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Article

Comparative Life Cycle Assessment of Four Municipal Water Disinfection Methods

by
Mehmet Zahid Demir
1,
Huseyin Guven
1,
Mustafa Evren Ersahin
1,2,
Hale Ozgun
1,2,
Mehmet Emin Pasaoglu
1,2 and
Ismail Koyuncu
1,2,*
1
Civil Engineering Faculty, Environmental Engineering Department, Istanbul Technical University, Ayazaga Campus, Maslak, Istanbul 34469, Turkey
2
National Research Center on Membrane Technologies, Istanbul Technical University, Ayazaga Campus, Maslak, Istanbul 34469, Turkey
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(14), 6104; https://doi.org/10.3390/su16146104
Submission received: 29 May 2024 / Revised: 21 June 2024 / Accepted: 26 June 2024 / Published: 17 July 2024
(This article belongs to the Special Issue Water Environmental Control of Pollutants and Environmental Sustainability)
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Abstract

:
The disinfection of treated water is an important process to provide healthy water to the public. The chosen disinfection methods can vary depending on the water source, regulations, targeted microorganisms, operating conditions, capital costs and operation and maintenance costs. Another important factor for decision-makers is the environmental impacts caused by the disinfection process. This paper will reveal the life cycle assessment (LCA) of four different water disinfection scenarios at a municipal scale from the operational phase. A comparison is made between chlorination systems, two ultraviolet disinfection systems that use different types of lamps and an ozonation system. The results demonstrate that the UV disinfection system with low-pressure lamps had the lowest environmental impact across all categories, followed by chlorination. In contrast, the ozonation system and the UV disinfection system with LED lamps showed the highest impacts in all categories, primarily due to their high electricity consumption. Changes in the electricity mix had a substantial influence on the impact categories for all disinfection methods, but the gradation of the water disinfection methods was not that significant. Studies on the environmental impacts of the water disinfection process need to be carried out for larger flow rates to increase the information on this topic.

1. Introduction

Historical recordings show that activities to improve the aesthetics of water go back to 4000 B.C. [1], when they made water treatments using physical methods. With the invention of the microscope and finding about animalcules [2], the connection between drinking water and health started to be investigated. An important milestone for water and health was the introduction of Germ Theory by Pasteur, which indicated that organisms were responsible for the spread of infectious diseases [3]. Water is a pathway for viruses, bacteria and protozoa to transmit to humans, and different types of effects on human health are observed when unsafe drinking water is consumed. The health effects include diarrhea, gastroenteritis, acute gastroenteritis, vomiting and nosocomial infections [4]. Annual causes of death related to unsafe water are around 829,000 worldwide [5] and around 255,500 of these are children [6]. These deaths have a major social impact on society, which also causes an economic impact. A person who is affected by a waterborne pathogen is treated, and while their treatment continues, there are direct costs, indirect costs and intangible costs that have an impact on public and personnel budgets [7]. Waterborne diseases are not only a concern for developing countries, but they also affect developed countries [8]. A study by Collier et al. [9] showed that around 7.15 million illnesses are caused by drinking water, and the burden on the economy in the USA is USD 3.33 billion. The solution for safe drinking water comes from comprehensive and proper disinfection following water treatment.
The need for water disinfection was understood after it was discovered that water is a pathway for transmitting diseases. Chlorine usage for drinking water disinfection started to spread after it was introduced for municipal water disinfection in 1902 in the city of Middelkerke, Belgium [10]. Different water disinfection methods, such as ozone and UV, were tested and started to be used in a similar time phase. The first country to use ozone as a water disinfectant was the Netherlands, and they used ozone in the water treatment plant in the city of Oudshoorn in 1893 [11]. Ozone disinfection remains widely used in major cities such as San Diego [12], Tokyo [13] and Zürich [14]. In 1910, the first ultraviolet (UV) water disinfection system was installed in Marseilles, France [15]. Since then, UV water disinfection systems have been implemented in numerous cities, including New York [16], Berlin [17], St Petersburg [18], Las Vegas [19] and Wien [17], showcasing their widespread usage and effectiveness. The working principles of UV, ozonation and chlorination are different. Chemical methods such as ozonation and chlorination inactivate microorganisms by oxidatively degrading amino acids, damaging DNA and RNA, and altering cell membrane permeability [20]. Chlorination has advantages, such as lower investment and operation costs, is an easy-to-operate well-known technique, and has a residual effect. Still, it also has disadvantages, such as the taste and odor of the water, the formation of disinfection by-products (DBPs) [21], not being effective for certain microorganisms, such as cryptosporidium, requiring care and attention for operators and being corrosive [22]. The ozonation process uses the ozone for the disinfection process and can work in a wide range of pH and temperature. While having a positive impact on the taste and odor of water, it is highly corrosive and requires corrosion-resistant material [23]. Unlike chlorine and ozone, UV is a physical disinfection method [24]. The working principle of UV disinfection is based on the UVC light produced by various types of UV lamps, such as low-pressure (LP) amalgam UV lamps, low-pressure high-output (LPHO) amalgam UV lamps, medium-pressure mercury UV lamps and light-emitting diode (LED) UV lamps. UVC light damages nucleic acid, which is responsible for the reproduction of microorganisms [25]. This process is called inactivation rather than destruction because the microorganisms are not killed. The implied UV dosage and contact time are very important for UV water disinfection systems because microorganisms can repair themselves if the suitable UV dosage and contact time are not applied [26,27]. The main consumption of the chlorination system is chemical, while for UV and ozonation systems, it is energy. When choosing a water disinfection method, multiple criteria, such as targeted microorganisms, disinfection by-products (DBPs), the need for residual disinfectant, land use, regulations and operational conditions, play an important role. In a study by Gelete et al. [28], UV disinfection was compared with ozonation, chlorination, chloramination and chlorine dioxide in terms of their operational aspects and efficiency. The results show that UV disinfection is significantly more convenient in terms of operational aspects and efficiency, although it is unsuitable for providing residual disinfection.
Life cycle assessment (LCA) is a tool that can be used to understand the environmental impacts of a product, process or service throughout its life cycle [29]. LCA was standardized by the International Organization for Standardization (ISO) in 1997 with the first publication of ISO 14040. The latest update was published in 2020 with the amendment of the 2006 version [30]. Reviewing the literature reveals that the availability of studies on the LCA of the drinking water disinfection process is limited. The LCA of the water disinfection process was managed as a part of the whole water treatment process, and the impacts of water disinfection were compared with other processes at a water treatment plant as a contributor. There are only a limited number of papers that compared UV disinfection with chemical disinfection and only focused on the LCA of water treatment disinfection techniques. It was observed that there were more articles on the LCA of wastewater disinfection than the LCA of water disinfection. There were more studies on wastewater disinfection due to the importance of the disinfection process having a key role in the reclamation [31] and reuse of treated wastewater [32]. In the case of residual disinfectant requirements, UV systems were combined with a chemical disinfectant. In a study by Jachimowski and Nitkiewicz [33], the authors compared gas chlorine with a combination of UV and sodium hypochlorite. Another study on the LCA of water disinfection was made by Mo et al. [34] in order to analyze four alternative disinfection methods’ environmental impacts in order to reduce DBPs. The comparison of water disinfection methods is sometimes combined with other research topics. Romanovski et al. [35] combined their LCA water disinfection study with the corrosion effect of disinfectants. Some LCA studies on the topic of our paper use more than one scenario to make a comparison between the disinfection methods. Busse et al. [36] compared solar radiation disinfection, UV LED disinfection, a low-pressure mercury UV lamp and chlorine-based disinfection on different amounts of water disinfected with different life spans. It can be clearly seen that LCA studies on water disinfection are studied individually or together with aspects that will provide information to the public, researchers and decision-makers.
Studies on the effects of residual disinfectants demonstrate that they have no significant influence on the protection of water distribution systems when used [37]. Furthermore, they have a favorable influence on the growth of biofilms [38]. Residual disinfectants are not utilized in water treatment and delivery systems in the Netherlands since they are thought to have more detrimental effects than advantages for end users. They strive to prevent contamination of the water supply system and create biologically stable water rather than utilize a residual disinfectant [39]. Another study on the subject found that utilizing a residual disinfectant is insufficient for protecting water supply systems against pathogens. The study evaluated the occurrence of E. coli in water supply systems and evaluated the situation in Germany, the Netherlands, and France [40].
The purpose of this study is to examine the function of four different full-scale (municipal-level) water disinfection technologies from an LCA standpoint. This research distinguishes itself through its unique dataset and innovative approach, concentrating exclusively on comprehensive water disinfection technologies. Utilizing onsite data from a large-scale, operational water treatment facility, this study encompasses established and emerging disinfection technologies. The findings identify critical environmental impact factors and delineate essential components of an effective water disinfection system, providing forward-looking insights.

2. Materials and Methods

2.1. Goal and Scope

The goal of this study is to compare the environmental impacts of different water disinfection methods for a municipal water treatment plant. The study compares the environmental impacts of four different water disinfection methods, including chlorination, ozonation, LP UV and LED UV, for the operational phase only. The reason for carrying out this study is to compare the alternative water disinfection methods to supply safe drinking water for public use with the lowest environmental impact. The findings of this study will serve as a valuable resource for future researchers, helping them fill the gap in the LCA for drinking water disinfection technologies. The Local Water Administration (LWA) wants to reduce the usage of gaseous chlorine and build an effective water disinfection system. The disinfection level is determined by meeting the limits regulated by the governmental authorities, which is in line with the EU drinking water regulations, requiring zero Escherichia coli and intestinal enterococci [41].
The functional unit (FU) chosen for this research was 1 m3 of disinfected water ready to be distributed to the main water supply network of the city. The current disinfection method, which is the baseline scenario, uses gaseous chlorine for disinfection that is transported to the WTP in tanks. The baseline scenario was compared with closed-vessel UV systems with LP amalgam lamps, an ozonation system and a closed-vessel UV system with UV LED lamps. It was accepted that the water supply network was free of contamination, and no residual disinfectant was required. The amount of residual disinfectant used in the baseline scenario was excluded from the calculations. Water disinfection systems were located straight after the treatment process. The system boundary for all four water disinfection systems was limited to energy consumption, chemicals and the transportation of equipment (except spare parts). The structural construction and dismantling phases were not included in the system boundary due to their low impact, which was negligible. Earlier publications on the LCA of water treatment facilities show that the environmental impacts generated by the construction and dismantling phases are insignificant when compared to the operational phases [42]. ReCiPe (representing the institutions that contributed: RIVM, Radbound University, CML and Pre Consultants) 2016 methodology, an LCIA calculation methodology, was applied, which addresses 18 midpoint impact category indicators. The addressed impact categories are global warming (GWP), stratospheric ozone depletion (ODP), ionizing radiation (IRP), ozone formation–human health (HOFP), fine particulate matter formation (PMFP), ozone formation–terrestrial ecosystems (EOFP), terrestrial acidification (TAP), freshwater eutrophication (FEP), marine eutrophication (MEP), terrestrial ecotoxicity (TETP), freshwater ecotoxicity (FETP), marine ecotoxicity (METP), human carcinogenic toxicity (HTPc), human non-carcinogenic toxicity (HTPnc), land use (LOP), mineral resource scarcity (SOP), fossil resource scarcity (FFP) and water consumption (WCP). Foreground data were gathered from the WTP operators and the literature, while for the background, the Ecoinvent database was used. Figure 1 shows the system boundary of this LCA study.

2.2. LCI

The second step of an LCA study is the Life Cycle Inventory (LCI), which is critical for the subsequent impact calculations. This phase includes key parts, such as data collection, calculation of the collected data and data validation. The water treatment plant used for this LCA analysis provides drinking water for a population of 607,502 and uses a lake as a water source. The treatment method comprises treatment tanks that utilize conventional water treatment processes (physical treatment, chemical treatment and disinfection). The WTP has a current capacity of 9072 m3/h, with a maximum capacity of 12,960 m3/h. Figure 2 illustrates the location of the Water Treatment Plant (WTP) in Turkey, situated at the coordinates 40°44′50.55″ N and 30°21′51.78″ E. The water network is monitored for DBP forms while being disinfected with gaseous chlorine. Despite the fact that the treated water is disinfected and extra disinfectants are used for residual disinfection, the LWA indicates that there are disease causes related to waterborne pathogens, particularly during the summer season.
The operational data for the WTP’s disinfection process were sourced from the LWA and served as a guideline for designing the other three disinfection systems. The operational on-site data for the baseline scenario were provided by the LWA for the year 2021. This includes the amount of chemicals used, their origin of production (needed to calculate the environmental impacts due to transportation of the material), and electricity consumption. Three companies provided data for the other water disinfection alternatives. The WTP’s treated water characteristics and disinfection objectives were shared with manufacturers. Based on the information provided, manufacturers developed disinfection methods. The manufacturers’ data regarding the operation of their water disinfection system were utilized to analyze the environmental impacts of the WTP disinfection process. The Ecoinvent database provides the material used for producing ozone and gaseous chlorine, but the material used for both UV systems is not provided except for the lamps. The materials used for UV systems were added manually to the software using the data from the report published by the United States Environmental Protection Agency [43].
The process of chlorine disinfection consists of three primary stages: the generation of chlorine gas, its transportation and dosing. Among the various disinfection methods assessed, the baseline scenario displays the lowest energy consumption. Both UV disinfection systems are based on UVC production from a light source. Light sources are installed in steel closed vessel systems. In this paper, two light sources, low-pressure high-output UV lamps and LED UV lamps, were used. The energy to produce UVC is provided by electricity and chemicals such as oxalic acid, and isopropyl acetate is used to clean the closed vessel UV systems, which is part of the operational element along with electricity. The energy demand of the UV LP system is lower than the ozone system, while the UV LED system has a higher energy demand. The equipment used in the ozone process is more complex compared to other disinfection methods. The ozone disinfection system contains an ozone generator, cooling unit, air preparation unit and ozone destruction unit, which are energy-intensive. The energy consumption of the compared water disinfection systems per 1 m3 of treated water is as follows: in the baseline scenario: 0.000314 kWh; UV LP: 0.007 kWh; UV LED: 0.054 kWh; and Ozone: 0.03744 kWh.

2.3. LCIA

Data from the LCI were used to calculate the environmental impacts of the disinfection methods for the chosen impact categories. The data were broken down to the FU at the LCI phase and loaded into the environmental impact assessment software for the impact calculations. SimaPro 9.4 was chosen as the software for modeling, which accommodates different environmental impact assessment methods. For this LCA study, ReCiPe 2016, developed by the Dutch National Institute for Public Health and the Environment, Radboud University, University of Leiden Department of Industrial Ecology and Pre-Consultants [44], was chosen as the impact assessment method, which consists of 18 midpoint impact categories, together with 3 endpoint categories. In this paper, only midpoint impact categories are covered. Table 1 shows the ReCiPe midpoint impact categories and units.

2.4. Interpretation

The findings of the LCIA phase are examined in this final step of an LCA study. In general, the LCI and LCIA steps serve as information for the examined system, whereas the goal and scope, along with the interpretation phase, comprise the body [45]. The last step of this study covers recommendations based on the outcomes of the LCI/LCIA phases, limitations and conclusions. This paper covers the interpretation part of the LCA in the conclusion part of the paper.

3. Results

The highest contributor to the baseline scenario is energy consumption except for terrestrial ecotoxicity, mineral resource scarcity and water consumption. The production of gaseous chlorine had the highest contribution in these categories. The impacts gained from the transportation of gaseous chlorine were less than 2% in all impact categories, except terrestrial ecotoxicity at 4.65%, which can be considered negligible. When the production of gaseous chlorine was examined for the impact categories terrestrial ecotoxicity, mineral resource scarcity and water consumption, the mining operations for the material, production stage of the mined materials, chlorine alkali processes, treatment of waste caused by the production, decarbonized water production and processes for electricity production were observed. Figure 3 shows the impact distribution of energy consumption, chlorine production and transportation on the 18 midpoint impact categories for the baseline scenario and the percentage of each input on the total impact.
An ozone generator was used on-site to generate ozone for ozone disinfection. The energy consumption for the ozone disinfection system includes the energy used to generate ozone and the energy consumption of the air compressor system. Ozone production has the greatest influence across all impact categories. The major input that was responsible for the ozone generation process was electricity usage. Except for terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity and mineral resource scarcity, electricity was responsible for more than 94% of impacts on ozone production. This result makes sense due to the fact that ozone production is an energy-intensive process. The air needed for the operation of the ozone disinfection system is supplied by compressors, which are also energy-driven. The air production stage had the second highest impact on all impact categories. Transportation of the ozone equipment had a very small impact in all categories, which was negligible compared to ozone and air production. Figure 4 shows the environmental impact contribution of the inputs for water disinfection with an ozone system on the 18 midpoint impact categories and the percentage of each input on the total impact.
The UV LP disinfection system employs vertically placed LP amalgam lamps in a closed vessel disinfection chamber. The use of energy for the operation of the UV LP system had the greatest impact across all 18 impact categories. The chemical (oxalic acid) used for cleaning the UV vessel had the second highest impact in all impact categories after energy. The highest contribution from the chemical cleaning agent is to stratospheric ozone depletion, ozone formation–terrestrial ecosystems and terrestrial acidification, with 12.87%, 7.55%, 7.51% and 3.09%, respectively. Environmental impacts caused by the transportation of the equipment were less than 1% in all impact categories. The environmental impacts due to UV LP disinfection and their distribution are depicted in Figure 5, with the percentage of each input on the total impact.
The UV LED system uses a closed vessel system similar to the UV LP system, but the UV LEDs mounted on the surface of the closed vessel disinfection chamber are used in the second UV disinfection system. As the UV disinfection process is reliant on the conversion of electric energy to UV light, electricity consumption is the most important aspect of the process. The LCA results of the UV LED system reveal that energy usage had the greatest influence on all impact categories. Transportation and cleaning chemical agents were together responsible for less than 1% of total impacts in all impact categories. Figure 6 shows the impact of inputs to disinfect one m3 of treated drinking water using UV LED systems, with the percentage of each input on the total impact. In the ionizing radiation impact category, disinfection with gaseous chlorine had major impacts together with the ozone and UV LED systems.
The calculated indicator results (characterization) provide numerical values for each impact category for the compared disinfection methods. LED UV disinfection had the highest overall impact in all categories when the four water disinfection technologies were evaluated. Due to their high energy consumption, the UV LED water disinfection system and ozone water disinfection system were responsible for the most environmental impacts in the impact categories generating the largest environmental footprints. The UV LP system was the most environmentally friendly disinfection technology, even though the energy demand was 22 times more than gaseous chlorine, with the least effect in all categories, followed by gaseous chlorine. The combined impact of chlorine production and its associated energy consumption contributed to this result. A study by Busse et. al. [36], where four disinfection methods were evaluated from an LCA perspective for a water system with a max flow rate of 1 m3/day, had similar results as the findings of our paper, showing that most impacts were caused by the UV LED disinfection system due to the higher energy consumption of other disinfection methods. One crucial point of the study was that the applied UV dosage was not the same in the UV systems, which does not provide a healthy comparison between the UV systems. In the study, chlorination was more environmentally friendly than the UV LP systems, which is not in line with this paper’s finding. Jachimowski and Nitkiewicz [33] compared gaseous chlorine to a medium-pressure UV system with sodium hypochlorite, a residual disinfectant, for water disinfection at a municipal level. The results show that gaseous chlorination caused less environmental impact than the UV system, which is not in line with the result of this paper. The reason for the different results is due to the UV lamp type—medium-pressure lamps are less efficient compared to low-pressure high-output lamps—and additional chemical residual disinfectant usage after the UV disinfection process. The findings of this paper are consistent with other earlier LCA studies in terms of the effect of factors, which were limited in scope and focused on the impact of electrical energy and chemicals.
The articles that focus on the LCA of water disinfection technologies were very limited and applied to small-scale water treatment systems. In a study by Jones et al. [46], the authors compared UV disinfection with chlorine disinfection. The distinctive part of this study is that it compares different scenarios based on the materials used for chlorination systems, such as tanks, baffles and pipes, with different UV dosages. In all scenarios, chlorination impacts on the environment were lower than UV systems. The outcome of this study shows that the major contributor to UV disinfection systems is caused by energy consumption, which is in agreement with our paper. The energy demand is based on the UV dosage applied to the water. A higher UV dosage requires more energy, which results in more environmental impacts. One critical element for UV disinfection systems is the manufacturers’ technology, causing different energy consumption. In UV LP systems, for example, the UVC output of each UV lamp varies according to the manufacturer, resulting in more or less equipment and energy, which has a direct influence on the LCA results. Another important result found in this study shows the lamp production of UV light-emitting diodes. Compared to low-pressure lamps, the production of LED lamps causes many more environmental impacts. The production of UV LED lamps has an environmental impact that was 13-to-2860 times higher than the production of UV LP lamps across all impact categories on a functional unit basis. One of the difficulties faced in our LCA study was the lack of UV LED studies in the literature that could be used to analyze the environmental impacts of UV LED systems. Figure 7 shows a comparison of four disinfection methods on 18 midpoint impact categories with their impact values.
The Ecoinvent database uses electricity mixes from different countries to obtain a median of electricity for the production of material and equipment for global value. The electricity used for operating the disinfection systems was chosen as the global medium voltage to obtain a global outlook. When the used electricity mix was changed to local conditions, the impact scores changed for the disinfection methods for all impact categories, together with a slight change in the gradation of the compared systems. The UV LED system was still the highest contributor in all impact categories except terrestrial ecotoxicity and mineral resource scarcity, whereas the ozone system had the highest impact and the UV LP system had the lowest impact in all categories. Another observation was that in all categories, improvements and deteriorations were seen for the disinfection methods. Table 2 presents the percentage of changes, both negative and positive, in the impact categories when utilizing international electricity mix data compared to local electricity mix data. The “+” symbol indicates an increase, and the “−” symbol indicates a decrease in the impact categories. These changes occur due to the methods used for electricity production and the electricity mix. The results gained by the change in the electricity mix show that the source of electricity is a critical issue in assessing the environmental impacts. The ANOVA test was conducted using the Minitab application to assess the statistical significance between the electricity mixes. Furthermore, SimaPro software was utilized to systematically adjust and model various electricity mix scenarios. When our study is compared with the current studies, it poses advantages due to its original data, which were gathered by the multiple site visits and archive searches of the LWA for verification. Another advantage is that the four main drinking water disinfection systems used widely around the world are compared in order to provide information for professionals in the field and at universities. When the literature is searched, it is seen that some studies are made comparing water disinfection systems at a lab-scale level or based on end users. This study focuses on large-scale water disinfection technologies that are operational. The main disadvantage faced in comparing these water disinfection systems is generating data that are now available from manufacturers.
At the municipal level, new and developing water disinfection technologies are being researched and implemented. Electrochemical disinfection (ED) is one of these technologies. Filho et al. [47] conducted research that compared ED to chlorine and exhibited the results. It has been suggested that the electricity consumption of ED is substantially higher than that of chlorination, which would result in larger environmental impacts owing to energy consumption. Unlike Filho et al. [47], Chaplin [48] suggested that electrochemical technology might consume less energy than other approaches if utilized to treat numerous pollutants rather than simply pathogens. Advanced Oxidation Processes (AOPs), such as photocatalysis [49], catalytic ozonation [50], and sonolysis [51], are also being investigated. Improvements in ozone disinfection are being researched in lab-scale experiments, which focus on increasing efficiency and decreasing energy use. According to Seridou and Kalogerakis [52], using micro and nano ozone bubbles instead of macro bubbles in the typical ozone disinfection procedure can boost disinfection efficiency while using less energy. UV LEDs and xenon excimer lamps are being explored more and more in the context of UV disinfection [53]. Naunovic et al. [54] investigated excimer lights and developed a lab-scale model to assess disinfection efficiency. The results were better than expected; however, the authors urged that further research should be conducted on this issue. Another significant characteristic of UV disinfection is that it may be utilized as a light source for photocatalysis water disinfection, which is an AOP [55]. The effectiveness and functioning mechanism of developing water disinfection systems are being explored, but their environmental impacts are not being considered due to a lack of real-world applications. New methods of drinking water disinfection combine the elimination of several contaminants from water, resulting in an upgrade and modification in the traditional treatment procedure. It is safe to say that the environmental implications of the disinfection process can be reduced if treatment systems become more effective with new technology.

4. Conclusions

Since their first use at the beginning of the 20th century, UV disinfection systems have significantly evolved, combining various types of UV lamps for diverse applications. As these systems depend on electricity, it is crucial to focus on enhancing their energy efficiency and operational performance. Using materials with lower light absorption values than the current standards, such as stainless steel, high-density polyethylene and polypropylene, can increase the efficiency of UV LP systems, leading to reduced energy consumption. These improvements could expand the global use of UV LP water disinfection systems, which are known for their safety and reliability.
Currently, UV LED lamps have a higher environmental impact and energy consumption compared to UV LP systems for equivalent disinfection levels. The future of UV LED systems depends on advancements in lamp technology and greener production processes to make them viable for water disinfection. This research demonstrates that UV LP systems present the lowest environmental impacts among water disinfection methods. Although chlorination remains the most common method worldwide, transitioning to UV LP systems can reduce the environmental footprints of water treatment plants. Reducing energy consumption is critical; if achieved, ozone and UV LED systems could become more favorable.
With the advancement of water disinfection technologies and increasing support for renewable energy, it is crucial to continuously update the LCA of water disinfection technologies. The findings from this LCA study, along with others, emphasize the significance of energy as the primary contributor to environmental impacts. By adopting more energy-efficient products, it is possible to shift the factors contributing to environmental repercussions. The growing environmental awareness and establishment of regulatory frameworks, such as the EU Drinking Water Directive and the US Safe Drinking Water Act, necessitate periodic enhancements in water safety protocols. These updates require the re-evaluation of pollutant removal methods and the exploration of innovative treatment technologies. In this context, LCA serves as an essential tool for comprehensively assessing the environmental impacts of processes or technologies in water disinfection, thereby addressing public concerns about their potential ecological consequences.
Future studies on the LCA of municipal water disinfection should be evaluated, together with the environmental impacts associated with both the production and operation of equipment. Currently, obtaining detailed data on the materials used in the manufacture of disinfection equipment, such as stainless steel, amalgam components, electronic parts, wires, diodes, plastics and other materials, is challenging due to its limited availability. To bridge this gap, manufacturers should be encouraged to share comprehensive material data or conduct LCA studies to provide critical data for researchers. Such transparency will enhance the accuracy of environmental impact assessments and support the development of more sustainable water disinfection technologies.
To align the future of water disinfection more closely with sustainability goals, it is crucial to focus on improving energy efficiency, promoting transparency in production data and leveraging advancements in technology. Ongoing research and collaboration between industry and academia are critical to drive these advancements and ensure that water disinfection technologies evolve in an environmentally responsible manner.

Author Contributions

Conceptualization, I.K.; methodology, M.Z.D.; investigation, M.Z.D.; resources, M.Z.D.; data curation, M.Z.D.; Software, writing—original draft preparation, M.Z.D.; writing—review and editing, H.G., H.O., M.E.E. and M.E.P.; supervision I.K.; project administration, I.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Restrictions may apply to the availability of these data. Data were obtained from water institution/manufacturers and are available on request from the corresponding author with the permission of in water institution/manufacturers.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. The system boundary of four disinfection methods.
Figure 1. The system boundary of four disinfection methods.
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Figure 2. Location of the Water Treatment Plant where LCI data are collected.
Figure 2. Location of the Water Treatment Plant where LCI data are collected.
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Figure 3. Distribution of inputs for chlorination water disinfection system.
Figure 3. Distribution of inputs for chlorination water disinfection system.
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Figure 4. Distribution of inputs for ozone water disinfection system.
Figure 4. Distribution of inputs for ozone water disinfection system.
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Figure 5. Distribution of inputs for UV LP water disinfection system.
Figure 5. Distribution of inputs for UV LP water disinfection system.
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Figure 6. Distribution of inputs for UV LED water disinfection system.
Figure 6. Distribution of inputs for UV LED water disinfection system.
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Figure 7. Comparison of the four disinfection methods on midpoint impact categories.
Figure 7. Comparison of the four disinfection methods on midpoint impact categories.
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Table 1. ReCiPe midpoint impact categories and units [44].
Table 1. ReCiPe midpoint impact categories and units [44].
Impact Category IndicatorUnit/MidpointImpact Category IndicatorUnit/MidpointImpact Category IndicatorUnit/Midpoint
Global warmingkg CO2 eq Terrestrial acidificationkg SO2 eqHuman carcinogenic toxicitykg 1.4-DCB
Stratospheric ozone depletionkg CFC-11 eq Freshwater eutrophicationkg P eq Human non-carcinogenic toxicitykg 1.4-DCB
Ionizing radiationkBq Co-60 eqMarine eutrophicationkg N eq Land usem2a crop eq
Ozone formation, Human healthkg NOx eqTerrestrial ecotoxicitykg 1.4-DCB Mineral resources kg Cu eq
Fine particulate matter formationkg PM2.5 eqFreshwater ecotoxicitykg 1.4-DCB Fossil resource scarcitykg oil eq
Ozone formation, Terrestrial ecosystemskg NOx eqMarine ecotoxicitykg 1.4-DCB Water consumption m3
Table 2. Percentage change in the results due to electricity mix used.
Table 2. Percentage change in the results due to electricity mix used.
Impact CategoryChlorine
Disinfection		Ozone
Disinfection		UV LED
Disinfection		UV LP
Disinfection
Global warming+8.24+11.42+11.51+11.39
Stratospheric ozone depletion+19.82+45.88+46.36+38.03
Ionizing radiation+333.54+1579.96+1699.56+1652.80
Ozone formation, Human health+3.97+5.54+5.61+5.13
Fine particulate matter formation−61.46−68.18−68.50−68.09
Ozone formation, Terrestrial ecosystems+4.05+5.65+5.72+5.24
Terrestrial acidification−12.83−16.62−16.98−16.50
Freshwater eutrophication−39.29−45.99−46.56−46.27
Marine eutrophication−31.12−39.93−40.15−40.10
Terrestrial ecotoxicity+12.93+20.84+41.25+32.00
Freshwater ecotoxicity−19.38−24.36−29.60−27.45
Marine ecotoxicity−19.67−24.78−29.87−27.72
Human carcinogenic toxicity−19.93−23.66−27.56−25.68
Human non-carcinogenic toxicity−22.21−28.04−30.62−29.47
Land use+61.88+118.55+130.01+12,614
Mineral resource scarcity+16.38+24.83+56.37+31.12
Fossil resource scarcity+8.22+11.35+11.42+11.30
Water consumption+3.07+6.74+6.94+6.87
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Demir, M.Z.; Guven, H.; Ersahin, M.E.; Ozgun, H.; Pasaoglu, M.E.; Koyuncu, I. Comparative Life Cycle Assessment of Four Municipal Water Disinfection Methods. Sustainability 2024, 16, 6104. https://doi.org/10.3390/su16146104

AMA Style

Demir MZ, Guven H, Ersahin ME, Ozgun H, Pasaoglu ME, Koyuncu I. Comparative Life Cycle Assessment of Four Municipal Water Disinfection Methods. Sustainability. 2024; 16(14):6104. https://doi.org/10.3390/su16146104

Chicago/Turabian Style

Demir, Mehmet Zahid, Huseyin Guven, Mustafa Evren Ersahin, Hale Ozgun, Mehmet Emin Pasaoglu, and Ismail Koyuncu. 2024. "Comparative Life Cycle Assessment of Four Municipal Water Disinfection Methods" Sustainability 16, no. 14: 6104. https://doi.org/10.3390/su16146104

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