Drops of energy: conserving urban water to reduce greenhouse gas emissions

Towards zero liquid discharge in hemodialysis. Possible issues

Scarcity of water and energy, and legal requirements for discharge of waste and wastewater are forcing hemodialysis facilities to change their approach to a more integrated concept of connecting the residual output (in terms of waste, wastewater and energy loss) to the input (in terms of water and energy). Zero liquid discharge is an expanding water treatment philosophy in which hemodialysis wastewater is purified and recycled, leaving little to no effluent remaining when the process is complete, thereby saving money and being beneficial to the environment. This article explores the possible ways to treat hemodialysis wastewater, thus achieving ZLD conditions.

Towards zero liquid discharge in hemodialysis. Possible issues

Scarcity of water and energy, and legal requirements for discharge of waste and wastewater are forcing hemodialysis facilities to change their approach to a more integrated concept of connecting the residual output (in terms of waste, wastewater and energy loss) to the input (in terms of water and energy). Zero liquid discharge is an expanding water treatment philosophy in which hemodialysis wastewater is purified and recycled, leaving little to no effluent remaining when the process is complete, thereby saving money and being beneficial to the environment. This article explores the possible ways to treat hemodialysis wastewater, thus achieving ZLD conditions.

Urban biocycles - Closing metabolic loops for resilient and regenerative ecosystem: A perspective

Cities are at crossroads, confronting challenges posed by increasing population growth, climate change and faltering livability. These problems are prompting urban areas to chart novel path towards adopting sustainable production/consumption strategies. The alluring concept of circular economy (CE) that focuses on reuse and recycling of materials in technical and biological cycles to reduce waste generation is a critical intervention. Present article aims on precisely highlighting the importance of biogenic materials which have an immense potential to be transformed into a source of value in an urban ecosystem. It also sets out to explore the scope of implementing 'urban biocycles' that strategically directs the flow of resources, their use, extracting value in the form of nutrients, energy and materials post consumption within an urban metabolic regime. The concepts discussed contribute to biocycle economy by outlining emerging requirements, identification of common strategies, policies and emerging areas of research in line with sustainable development goals.

Assessing water, energy and emissions reduction from water conservation measures in buildings: a methodological approach

Water-energy nexus is a cornerstone in modern societies, with significant impacts at social, environmental, and economic levels. In addition to the issue of water scarcity that several regions of the world already face or are forecasted to face in the near future due to demand increase and availability reduction (e.g. pollution, climate changes), water consumption in buildings entails substantial energy consumption. In most cases, part of this energy is produced from non-renewable sources, encompassing greenhouse gas emissions. The present research effort presents a generic methodology to assess the cascade impact of water efficiency measures in buildings in terms of water, energy and emissions reduction. The methodology is applied to the Mediterranean climate zone context for two different types of non-residential buildings: university buildings and hotels, with very distinct water end use and consumption patterns. Lastly, are performed sensitivity analyses between the proposed methodology and simplified approaches. Is observed that assuming a linear relationship between flow rate and water consumption can lead to overestimations of up to 64% in water savings. Is also explored the relevance of the water consumption and energy mix seasonality typical of climates with marked dry and wet seasons, such as the Mediterranean region. The importance of the seasonality is discussed in terms of the time scale considered to apply the methodology, revealing that adopting a simplified (annual) approach, instead of the proposed approach, can lead to relative differences between - 62 and 233% in the presented case studies.

Analysis of the Water-Energy Coupling Efficiency in China: Based on the Three-Stage SBM-DEA Model with Undesirable Outputs

Although the relationships between water and energy systems have been widely researched globally, such studies have not properly considered the coupling and driving mechanisms of the nexus between water and energy. Based on panel data from 30 Chinese provinces and cities, we used a three-stage Slacks-Based Measure model for Data Envelopment Analysis (SBM-DEA) to estimate the Water-Energy coupling efficiency in China from 2003–2015. Using the Stochastic Frontier Approach (SFA) regression model, we constructed an index of environmental factors that affect the Water-Energy coupling efficiency from the four aspects of resource environment, social environment, economic environment, and ecological environment. The results indicate that the Water-Energy coupling efficiency scores in most provinces in China are high and stable, and that the coupling efficiency of water and energy in China has a distribution pattern of northeast > east > west > central. Compared to the results in the first stage of analysis, the efficiency values in the third stage (after removal of environmental and stochastic factors) were smaller, illustrating that the coupling efficiency of water and energy in China depends on a favorable external environment. In the sample period, we also found that the improvement of the resource and social environments was the most conducive way to improve the Water-Energy coupling efficiency. Overall, the management level of technological innovation in China still has some room for improvement.

Cross-Scale Water and Land Impacts of Local Climate and Energy Policy—A Local Swedish Analysis of Selected SDG Interactions

This paper analyses how local energy and climate actions can affect the use of water and land resources locally, nationally and globally. Each of these resource systems is linked to different Sustainable Development Goals (SDGs); we also explore related SDG interactions. A municipality in Sweden with the ambition of phasing out fossil fuels by year 2030 is used as illustrative case example. The local energy system is modelled in detail and indirect water and land requirements are quantified for three stylised decarbonisation scenarios of pathways to meeting climate and energy requirements (related to SDG13 and SDG7, respectively). Total local, national and global implications are addressed for the use of water and land resources, which relate to SDG6 for water, and SDG2 and SDG15 for land use. We find that the magnitude and location of water and land impacts are largely pathway-dependent. Some scenarios of low carbon energy may impede progress on SDG15, while others may compromise SDG6. Data for the studied resource uses are incoherently reported and have important gaps. As a consequence, the study results are indicative and subject to uncertainty. Still, they highlight the need to recognise that resource use changes targeting one SDG in one locality have local and non-local impacts that may compromise progress other SDGs locally and/or elsewhere in the world.

The problem of drinking water access: A review of disinfection technologies with an emphasis on solar treatment methods

The lack of access to safe drinking water is one of the biggest challenges facing humanity in the 21st century. Despite the collective global effort that has been made, the drinking water sources of at least 2 billion people are faecally contaminated, resulting in more than half a million diarrhoeal deaths each year, with the majority occurring in developing countries. Technologies for the inactivation of pathogenic microorganisms in water are therefore of great significance for human health and well-being. However, conventional technologies to provide drinking water, although effective, present limitations that impede their global application. These treatment methods often have high energy and chemical demands, which limits their application for the prevention of waterborne diseases in the most vulnerable regions. These shortcomings have led to rapid research and development of advanced alternative technologies. One of these alternative methods is solar disinfection, which is recognised by the World Health Organization as one of the most appropriate methods for producing drinkable water in developing countries. This study reviews conventional technologies that are being applied at medium to large scales to purify water and emerging technologies currently in development. In addition, this paper describes the merits, demerits, and limitations of these technologies. Finally, the review focuses on solar disinfection, including a novel technology recently developed in this field.

Assessment of the municipal water cycle in China

Water produced from municipal utilities accounts for nearly 10% of the sum water demand in China. The municipal water cycle that integrates processes of urban water supply, water use, sewage treatment, and water reclamation has been assessed for 655 cities across nine drainage areas in mainland China in 2012. These cities in total extracted 55km³ raw water for municipal use from surface waterbodies and ground aquifers, approximate to the countrywide freshwater extraction of Russia or Italy. After purification and transmission, 45km³ water was distributed to industrial, service, and domestic users. 36km³ of post-use sewage was collected and environmentally safely treated; merely 3.2km³ of the treated water was reclaimed. Driven by increasing urbanization, the municipal water demand in cities of China may grow 70% by 2030. The Hai River and the Huai River basins, which harbor 137 cities and occupy a majority of the densely populated North China Plain, are most exposed to physical water scarcity. The municipal water abstraction in these cities can remain constant by promoting demand-side and process conservation in the next two decades. Interbasin transfer and unconventional sources will provide municipal water double than the cities' need. Whereas the urban water security can be technically enhanced, the challenges are to better improve water use efficiency and mitigate economic and environmental costs of the municipal system.

Energy for Conventional Water Supply and Wastewater Treatment in Urban China: A Review

This review seeks to provide a better understanding of energy used in the urban water system in China. Electricity is a major contributor to the environmental impact of water supply and wastewater treatment, particularly in countries like China where electricity is largely generated using coal and has a significant impact on greenhouse gas emissions. Electricity use can also constitute one of the main costs for water and wastewater companies. China is an important country for the study of energy for water, particularly in urban areas where population is rapidly increasing. China's daily wastewater treatment capacity has increased dramatically over the last decade and a half, and energy use for both wastewater treatment and potable water supply has grown significantly. This paper deals with the challenge of energy for water in China. It reviews the growing body of work on energy for conventional water supply and wastewater treatment in urban China. The review covers energy for all parts of conventional water supply and wastewater treatment, including energy for sourcing, treating and distributing groundwater and surface water, and energy for primary and secondary treatment and sludge treatment and disposal.

Carbon Dioxide Reduction Targets of Hot Water Showers for People in Hong Kong

Improving water and energy efficiency in buildings is one of the best ways to reduce greenhouse gas emissions. This study examines various energy-related carbon dioxide (CO2) reduction measures, including the use of water efficient showerheads and shower drain water heat recovery, in order to distinguish the significance of user influence on the water usage of a shower. The probability of taking a hot shower and the number of showers taken by an occupant per day, which can be evaluated from open literature data, are used as the parameters of user responses to water conservation measures in this study. A Monte Carlo model of water consumption and CO2 reduction for showering is adopted to determine the contributions of user responses. The results demonstrate that the influence of users on CO2 reduction is significant and compatible to the influence of water efficient showerheads. This study can be used as a reference to enhance water and energy incentives and to facilitate continuous improvement in building water systems.

City-scale analysis of water-related energy identifies more cost-effective solutions

Energy and greenhouse gas management in urban water systems typically focus on optimising within the direct system boundary of water utilities that covers the centralised water supply and wastewater treatment systems, despite a greater energy influence by the water end use. This work develops a cost curve of water-related energy management options from a city perspective for a hypothetical Australian city. It is compared with that from the water utility perspective. The curves are based on 18 water-related energy management options that have been implemented or evaluated in Australia. In the studied scenario, the cost-effective energy saving potential from a city perspective (292 GWh/year) is far more significant than that from a utility perspective (65 GWh/year). In some cases, for similar capital cost, if regional water planners invested in end use options instead of utility options, a greater energy saving potential at a greater cost-effectiveness could be achieved in urban water systems. For example, upgrading a wastewater treatment plant for biogas recovery at a capital cost of $27.2 million would save 31 GWh/year with a marginal cost saving of $63/MWh, while solar hot water system rebates at a cost of $28.6 million would save 67 GWh/year with a marginal cost saving of $111/MWh. Options related to hot water use such as water-efficient shower heads, water-efficient clothes washers and solar hot water system rebates are among the most cost-effective city-scale opportunities. This study demonstrates the use of cost curves to compare both utility and end use options in a consistent framework. It also illustrates that focusing solely on managing the energy use within the utility would miss substantial non-utility water-related energy saving opportunities. There is a need to broaden the conventional scope of cost curve analysis to include water-related energy and greenhouse gas at the water end use, and to value their management from a city perspective. This would create opportunities where the same capital investment could achieve far greater energy savings and greenhouse gas emissions abatement.

Quantifying Energy and Water Savings in the U.S. Residential Sector

Stress on water and energy utilities, including natural resource depletion, infrastructure deterioration, and growing populations, threatens the ability to provide reliable and sustainable service. This study presents a demand-side management decision-making tool to evaluate energy and water efficiency opportunities at the residential level, including both direct and indirect consumption. The energy-water nexus accounts for indirect resource consumption, including water-for-energy and energy-for-water. We examine the relationship between water and energy in common household appliances and fixtures, comparing baseline appliances to ENERGY STAR or WaterSense appliances, using a cost abatement analysis for the average U.S. household, yielding a potential annual per household savings of 7600 kWh and 39 600 gallons, with most upgrades having negative abatement cost. We refine the national average cost abatement curves to understand regional relationships, specifically for the urban environments of Los Angeles, Chicago, and New York. Cost abatement curves display per unit cost savings related to overall direct and indirect energy and water efficiency, allowing utilities, policy makers, and homeowners to consider the relationship between energy and water when making decisions. Our research fills an important gap of the energy-water nexus in a residential unit and provides a decision making tool for policy initiatives.

Energy's thirst for water in China

Water scarcity and uneven water distribution pose significant challenges to sustainable development and energy production in China. Based on the International Energy Agency (IEA)'s energy strategy scenarios for China, we evaluated the water withdrawal for energy production from 2011 to 2030. The results show that the amount of water withdrawal will be increased by 77% in 2030, which will aggravate China's water scarcity risk under current energy strategy. We also observed that 67% of the energy production in China occurs in areas that are facing water scarcity. Moreover, China's 12th Five-Year Plan of Energy Development does not change the existing energy strategies, and the planned total energy production is much higher than the IEA's projection, which will result in an increased demand for water resources. However, if China were to apply broad policies to reduce CO2 emissions, the amount of water withdrawal would also decline compared with current energy strategy. Thus, reforming China's energy structure and reducing energy usage are not only urgent because of climate challenges and air pollution but also essential to reducing the pressure of water scarcity.