Life cycle assessment of package and ultrafiltration systems and four disinfection technologies for a full-scale water treatment plant

Abstract

A growing global population underscores the urgent need for access to adequate drinking water, a basic human need. As recognized by the United Nations, access to safe and clean drinking water is a basic human right and obliges governments to ensure this right. To meet this need, various treatment and disinfection methods are used depending on the water source. The materials and equipment used in these processes are sourced from different sectors and discarded after use, potentially leading to significant environmental consequences such as depletion of natural resources, emissions and waste generation. To comprehensively assess these environmental impacts, Life Cycle Assessment is one of the most comprehensive and accuratemethodologies available. Today's approaches to improving drinking water quality are mainly based on physical and chemical processes as well as combination of those. Package treatment systems offer several advantages over conventional plants by treating water through pre-built treatment tanks using both physical and chemical processes. These systems are characterized by relatively low initial investment cost, minimal spatial footprint, quick installation and ease of operation. Furthermore, the materials used in these systems are recyclable, reducing their environmental impact. In contrast, ultrafiltration systems rely on physical processes which provide advantages such as reduced chemical use, minimal space requirements, operational simplicity and potential for capacity expansion. Regardless of the treatment method, disinfection of water is essential to ensure safety for consumption. Drinking water must be free of pathogenic microorganisms to be considered safe for human consumption. Common water disinfection techniques include chemical methods such as chlorination and ozonation, physical methods such as ultraviolet (UV) irradiation, advanced oxidation processes and electrochemical methods. UV irradiation is increasingly preferred because it is effective against a wide range of microorganisms and easy to use. From an economic point of view, chemical disinfection methods are generally more cost-effective, with the exception of ozone due to its high investment and operational costs. Although the adoption of UV systems has been increasing, it is supported by installations that utilize a variety of UV sources despite its relatively high investment cost. The aim of this thesis is to present a comparative analysis of the environmental impacts of the most widely used disinfection systems, including gas chlorine, ultraviolet and ozone, as well as package treatment and ultrafiltration water treatment systems, using the Life Cycle Assessment methodology. This study aims to achieve a thorough comprehension of the ecological consequences associated with both water treatment and water disinfection systems, with the objective of facilitating knowledgeable decision-making in the pursuit of environmentally sustainable water treatment and disinfection alternatives. The comparisons were made by following the steps of ISO 14040 "Environmental management - Life cycle assessment - Principles and framework" standard. ISO 14040 specifies the steps to be applied in LCA studies and how they should be, and ISO 14044 "Environmental management - Life cycle assessment - Requirements and guidance" explains these steps in detail. The treatment and disinfection systems examined in this thesis include phases i) Goal and scope definition ii) Life cycle inventory analysis (LCI) iii) Life cycle impact assessment (LCIA) and iv) Life cycle interpretation. The data used for the environmental impact calculations were collected through site visits, literature and market researchThe data collected were arranged in accordance with the functional unit and utilized in the computational process.. For the calculation of environmental impact values, SimaPro, an LCA software, was used to evaluate 18 impact categories together with the ReCiPe LCA methodology. The results of the water treatment and disinfection systems examined within the scope of the thesis were analyzed and the results were compared with the existing studies in the literature in line with the thesis subject. The water treatment systems were compared in terms of their environmental impacts from both operation and construction. Although more material is used to produce package water treatment system than ultrafiltration water treatment system, it is seen that the environmental impact of package treatment systems is less in all impact categories. The main reason for this is the high environmental impact of the production of materials used in the production of ultrafiltration systems and the high energy consumption required for operation. Another important aspect is that the materials used in the production of the treatment tanks used in package treatment systems (e.g. stainless steel, galvanized sheet) can be reused instead of being disposed of at the end of their useful life. The comparison of water disinfection systems considers only the impacts caused by the operational phase. Environmental impacts caused by the production of the water disinfection equipment are not included in the calculations. The reason for this is that there is no literature information about the production of the disinfection equipment examined and the manufacturers do not share this information. Among the water disinfection equipment compared, the systems with the lowest environmental impact were the UV system using low pressure amalgam ultraviolet lamps and the gas chlorine system. The ozone system and the UV system using LED ultraviolet lamps had the highest environmental impact. The main reason for this result is the amount of energy required for operation. The results show that the environmental impacts of the water treatment and disinfection processes are important for the source of the energy and material production steps used in the plant. When utilizing two separate sets of electricity generation data - one encompassing global electricity generation and the other focusing on local electricity generation - no alteration was observed in the ecological impact rating of water disinfection systems. However, variations were evident in each impact category, both showing increases and declines. The use of renewable energy sources will reduce the environmental impacts of drinking water treatment and disinfection systems.