Flexible design in water and wastewater engineering--definitions, literature and decision guide

Techno-environmental and economic assessment of color removal strategies from textile wastewater

The textile industry is one of the most chemical-intensive processes, resulting in the unquestionable pollution of more than a quarter of the planet's water bodies. The high recalcitrant properties of some these pollutants resulted on the development of treatment technologies looking at the larger removal efficiencies, due to conventional systems are not able to completely remove them in their effluents. However, safeguarding the environment also implies taking into account indirect pollution from the use of chemicals and energy during treatment. On the other hand, the emerged technologies need to be economically attractive for investors and treatment managers. Therefore, the costs should be kept under control. For this reason, the present study focuses on a comparative Life Cycle Assessment and Life Cycle Costing of four scale-up scenarios aiming at mono and di-azo reactive dyes removal from textile wastewater. Two reactors (sequencing batch reactor and two-phase partitioning) were compared for different reaction environments (i.e., single anaerobic and sequential anaerobic-aerobic) and conditions (different pH, organic loading rates and use of polymer). In accordance with the results of each scenario, it was found that the three technical parameters leading to a change in the environmental profiles were the removal efficiency of the dyes, the type of dye eliminated, and the pollutant influent concentration. The limitation of increasing organic loading rates related to the biomass inhibition could be overcame through the use of a novel two-phased partitioning bioreactor. The use of a polymer at this type of system may help restore the technical performance (84.5 %), reducing the toxic effects of effluents and consequently decreasing the environmental impact. In terms of environmental impact, this is resulting into a reduction of the toxic effects of textile effluents in surface and marine waters compared to the homologous anaerobic-aerobic treatment in a sequencing batch reactor. However, the benefits achieved for the nature comes with an economic burden related to the consumption of the polymer. It is expected that the cost of investment of the treatment with the two-phase partitioning bioreactor rises 0.6-8.3 %, depending on market prices, compared to the other analyzed sequential anaerobic-aerobic technologies. On the other side, energy and chemical consumption did not prove to be limiting factors for economic feasibility.

Integrating water science, economics, and policy for future climate adaptation

Water science, water economics, and water policy issues continue to rise in importance internationally as elevated population, income growth, and climate change magnify scarcity, shortages, and injustices in water access. Based on the unique physical, institutional, and economic characteristics of water, this work's first contribution is to characterize a road forward for research innovations that enable better integration of water science, water economics, and water policy. Meeting water's sustainable development and justice goals calls for several research innovations that humanity awaits. The advances called for in this work include deep uncertainty management, red team reviews, innovative water rights design, accelerating SDG achievement, valuing water infrastructure, valuing natural water retention, incentivizing water conservation, improving financial performance of rural water systems, water network modularization, non-price scarcity signals, optimization model calibration, remote sensing, transboundary benefit sharing, optimal growth, and water valuation. The work's second contribution is to present a prototype scalable basin scale hydroeconomic analysis (HEA) as a framework for integrating these above innovations when they occur. Results of the HEA show that losses from a 50% shortage in the basin's surface water supply can continue to protect 93% of total economic benefits across economic sectors if an efficient water trading system is established to move water from lower to higher valued uses when shortages occur. The work concludes by noting that great advances remain needed for better and longer lives.

Urban water as an alternative freshwater resource for matching irrigation demand in the Bengal delta

Rapid changes in climate patterns, population growth, urbanization, and rising economic activities have increased the pressure on the delta's freshwater availability. Bangladesh's coastal planes suffer from a shortage of good quality irrigation water, which is crucial for peri-urban agriculture and at the same time, a high volume of untreated wastewater is discharged into the surface water. This calls for a transition towards efficiently managing and (re)using available urban water resources for irrigation, which is addressed in this paper. A quantitative match between the irrigation demand and potential freshwater supply has been assessed considering different urban water generation scenarios. The FAO AquaCrop model has been used to calculate the irrigation water demand for Boro rice during the dry period. Results indicate that 7.4 million m³ of irrigation water is needed, whereas over 8.2 million m³ of urban water is being generated during the dry season. Simultaneously, mismatches between irrigation demand and alternative water supply mainly occurred in February and March, which could be resolved with water storage capacities. However, to make urban water reuse a reality, the water management policy needs to change to facilitate the construction of required infrastructures for collection, treatment, and storage. The proposed method helps realize the urban water's hidden potential to sustain agricultural activities in the delta areas.

A projects portfolio selection for water security addressing future increasing water demand and salinity intrusion in Zhuhai City, coastal China

Water security is essential for sustainable economic and social development. To ensure water security, water engineering projects play an important role in regional developing program. The coastal city-Zhuhai City suffers a challenge from both future increasing water demand and salinity intrusion, To keep water security of the city, several alternative projects are designed. However, as the high cost of the projects and the potential adverse influence, a final projects portfolio, as well as their construction order has not be decided. To assist a proper decision of projects portfolio for local water security, this study proposed a combined method with one-vote veto and Analytic Hierarchy Process, to evaluate every projects portfolio from various perspectives. The results show: 1) to satisfy future water demand of 150 thousands m³/h, it is recommended to adopt a projects portfolio including expanding existing reservoirs and constructing new reservoirs, as its higher capacity utilization (96.87%), relatively lower construction and operation costs (8.59 billion and 57 million respectively), and lower ecological impact; 2) to satisfy future water demand of 160 thousands m³/h or more, transferring water from other cities should be an indispensable part for water security; 3) channel reservoir is not recommended as its high construction and operation costs, and high ecological impact. This study evaluated different alternative projects for cities' water security and provided a strong support for local government to decide their long-term projects portfolio and their construction order. The proposed method may be readily applied in other regions.

An integrated assessment of environmental, economic, social and technological parameters of source separated and conventional sanitation concepts: A contribution to sustainability analysis

Resource recovery and reuse from domestic wastewater has become an important subject for the current development of sanitation technologies and infrastructures. Different technologies are available and combined into sanitation concepts, with different performances. This study provides a methodological approach to evaluate the sustainability of these sanitation concepts with focus on resource recovery and reuse. St. Eustatius, a small tropical island in the Caribbean, was used as a case study for the evaluation. Three source separation-community-on-site and two combined sewerage island-scale concepts were selected and compared in terms of environmental (net energy use, nutrient recovery/reuse, BOD/COD, pathogens, and GHG emission, land use), economic (CAPEX and OPEX), social cultural (acceptance, required competences and education), and technological (flexibility/adaptability, reliability/continuity of service) indicators. The best performing concept, is the application of Upflow Anaerobic Sludge Bed (UASB) and Trickling Filter (TF) at island level for combined domestic wastewater treatment with subsequent reuse in agriculture. Its overall average normalised score across the four categories (i.e., average of average per category) is about 15% (0.85) higher than the values of the remaining systems and with a score of 0.73 (conventional activated sludge - centralised level), 0.77 (UASB-septic tank (ST)), 0.76 (UASB-TF - community level), and 0.75 (ST - household level). The higher score of the UASB-TF at community level is mainly due to much better performance in the environmental and economic categories. In conclusion, the case study provides a methodological approach that can support urban planning and decision-making in selecting more sustainable sanitation concepts, allowing resource recovery and reuse in small island context or in other contexts.

Mathematically formulated key performance indicators for design and evaluation of treatment trains for resource recovery from urban wastewater

While urban wastewater infrastructure is aging and no longer adequate, climate change and sustainability are urging the transition from pollution management to resource recovery. Lacking evidence-based quantitative evaluation of the potential benefits and consequences of resource recovery from wastewater hinders the negotiation amongst stakeholders and slows down the transition. This study proposes mathematical formulations for technical, environmental, economic, and social key performance indicators (KPIs) that can be used to quantify the benefits and the risks of resource recovery. The proposed formulations are derived from the literature and validated with stakeholders. Each KPI is mathematically formulated at treatment train level by considering: (1) the characteristics of individual unit processes (UPs) in the treatment train (TT), (2) the context in which the TT is installed, and (3) the resources to be recovered. The mathematical formulations of the KPIs proposed in this study enable a transparent, consistent and informative evaluation of existing treatment trains, as well as support the (computer aided) design of new ones. This could aid the transition from urban wastewater treatment to resource recovery from urban wastewater.

Industrial wastewater plants conversion for synergy use and the impact of inflows variability

A company, traditionally making brass products, undergone profound changes in the productive process, due to the inclusion of new products made of aluminium. The former industrial wastewater treatment consisted of two independent plants; one for the electroplating process and the other for the vibratory finishing process. The aluminium finishing gave rise to the inability to treat the generated industrial effluent, and consequently to a loss in the industrial production capacity. To overcome this problem, it was implemented an innovative synergistic, high level automated wastewater metal finishing treatment system, connecting both plants and assigning to each, different specific operations in the global process. To ensure and sustain the strict continuous compliance with local discharge limits it was done a set of industrial experiments according to an orthogonal L12 array design, applying innovatively the Taguchi methods and ANOVA, assessing the variability of the various streams of wastewater flows to be treated. The impact of the connection between the two plants was evaluated positively and, for each treated water parameter (pH, chemical oxygen demand, total suspended solids, total chromium, hexavalent chromium, nickel, zinc, copper, aluminium and iron) was found the specific process wastewater inflow that most influence their variability.

A composite indicator approach to assess the sustainability and resilience of wastewater management alternatives

Evaluating the sustainability of wastewater management alternatives is a challenging task. This paper proposes an innovative methodology to assess and compare the sustainability of four wastewater management alternatives: a) centralised water resource recovery facility (WRRF) based on activated sludge (AS); b) centralised WRRF with membrane bioreactors (MBR); c) decentralised WRRFs with upflow anaerobic sludge blanket reactors and trickling filters; d) centralised-decentralised hybrid system. In doing so, a composite indicator embracing total annual equivalent costs, carbon emission intensity, eutrophication and resilience (based on robustness and rapidity metrics) was developed using the analytic hierarchy process (AHP) method. The results show that decentralised and hybrid systems contribute less to carbon emission and eutrophication because of energy and fertilizer harvest and with a trade-off of higher costs of 7-17% than the ones of AS and MBR. In addition, decentralised and hybrid systems are more resilient, contributing to lower environmental impacts facing natural disasters. Based on the weights obtained by AHP, the decentralised alternative appears to be the most sustainable option due to its best performance in terms of carbon emission intensity and resilience. By contrast, the MBR alternative appeared the least sustainable evaluated wastewater management alternative. However, this alternative is sustainable option when the eutrophication criterion is heavily prioritized. The proposed approach contributes to the selection of the most sustainable wastewater management alternative from a holistic perspective.

Essential components of institutional and social indicators in assessing the sustainability and resilience of urban water systems: Challenges and opportunities

There has been increasing focus on the resilience and sustainability of Urban Water Systems (UWS) due to the increase in urban population and rise of imminent threats (e.g. floods). This focus has brought about numerous studies attempting to develop a framework of assessment of UWS that can be benchmarked and adopted by different jurisdictions. The use of composite indicators has been the most common approach in many of the studies appearing in the past two decades. While there seems to be a consensus on the relevant technical and economic indicators in assessing UWS, the situation is different when it comes to social and institutional indicators. In this paper, a discussion of the most common institutional and social indicators used in conducting a sustainability or resilience assessment of UWS is presented. A framework of criteria which describes four key ways for ensuring that indicators are appropriate for use in UWS is proposed. The framework is described as a tool to mitigate common challenges in the development and evaluation of institutional and social indicators. While social and institutional indicators have been used in a variety of studies, the framework offers a way to better ensure that regardless of the chosen indicators, they are developed and used in a way that is consistent with the merits of social research, notably reliability and validity.

Integrating uncertainty of preferences and predictions in decision models: An application to regional wastewater planning

Decision-making in environmental management requires eliciting preferences of stakeholders and predicting outcomes of decision alternatives. Usually, preferences and predictions are both uncertain. Uncertainty of predictions can be tackled by multi-attribute utility theory, but the uncertainty of preferences remains a challenge. We demonstrate an approach for including both uncertainties in a multi-criteria decision analysis (MCDA), using utility theory and the concept of expected expected utility. For a decision regarding a regional merger of wastewater infrastructure in Switzerland, we constructed preference models for four stakeholders. These models also allowed for non-additive interactions between objectives. We evaluated the performance of eleven decision alternatives for which we predicted potential outcomes. Even though uncertainties were high, we could draw conclusions based on the expected expected utility of alternatives. Building a pipeline to discharge treated wastewater to a larger river emerged as a potential consensus alternative to mitigate the problem of micropollutants in a small stream. We investigated the robustness of the findings with sensitivity analysis regarding the preference parameters and the included objectives. In their actual decision, the stakeholders partly preferred other alternatives than those proposed by the model. Their choices could be explained by reduced decision models in which only few objectives were included. This may indicate the use of simplified choice heuristics by the stakeholders. The presented approach is feasible for supporting other difficult environmental or engineering decisions in practice, for which we give a number of recommendations.

A Comparative Study on Rapid Wastewater Treatment Response to Refugee Crises

Large-scale population displacement can overwhelm wastewater treatment facilities and increase environmental pollution in the host communities. Academic research has discussed features that improve wastewater treatment systems' resiliency toward other types of disasters and rapidly changing operation conditions. Concepts that contribute to successful startup, refurbishment, and operation of biological treatment systems during refugee responses are yet to be identified. This study takes a novel approach to analyzing wastewater treatment system resiliency by presenting an input-mediator-output model analysis on advanced wastewater treatment delivery during refugee response in Jordan and Finland in 2015-2016. By comparing two distinctively different case studies, the research identifies principles that contribute to timely refugee response in advanced wastewater treatment systems on the dimensions of human resources, project environment, and wastewater treatment technology. These principles include 1) clear role division between agencies and stakeholders, 2) improving "human capacity" for rapid response decisions, 3) selecting a process that fits the regulative and operational environment, 4) enabling direct and fast information sharing, and 5) establishing fast-track permitting processes for disaster conditions. Wastewater treatment system operators, regulative authorities, and aid organizations can use these findings to support rapid decision-making in future disaster response situations.

Many-objective optimization model for the flexible design of water distribution networks

This paper proposes a many-objective optimization model for the flexible design of water distribution networks (WDNs), including four objectives. Two objectives are related to the WDNs' hydraulic capacity, the minimization of the pressure deficit and the undelivered demand. The third objective is the traditional cost minimization while the fourth minimizes carbon emissions. These objectives concern network reliability, and financial and environmental concerns. They can give rise to solutions embedding new trade-off in design perspectives. There is a gap in the literature when it comes to dealing with many-objective problems for designing and constructing a WDN over a long-term planning horizon and using a staged design scheme that includes the consideration of uncertainty. A solution obtained through this process can be implemented in the first stage and the WDN is prepared for the possible occurrence of various future scenarios. These scenarios can consider expansions of WDNs to different development areas, in different time stages. Furthermore, defining a multi-staged design allows implementing the design of the first stage and reassessing the whole process in the end of each stage when more plausible future scenarios can be investigated. The solution of complex problems such as these needs improved algorithms to produce the Pareto front and so enable the trade-off between the objectives to be examined. An enhanced algorithm, based on the simulated annealing concept and capable of handling the critical scalability issues encountered in previous algorithms with respect to drawing the Pareto front for many-objective problems where a high-dimensional space is involves, is presented. The results obtained allow a thorough analysis of trade-offs between objectives and confirm the importance of considering the minimization of all those four objectives and the advantages of using a flexible approach to design WDNs to better inform decision makers.

Appraising longitudinal trends in the strategic risks cited by risk managers in the international water utility sector, 2005-2015

We report dynamic changes in the priorities for strategic risks faced by international water utilities over a 10year period, as cited by managers responsible for managing them. A content analysis of interviews with three cohorts of risk managers in the water sector was undertaken. Interviews probed the focus risk managers' were giving to strategic risks within utilities, as well as specific questions on risk analysis tools (2005); risk management cultures (2011) and the integration of risk management with corporate decision-making (2015). The coding frequency of strategic (business, enterprise, corporate) risk terms from 18 structured interviews (2005) and 28 semi-structured interviews (12 in 2011; 16 in 2015) was used to appraise changes in the perceived importance of strategic risks within the sector. The aggregated coding frequency across the study period, and changes in the frequency of strategic risks cited at three interview periods identified infrastructure assets as the most significant risk over the period and suggests an emergence of extrinsic risk over time. Extended interviews with three utility risk managers (2016) from the UK, Canada and the US were then used to contextualise the findings. This research supports the ongoing focus on infrastructure resilience and the increasing prevalence of extrinsic risk within the water sector, as reported by the insurance sector and by water research organisations. The extended interviews provided insight into how strategic risks are now driving the implementation agenda within utilities, and into how utilities can secure tangible business value from proactive risk governance. Strategic external risks affecting the sector are on the rise, involve more players and are less controllable from within a utility's own organisational boundaries. Proportionate risk management processes and structures provide oversight and assurance, whilst allowing a focus on the tangible business value that comes from managing strategic risks well.

Measuring adaptive capacity of urban wastewater infrastructure - Change impact and change propagation

The ability of urban wastewater systems to adapt and transform as a response to change is an integral part of sustainable development. This requires technology and infrastructure that can be adapted to new operational challenges. In this study the adaptive capacity of urban wastewater systems is evaluated by assessing the interdependencies between system components. In interdependent and therefore tightly coupled systems, changes to one systems component will require alteration elsewhere in the system, therefore impairing the capacity of these systems to be changed. The aim of this paper is to develop a methodology to evaluate the adaptive capacity of urban wastewater systems by assessing how change drivers and innovation affect existing wastewater technology and infrastructure. The methodology comprises 7 steps and applies a change impact table and a design structure matrix that are completed by experts during workshops. Change impact tables quantify where change drivers, such as energy neutrality and resource recovery, require innovation in a system. The design structure matrix is a tool to quantify "emerging changes" that are a result of the innovation. The method is applied for the change driver of energy neutrality and shown for two innovations: a decentralised upflow anaerobic sludge blanket reactor followed by an anammox process and a conventional activated sludge treatment with enhanced chemical precipitation and high temperature-high pressure hydrolysis. The results show that the energy neutrality of wastewater systems can be address by either innovation in the decentralised or centralised treatment. The quantification of the emerging changes for both innovations indicates that the decentralised treatment is more disruptive, or in other words, the system needs to undergo more adaptation. It is concluded that the change impact and change propagation method can be used to characterise and quantify the technological or infrastructural transformations. In addition, it provides insight into the stakeholders affected by change.

Separating grey- and blackwater in urban water cycles - sensible in the view of misconnections?

The infrastructure approach SEMIZENTRAL has been developed for fast growing cities, to meet their challenges regarding water supply as well as biowaste and wastewater treatment. The world's first full-scale SEMIZENTRAL Resource Recovery Center (RRC) has been implemented in Qingdao (PR China). Greywater (GW) and blackwater (BW) are collected and treated separately. Measurement of influent concentrations differ significantly from the design values. Thus, the operation strategy for the RRC had to be adapted. Amongst other reasons, the changed influent characteristic was caused by misconnections of GW and BW sewers. Already a misconnection rate of 6-8% requires an extension of the GW treatment process for nitrification/denitrification to fulfill effluent standards. Hence, measures should be taken to avoid or reduce misconnections. Nonetheless, in a semi-centralized scale (>10,000 inhabitants) a 100% avoidance might not be possible. Thus, consequences from misconnections should be considered during the design of source-oriented infrastructure systems.

Semicentralized greywater and blackwater treatment for fast growing cities: how uncertain influent characteristics might affect the treatment processes

The SEMIZENTRAL infrastructure approach has been developed for fast growing cities, to meet their challenges regarding water supply as well as biowaste and wastewater (WW) treatment. The world's first full-scale SEMIZENTRAL Resource Recovery reference plant has been implemented in Qingdao (PR China). Greywater (GW) and blackwater (BW) are collected and treated separately. Measurement of influent concentrations revealed significant differences, compared with the design values. Values from the literature for GW and BW characteristics vary more markedly than for municipal WW; recommended design values are still lacking. Moreover, cross-connections between GW and BW can influence the influent characteristics considerably. Consequences for the design of GW and BW treatment are evaluated for boundary conditions, which require high effluent quality for both treatment modules. Model calculations illustrate the significant influence of uncertain WW characteristics on the required aeration basin volume and oxygen demand for GW and BW treatment; however, uncertainties are considerably reduced for the combination of these modules. Thus, a flexible design of the treatment plant is required. A possible concept for such a design is presented.

The Potential of Knowing More: A Review of Data-Driven Urban Water Management

The promise of collecting and utilizing large amounts of data has never been greater in the history of urban water management (UWM). This paper reviews several data-driven approaches which play a key role in bringing forward a sea change. It critically investigates whether data-driven UWM offers a promising foundation for addressing current challenges and supporting fundamental changes in UWM. We discuss the examples of better rain-data management, urban pluvial flood-risk management and forecasting, drinking water and sewer network operation and management, integrated design and management, increasing water productivity, wastewater-based epidemiology and on-site water and wastewater treatment. The accumulated evidence from literature points toward a future UWM that offers significant potential benefits thanks to increased collection and utilization of data. The findings show that data-driven UWM allows us to develop and apply novel methods, to optimize the efficiency of the current network-based approach, and to extend functionality of today's systems. However, generic challenges related to data-driven approaches (e.g., data processing, data availability, data quality, data costs) and the specific challenges of data-driven UWM need to be addressed, namely data access and ownership, current engineering practices and the difficulty of assessing the cost benefits of data-driven UWM.

Adaptive capacity indicators to assess sustainability of urban water systems - Current application

Sustainability is commonly assessed along environmental, societal, economic and technological dimensions. A crucial aspect of sustainability is that inter-generational equality must be ensured. This requires that sustainability is attained in the here and now as well as into the future. Therefore, what is perceived as 'sustainable' changes as a function of societal opinion and technological and scientific progress. A concept that describes the ability of systems to change is adaptive capacity. Literature suggests that the ability of systems to adapt is an integral part of sustainable development. This paper demonstrates that indicators measuring adaptive capacity are underrepresented in current urban water sustainability studies. Furthermore, it is discussed under which sustainability dimensions adaptive capacity indicators are lacking and why. Of the >90 indicators analysed, only nine are adaptive capacity indicators, of which six are socio-cultural, two technological, one economical and none environmental. This infrequent use of adaptive capacity indicators in sustainability assessments led to the conclusion that the challenge of dynamic and uncertain urban water systems is, with the exception of the socio-cultural dimension, not yet sufficiently reflected in the application of urban water sustainability indicators. This raises concerns about the progress towards urban water systems that can transform as a response variation and change. Therefore, research should focus on developing methods and indicators that can define, evaluate and quantify adaptive capacity under the economic, environmental and technical dimension of sustainability. Furthermore, it should be evaluated whether sustainability frameworks that focus on the control processes of urban water systems are more suitable for measuring adaptive capacity, than the assessments along environmental, economic, socio-cultural and technological dimensions.

A new approach to nationwide sanitation planning for developing countries: Case study of Indonesia

Many developing countries struggle to provide wastewater and solid waste services. The backlog in access has been partly attributed to the absence of a functional sanitation planning framework. Various planning tools are available; however a comprehensive framework that directly links a government policy to nationwide planning is missing. Therefore, we propose a framework to facilitate the nationwide planning process for the implementation of wastewater and solid waste services. The framework requires inputs from government planners and experts in the formulation of starting points and targets. Based on a limited number of indicators (population density, urban functions) three outputs are generated. The first output is a visualization of the spatial distribution of wastewater and solid waste systems to support regional priority setting in planning and create awareness. Secondly, the total number of people served, budget requirements and distribution of systems is determined. Thirdly, the required budget is allocated to the responsible institution to assure effective implementation. The determined budgets are specified by their beneficiaries, distinguishing urban, rural, poor and non-poor households. The framework was applied for Indonesia and outputs were adopted in the National Development Plan. The required budget to reach the Indonesian government's 2019 target was determined to be 25 billion US$ over 5years. The contribution from the national budget required a more than fivefold increase compared to the current budget allocation in Indonesia, corresponding to an increase from 0.5 to 2.7 billion US$ per year. The budget for campaigning, advocacy and institutional strengthening to enable implementation was determined to be 10% of the total budget. The proposed framework is not only suitable for Indonesia, but could also be applied to any developing country that aims to increase access to wastewater and solid waste facilities.