Sustainability assessment for a large water treatment plant via life cycle approach

The environmental impact of water production industry in coming few years will be higher due to population growth. Therefore, most developed countries interest with the sustainability as an environmental protection strategy to increase efficiency of environmental preservation and energy. In Turkey, Istanbul has the biggest urban and industrial growth. That is why that the main objective of this work is to apply life cycle assessment approach to evaluate the environmental impact for one of the main water treatment plants in Istanbul-Turkey. This work studied the environmental impact of Büyükçekmece Water Treatment Plant using life cycle assessment approach. The Büyükçekmece Lake is water source of the treatment plant located in western side of Istanbul. After determination of system function and functional unit of water treatment system, data inventory of plant was collected for one year. The materials and electricity consumption was calculated per 1 m3 of potable water. The system boundary of plant includes main and sub treatment processes. The input/output pumps, aeration, slow/rapid mixing, clarification, filtration, disinfection and reservoir are the main processes in the plant. There are many subprocess units such as chemical mixing, sludge dewatering, backwash water, blower and sludge pump unit. The chemicals are utilized to treat raw water as aluminum sulfate, polyelectrolyte, activated carbon and chlorine. Moreover, operation/monitoring system, and valves are considered in this work. GaBi 7.3 software is applied as tool of life cycle assessment approach. The processes and flows are constructed in GaBi 7.3 software depending on the system boundary of water treatment plant. The input and output in each process are determined according to LCA requirement. After the entry of inventory data, GaBi 7.3 software is normalized all data entry and balances it. Many environmental impact categories are available in this software. In this study it has been selected the Centre for Environmental Studies (CML 2001) method to evaluate the environmental effects. Finally, the results are interpreted according to the goal of study. The impacts categories are evaluated by GaBi software in terms of Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), Ozone Layer Depletion Potential (ODP), Abiotic Depletion Potential (ADP elements), Abiotic Depletion Potential (ADP fossil), Freshwater Aquatic Ecotoxicity Potential (FAEP), Human Toxicity Potential (HTP), Marine Aquatic Ecotoxicity Potential (MAEP), Photochemical Ozone Creation Potential (POCP), Terrestric Ecotoxicity Potential (TETP). It was calculated the environmental impacts of a Turkish water treatment plant via LCA approach. The environmental impacts of the investigated water treatment facility are in accordance with the literature values. The highest shares to GWP and EP come from output pumps, chlorination and input pumps. The main contributors to AP can be enlisted as output pumps, coagulation-flocculation, chlorination and input pumps. Mainly output and input pumps and chlorination stages contribute to ODP. A total ADP element mostly arises from chlorination. Output pumps, chlorination, input pumps, coagulation-flocculation and aeration stages have significant shares in ADP fossil and FAEP. Output pumps, chlorination and input pumps are the stages mainly responsible for HTP, TETP and MAEP. Output pumps, coagulation-flocculation, chlorination and input pumps can be encountered as the main contributors to POCP. The results show that electricity consumption contributes most to environmental impacts. Büyükçekmece Water Treatment Plant utilizes grid mix electricity as power source. To understand the effect of different electricity sources on the results LCA model is reconstructed with renewable (solar and wind), non-renewable (fossil) and grid mix electricity which used in Turkey as a power source. The results show if wind energy is consumed as electricity source all of the impact categories decrease more than solar panels, grid mix and hard coal electricity. Whereas the hard coal power consumption increases most impact categories. Solar panels electricity has moderate effect when reduces impacts categories excluding ADP elements and HTP categories. Consumption of wind or solar energy could improve the system in terms of environmental impacts. All impact categories except GWP, ADP elements and MAEP, decrease when grid mix electricity for Turkey is utilized. In this study, also effects of transportation is investigated in two parts: chemicals transportation and sludge transportation to landfill. The results show that impact categories of chemicals transporting affected by several parameters, the quantity, distance and shipping routes are the main factors. It was found that impact categories are not increasing noticeably with/without chemicals transportation. So that this increase does not exceed more than 2%. The environmental impacts for all the categories were calculated to illustrate the effect of inlet/outlet pumps efficiency. That leds to minimize the electricity consumption and environmental impact. The results show that the impacts decrease when the efficiency of the pumps are increased from 80% to 85% due to lowering the electricity requirements.