Brine entering the Mediterranean, 300 metres off the coast of Israel. (Image: Hagai Nativ / Alamy) ESR4 - Salem Alkharabsheh

Environmental Impacts of brine discharge from Desalination plant on…

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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.

References

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

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Covid-19: Potential Wastewater Risks

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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.

References

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