has also recorded a drop of 89% below historical levels in the number of newly born larval landing on the reefs [4]. Climate change impact on coral wealth also includes weakening of coral skeletons due to water acidification and the reduction of sunlight due to sea level rise. The extent of these events seriously increases the concern among the scientific community.

Picture of a healthy coral (on the left), compared to a bleached coral (on the right), (Source – Great Barrier Reef Foundation, accessed 25th February 2021). 

Scientists around the world are currently working to increase our understanding on coral reef adaptability and restoration. For example, genetics studies are being undertaken with the hope that in the future reefs could be restored with heat tolerant coral [5]. Many innovative and interesting projects have been launched on artificial 3D printed reef structures, with the aim of saving this ecosystem from a complete disappearance. The Caribbean Marine Biological Institute (CARMABI) research station conducted a study to understand where corals prefer to anchor. The highest rate of repopulation was observed for pink and white coloured structures with holes and crevices [6]. Moreover, researchers from Cambridge University and University California San Diego have made 3D scans of living coral and managed to bio-print reproductions using polymers and hydrogels that contain cellulose materials which imitates optical properties of corals [7]. Furthermore, SECORE International is trying to produce cost-efficient 3D printing seeding substrates to improve the survival rate of coral larvae [8].

In conclusion, mass coral bleaching, and consequent deterioration of coral reefs, is one of the consequences of climate change on large scale. This hidden underwater ecosystem is undergoing tremendous changes, which are not as easily observable as other devastating events occurring on the Earth’s surface. It is important to bring scientific and technologic innovations towards rescuing these unique marine ecosystems and their incomparable biodiversity. Until we can mitigate climate change, it is necessary to raise social awareness on the preservation of any threated ecosystems, including the ones hidden from our view.

[1]        Hoegh-Guldberg O, Pendleton L and Kaup A 2019 People and the changing nature of coral reefs Reg. Stud. Mar. Sci. 30 100699


[3]        Dietzel A, Bode M, Connolly S R and Hughes T P 2020 Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef Proc. R. Soc. B Biol. Sci. 287 20201432

[4]        Hughes T P, Kerry J T, Baird A H, Connolly S R, Chase T J, Dietzel A, Hill T, Hoey A S, Hoogenboom M O, Jacobson M, Kerswell A, Madin J S, Mieog A, Paley A S, Pratchett M S, Torda G and Woods R M 2019 Global warming impairs stock–recruitment dynamics of corals Nature 568 387–90



[7]        Wangpraseurt D, You S, Azam F, Jacucci G, Gaidarenko O, Hildebrand M, Kühl M, Smith A G, Davey M P, Smith A, Deheyn D D, Chen S and Vignolini S 2020 Bionic 3D printed corals Nat. Commun. 11 1748


UV and COVID-19


he coronavirus vaccine gives us much needed hope that the end of this global pandemic is approaching, as many people want to leave their homes, return to work and get life back to normal. Social distancing, masks, sanitization and hand washing have become a part of, what is being termed, “the new normal”. While these measures have helped limit the spread of the virus to a certain extent, not all forms of transmission have been prevented. Particularly indoors and on surfaces have been a point of major concern for health authorities and countries. The scientific community studying the virus suggest that the novel SARS-CoV-2 stays alive in the air for a number of hours and on some surfaces – for days, going to a normal state of life seems to be a far-fetched hope for citizens.[1]

Universities and companies all over the world have been trying to find ways to disinfect surfaces and air to provide a safe environment for all. Ultraviolet light has been known for its disinfection capabilities since the late 1800s. Scientists discovered that shorter wavelengths, now called UV-C, of UV emitted by the sun, could kill bacteria. UV-C is the shortest and most effective form of ultraviolet, also called germicidal UV, which has been studied for its sterilization properties.   Unlike the longer wavelengths of UV from the sun, UV-C rays are mostly filtered out by the ozone layer protecting the earth’s surface. This has enabled the use of this form of light for effective disinfection as the microbes have not had a chance to adapt to them. Hospital and water treatment plans have relied on UV-C to kill mold, viruses and other microorganisms.

Promising research has been conducted into the study of the effectiveness of UV-C Light on SARS-CoV-2. One of the first studies was done by Christiane et al. in December 2020 to prove the use of UV irradiation on the virus. The paper highlighted that the virus is highly susceptible to irradiation with ultraviolet light [1]. The team of researchers isolated the virus from the nasal swab of a patient suffering from COVID-19. UV exposure was conducted with UVC (254nm) and UVA (365nm) sources from Herolab, Germany. They achieved complete inactivation of the SARS-CoV-2 in 9 minutes at a total emitted dose of 1048mJ/cm2 and confirmed that UV-C irradiation is an effective method for inactivation of the virus.

Another study, published in November 2020, by researchers of Tel Aviv University (TAU) provided similar findings. These researchers used UV-LEDs and have concluded the optimal wavelength for killing the coronavirus. They reported that UV-LEDs operating at a peak wavelength of 285 nm was most efficient considering cost and availability.  [2]

“It doesn’t kill the virus — it renders it unable to reproduce,” says Jim Bolton, Environmental engineer, University of Alberta in conversation with Leslie Nemo

As a result of some studies, UV-C light emitting machines are being utilized in empty subway cars, buses and trams for sterilization. The technology has slowly made its way into consumer culture as well in the form of UV-C wands, lamps and devices for homes and office spaces.

UV-C has found its way into multiple applications during the course of the global pandemic. It has been proven for its effectiveness in the removal of bacteria from water and disinfects surfaces. Some new devices have been introduced into the market. LARQ self-cleaning bottle is one of them. Labelled as “the world’s first self-cleaning bottle and purification system”, it uses UV-C LED light to eliminate bio-contaminants from the bottle [5]. Some other products that were introduced during this time are – the LG wireless earbuds [4], SEIT-UV Autonomous disinfection Robot [3] and Perscientx Violet [6]

With UV light making a mark as an efficient way to kill the virus, more and more interest grew in the use of it to disinfect spaces and surfaces. The city of New York tested the use of ultraviolet lamps to kill the virus on buses and subways. [7]

UV technology at a subway maintenance facility in NYC (Source – CBSnews article dated May 20,2020)

There is an increasing focus on the addition of UV technology for air treatment in the transport industry. The Sonoma Marin Area Rail Transit (SMART) installed UV Light sterilization on their trains on a trial run in 2020 and have been using this technology since. [8]

As a result of increased interest and results, many governments across the globe have taken measures to fully understand the use of UV light to provide safety to their citizens. A new initiative announced in Australia, according to SBS News, mentioned that the federal government has announced 10 million USD for clinical trials of some coronavirus-related technologies. [9]

There has been a huge rise in the number of UV devices in the market due to COVID-19. But, here is the bad news- yes, there are some great results that have been seen using a UV light for disinfection, but not all devices in the market do the job. Some manufacturers use words such as “sterilizing”, “disinfecting” and “germicidal” to reference a device’s ability to kill germs but do not mention which germs. UV-C rays are not safe for human exposure. Some of the devices in the market, claiming to be UV-C, emit completely different wavelengths of light. UV-C light is in the range of 100-290nm whereas the devices that are in the market emit light in the range of 400-500nm(giving a purple hue when seen by the user).

UV Wand on Amazon UK

Be aware of such devices and it is highly recommended not to buy them. The international organization for standardization(ISO) has set out documents for safety limits while handling UV-C Devices in ISO 15858:2016. The European Commission has a safety gate alert system that will help to stay away from these dangerous devices. It can be found on . If you type in – UVC in the free text category, a large list of products that have been banned from the market can be seen. The lighting industry association of UK, in September 2020, released an article warning all users about potentially dangerous products and advising not to buy any UV-C products without seeks assurances that they are safe for use.[10]

Bottom Line

The most effective type of UV light to kill the coronavirus is UV-C. It can effectively disinfect surfaces and spaces. Due care must be taken while choosing the device to do the task depending on the target. While it can disinfect and sterilize the region targeted, the user must be at a safe distance and limit exposure to UV irradiation.


  1. Heilingloh, C.S., Aufderhorst, U.W., Schipper, L., Dittmer, U., Witzke, O., Yang, D., Zheng, X.,Sutter, K., Trilling, M., Alt, M., Steinmann, E., Krawczyk, A., 2020. Susceptibility ofSARS-CoV-2 to UV irradiation. Am. J. Infect. Control 48, 1273–1275.
  2. Gerchman, Y., Mamane, H., Friedman, N., Mandelboim, M., 2020. UV-LED disinfection ofcoronavirus: wavelength effect. J. Photochem. Photobiol. B Biol. 212, 112044.