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Many regions around the world are suffering from water stress, and desalinated water and recycled water are seen asalternatives for meeting the water demand. However, high energy consumption and associated greenhouse gas emis-sions are some of the main environmental impacts. This is notable for many arid and semi-arid countries where desa-lination and water recycling are considered options for ensuring water resources availability. This research presentsthe incorporation of the quantification of greenhouse gas emissions generated during the operation of desalinationand wastewater treatment plants in the assessment of water stress levels using the water stress indicator adopted bythe 2030 Agenda for Sustainable Development. Chile was chosen as a case study, as it is a country where there is a con-siderable difference between the availability of conventional water sources and the water demand, and the electricalgrid is fed mainly by fossil fuels. The methodology proposed allows calculating the indirect greenhouse gas emissionsdue to electrical consumption for the operation of desalination and wastewater treatment plants, and the direct green-house gas emissions coming from biological processes used in wastewater treatment plants. The results showed thatChilean arid climate zones will not experience water stress in the future at the regional level, mainly because of theinstallation of several desalination plants by 2030. Meanwhile, recycled water from the urban sector will slightly con-tribute to the reduction in the level of water stress in almost all Chilean regions by 2030. Moreover, desalination andwastewater treatment plant will contribute only between 0.34% and 0.75% of total greenhouse gas emitted in Chile by2030. Therefore, the operation of these industrial systems for facing water scarcity problems in northern and centralzones of Chile is a suitable alternative because it does not generate large environmental problems. Post-print / Final draft

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO2. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O3/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO2. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O3/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO2. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O3/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.