Assessment of energy performance and GHG emissions for the urban water cycle toward sustainability

ASAT

Antalya Water and Wastewater Authority

BOD₅

5-day biochemical oxygen demand

CF

carbon footprint

ECAM

Energy Performance and Carbon Emissions Assessment and Monitoring

EF

energy footprint

ETS

Emissions Trading System

EU

European Union

GHG

greenhouse gas

GWP

global warming potential

IPCC

Intergovernmental Panel on Climate Change

IWA

International Water Association

LCA

life cycle assessment

MMA

Metropolitan Municipality of Antalya

NDCs

Nationally Determined Contributions

NRW

non-revenue water

SIV

system input volume

TN

total nitrogen

TP

total phosphorus

WDN

water distribution network

WWTP

wastewater treatment plant

Climate change is a very crucial global issue that threatens all nations by raising the Earth's surface temperature, causing sea-level rise, changes in precipitation patterns and intensities, evapotranspiration rates, and more intense and frequent occurrences of floods and droughts (Valipour 2017; Hamdi et al. 2020). These consequences lead to adverse impacts on the quality and quantity of water resources, human life, houses and infrastructure, agricultural production and the ecosystem. The threats of water scarcity and desertification impose challenges to ecosystems, social and economic activities that require effective water stress mitigation measures (Tsanov et al. 2020) and the evaluation of public services delivery performance mainly in developing countries (Siddiqui et al. 2021). The urban water cycle, which is composed of water supply, wastewater collection, treatment and disposal, is one of the critical sectors threatened by climate change. Increasing demand for adequate and hygienic water supply and more stringent quality standards for wastewater treatment plant (WWTP) effluents cause increases in energy consumption and consequently greenhouse gas (GHG) emissions. The urban water cycle was reported to account for 1–3% of total electric energy consumption (Longo et al. 2016), as much as 40% of municipal energy use, and 3–10% of the global warming potential (GWP) by direct and indirect GHG emissions, in many European countries (Samuelsson et al. 2018). Increasing energy demand and global commitments to reduce GHG emissions led many countries to renewable energy production, and therefore, small-scale hydropower plants showed a massive expansion (Kuriqi et al. 2019). However, the balance between hydropower production and ecosystem conservation needs to be studied in detail by coupling hydrologic and ecohydraulic approaches (Kuriqi et al. 2020), analyzing ecological impacts (Kuriqi et al. 2021) and assessing energy storage benefits (Malka et al. 2022). Sustainable management of the urban water cycle, which leads to low-carbon emissions, is highly dependent on water-use efficiency, energy efficiency, energy recovery, reuse of treated wastewater and nutrient recycling.

In the last two decades, the estimation of water and carbon footprint (CF) studies gained high interest. Several models and tools have been presented in the literature to estimate CF from different components of the urban water cycle (WWTPs, water and wastewater services and biological treatment units). In addition, different emission categories have been addressed, namely, direct and dissolved GHG, sludge disposal, energy, chemicals and transport. CFCT (Gustavsson & Tumlin 2013), CF-TOOL CTRL (Baeza et al. 2017), CHEApet (2011), BSM2G (Flores-Alsina et al. 2012) and BSM2-e (Sweetapple et al. 2013) models are applicable to WWTPs, whereas DEEM and ASMN (Guo et al. 2012) are used to estimate CF from biological wastewater treatment units. WESTWeb (2022), Energy Performance and Carbon Emissions Assessment and Monitoring (ECAM; WaCCliM 2022) and WWEECarb (Marinelli et al. 2021) tools address urban water and wastewater services for the assessment of carbon emissions. There are several studies for the application of the life cycle assessment (LCA) approach to estimate CF of water and wastewater services, such as for Pamplona, Columbia (Ortiz-Rodriguez et al. 2020), Ukraine (Levkovska et al. 2020), Denmark and Sweden (Delre et al. 2019), Gold Coast region of Australia (Lane et al. 2015), municipality of Aveiro in Portugal (Lemos et al. 2013) and USA (Zib et al. 2021).

The recent research studies related to the sanitation stage of the urban water cycle addressed the analysis of wastewater infrastructure for total energy and GHG emissions considering the water–energy–carbon nexus (Singh & Kansal 2018), carbon neutrality of wastewater treatment systems for energy, nutrient and water recovery (Mo & Zhang 2012), comparison of different wastewater and sludge treatment technologies and disposal alternatives for the lowest CF (Chai et al. 2015), analysis of energy consumption in WWTPs to evaluate water, CF and energy footprints (EF), and gray water footprint reduction (Gu et al. 2016), application of a new methodological approach to determine direct and indirect emissions from WWTPs according to the guidelines of ISO 14064-1 (Marinelli et al. 2021) and CF estimation of municipal water and wastewater services by embodied energy associated with topographic characteristics, efficiency of water and wastewater treatment systems and pumps (Bakhshi & Demonsabert 2012). In the case of the water supply stage, the relevant research studies focused on the evaluation of alternatives for the water supply infrastructure system by integrated CF and cost–benefit analysis (Qi & Chang 2012), analysis of the water cycle by LCA considering the impacts of water treatment and desalination plants, water losses in the water works, electrical consumptions and network maintenance (Del Borghi et al. 2013), implementation of performance indicators to compare impacts of energy-saving, energy production and water losses reduction on water supply (Puleo et al. 2015), evaluation of water cycle for hot spots of carbon emissions and pumping efficiency (Lin & Kang 2019) and comparison of current and future alternative water reclamation and resource recovery scenarios (Lahmouri et al. 2019).

In the literature, there is no holistic study for the assessment of CF, energy performance and GHG emissions for both water supply and sanitation stages of the urban water cycle, which considers critical management scenarios such as the reduction of non-revenue water (NRW), an increase of wastewater reuse and improvements in wastewater treatment processes. Therefore, the main objective of this study is to present a holistic approach for evaluating CF, energy performance and GHG emissions of the urban water supply (abstraction, treatment and distribution) and sanitation stages (wastewater collection, treatment, discharge, sludge management and onsite sanitation) with the consideration of critical management scenarios for NRW reduction, improvements in wastewater treatment processes and wastewater reuse. The application site is Antalya city, which faces the common problems of high NRW and very limited recovery of treated water and nutrients. Consequently, there is an urgent need to improve the sustainable management of urban water by increasing water and energy efficiency and reducing GHG emissions. For this purpose, ECAM methodology was implemented. In the ECAM tool, GHG emissions are assessed in consistency with the methodology of the Intergovernmental Panel on Climate Change (IPCC), and the performance indicators of the International Water Association (IWA) are used for water supply and sanitation service levels and energy performance (ECAM 2018). The novelty of this research is to assess the impacts of several management scenarios related to the urban water supply (reduction of physical water losses and energy recovery from the excess water pressure in water distribution networks (WDN)) and sanitation stages (preventing onsite sanitation, increasing energy efficiency, biogas production and reuse of treated wastewater) on CF, energy performance and GHG emissions. The outcomes of this research are expected to provide a valuable contribution to the reduction of indirect and direct emissions of the urban water cycle to combat climate change. The presented study for Antalya city covers the urban water cycle in a holistic approach with several management scenarios, being different from the previous studies in the literature. The paper is organized as follows: the section ‘Material and Methods’ presents information about the study area and methodology, the section ‘Results and Discussion’ includes the results of applied scenarios and their discussion, and finally, the last section presents the conclusions.

The sources of water supply, served population, abstracted volumes of water and the energy consumed for water abstraction are given in Table 1. Arsenic treatment by pressurized filters and disinfection is applied at Termessos Wells, whereas only disinfection by chlorine is applied at the rest of the water supply sources. The annual energy consumed for arsenic treatment was estimated at 2,756,179 kWh in 2020. There is an increasing demand for urban water supply in Antalya province as the per capita water consumption increased from 293 to 329 L/person/day between the years 2010 and 2018 (TSI 2021). The level of NRW in Antalya city WDN was reported as 44.1%, which corresponds to more than 63 million m³ of water for the year 2020 and the physical water losses level was 35.37%. The water balance for Antalya city in 2020 is depicted in Supplementary Table S1.

Approximately 87% of the population of Antalya city is connected to sewers, and the entire collected wastewater receives an advanced level of treatment. There are two WWTPs, namely Hurma and Lara, in Antalya city, and the plant effluents are discharged to the Mediterranean Sea by deep sea outfall systems following disinfection. Treatment capacities, influent pollution loads and treatment efficiencies of these WWTPs are presented in Table 1. About 1.3% of Hurma WWTP effluents (1.14 million m³/year) are reused for in-plant green area irrigation and as cooling water in the thermal sludge drying unit. Mechanical thickening, anaerobic digestion, dewatering and thermal drying processes are applied for sludge treatment at the Hurma WWTP, and the biosolids with more than 90% dry solids are transported to a cement factory for incineration. In the case of Lara WWTP, the excess sludge is mechanically dewatered up to 25% dry solids and then transferred to the Hurma WWTP for thermal drying. The volume of biogas produced at the Hurma WWTP is more than 5.5 million m³/year, and 50% of the biogas is valorized at the cogeneration unit to obtain heat and electricity simultaneously, which is used to heat the anaerobic digester and the thermal drying units. As depicted in Supplementary Figure S1, the biological units of the Lara WWTP are fully covered by a football field and the sedimentation tanks are covered by a special design of caps. This unique design of the treatment plant was selected to improve the landscape view, as this plant is located within an intense tourism area.

The total electricity consumption of ASAT in Antalya province was reported approximately 349.5 million kWh/year, which corresponds to 4.5% of electricity consumption in Antalya province (ASAT 2021). Furthermore, the consumed electricity for water and wastewater services in Antalya city was nearly 95.7 and 40.6 million kWh/year in 2020, respectively. There is a need for a holistic study to assess the energy performance and GHG emissions from the urban water cycle and to propose alternative solutions to improve water and energy efficiency in Antalya city.

In this equation, the emission factor was defined as 0.36 kgCO₂e/kWh for Turkey (EIB 2020).

CH₄ and N₂O emissions from sewers, CO₂, CH₄ and N₂O emissions from truck transport of water, emissions from the manufacture and transport of chemicals and emissions from the construction materials used are not included in the ECAM tool. The scope of application, methodology, conceptual background and all the mathematical formulations are presented elsewhere (ECAM 2018). In the ECAM tool, the emissions are counted in terms of CO₂ equivalents. In this study, the 100-year GWP for CH₄ and N₂O were taken as 34 and 298 times of CO₂ according to the IPCC 5th Assessment Report (IPCC 2013). The emission factor for grid electricity in Turkey was taken as 0.36 kg CO₂eq/kWh (EIB 2020). The main inputs for the sanitation stage are given in Supplementary Table S2. Emission factors for CH₄ and N₂O were 0.018 kg CH₄/kg BOD_removed and 0.016 kg N₂O-N/kg N for wastewater treatment and 0.068 kg CH₄/kg BOD_removed and 0.005 kg N₂O-N/kg N_removed for treated wastewater discharge.

The ECAM tool was applied to evaluate different management scenarios for urban water supply and sanitation stages as described below:

• • Baseline scenario: The current conditions of water and wastewater services in Antalya city were investigated as the baseline scenario. Physical water losses level is given as 35.37% in the year 2020 (ASAT 2021).

• • Improved water supply scenario: The related Turkish legislation states that total water losses should not be higher than 25% of the system input volume (SIV) (MFWA 2014). Physical water losses usually make up 60% of the total water losses in Turkey (Muhammetoglu & Muhammetoglu 2017). Thus, physical water losses should not be higher than 15% of SIV according to Turkish legislation. This means that the existing physical water losses in Antalya city should be reduced from 35.37 to 15%. The improved water supply scenario includes two components.

• • - reduction of NRW (reducing total water losses to 25% which implies reducing physical water losses to 15% of SIV) and

  • - energy production from excess pressure in water transmission lines.

• • Improved sanitation-stage scenario: This scenario includes four components as given below:

• • - increasing the population connected to sewers to 100%,

  • - increasing energy efficiency in WWTPs by 10%,

  • - increasing biogas production in the Hurma WWTP by 5%, and

  • - increasing reuse of treated wastewater to 5%.

The above-mentioned scenario components were reported as performance improvement targets by ASAT in their yearly progress reports (ASAT 2022). These components are to be realized by operational improvements in the WWTP processes, the use of more energy-efficient equipment and increased reuse of treated wastewater. Likewise, operational optimization and technology improvements in WWTPs were reported to achieve 5–30% energy-savings (Longo et al. 2016). In fact, the improved water supply and sanitation-stage scenarios are realistic for Antalya city and all the other metropolitan municipalities in Turkey because the water utilities are enforced to reduce total water losses in urban WDNs below 25% of system input volume till 2028, and also there are national projects to increase reuse of treated wastewater in Turkey. Furthermore, many water utilities in the metropolitan cities of Turkey have similar operational targets and projects to improve urban water supply and sanitation services.

GHG emissions and specific energy of the different water sources demonstrated wide variations as shown in Table 4 for the abstraction substage for the baseline and improved urban water supply scenarios. As the energy consumed for abstraction, treatment and distribution was null for Gurkavak Springs, there were no GHG emissions for this source. For the baseline scenario, the GHG emissions of different water supply sources varied between 17.16 and 31.27 kgCO₂eq/year/capita. However, GHG emissions for the abstraction substage of the improved water supply scenario were reduced, and the values were between 12.85 and 23.41 kgCO₂eq/year/capita for the same water supply sources.

The second component of the improved water supply scenario involved energy production from excess pressure in water transmission lines. Termessos Wells is an important water supply source for Antalya city which is 375 m above mean sea level (asl), and it supplies water by gravity to residential areas close to the sea level with a 1,000 mm diameter steel pipe. Additionally, the surface level of Gurkavak Springs is 260 m asl which supplies water by gravity to much lower elevations by a 350 mm cast iron pipe. Currently, break pressure tanks are used to break the excess pressure; however, ASAT prepared feasibility projects to produce energy from this excess pressure. Energy production from the excess water pressure in these two water transmission lines was designed as follows:

• Termessos-2 Pressure Reduction Power Station with a capacity of 0.98 Mwe, yearly electricity production of 7,816,000 kWh and a pay-back period of 5 years

• Kutukcu Pressure Reduction Power Station with a capacity of 1.5 Mwe, yearly electricity production of 8,898,120 kWh and a pay-back period of 4 years for Gurkavak Springs

Thus, the total energy production is estimated at 16,714,120 kWh/year, which corresponds to 12.26% of all urban water energy consumption for the baseline scenario. Consequently, the energy recovered from excess water pressure corresponds to a saving of 6,017,083 kg CO₂eq/year of GHG emissions.

For the implementation of the improved sanitation-stage scenario, all the scenario components (extension of wastewater collection and treatment services to the whole resident population of Antalya city, increasing wastewater reuse to 5%, increasing biogas production by 5% and increasing energy efficiency in WWTPs by 10%) were applied simultaneously. GHG emissions and energy consumption levels for the improved sanitation stage are presented in Table 3 and Figure 4. GHG emissions and total energy consumption of the improved sanitation stage were estimated at 70,025 tCO₂eq/year and 42,176 MWh/year, respectively. Wastewater collection and treatment substages constituted 0.77 and 72.30% of total GHG emissions, respectively. In the case of energy consumption, collection and treatment substages consumed 1.80 and 35.24% of all urban water energy use, respectively. GHG emissions of the improved sanitation stage contributed to 73.07% of the total GHG emissions and 37.04% of the total urban water energy use. Since there is no onsite sanitation for the case of the improved sanitation stage, which implies full coverage of wastewater collection and treatment, GHG emissions and energy consumption were null for onsite sanitation (Figure 4). With the implementation of the improved sanitation stage scenario, 29% reduction in GHG emissions was achieved with respect to the baseline scenario. The energy consumed for the sanitation stage increased by 3.85% with respect to the baseline scenario due to the extension of wastewater collection and treatment services to the whole resident population of Antalya city. A detailed assessment of GHG emissions, energy performance and service level indicators for improved sanitation-stage scenario are given in Table 5.

The improved sanitation-stage scenario was effective to reduce energy consumption for wastewater collection (from 0.022 to 0.02 kWh/m³) and wastewater treatment (from 0.43 to 0.39 kWh/m³). With the prevention of onsite sanitation, the organic material removed at the WWTPs increased to more than 35,812 tBOD₅/year and energy consumed for the removal of organic material decreased to 1.12 kWh/kg BOD. Energy production from biogas valorization, unit biogas produced per BOD₅ mass removed in wastewater treatment and sludge production rate were all improved and classified as good operation. Moreover, service level indicators were improved for indirect GHG emissions of electric use and direct GHG emissions due to biogas production.

The ECAM tool was very effective in analyzing CF, energy performance and GHG emissions for the urban water cycle of Antalya city and comparing water supply and sanitation stages. The results showed that the contribution of the sanitation stage to GHG emissions (CF) was significantly higher than the water supply stage in Antalya city where wastewater treatment and onsite sanitation were the most contributing substages. Conversely, the energy consumption of the water supply stage (EF) was significantly higher than the sanitation stage mainly due to the high energy consumption of groundwater abstraction to supply urban water to Antalya city. There were no emissions of CH₄ and N₂O from the water supply stage, whereas wastewater treatment caused emissions of CO₂, CH₄ and N₂O and onsite sanitation caused only CH₄ emissions.

The ECAM tool was previously applied in several countries such as Mexico, Peru, Burkina Faso, Egypt, Jordan, Zambia, India and Thailand to analyze energy efficiency and GHG emissions (WaCCliM 2022). In the study of Arsene et al. (2019), only the sanitation stage of the urban water cycle was evaluated by the ECAM tool for four Italian and Romanian WWTPs. In that study, two scenario conditions related to served population and energy efficiency were also investigated, being similar to the current study. Biogas recovery was reported to improve energy performance, while the largest contributions to GHG emissions were caused by energy consumption and methane production in wastewater treatment. Additionally, the national conversion factor, which is linked to each country's local energy mix, was mentioned as a key parameter. In another study, the baseline carbon emission assessment was conducted by the ECAM tool for water utilities in Madaba, Jordan considering the whole urban water cycle (Saidan et al. 2019). In that study, abstraction and distribution substages of water supply were estimated to consume approximately 90% of the total energy used in the urban water cycle and also water supply stage was the major contributor to the GHG emissions. In a recent study, CF and EF for the urban water cycle in Amman, Jordan were also investigated using the ECAM tool (Al-Omari et al. 2022). The results of the study showed that energy and CFs of the water supply stage were significantly higher than the sanitation stage mainly due to high energy consumption for the abstraction substage. CF of the sanitation stage was attributed to emissions of CH₄ and N₂O in WWTPs in addition to fossil fuel combustion for electricity production. Additionally, CF and EF for NRW in Amman were reported to be high, like Antalya city of Turkey.

There are global and regional actions to reduce GHG emissions and one of these attempts was the 2020 climate and energy package, set by the leaders of the European Union (EU) in 2007 and enacted in 2009. The package set three targets for the EU member state for 2020: (i) a 20% reduction in GHG emissions from the levels of 1990, (ii) a 20% increase in renewable energy share of the total energy mix and (iii) 20% improvement in energy efficiency (EC 2022). The EU has achieved these 2020 targets by reducing GHG emissions by 31% from the 1990 levels, mainly due to the reduction of GHG emissions from the power plants, industry and aviation sectors included within the EU Emissions Trading System (ETS). Additionally, the share of renewable energy sources was 21.3% in 2020. However, 60% of total EU GHG emissions originate from the sectors not covered by the EU ETS such as housing, waste, non-ETS industry, agriculture and transport fields (EC 2022). Furthermore, all EU member states have their national targets for reducing GHG emissions from these sectors. According to the EU Green Deal Action Plan Declaration in 2019, the new EU targets were adopted to achieve 55% net emission reductions by 2030 and climate neutrality by 2050 (EC 2019).

On the global scale, the Paris Agreement was the first legally binding universal agreement for climate change, which was adopted by 196 parties at the Paris Climate Conference (COP21), in December 2015, and enacted in 2016. According to this agreement, governments agreed to take necessary actions that will keep the global average temperature increase to well below 2 °C, with the aim of 1.5 °C, above the pre-industrial levels. The Paris Agreement further aims to reduce global carbon emissions by 50% by 2030 and to achieve net-zero emissions by 2050. To achieve these global targets, countries submit their own national climate action plans, known as their Nationally Determined Contributions (NDCs). Turkey signed the Paris Agreement in 2016 and ratified it on October 6, 2021. Turkey's carbon emissions were reported to increase over the last decade with an average economic growth rate of 6.41% between the years 2010 and 2018. Turkey produced 369.5 million metric tons of CO₂ emissions in 2020 and is ranked 16th among the countries with the highest GHG emissions in the world, with a share of around 1% (Statista 2022). Recently, Turkey has committed to reducing CO₂ emissions by 21% by 2030 and to adopt net-zero emissions by 2053. The actions to achieve these goals were defined within the Green Deal Action Plan of Turkey, in addition to the major actions related to the water sector such as the sustainable management of water resources, the sustainable use of water in production and consumption, increasing the reuse of wastewater, controlling water losses in WDNs, increasing water efficiency and water saving, and reducing water consumption. In Turkey, water losses in urban water supply and distribution networks are challenging issues for all water utilities. The average value of NRW in Turkey was officially reported at 35% in 2018, but the actual NRW level is estimated to be much higher (Muhammetoglu & Muhammetoglu 2017). Additionally, the reuse of treated urban wastewater is very limited in Turkey being less than 2% (Nas et al. 2020). Consequently, there is an urgent need to reduce NRW (Firat et al. 2021), to increase the reuse of treated wastewater and nutrient recovery in Turkey, like many countries in the world.

Cities are among the large emitters of GHG emissions, and there is a need to estimate GHG emissions from urban areas (Kanakoudis & Papadopoulou 2014). According to the Sustainable Energy Action Plan of Metropolitan Municipality of Antalya (MMA), GHG emissions of Antalya city were investigated and the distribution of GHG emissions was estimated as follows: 40.9% from houses, 30.2% from transportation, 8.5% from energy production, 8.2% from the urban water cycle, 6.1% from industry and 6% from agriculture and husbandry (MMA 2021). Based on this Action Plan, CO₂ emissions per capita were reported as 4.25 ton CO₂eq (including industry) for the year 2019. MMA is a partner in the Covenant of Mayors for Climate & Energy, and it aims to reduce 40% of CO₂ emissions by 2030 and achieve net-zero emissions by 2050. MMA received the ‘Climate Friendly Organization Certificate’ from the Turkish Standards Institute in 2021 as the first organization in Turkey. In this current study, the reduction of GHG emissions and energy consumption were estimated by the ECAM tool for the improved water supply and sanitation stages of Antalya city as 36,628,585 kg CO₂eq/year (equivalent to carbon sink of around 3.6 million trees) and 22,476,241 kWh/year (equivalent to the annual electricity demand of around 8,500 houses), respectively. The implementation of an improved urban water cycle will contribute to the climate change mitigations of Antalya city. Furthermore, these actions are very crucial to manage urban water resources, increase water and energy efficiency in the urban water cycle, comply with the national Green Deal Action Plan for reducing GHG emissions and achieve sustainable cities. The research outcomes showed the importance of increasing energy and water efficiency in the urban water cycle that contributes to GHG emissions, but there is an urgent need for a broader study to further reduce GHG emissions from the houses and transportation in Antalya city.

This study presents a holistic approach to assess CF, energy performance and GHG emissions from the urban water cycle by considering critical management scenarios for water supply and sanitation stages. The study was conducted for Antalya city in Turkey, which faces common problems of high NRW in WDNs, the existence of onsite sanitation and very low levels of treated wastewater reuse. GHG emissions and energy consumption were compared for the baseline and improved water supply and sanitation stages for the year 2020 using the ECAM tool. Regarding the current applications of urban water and wastewater services as the baseline scenario, considerably high GHG emissions (132,457 tCO₂eq/year) and energy consumption (136,328 MWh/year) were estimated where water supply contributed to approximately 26% of all urban water GHG emissions and 70% of all urban water energy consumption. One important conclusion for the study is that the EF of the water supply stage was much higher than the sanitation stage, but the CF of the sanitation stage was much higher than the water supply. In the case of improved water supply and sanitation stages, total GHG emissions and energy consumption were estimated at 95,828 tCO2eq/year and 113,852 MWh/year, respectively, which imply 27.65% reduction in GHG emissions and 16.48% reduction in energy consumption with respect to the baseline scenario. The management scenarios are effective to accomplish considerable reductions in GHG emissions and energy consumption to combat the adverse impacts of climate change. Reduction of NRW and energy recovery from excess water pressure are effective to produce renewable energy and to reduce CF and EF in the water supply stage. Likewise, the prevention of onsite sanitation, reuse of treated wastewater, biogas valorization, improving energy efficiency in WWTPs by operational optimization and technology improvements are effective to reduce GHG emissions and to increase energy performance. There is a need for a more decisive and effective mechanism to force water utilities to improve their water and wastewater services at the urban scale. The presented study provides a good example to practitioners and researchers for the low-carbon operation of the urban water cycle and to increase water and energy efficiency, energy recovery and reuse of water and nutrients.

This publication is the outcome of the cooperation between the Environmental Engineering Department at Akdeniz University, Antalya, Turkey and the Water, Energy and Environment Center of the University of Jordan, Amman within the framework of the SWINDON/EXCEED project funded by the German Academic Exchange (DAAD). The authors wish to express their gratitude to the DAAD for funding this cooperation.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.