The influence of airtightness on contaminant spread in MURBs in cold climates.

Tall buildings in cold climates have unique challenges in maintaining indoor air quality due to stack effect. During the heating season, interior air buoyancy creates large pressure differentials in vertical shafts that can drive airflow from lower floors into upper floors. This pressure differential can result in the spread of contaminants throughout a building. Most recently, concern over COVID-19 has increased attention to the potential spread of airborne diseases in densely populated buildings. For many multi-unit residential buildings, suite ventilation has traditionally relied upon fresh air supplied through a mechanically pressurized corridor. In cold climates, large pressure differentials created by stack-effect can reduce the effectiveness of this approach. Multizone and CFD simulations are employed to analyze airflow and contaminant spread due to stack effect. Simulations are conducted on an idealized model of a 10-storey building using a range of experimentally derived airtightness parameters. Simulations demonstrate stack effect can reduce corridor ventilation to suites and even reverse the airflow for leakier buildings. Reduced airflow to suites can result in the accumulation of contaminants. Reversal of the airflow can allow contaminants from a suite to spread throughout the building. Contaminant spread is illustrated as a function of mechanical ventilation, building airtightness, and ambient temperatures. Strategies to reduce the influence of stack effect on mechanically pressurized corridors are discussed.

Phosphorus immobilization in water and sediment using iron-based materials: A review.

As an essential element for life, phosphorus (P) is very important for organisms. However, excessive P in water and sediment can cause eutrophication, which poses a potential risk to drinking water safety and the sustainability of aquatic ecosystems. Therefore, effective phosphorus-control in water and sediment is the key strategy to control eutrophication. Iron-based materials exhibit high efficiency for P immobilization due to their strong affinity with P, low cost, easy availability, and environmentally friendliness. They are promising materials for controlling P in application. This work comprehensively summarizes the recent advances on P immobilization in water and sediment by different iron-based materials, including iron (hydr)oxides, iron salts, zero-valent iron and iron-loaded materials. This review is focused on the mechanism of the processes and how they are impacted by major influencing factors. The combination of iron-containing materials with other assisting materials is a good strategy to enhance P-fixation efficiency and selectivity. Finally, the current challenges and prospects of P-control technologies based on iron-containing materials are proposed. This review provides a systemic theoretical and experimental foundation for P-immobilization in water and sediment using iron-based materials.

Method for converting CWEEDs weather files to EPW format for multiyear simulation of building thermal dynamics.

This paper outlines a method in converting Historical CWEEDs (Canadian Weather Energy and Engineering Datasets) stored in WY3 format into individual weather files in EPW format so it could be used for Building Energy Simulation (BES). The method outlined is independent of the programming language used, however, a sample MATLAB script is presented to illustrate its feasibility. Highlights of the methodology are as follow:•Key feature in weather converters created under this methodology is the ability to divide multiyear weather data stored in WY3 format (with. wy3 extension) into individual years in EPW format (Standard mode)•And provide ability to extract weather data within a defined time range.

Assessment of Water Footprints of Consumption and Production in Transboundary River Basins at Country-Basin Mesh-Based Spatial Resolution.

Water is unevenly distributed globally. This uneven distribution is the reason behind the differences among geographical areas in terms of their water footprint of consumption and production. This gives the global trade of goods a unique feature. This characteristic of the water footprint might be used to address water scarcity and conflicts because water availability also has the same trend. Transboundary river basins are freshwater resources with a high probability of water scarcity and conflict because the water is claimed by multiple sovereign countries. In order to design sharing mechanisms for transboundary river basins that incorporate virtual water concept, it is key to identify the virtual water balance of country-basin units. A study addressing this research gap is not yet available. This article identified and discussed net virtual water importer and exporter sub-basins of transboundary rivers at a country-basin mesh based spatial resolution. The results of our study show that out of the 565 country-basin units surveyed in this article 391, 369, and 461 are net gray, green, and blue virtual water importers respectively. These sub-basins covers 58.37%, 47.52% and 57.52% of the total area covered by transboundary river basins and includes 0.65, 1.9, and around 2 billion people, respectively. The results depict that not only the water endowment of sub-basins is a determining factor for their water footprint of consumption and production, but also their social, economic, and demographic profiles. Furthermore, the water footprint of consumption and production within most of the country-basin units have a global feature. Hence, sustainable water management schemes within border-crossing basins should take into account not only the local but also the global water footprints of consumption and production. This can offer more options for sharing transboundary river basins water capital, thereby minimizing the probability of water scarcity and water conflicts.

The Impact of Upstream Sub-basins' Water Use on Middle Stream and Downstream Sub-basins' Water Security at Country-Basin Unit Spatial Scale and Monthly Temporal Resolution.

Water, in most of the transboundary river basins, is a bone of contention among their riparian states. Taking this into account, this article assessed the monthly impact of upstream water withdrawal on the water security of middle stream and downstream sub-basins at a country-basin mesh spatial resolution. Roughly 2.18 billion people in 442 sub-basin areas experience water stress intensification by less than 1% throughout the year. In addition, 2.12 billion people in 336 sub-basin areas experience water stress level change, from no water stress to one of the water stress categories, for at least one month as the result of upstream withdrawal. Even though there is a clear upstream impact in many of the basins, water disputes with severe social, economic, political, and environmental consequences are nonexistent. This might be an indication that grave water disputes are the result of complex socio-economic and political interactions, not merely because of water deficits due to upstream water withdrawal. Therefore, understanding this relationship is crucial in identifying inflection points for water conflicts within transboundary river basins.

Spatial Patterns of Urban Wastewater Discharge and Treatment Plants Efficiency in China.

With the rapid economic development, water pollution has become a major concern in China. Understanding the spatial variation of urban wastewater discharge and measuring the efficiency of wastewater treatment plants are prerequisites for rationally designing schemes and infrastructures to control water pollution. Based on the input and output urban wastewater treatment data of the 31 provinces of mainland China for the period 2011⁻2015, the spatial variation of urban water pollution and the efficiency of wastewater treatment plants were measured and mapped. The exploratory spatial data analysis (ESDA) model and super-efficiency data envelopment analysis (DEA) combined Malmquist index were used to achieve this goal. The following insight was obtained from the results. (1) The intensity of urban wastewater discharge increased, and the urban wastewater discharge showed a spatial agglomeration trend for the period 2011 to 2015. (2) The average inefficiency of wastewater treatment plants (WWTPs) for the study period was 39.2%. The plants' efficiencies worsened from the eastern to western parts of the country. (3) The main reasons for the low efficiency were the lack of technological upgrade and scale-up. The technological upgrade rate was -4.8%, while the scale efficiency increases as a result of scaling up was -0.2%. Therefore, to improve the wastewater treatment efficiency of the country, the provinces should work together to increase capital investment and technological advancement.

High-load domestic wastewater treatment using a combined anaerobic-aerobic bio-filter with coal cinder as medium.

A combined anaerobic-aerobic bio-filter technology was used for field treatment of high-organic-load domestic wastewater with coal cinder as the bio-filter medium. The effects of parameters, including hydraulic retention time (HRT) and backflow ratio, on the decrease in the chemical oxygen demand (COD), NH3-N, total nitrogen (TN), total phosphorus (TP), and turbidity were investigated. The results showed the obvious influence of the HRT and ratio of backflow on wastewater treatment. Under the optimal HRT condition of 18 h, the removal efficiencies of COD, NH3-N, TN, TP, and turbidity were 67.9%, 95.6%, 30.4%, 65.6%, and 83.8%, respectively. When the backflow ratio (2:1) was added to the treatment system, the TN removal obviously increased, and the removal efficiencies of COD, NH3-N, TN, TP, and turbidity were 88.1%, 91.7%, 69.9%, 69.6%, and 97.5%, respectively. These results indicated that the combined technology has the potential as a treatment method for high-organic-load domestic wastewater.

Historical Accountability for Equitable, Efficient, and Sustainable Allocation of the Right to Emit Wastewater in China.

Establishing policies for controlling water pollution through discharge permits creates the basis for emission permit trading. Allocating wastewater discharge permits is a prerequisite to initiating the market. Past research has focused on designing schemes to allocate discharge permits efficiently, but these schemes have ignored differences among regions in terms of emission history. This is unfortunate, as fairness may dictate that areas that have been allowed to pollute in the past will receive fewer permits in the future. Furthermore, the spatial scales of previously proposed schemes are not practical. In this article, we proposed an information entropy improved proportional allocation method, which considers differences in GDP, population, water resources, and emission history at province spatial resolution as a new way to allocate waste water emission permits. The allocation of chemical oxygen demand (COD) among 30 provinces in China is used to illustrate the proposed discharge permit distribution mechanism. In addition, we compared the pollution distribution permits obtained from the proposed allocation scheme with allocation techniques that do not consider historical pollution and with the already established country plan. Our results showed that taking into account emission history as a factor when allocating wastewater discharge permits results in a fair distribution of economic benefits.