Water-energy nexus: Sustainable water management and energy recovery from wastewater in eco-cities

• Published in: Smart and sustainable built environment 2020-04, Vol.9 (1), p.54-70
• Main Authors: Guven, Huseyin, Tanik, Aysegul
• Format: Article
• Language: English
• Subjects: Annual precipitation; Annual rainfall; Blackwater; Cities; Climate change; Developing countries; Domestic wastewater; Domestic water; Electric power demand; Electricity; Energy conservation; Energy consumption; Energy harvesting; Energy recovery; Environmental impact; Environmental science; Geographical distribution; Geographical locations; Green city concept; Greywater; Households; Hydrologic data; Irrigation; Irrigation water; LDCs; Mathematical analysis; Megacities; Precipitation; Rain water; Rainwater recovery systems; Recycling; Residential areas; Roofs; Sound; Surface water; Sustainable use; Thermal energy; Urbanization; Waste recovery; Wastewater; Wastewater reuse; Water conservation; Water consumption; Water demand; Water harvesting; Water management; Water resources; Water reuse; Water treatment; Water use
• ISSN: 2046-6099; 2046-6102
• DOI: 10.1108/SASBE-07-2017-0030

PurposeRough estimations of water gain through greywater reuse and rainwater harvesting together with energy recovery from wastewater generated from a fictitious eco-city of population 100,000 located in Istanbul, Turkey form the main framework of the study. As such, the highly important concept of water–energy nexus will be emphasised and domestic wastewater will be partly considered for water recycling and the rest for energy recovery. The paper aims to discuss these issues.Design/methodology/approachDistribution of daily domestic water consumption among different household uses and the population in the residential area are the two governing parameters in the practical calculation of daily wastewater generated. Therefore, domestic wastewater will be initially estimated based on population, and in turn, the amount of greywater will be found from the per cent distribution of water use. After segregation of greywater, the energy equivalency of the rest of the wastewater, known as blackwater, will further be calculated. Besides, the long-term average precipitation data of the geographical location (Istanbul) are used in determining safe and sound rainwater harvesting. Harvesting is considered to be only from the roofs of the houses; therefore, surface area of the roofs is directly taken from an actual residential site in Turkey, housing the same population which is constructed in four stages. Similarly, the fictitious eco-city in Istanbul is assumed to be constructed in a stage-wise manner to resemble real conditions.FindingsThe water consumption of the fictitious eco-city ABC is considered as 15,000 m3/day by taking the unit water consumption 150 L/capita.day. Therefore, total water savings through on-site reuse and reuse as irrigation water (9,963 m3/day) will reduce water consumption by 64 per cent. Minimum 40 per cent water saving is shown to be possible by means of only greywater recycling and rainwater harvesting with a long-term average annual precipitation of 800 mm. The energy recovery from the rest of the wastewater after segregation of greywater is calculated as 15 MWh/day as electricity and heat that roughly correspond to electricity demand of 1,300 households each bearing four people.Research limitations/implicationsA fictitious eco-city rather than an actual one located in Istanbul is considered as the pilot area in the study. So far, an eco-city with population around 100,000 in Turkey does not exist. An important implication relates to rainw