Wastewater treatment and reuse in urban agriculture: exploring the food, energy, water, and health nexus in Hyderabad, India

Abstract

Nutrients and water found in domestic treated wastewater are valuable and can be reutilized in urban agriculture as a potential strategy to provide communities with access to fresh produce. In this paper, this proposition is examined by conducting a field study in the rapidly developing city of Hyderabad, India. Urban agriculture trade-offs in water use, energy use and GHG emissions, nutrient uptake, and crop pathogen quality are evaluated, and irrigation waters of varying qualities (treated wastewater, versus untreated water and groundwater) are compared. The results are counter-intuitive, and illustrate potential synergies and key constraints relating to the food-energy-water-health (FEW-health) nexus in developing cities. First, when the impact of GHG emissions from untreated wastewater diluted in surface streams is compared with the life cycle assessment of wastewater treatment with reuse in agriculture, the treatment-plus-reuse case yields a 33% reduction in life cycle system-wide GHG emissions. Second, despite water cycling benefits in urban agriculture, only <1% of the nutrients are able to be captured in urban agriculture, limited by the small proportion of effluent divertible to urban agriculture due to land constraints. Thus, water treatment plus reuse in urban farms can enhance GHG mitigation and also directly save groundwater; however, very large amounts of land are needed to extract nutrients from dilute effluents. Third, although energy use for wastewater treatment results in pathogen indicator organism concentrations in irrigation water to be reduced by 99.9% (three orders of magnitude) compared to the untreated case, crop pathogen content was reduced by much less, largely due to environmental contamination and farmer behavior and harvesting practices. The study uncovers key physical, environmental, and behavioral factors that constrain benefits achievable at the FEW-health nexus in urban areas.

A Comparative Life Cycle Assessment of Crop Systems Irrigated with the Groundwater and Reclaimed Water in Northern China

“…The syntheses of three existing studies and this study indicated that the irrigated crop systems resulted in diverse environmental impacts ranging from energy consumption and global warming to water and soil quality impacts [15][16][17]. The top contributors varied across different environmental impact categories, which suggested that different strategies should be adopted for effectively remediating the corresponding environmental impacts.…”

“…Munoz et al [17] and this study excluded wastewater treatment processes from the system boundary, since municipal wastewater is treated to meet the discharge standard regardless of reuse as an irrigation source. In contrast, Moretti et al [15] and Miller-Robbie et al [16] included wastewater treatment processes in the system boundary. Also, the assessed crop types and geographical contexts varied significantly.…”

“…Moretti et al studied fruit orchards in Southern Italy. Miller-Robbie et al [16] assessed spinach in India. In contrast, this study is the only study focusing on corn, soybean and wheat in Northern China.…”

A Literature Review to Propose a Systematic Procedure to Develop “Nexus Thinking” Considering the Water–Energy–Food Nexus

“…In agriculture, issues such as (a) irrigated agriculture [44,110], (b) wastewater treatment and reuse in urban agriculture [111], (c) food waste [112], (d) agricultural water management [71,113], and (e) the role of phosphorus (P) in nexus relations [103] were covered. In the energy sector, issues such as (a) bioenergy [86,114,115], (b) water consumption during energy production [116], and (c) impact on aquatic species through the release of thermoelectric effluents [68] were considered.…”

Synergies within the Water-Energy-Food Nexus to Support the Integrated Urban Resources Governance

“…When it comes to the research scales, the prevailing opinions largely see Nexus as the local scale that often proved to be unsustainable, owing to inadequate cross-sectoral synergies. In recent times, more scholars turn to the study of Nexus system at city level [29][30][31][32]. As is well known, urbanization is prevalent worldwide, with the global urbanization rate reaching 54% in 2017.…”