Water-energy Nexus Research Articles

Energy efficiency of drinking water treatment plants: A methodological approach for its ranking

Drinking water treatment systems (DWTSs) are energy intensive facilities, and are an example of the water-energy nexus. Benchmarking energy efficiency is a valuable tool for improving the economic and environmental performance of such facilities. Data envelopment analysis (DEA) is typically used to assess efficiency, allocating flexible weights (FSW) to variables that maximise energy efficiency scores for each DWTS (DEA-FSW). It means that different conditions are applied to each DWTS. Moreover, the DEA-FSW approach has finite discriminatory power which limits cross-unit comparison of energy efficiency hindering the benchmarking of DWTSs. To overcome these limitations, our study explored the effect of estimating the energy efficiency scores of DWTSs by allocating common sets of weights (CSW) within DEA (DEA-CSW). This approach was applied empirically on a sample of 146 DWTSs. Evaluated DWTSs had poor energetic performance based on both DEA-FSW and DEA-CSW estimates (low energy efficiency scores: 0.329 and 0.163, respectively). Even in the optimistic scenario, the average energy efficiency score was low (0.220), with potential electricity savings of 78 % by DWTPs when energy efficient. Unlike DEA-FSW, DEA-CSW allowed energy efficient DWTSs to be distinguished from the 146 facilities. Significant differences in the weights allocated to electricity and pollutants removed from raw water were reported for both approaches, and contributed to diverging energy efficiency scores. In conclusion, this study demonstrated the relevance of using suitable methods to generate comparable results for water companies, allowing the energy performance of DWTSs to be objectively evaluated for benchmarking purposes.

Optimization of the Water-Energy Nexus in Hydraulic Fracturing Processes Using CO2 and Water as Fracturing Fluids

Hydraulic fracturing has paved the way for the extraction of substantial quantities of shale gas. Traditionally, water (in significant quantities) has been used as the primary fracturing fluid. In addition to the significant water usage in fracturing, large quantities of shale gas wastewater have been generated. Driven by the need for better management of water resources in hydraulic fracturing, the introduction of CO2 (captured from industrial emissions) has been considered an element in the fracturing fluid. This paper proposes a mathematical programming formulation to synthesize the best configuration for the use of water and CO2 associated with shale gas hydraulic fracturing operations while taking into account the fluctuations in water availability, generation of CO2, and the flowback water based on a time horizon. The proposed formulation incorporates a strategic planning that minimizes the total annual cost (TAC) considering water requirements, generation and capture of CO2, as well as the capacity of the equipment for treatment technologies, transportation fees, storage units, and disposal. A case study is presented to demonstrate the usefulness of the proposed methodology. The results show that at a higher percentage of CO2 in the fracturing fluid, the TAC increases but the freshwater required decreases. Furthermore, the trade-offs and impact of freshwater availability have been identified.

Small-Scale Solar-Powered Desalination Plants: A Sustainable Alternative Water-Energy Nexus to Obtain Water for Chile’s Coastal Areas

The natural potential of Chile—solar energy and 8 km of coastline—make the implementation of small-scale reverse osmosis desalination plants (RODPs) in coastal areas energetically supported with photovoltaic systems (PVs) feasible. This work considers a survey of the plants in Chile. As a demonstration of a RODP, a technical/economic evaluation is carried out, analyzing four possible cases in which different energy configurations are proposed: electric grid, diesel generator, and photovoltaic systems, without or with batteries. Finally, the challenges and opportunities of these plants are presented. The results obtained indicate that there are 39 plants in operation, which produce an average permeate water flow of Qp 1715 m3d−1. Solar Explorer, and Homer Pro software are used for a plant that generates 8 m3day−1 of permeate water, resulting in the conclusion that Case 3 is the most economically viable, as it has a useful life of 20 years and will have an annual solar contribution of more than 65%. The levelized cost of water production is 0.56 USDm−3 (RODP/PV) and 0.02 USDkW−1h−1 was obtained for the LCOE. Finally, this case contributes to the mitigation of climate change.

Comprehensive reliability evaluation of water-energy nexus systems

• New reliability model is developed for integrated Water-Energy Nexus (WEN). • An augmented probabilistic algorithm is devised to evaluate the reliability of WEN. • Renewable energy sources and energy storage are considered in reliability analysis. • Both mechanical failures and hydraulic analysis of the water system are considered. • Three reliability indices for water system considering power reliability are devised. • Power supply reliability is an unneglectable factor as three overall reliability indices of water system increase by 19.7%, 32.6%, and 26.9% respectively when it is considered. Water and power systems are two national critical infrastructures which support our daily life and economic growth. Both are highly interconnected and complex networks, which consist of various system elements. The core functions of water and power distribution systems are to deliver satisfactory water and electric services to consumers by satisfying the demands at all load points. Besides the factors in the water distribution system itself, power supply may affect the performance of the water distribution system. Therefore, the two systems are in fact physically connected and coupled. The purpose of this study is to develop an appropriate model and an efficient evaluation algorithm to quantify the reliability of the water distribution and power supply system as an integrated Water-Energy Nexus (WEN). This paper proposes a probabilistic reliability evaluation method for the micro-WEN model based on the sequential Monte Carlo Simulation (MCS) procedure. In the proposed evaluation procedure, both mechanical failures and hydraulic analysis are taken into consideration. Case studies are performed based on a representative water-energy nexus system to demonstrate the effectiveness of the proposed method.

Numerical and experimental study of a single-slope double-effect solar still integrated with paraffin wax

• The condensation theory takes into cognizance the heat and mass transfers in the humid air medium in estimating the freshwater yield. • The productivity of a solar distillation system can be improved by increasing the number of condensing surfaces. • The double-effect unit performed better than the single-effect unit by 48.7%. • The upper and lower chambers had different phases of production due to the effect of the ambient environment and the heat retention capability of the lower condensing cover. • The lower chamber of the double-effect unit had a maximum yield rate of 0.28kg/m 2 /h while the system had a maximum cumulative yield of 4.06kg/m 2 /day. The demand for freshwater has continued to soar amidst an increasing population, industrialization, and environmental pollution. The continuous shrinkage of this important resource has necessitated the need for a concerted effort on seawater desalination. Solar-powered desalination occupies a strategic position in the water-energy nexus and offers an alternative to taking off pressure from the already stressed freshwater sources. A numerical study with experimental validation of a single-slope double-effect solar still integrated with paraffin wax is thus presented. A transient mathematical model considering the humid air media in the upper and lower chambers was developed. Previous works in this area ignored the thermal analysis of the humid air medium, and as such, adopted the evaporation theory in the estimation of the freshwater yield. However, this study considers the thermal resistance offered by the humid air in the computation of the yield using the condensation theory. The energy-balance equations were discretized using the finite element method and solved with the aid of version 7.12 of the FlexPDE numerical solver. The model was validated with data from the experimental study. The correlation coefficients between the predicted and experimental data showed good agreement with values in the range of 0.97 ≤ r ≤ 0.99 , and values of root mean square percent deviation of 3.2 % ≤ e ≤ 16.8 % . The system achieved its best performance in November with a daily yield of 4.06 kg/m 2 and a mean efficiency of 33.7%. The upper basin contributed an average of 52% of the total yield with a greater percentage of its yield occurring during the nocturnal phase. The effects of the upper basin and the PCM on the diurnal performance of the system were evaluated.

Leveraging Automation and Data-driven Logistics for Sustainable Farming of High-value Crops in Emerging Economies

Technology innovations present an opportunity for the agricultural sector to leverage in-field data and inform resource-demanding operations to ultimately promote Sustainable Development Goals (SDGs). The need for data-driven innovations in farming is particularly pertinent to resource-scarce regions, such as the Indian Punjab, where an amalgam of obscure policies and lack of real-time visibility of crops typically leads to the excessive use of farming inputs like freshwater. To this end, this research investigates the use of Internet of Things (IoT) implementations to cultivate Kinnow (a high-value citrus fruit) for assessing the impact of data-informed irrigation practices on the appropriation of natural sources, farming operations efficiency, and the well-being of smallholder farmers. First, a literature taxonomy demonstrates that studies on agri-field logistics often do not consider operations’ environmental and energy impact. In addition, the application of IoT and automated guided vehicles (AGVs) for informing farmers about precision irrigation planning has not been sufficiently explored. Second, an empirical-driven numerical investigation explores four alternative irrigation scenarios for cultivating Kinnow, namely: (i) flood irrigation; (ii) manual irrigation; (iii) AGV-informed manual irrigation; and (iv) AGV-assisted irrigation, which was cast as a Capacitated Vehicle Routing Problem. The analysis results compare the overall sustainability impact of the investigated practices on the water-energy nexus. This research is innovative as it focuses on data-driven logistics operations on the environmental, energy and farmers’ well-being impact associated with irrigation practices in agronomy. This study further supports the role of data-driven technology innovations towards the transition to SDG-centric food supply chains by providing guiding principles for community-led in-field logistics planning.

An Approach for Water and Energy Savings in Public Buildings: A Case Study of Brazilian Rail Company

Water scarcity is a current problem in many parts of the planet and there is a worldwide concern about water availability to meet future water demand. In countries like Brazil, where most of the electricity is produced by hydroelectric power plants, water scarcity directly impacts energy production. The water–energy nexus is directly related and impacted by CO2 emissions and its climate consequences, which calls to a broader approach: energy–carbon–water nexus. In this context, the Sustainable Water and Energy Consumption (SWEC) Program was developed to mitigate water and energy supply problems in a railway company in Brazil. The actions took place in four main areas: (a) users conscientization, (b) consumption diagnosis, (c) indicators for evaluating water and energy consumption, and (d) evaluation of implementing alternative cleaner water and energy sources. The per capita consumption of water and energy were reduced by 10% and 19%, respectively. Permanent results were achieved by the SWEC Program, such as the acquisition of two photovoltaic systems with a total capacity of 96.5 kWp. The investment made provided an average monthly reduction in energy consumption of 56% in 2022. This work contributed to the UN Agenda 2030 and the findings may help companies and industries, and other institutions, such as universities and schools, to improve their water and electricity consumption.

Systematic Modeling and Policy Analysis on the Urban Water–Energy Nexus for Sustainable Resources Management

Urbanization in developing countries has imposed great pressure on the availability of water and energy (WE) resources, while single-sector strategies may cause several unanticipated consequences. To find sustainable solutions for resource management, this study develops an integrated approach to assess urban WE from a nexus perspective. With the city Shenzhen as a case study, the existing WE nexus on the supply and demand sides of urban areas is first quantified. Subsequently, a system dynamics model (SDM) is constructed to reveal the complex interactions in the urban nexus, and the trends of WE supply and demand by 2035 are simulated. To narrow the potential resources gap, a policy analysis considering the interest and influence of various stakeholders is conducted to formulate policy scenarios. As revealed from the results, the resources gap will expand continuously by 2035, especially for water resources. Compared to the demand side, the policies implemented on the supply side exhibit a better performance, and the scenario of import expansion could independently achieve the desirable result. Moreover, as the demand side displayed more complexities, the implementation of future policies should rigorously weigh the priorities and difficulties of a range of stakeholders’ involvements.

A novel green hydrogen production using water-energy nexus framework

The transformation of electrical energy to hydrogen via water electrolysis consumes considerable amount of fresh water and a productive use of nontraditional water sources enhances the reliability and resilience of energy and water systems. In this study, we have designed a solid oxide electrolysis cell (SOEC) system which is an evolving hydrogen production technology at high temperatures for water electrolysis. The SOEC uses steam generated from flue gas as its feedstock and is fully integrated with numerous power production units, including coal and natural gas-fired power plants as its energy feedstock. While there is a hasten global shift away from fossil fuel, integrating its asset into this technology helps limit the risk and future losses of stranded assets and reduce the cost of investment in the new technologies. But high capital expenditures and doubt concerning the future cost and efficiency upgrade are obstacles to investing inwater electrolysis. Such a detailed Levelized cost of hydrogen and techno-economic analysis is conducted to show the viability and environmental impacts of this novel technology. The results show SOEC efficiency of 97.4 % and 56.3 % as thermal-to-hydrogen efficiency of the system with a daily hydrogen production of 242,400 kg at $2.9–3.5/kg H2. The estimates show a positive gain prospect in this technology and techno-economic challenges.

Techno-Economic Analysis of Selected PV-BWRO Desalination Plants in the Context of the Water–Energy Nexus for Low–Medium-Income Countries

Jordan was late in adopting seawater and brackish water desalination as a source until the late 1990s and early 2000s. However, ongoing studies are still discussing the technical, economic, and socio-political aspects of brackish water reverse osmosis (BWRO) desalination plants. In this study, the water–energy nexus was considered, in order to highlight the main challenges facing BWRO desalination. We discuss the use of photovoltaic (PV) technology, together with BWRO desalination, as an approach to compensate for ecological, financial, and social challenges in Jordan. For this purpose, the performance of nine existing BWRO desalination plants in the agricultural, domestic, and industrial sectors is assessed. The water performance is assessed based on water consumption, safe yield extraction, plant recovery rate (R, %), and compliance to local and international water quality standards; the Specific Energy Consumption (SEC, kWh/m3) is taken as the main evaluation criterion to assess the energy performance of the BWRO desalination plants; and economic performance is assessed based on the overall cost of water produced per cubic meter (USD/m3). The main environmental component is the brine disposal management practice utilized by each plant. Based on this assessment, the main challenges in BWRO desalination are the unsustainable patterns of water production, mismanaged energy performance, low recovery rates, and improper brine disposal. The challenges in domestic and industrial BWRO desalination, which are completely dependent on the electricity grid, are associated with critical energy and costs losses, as reflected by the high SEC values (in the range of 2.7–5.6 kWh/m3) and high water costs per cubic meter (0.60–1.18 USD/m3). As such, the use of PV solar panels is suggested, in order to reduce the electricity consumption of the assessed BWRO plants. The installation of PV panels resulted in significantly reduced energy costs (by 69–74%) and total costs (by 50–54%), compared with energy costs from the electricity grid, over the lifetime of the assessed BWRO desalination plants.

Optimization Modeling for Regional Energy System Management Coupled with Energy–Water Nexus and Carbon Emission Reduction: A Case Study

Under global climate change and resource crisis, the correlation and restriction between energy, water, and carbon emission are increasingly prominent, which has posed great challenges for the sustainable development of energy systems. This article develops a dual-interval stage-fuzzy credibility-constrained programming model for regional energy system management problems with energy–water nexus (EWN) and carbon emission reduction, in which uncertainties expressed as discrete intervals, probability distributions, and dual-interval fuzzy numbers can be addressed. It can provide a trade-off among economic cost, system risk, and environmental objective. Then, the hybrid programming method is applied to a case of Guangdong Province, China to verify its applicability, where a series of scenarios with respect to water resources and carbon emission constraints are explored and examined. The robust solutions of optimal strategies for electricity generation, capacity expansion, water supply, and carbon capture are investigated and obtained. Results disclose that different scenarios associated with water resource availability and carbon emissions would deeply affect the EWN system planning: (1) Compared with low carbon emission standard, the proportion of renewable power generation under high carbon emission scenario would increase by [1.39, 1.68] %, [1.69, 2.35] %, and [1.49, 1.94] % in periods 1–3, respectively. (2) Scarce water availability scenario would restrict coal-fired power generation and simulate the development of renewable energy. These findings can be useful for decision makers to gain deep insights into energy system management in a sustainable way considering energy structure adjustment, multiple uncertainties, EWN, and carbon emission reduction.

Comparing the importance of farming resource endowments and agricultural livelihood diversification for agricultural sustainability from the perspective of the food–energy–water nexus

Sustainable agricultural development, which aims to optimize income and minimize resource consumption and environmental impacts, is strongly influenced by farming resource endowments and agricultural livelihood strategies. However, quantifying the impacts of these factors on agricultural sustainability remains a challenge. Here, we proposed a framework that incorporated the agricultural food–energy–water (FEW) nexus into a sustainable livelihood framework, to explore agricultural sustainability. We then applied a partial least squares–structural equation model (PLS-SEM), based on household survey data from MiYun Reservoir watershed, China, to identify the complex pathways of the impact of household farming resource endowments and livelihood diversification on agricultural sustainability. Our study indicated that diversified farming achieved a better performance in the FEW nexus via the mediating factor of farming inputs (β = 0.335, p < 0.01). Meanwhile, diversified farming had positive effects on economic profits and environmental sustainability (β = 0.531, p < 0.01). Increasing farming resource endowments also had a better performance in the FEW nexus (β = 0.211, p < 0.01); however, that may lead to economic and environmental costs (β = −0.445, p < 0.01). The framework can be used to identify the relationship between household livelihoods and the FEW nexus to better achieve resource security and sustainable development goals.

A novel framework for technical performance evaluation of water distribution networks based on the water-energy nexus concept

Today energy recovery using Micro-Hydropowers (MHPs) in Water Distribution Networks (WDN) is a well-known approach for recycling the wasted energy in infrastructures as a sample of circular economy. Likewise, in this study for the first time a framework for evaluation of WDN for energy harvesting have been designed with the application of statistical optimization, simulation, and artificial intelligence concepts. In this study, after modelling a WDN in Mashhad, Iran, with Environmental Protection Agency Network Evaluation Tool (EPANET) software, the potential of energy recovery using MHP technology was optimized with the application of Design of Experiment (DOE) methods, including Taguchi and Response Surface Methodology (RSM) and then the model prediction ability was improved by Artificial Neural Network (ANN) technique. Results of this investigation revealed that the combination of Taguchi and RSM methods could successfully optimize the energy recovery potential with consideration of improving the hydraulic parameters of WDN. With the application of RSM and Taguchi, high potential positions for MHP placement are detected and analyzed based on a high-performance operational decision-making methodology. According to Artificial Intelligence (AI) computations, energy harvesting and hydraulic responses can be estimated with more than a 99 % correlation coefficient. Also, it shows that the soft-operator can be executed to control the features of MHPs in WDNs. The outputs of this research demonstrated that MHP harvested energy is more than 400KW for the run time of this study with consideration of hydraulic parameters.

Energy and water: COVID-19 impacts and implications for interconnected sustainable development goals.

The COVID-19 pandemic presented a chance to investigate the effects of system-wide emergencies on major global commodities such as water and energy. In terms of environmental policies and attaining supply security, these developmental goals are interrelated. Despite pandemic disruptions, there is a compelling need for a systematization in these areas for the transition to clean water access and sustainable energy. This article presents a comprehensive assessment of the effects of COVID-19 on these two sustainable development goals. Further, an integrated aspect of water and energy access for sustainable development is evaluated with insights on the effects of COVID-19 on the water-energy nexus. Additionally, technological evolution for building better water and energy supply systems is presented. An insight into developing robust healthcare systems and how the water and energy SDGs affect population dynamics is also speculated, which indicates varied short-term adaption experiences, and highlights the need for a re-evaluation of the water-energy nexus. The integrated solutions contributing to stability of the water supply chain, energy storage, and policy making during and after an outbreak are critical to achieving developmental goals.

Phosphorene nanosheet decorated graphitic carbon nitride nanofiber for photoelectrochemically enhanced hydrogen evolution from water splitting

BackgroundPhosphorene nanosheet is a p-type semiconductor with excellent optoelectronic property and large surface area, while graphitic carbon nitride (g-C3N4) nanofiber is a n-type visible-light-driven photocatalyst. The fabrication of p-n heterostructured nanocomposites for hydrogen evolution from water splitting via photoelectrochemistry is an exceptionally promising technique. MethodPhosphorene and g-C3N4 were prepared by electrospinning and ultrasonic exfoliation procedures, respectively, and then mixed physically by Van deer Waal force to form the p-n heterojunction. The photoelectrochemical hydrogen evolution from water splitting was performed under solar light irradiation. Significant findingsThe morphological analysis show that 100–200 nm phosphorene nanosheets are successfully decorated on 450-nm g-C3N4 nanofibers. After adding 4–18 wt% phosphorene onto g-C3N4 nanofiber (P/CN), the specific surface area of P/CN nanocomposites is in the range of 52.1–68.3 m2 g−1. The addition of 13 wt% phosphorene is optimal for P/CN nanocomposite to maximize the hydrogen evolution rate of 2,208 μmol h−1 g−1 by accelerating the electron transfer to enhance the PEC performance in P/CN heterostructure under illumination. Results have signified that the metal-free P/CN photocatalyst can provide an effective solar-light-responsive capability toward water splitting, which can create a promising strategy to fabricate low-dimensional electrode materials for a wide variety of water-energy nexus and green energy applications.

Global and regional models for identification of cooling technology in thermal power generation for water demand estimations in water-energy nexus studies

Water-energy nexus studies aim to connect the process of power generation with the corresponding water demand. The lack of information on the currently installed cooling systems at individual power plants is a challenge for the assessment of the water use on the power plant-level, which complicates decision-making in water management, especially in water-stressed regions. In this study, we investigate the spatial and temporal trends in cooling technology installations globally. Based on that, we propose a machine learning model for cooling technology identification on a regional and global level, which uses a combination of feature selection and classification algorithms. The global model demonstrates an average test set accuracy of 85.42%, which corresponds to only a minor underestimation of the actual global water footprint of 1.78% when the cooling technology and water footprint of individual power plant units is unknown. Apart from that, a special emphasis was placed on regions characterized by high and extremely high water stress, where mistakes in water policy planning and water management may lead to an unsustainable water use or even to an overexploitation of water resources. In these regions, the calculated test set accuracy was 80.83%, which is significantly larger than the average accuracy of a majority class model. The results and the method proposed in this study enable cooling system identification in individual power units using information available from other sources, such as the water stress score or seasonal freshwater availability in the region.

Pathways to Energy-efficient Water Production from the Atmosphere.

Atmospheric water harvesting (AWH) provides a fascinating chance to facilitate a sustainable water supply, which obtains considerable attention recently. However, ignoring the energy efficiency of AWH leads to high energy consumption in current prototypes (ca. 101 to 102 MJ kg-1 ), misfitting with the high-strung and complicated water-energy nexus. In this perspective, a robust evaluation of existing AWHs is conducted and a detailed way to high-efficiency AWH is paved. The results suggest that using cooling-assisted adsorption will weaken the bounds of climate to sorbent selections and have the potential to improve efficiency by more than 50%. For device design, the authors deeply elucidate how to perfect heat/mass transfer to narrow the gap between lab and practices. Reducing heat loss, recovering heat and structured sorbent are the main paths to improve efficiency on the device scale, which is more significant for a large-scale AWH. Besides efficiency, the techno-economic evaluation reveals that developing a cost-effective AWH is also crucial for sustainability, which can be contributed by green synthesis routes and biomass-based sorbents. These analyses provide a uniform platform to guide the next-generation AWH to mitigate the global water crisis.

Front Cover: Solar‐Driven Catalytic Urea Oxidation for Environmental Remediation and Energy Recovery (ChemSusChem 21/2022)

The Front Cover shows that solar-driven catalytic urea conversion greatly promotes a sustainable water-energy nexus, promisingly achieving the purpose of killing two birds (energy and environment) with one stone (solar light). More information can be found in the Review by W. Sun, M. Zhang, et al.

Anion-cation heterostructured hydrogels for all-weather responsive electricity and water harvesting from atmospheric air

Despite the recent boom in moisture-enabled electricity generation (MEG), it suffers from fabrication intricacy and materials inadequacy for water and energy harvesting purposes. Moreover, conventional MEGs face challenges in restricted operating humidity, inertness to subtle humidity fluctuations and inability to sustain long-lasting power output under high humidity due to limitations in hydrophilicity and hydration. Here, we exploit a unique oppositely-charged hydrogel heterojunction for electricity and fresh water harvesting from atmospheric air without trade-offs in process simplicity and humidity limits. This anion-cation heterostructure engages two oppositely polarized ions and features a self-regulating ionic gradient for MEG in a dynamically fluctuating ambient, making it not only capable of responding to sluggish and subtle humidity fluctuations but delivering undisrupted power even under extremely wet conditions. Different from other MEGs, moisture can be captured and largely stored in the hydrogel and then released as fresh water. This moisture absorption/desorption, interestingly, is accompanied by electricity generation, indicating a two-in-one strategy to address the water-energy nexus. In such a hydrogel heterojunction, multiple environmental elements like moisture, light, temperature, wind, etc., are feasibly mobilized for energy harvesting. This work provides a promising autonomous and continuous operation of an energy-water system for sustainable and decentralized purposes.

Development of a crossflow nanofiltration process for polishing of wastewater by-product from biogas production processes

The growing adoption of biogas production from source-separated organics (SSOs) has resulted in a need for advanced treatment processes for the resulting liquid waste by-products. While previous studies have demonstrated the potential of using nanofiltration (NF) membranes to polish the outlet stream of a membrane bioreactor (MBR) in municipal wastewater applications, there is little known about the performance of such membranes to treat the more complex multi-component streams that result from the processing of SSOs. In this study, crossflow filtration experiments with three commercial flat-sheet NF membranes (NFS, NFX, NF90) were run on two batches of MBR permeate (identified as Batch A and Batch B) which were sourced four months apart from a biogas production facility. For each batch, there was a remarkable difference in performance of the three NF membranes, where a clear trade-off between permeate quality and recovery was observed. For example, the NF90 membrane gave the best permeate quality but the lowest recovery. Interestingly, the NFS permeate COD for Batch B was approximately 60 % lower than that for Batch A; it is believed that this was due to differences in the amount of ammonia between the two batches. This work bridges a technical gap in the water-energy nexus by demonstrating the viability of using NF technology to polish liquid waste streams from biogas production processes, while also highlighting their susceptibility to variable feed conditions caused by upstream process deviations.