Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination?
2. Materials and Methods
2.1. Proposed Scenarios
- Scenario 1. This scenario is based on a city whose wastewater is treated by a WWTP with both primary and secondary treatments. In this case, a post-treatment of the WWTP effluent would be implemented by means of a hybrid ultrafiltration (UF) and reverse osmosis (RO) system. First, the secondary treated effluent is passed through the UF membrane to remove particles and colloids and then through RO membrane to remove the remaining pollutants. It was considered that UF and RO membranes are periodically cleaned using reagents to maintain a suitable pressure drop. The recovery ratio was set to 70% in relation to the inlet wastewater volume .
- Scenario 2. This scenario is based on a coastal city whose wastewater is treated by a primary treatment and its effluent is sent to sea by means of a submarine outfall. For this reason, in this proposed scenario, the construction of an activated sludge unit followed by a hybrid UF-RO system was considered.
- Scenario 3. This scenario involves the complete implementation of a seawater desalination plant based on the reverse osmosis process. The recovery ratio of the reverse osmosis system was set to 50% in relation to the initial volume of the feedwater (seawater) .
2.2. Methodology for Economic Assessment
- The required water flow rate was calculated. The annual flow of the water demand (m3/year) of the studied city was estimated based on its population and water consumption (m3/cap/year).
- The total water production costs (USD/m3) for the proposed scenarios were estimated. First, total production costs were calculated based on the total capital costs (CAPEX) and the operating and maintenance costs (OPEX) (Equation (1)).
- Scenario 1. The total capital costs included the cost related to the purchase of equipment (UF and RO units), the required equipment for piping, instrumentation/electricity, engineering costs and civil works (Table 2). The operating and maintenance costs included energy consumption, reagents consumption, membrane replacement, and maintenance and labor costs (Table 2). The capital costs and operating and maintenance costs related to the UF-RO system were calculated using cost functions that were developed based on the data reported by Plumlee et al. (2014) .
- Scenario 2. The total capital costs included costs related to the construction or purchase of the equipment (activated sludge system, UF and RO units) and the required equipment for piping, instrumentation/electricity, engineering costs, and civil works (Table 2). The costs associated with the operation of the activated sludge system were energy and reagents consumption, labor, waste management and maintenance. The total capital costs and operating and maintenance costs for the UF-RO system included the items described for scenario 1 (Table 2). The total capital costs and operating and maintenance costs of the activated sludge were calculated based on the data reported by Guo et al. (2014)  and Molinos-Senante et al. (2010) , respectively.
- Scenario 3. The total capital costs for the desalination plant included 5 cost items, which were construction and infrastructure costs (main equipment, piping, instrumentation/electricity, among others), land acquisition costs, engineering costs, and development and management costs (Table 2). The operating and maintenance costs included energy consumption, membrane replacement, maintenance, reagents consumption and labor costs (Table 2). Based on the salinity concentration and average temperature of the coast of Chile, around 35,000 ppm and 17 °C, respectively , it was assumed that the energy consumption of seawater desalination was 3.5 kWh/m3. The capital costs and operating and maintenance costs were estimated using cost functions that were developed based on the results reported by Molinos-Senante and González (2019) . The cost functions and the economic parameters for the proposed scenarios are given in Table 2. The price of electricity was set at 0.109 USD/kWh . All costs used in this work were normalized to the USD of 2019.
- The best scenario to produce water was determined. A pairwise comparison in terms of the total production costs for the proposed scenarios was developed in order to determine the most profitable scenario. The total production costs for the proposed scenarios were compared and used to estimate the maximum distance that produced water can be transported from the water plant production to the water demand city if the cheaper scenario were selected. This distance (ΔDmax) was expressed as a function of the total production costs (USD/m3), the transportation costs for horizontal distance (a, 0.05 USD/m3/km/year) and the lifetime of the facility (t, 20 years) (Equation (3)). The transportation costs, a, was determined as a function of the piping and pumping costs for the horizontal distance, using the data reported by Caldera et al. (2018)  and ESCWA (2009) . It should be noted that scenarios 1 and 2 have not been compared among them because it is only possible to implement one of these scenarios for a particular city, and their selection depends on the actual wastewater treatment system.
- The selection of possible water sources for the studied city was carried out. Once the suitable scenario was determined, the selection of the potential water sources was developed based on the flow rate of water that would be supplied and the distance between the water source and water demand site. It should be noted that water transportation distance is comprised of the horizontal and vertical distances, respectively, and they have a different impact on the water production cost. Vertical distance has a larger impact on water transportation costs than horizontal distance , and thereby an equivalent distance from the water source to water demand site for wastewater reuse scenarios (deq_ww) and seawater desalination (deq_coast) was determined (Equation (4)):
- Finally, the best option to supply water to the water-demanding city was selected based on the maximum distance that produced water can be transported from the water plant production to the water-demanding city (ΔDmax), and the equivalent distance that water should be transported was obtained for the potential water sources. Therefore, if ΔDmax > (deq_ww − deq_coast), the reuse of wastewater is more favorable than seawater desalination. In contrast, if ΔDmax < (deq_ww − deq_coast), the desalination of seawater is more economical than wastewater reuse.
2.3. Case Study
3. Results and Discussion
3.1. Cost Associated with Water Production
3.2. Economic Analysis
3.3. Water Production from Non-Conventional Water Resources: Case Studies from Chile
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
- UN (United Nations Water). World Water Development Report 2019. Available online: https://unwater.org/publications/world-water-development-report-2019/ (accessed on 4 February 2021).
- Voulvoulis, N. Water reuse from a circular economy perspective and potential risks from an unregulated approach. Curr. Opin. Environ. Sci. Health 2018, 2, 32–45. [Google Scholar] [CrossRef]
- Hussain, M.I.; Muscolo, A.; Farooq, M.; Ahmad, W. Sustainable use and management of non-conventional water resources for rehabilitation of marginal lands in arid and semiarid environments. Agric. Water Manag. 2019, 221, 462–476. [Google Scholar] [CrossRef]
- Jones, E.; Qadir, M.; van Vliet, M.T.H.; Smakhtin, V.; Kang, S. The state of desalination and brine production: A global outlook. Sci. Total Environ. 2019, 657, 1343–1356. [Google Scholar] [CrossRef] [PubMed]
- Qadir, M.; Jiménez, G.C.; Franum, R.L.; Dodson, L.L.; Smakhtin, V. Fog Water Collection: Challenges beyond Technology. Water 2018, 10, 372. [Google Scholar] [CrossRef][Green Version]
- Yusuf, A.; Sodiq, A.; Giwa, A.; Eke, J.; Pikuda, O.; De Luca, G.; Di Salvo, J.; Chakraborty, S. A review of emerging trends in membrane science and technology for sustainable water treatment. J. Clean. Prod. 2020, 266, 121867. [Google Scholar] [CrossRef]
- Aliyu, U.M.; Rathilal, S.R.; Isa, Y.M. Membrane desalination technologies in water treatment: A review. Water Pract. Technol. 2018, 13, 738–752. [Google Scholar] [CrossRef]
- Amy, G.; Ghaffour, N.; Li, Z.; Francis, L.; Valladares Linares, R.; Missimer, T.; Lattemann, S. Membrane-based seawater desalination: Present and future prospects. Desalination 2017, 401, 16–21. [Google Scholar] [CrossRef]
- Gude, V.G. Desalination and sustainability-an appraisal and current perspective. Water Resour. 2016, 89, 87–106. [Google Scholar] [CrossRef]
- Ahmed, F.E.; Hashaikeh, R.; Hilal, N. Hybrid technologies: The future of energy efficient desalination—A review. Desalination 2020, 495, 114659. [Google Scholar] [CrossRef]
- Caldera, U.; Bogdanov, D.; Breyer, C. Desalination costs using renewable energy Technologies. In Renewable Energy Powered Desalination Handbook; Elsevier: Amsterdam, The Netherlands, 2018; pp. 287–329. [Google Scholar]
- Elsaid, K.; Kamil, M.; Sayed, E.T.; Abdelkareem, M.A.; Wilberforce, T.; Olabi, A. Environmental impact of desalination technologies: A review. Sci. Total Environ. 2020, 748, 141528. [Google Scholar] [CrossRef]
- Okamoto, Y.; Lienhard, J.H. How RO membrane permeability and other performance factors affect process cost and energy use: A review. Desalination 2019, 470, 114064. [Google Scholar] [CrossRef]
- World Bank. The Role of Desalination in an Increasingly Water-Scarce World; World Bank: Washington, DC, USA, 2019. [Google Scholar]
- Mollahosseini, A.; Abdelrasoul, A.; Sheibany, S.; Amini, M.; Salestan, S.K. Renewable energy-driven desalination opportunities—A case study. J. Environ. Manag. 2019, 239, 187–197. [Google Scholar] [CrossRef]
- Ghaffour, N.; Missimer, T.M.; Amy, G.L. Technical review and evaluation of the economics of water desalination: Current and future challenges for better water supply sustainability. Desalination 2013, 309, 197–207. [Google Scholar] [CrossRef][Green Version]
- Garcia, X.; Pargament, D. Reusing wastewater to cope with water scarcity: Economic, social and environmental considerations for decision-making. Resour. Conserv. Recy. 2015, 101, 154–166. [Google Scholar] [CrossRef]
- Al-Karaghouli, A.; Kazmerski, L.L. Energy consumption and water production cost of conventional and renewable-energy-powered desalination processes. Renew. Sustain. Energy Rev. 2013, 24, 343–356. [Google Scholar] [CrossRef]
- Zhou, Y.; Tol, S.J. Evaluating the costs of desalination and water transport. Water Resour. Res. 2005, 41, W03003, 1–10. [Google Scholar] [CrossRef]
- Abdulbaki, D.; Al-Hindi, M.; Yassine, A.; Najm, M.A. An optimization model for the allocation of water resources. J. Clean. Prod. 2017, 164, 994–1006. [Google Scholar] [CrossRef]
- Goh, P.S.; Matsuura, G.T.; Ismail, A.F.; Ng, B.C. The water-energy nexus: Solutions towards energy-efficient desalination. Energy Technol. 2017, 5, 1136–1155. [Google Scholar] [CrossRef]
- Pinto, F.S.; Marques, R.C. Desalination projects economic feasibility: A standardization of cost determinants. Renew. Sustain. Energy Rev. 2017, 78, 904–915. [Google Scholar] [CrossRef]
- Papapetrou, M.; Cipollina, A.; La Commare, U.; Micale, G.; Zaragoza, G.; Kosmadakis, G. Assessment of methodologies and data used to calculate desalination costs. Desalination 2017, 419, 8–19. [Google Scholar] [CrossRef]
- Livi-Bacci, M. A Concise History of World Population; John Wiley & Sons: Hoboken, NJ, USA, 2012. [Google Scholar]
- Ventura, D.; Consoli, S.; Barbagallo, S.; Licciardello, F.; Cirelli, G.L. How to overcome barriers for wastewater agricultural reuse in Sicily (Italy)? Water 2019, 11, 335. [Google Scholar] [CrossRef][Green Version]
- EPA (U.S. Environmental Protection Agency). Guidelines for Water Reuse; U.S. Environmental Protection Agency: Washington, DC, USA, 2012.
- Vicuña, S.; Vargas, X.; Boisier, J.P.; Mendoza, P.A.; Gómez, T.; Vásquez, N.; Cepeda, J. Impacts of climate change on water resources in Chile. In Water Resources of Chile; World Water Resources; Fernández, B., Gironás, J., Eds.; Springer Nature: Cham, Switzerland, 2021. [Google Scholar] [CrossRef]
- Alvez, A.; Aitken, D.; Rivera, D.; Vergara, M.; McIntyre, N.; Concha, F. At the crossroads: Can desalination be a suitable public policy solution to address water scarcity in Chile’s mining zones? J. Environ. Manag. 2020, 258, 110039. [Google Scholar] [CrossRef]
- Herrera-León, S.; Cruz, C.; Kraslawski, A.; Cisternas, L.A. Current situation and major challenges of desalination in Chile. Desalination Water Treat. 2019, 171, 93–104. [Google Scholar] [CrossRef]
- CNID (Consejo Nacional de Innovación para el Desarrollo). Evaluation of the Socio-Economic Conflicts of Large Projects with Focus on Water and Energy for 1998–2015. Available online: http://www.cnid.cl/wp-content/uploads/2017/04/Informe-final-CNID-Evaluacio%CC%81n-de-Conflictos-Socioambientales-1.pdf (accessed on 24 February 2021).
- Yang, J.; Monnot, M.; Ercolei, L.; Moulin, P. Membrane-Based Processes Used in Municipal Wastewater Treatment for Water Reuse: State-Of-The-Art and Performance Analysis. Membranes 2020, 10, 131. [Google Scholar] [CrossRef] [PubMed]
- Plumlee, M.; Stanford, B.D.; Debroux, J.F.; Hopkins, D.C.; Snyder, S.A. Cost of advanced treatment in water reclamation. Ozone Sci. Eng. 2014, 36, 485–495. [Google Scholar] [CrossRef]
- Guo, E.; Englehardt, J.; Wu, T. Review of cost versus scale: Water and wastewater treatment and reuse processes. Water Sci. Technol. 2014, 69, 223–234. [Google Scholar] [CrossRef]
- Molinos-Senante, M.; Hernández-Sancho, F.; Sala-Garrido, R. Economic feasibility study for wastewater treatment: A cost–benefit analysis. Sci. Total Environ. 2010, 408, 4396–4402. [Google Scholar] [CrossRef] [PubMed]
- Molinos-Senante, M.; González, D. Evaluation of the economics of desalination by integrating greenhouse gas emission costs: An empirical application for Chile. Renew. Energy 2019, 133, 1327–1337. [Google Scholar] [CrossRef]
- ENEL. Tarifas Vigentes. Available online: https://www.enel.cl/es/clientes/informacion-util/tarifas-y-reglamentos/tarifas.html (accessed on 4 February 2021).
- ESCWA (Economic and Social Commission for Wester Asia). ESCWA Water Development Report 3: Role of Desalination in Addressing Water Scarcity; United Nations Publications: New York, NY, USA, 2009. [Google Scholar]
- Sarricolea, P.; Herrera-Ossandon, M.; Meseguer-Ruiz, O. Climatic regionalisation of continental Chile. J. Maps 2017, 13, 66–73. [Google Scholar] [CrossRef]
- Aitken, D.; Rivera, D.; Godoy-Faúndez, A.; Holzaptel, E. Water Scarcity and the Impact of the Mining and Agricultural Sectors in Chile. Sustainability 2016, 8, 128. [Google Scholar] [CrossRef][Green Version]
- Murashko, K.; Nikku, M.; Sermyagina, E.; Vauterin, J.J.; Hyppänen, E.; Pyrhónen, J. Techno-economic analysis of a decentralized wastewater treatment plant operating in closed-loop. A Finnish case study. J. Water Process. Eng. 2018, 25, 278–294. [Google Scholar] [CrossRef]
- Melgarejo, J.; Prats, D.; Molina, A.; Trapote, A. A case study of urban wastewater reclamation in Spain: Comparison of water quality produced by using alternative processes and related costs. J. Water Reuse Desalination 2016, 6, 72–81. [Google Scholar] [CrossRef][Green Version]
- Plappally, A.K.; Lienhard, J.H. Costs for water supply, treatment, end-use and reclamation. Desalination Water Treat. 2012, 51, 1–33. [Google Scholar] [CrossRef]
- Valladares Linares, R.; Li, Z.; Yangali-Quintanilla, V.; Ghaffour, N.; Amy, G.; Leiknes, T.; Vrouwenvelder, J.S. Life cycle cost of a hybrid forward osmosis e low pressure reverse osmosis system for seawater desalination and wastewater recovery. Water Res. 2016, 88, 225–234. [Google Scholar] [CrossRef] [PubMed][Green Version]
- Fundación Chile. Aguas Residuales como Nueva Fuente de Agua. Diagnóstico del Potencial Reúso de Aguas Residuales en la Región de Valparaíso; Fundación Chile: Santiago-Valparaíso, Chile, 2016. [Google Scholar]
- SISS. Superintendencia de Servicios Sanitarios. Informe de Gestión del Sector Sanitario. 2019. Available online: https://www.siss.gob.cl/586/articles-17955_recurso_1.pdf (accessed on 4 February 2021).
|City, Country||Distance (km)||Elevation (m)||Cost (USD/m3)|
|México city, México||225||2500||2.44|
|1. Municipal wastewater|
|Reverse osmosis system||y = 272.54·x + 4.9835·106|||
|Ultrafiltration system||y = 136.38·x +2.4859·106|
|Yard piping||y = 40.97·x + 7.3826·105|
|Sitework land scaping||y = 20.38·x + 3.7647·105|
|Site electrical and controls||y = 81.86·x + 1.4916·106|
|Activated sludge system||log(y) = 0.256·(log(x))1.556 + 4.545|||
|Construction and infrastructure||y = 8.996·105·x + 6.20·106|||
|Land acquisition||y = 17.995·x + 1.2363·105|
|Engineering||y = 31.53·x + 2.1608·105|
|Development and management||y = 4.5263·x + 3.0165·104|
|Operating and maintenance costs|
|1. Municipal wastewater|
|Reagents UF||y = 3.1224·10−2 + x·2.2448·10−5|
|Membrane replacement UF||y = 4.6073·10−3 + x·8.9988·10−6|
|Energy consumption UF||y = −5.4386·10−3 + x·4.0363·10−6|
|Reagents RO||y = 2.2126·10−2 + x·2.2727·10−5|
|Membrane replacement RO||y = 1.1905·10−2 + x·8.8019·10−6|
|Energy consumption RO||y = −3.0484·10−2 + x·4.0087·10−5|
|Activated sludge system|
|Energy consumption||0.033 USD/m3|||
|Waste management||0.029 USD/m3|
|Energy consumption||y = 1.461·10−3·x + 4.946·106|||
|Membrane replacement||y = 8·10−2·x−1.57·10−1|
|Reagents||y = 4·10−2·x−7.85·10−2|
|Labor||y = 1.496·10−2·x + 1.44·105|
|Maintenance||y = 8.086·10−5·x + 7.883·103|
|Water Production Capacity (m3/d)||Scenario 1||Scenario 2||Scenario 3|
|Capital Costs||O&M Costs||Total Costs||Capital Costs||O&M Costs||Total Costs||Capital Costs||O&M Costs||Total Costs|
|City||Water Demand (m3/d)||WWTP||Potential Water Supplier City||Produced Water (m3/d)||deq_ww (km)||deq_coast|
|Quillota||17,624||conventional||Viña del Mar||50,772||49.8||25.1||89.0|
|Quilpué||33,659||submarine outfalls||Viña del Mar||50,772||34.6||11.9||−2.7|
|City||Water Resource||Water Price (USD/m3)|
|Alto Hospicio||Wastewater reuse (from Iquique)||0.63|
|Andacollo||Wastewater reuse (from Ovalle)||1.31|
|Limache||Wastewater reuse (from Quillota)||0.69|
|Quillota||Wastewater reuse (from Viña del Mar)||0.66|
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Crutchik, D.; Campos, J.L. Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination? Sustainability 2021, 13, 6815. https://doi.org/10.3390/su13126815
Crutchik D, Campos JL. Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination? Sustainability. 2021; 13(12):6815. https://doi.org/10.3390/su13126815Chicago/Turabian Style
Crutchik, Dafne, and José Luis Campos. 2021. "Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination?" Sustainability 13, no. 12: 6815. https://doi.org/10.3390/su13126815