Toward General Principles for Resilience Engineering.

Maintaining the performance of infrastructure-dependent systems in the face of surprises and unknowable risks is a grand challenge. Addressing this issue requires a better understanding of enabling conditions or principles that promote system resilience in a universal way. In this study, a set of such principles is interpreted as a group of interrelated conditions or organizational qualities that, taken together, engender system resilience. The field of resilience engineering identifies basic system or organizational qualities (e.g., abilities for learning) that are associated with enhanced general resilience and has packaged them into a set of principles that should be fostered. However, supporting conditions that give rise to such first-order system qualities remain elusive in the field. An integrative understanding of how such conditions co-occur and fit together to bring about resilience, therefore, has been less clear. This article contributes to addressing this gap by identifying a potentially more comprehensive set of principles for building general resilience in infrastructure-dependent systems. In approaching this aim, we organize scattered notions from across the literature. To reflect the partly self-organizing nature of infrastructure-dependent systems, we compare and synthesize two lines of research on resilience: resilience engineering and social-ecological system resilience. Although some of the principles discussed within the two fields overlap, there are some nuanced differences. By comparing and synthesizing the knowledge developed in them, we recommend an updated set of resilience-enhancing principles for infrastructure-dependent systems. In addition to proposing an expanded list of principles, we illustrate how these principles can co-occur and their interdependencies.

Antifouling effect of water-soluble phosphate glass frit for filtration plants.

The antifouling, antimicrobial, elution behavior, skin irritant, and cytotoxicity properties of water-soluble phosphate glass on stainless steel were evaluated. Water-soluble phosphate glass samples with 35% Cu (mol/mol) were prepared by altering the network modifier (Na2O, K2O) and network former (P2O5, B2O3) compositions. The materials were melted at temperatures within the range of 850-950 °C. The melt was then quenched and ground into fine particles using a twin roll mill. The resulting water-soluble glasses were prepared as glass frit (size < 100 µm) using a sieve. The amorphous phase was determined by X-ray diffraction and differential thermal analysis. Water-soluble glasses with a reduced Cu ion elution rate of 1.2 ppm per week were formed because the chemical resistances of the formulated glasses improved as the P2O5 content decreased and the B2O3 content increased. To test its antifouling properties, the glass frit was mixed with paint and coated onto a STS316L sheet. The surface roughness was increased markedly from 1.4 to 19.2 nm, increasing the specific surface area for antimicrobial activity. It was demonstrated that the proposed method was able to form noncytotoxic, nonirritant, water-soluble glasses with 99.9% antimicrobial activity against Staphylococcus aureus. These results suggest that water-soluble phosphate glass on STS316L sheets could be useful in filtration plants.

Innovation of flux chamber network design for surface methane emission from landfills using spatial interpolation models.

Solid waste landfills are one of the primary anthropogenic sources of methane emissions which are often estimated by flux chamber measurements on landfill surfaces. Due to the small footprint of the flux chamber on the surface coverage, however, it is important to design a proper spatial deployment of the chambers with an optimal number of measurement points such that the measured fluxes are correctly scaled up to the whole landfill area. In order to improve the design of flux chamber network, several deterministic interpolation models were applied and results of reproducibility tests with 22 flux measurement data sets from ten municipal solid waste landfills in the Republic of Korea were compared one another. The bilinear model and natural neighbor model among the deterministic models showed stable results in all cases. The surface methane emissions estimated from arithmetic or geometric mean resulted in significant under- or overestimation compared to spatial interpolation methods in all data sets. As a result of this study, minimal number of flux measurement points could be determined for target error levels. Innovative flux chamber network design with proper measurement points will improve the accuracy of methane emission estimate from solid waste landfills.

Overcoming the Challenges of Water, Waste and Climate Change in Asian Cities.

Unprecedented challenges in urban management of water, waste and climate change-amplified by urbanisation and economic growth-are growing in Asia. In this circumstance, cities need to be aware of threats and opportunities to improve their capacity in addressing these challenges. This paper identifies priorities, barriers and enablers of these capacities. Through the City Blueprint® Approach-an integrated baseline assessment of the urban water cycle-11 Asian cities are assessed. Three cities are selected for an in-depth governance capacity analysis of their challenges with a focus on floods. Solid waste collection and treatment and access to improved drinking water and sanitation can be considered priorities, especially in cities with considerable slum populations. These people are also disproportionately affected by the impacts of climate-related hazards. The high variation of water management performance among Asian cities shows high potential for city-to-city learning by sharing best practices in water technology and governance. Combining interventions, i.e., by exploring co-benefits with other sectors (e.g., transport and energy) will increase efficiency, improve resilience, and lower the cost. Although governance capacities varied among cities, management of available information, monitoring and evaluation showed to be reoccurring points for improvement. Cities are also expected to increase implementation capacities using better policy, stricter compliance and preparedness next to promoting community involvement. Consequently, the city transformation process can be more concrete, efficient and inclusive.

Methane utilization in aerobic methane oxidation coupled to denitrification (AME-D): theoretical estimation and effect of hydraulic retention time (HRT).

Even though aerobic methane-oxidation coupled to denitrification (AME-D) has been extensively studied, the exact estimation of CH4 utilization during this process still requires better understanding because effective utilization of CH4 is essential in denitrification performance, CH4 emission and economy. This study presents the effect of hydraulic retention time (HRT) on CH4 utilization in an AME-D bioreactor. Stoichiometries for AME-D were newly established by using the energy balance and the thermodynamic electron equivalent model. The theoretically determined CH4 utilized/NO3- consumed (C/N) ratio from the stoichiometry was 2.0. However, the C/N ratios obtained from the experiment varied with increasing tendency as the HRT increased. Specifically, the C/N ratio increased from 1.38 to 2.85 when the HRT increased from 0.5 to 1.0 days, which placed the theoretical C/N ratio at the HRT between 0.5 and 1.0 days. The higher C/N ratio at the longer HRT was associated with a larger CH4 utilization by methanotrophs than denitrifiers. The results obtained in this study together with those obtained in previous studies clearly illustrated that a variety of conditions affect the utilization of CH4 which is essential for optimizing the AME-D process.

Field measurement of greenhouse gas emissions from biological treatment facilities of food waste in Republic of Korea.

The Republic of Korea is trying to reduce greenhouse gas emissions by 37% from business-as-usual levels by 2030. Reliable greenhouse gas inventory is prerequisite to making effective greenhouse gas reduction plans. Currently, Intergovernmental Panels on Climate Change default emission factors were used in biological treatment of the solid waste sector without any consideration of the biological treatment process in the Republic of Korea. In this study, greenhouse gas emissions from biological treatment facilities of food waste have been monitored in order to develop country-specific emission factors in the Republic of Korea. Greenhouse gas emissions were monitored in two composting facilities and one anaerobic digestion facility. All study sites possess a local exhaust ventilation system and odour treatment system. Continuous greenhouse gas monitoring has been conducted on gathered gases using a non-dispersive infrared detector before entering odour treatment systems. At composting facilities, the emission factors of CH4 and N2O were 0.17-0.19 g-CH4 kg-waste-1 and 0.10-0.13 g-N2O kg-waste-1, respectively. Especially, the emission factors of CH4 in composting facilities showed significantly low values compared with other countries owing to the air blowing by a pump at the studied sites. At anaerobic digestion facilities, the emission factors of CH4 and N2O were 1.03 g-CH4 kg-waste-1 and 0.53 g-N2O kg-waste-1. The emission factors estimated in this study showed a significant difference from the Intergovernmental Panels on Climate Change default value. Therefore, it is recommended to develop a country-specific emission factor in order to reflect the different processes of biological treatment of solid waste.

Regime shifts under forcing of non-stationary attractors: Conceptual model and case studies in hydrologic systems.

We present here a conceptual model and analysis of complex systems using hypothetical cases of regime shifts resulting from temporal non-stationarity in attractor strengths, and then present selected published cases to illustrate such regime shifts in hydrologic systems (shallow aquatic ecosystems; water table shifts; soil salinization). Complex systems are dynamic and can exist in two or more stable states (or regimes). Temporal variations in state variables occur in response to fluctuations in external forcing, which are modulated by interactions among internal processes. Combined effects of external forcing and non-stationary strengths of alternative attractors can lead to shifts from original to alternate regimes. In systems with bi-stable states, when the strengths of two competing attractors are constant in time, or are non-stationary but change in a linear fashion, regime shifts are found to be temporally stationary and only controlled by the characteristics of the external forcing. However, when attractor strengths change in time non-linearly or vary stochastically, regime shifts in complex systems are characterized by non-stationary probability density functions (pdfs). We briefly discuss implications and challenges to prediction and management of hydrologic complex systems.

Lessons in risk- versus resilience-based design and management.

The implications of recent catastrophic disasters, including the Fukushima Daiichi nuclear power plant accident, reach well beyond the immediate, direct environmental and human health risks. In a complex coupled system, disruptions from natural disasters and man-made accidents can quickly propagate through a complex chain of networks to cause unpredictable failures in other economic or social networks and other parts of the world. Recent disasters have revealed the inadequacy of a classical risk management approach. This study calls for a new resilience-based design and management paradigm that draws upon the ecological analogues of diversity and adaptation in response to low-probability and high-consequence disruptions.

A resilience perspective on biofuel production.

The recent investment boom and collapse of the corn ethanol industry calls into question the long-term sustainability of traditional approaches to biofuel technologies. Compared with petroleum-based transportation fuels, biofuel production systems are more closely connected to complex and variable natural systems. Especially as biofeedstock production itself becomes more independent of fossil fuel-based supports, stochasticity will become an increasingly important, inherent feature of biofuel feedstock production systems. Accordingly, a fundamental change in design philosophy is necessary to ensure the long-term viability of the biofuels industry. To respond effectively to unexpected disruptions, the new approach will require systems to be designed for resilience (indicated by diversity, efficiency, cohesion, and adaptability) rather than more narrowly defined measures of efficiency. This paper addresses important concepts in the design of coupled engineering-ecological systems (resistance, resilience, adaptability, and transformability) and examines biofuel conversion technologies from a resilience perspective. Conversion technologies that can accommodate multiple feedstocks and final products are suggested to enhance the diversity and flexibility of the entire industry.