Civil and Environmental Engineering

1,2-Dichloroethane (1,2-DCA) is among the most frequently detected chlorinated organic compounds (COCs) at contaminated sites. Possible carcinogenicity and recalcitrance towards abiotic dechlorination has created considerable interest in developing remediation technologies to successfully treat 1,2-DCA. Recently, aqueous-phase catalyzed hydrodechlorination has emerged as a field-applicable technology showing promising results in reducing various COCs. However, there has been limited success in applying this technology to treat 1,2-DCA, even at the bench scale. In the current study, the feasibility of aqueous-phase catalyzed hydrodechlorination of 1,2- DCA was investigated over Pd nanoparticles (nPd) with the residual borohydride from nPd synthesis as a hydrogen (H2) source. nPd particles were synthesized via aqueous chemical reduction by sodium borohydride. Complete removal of 1,2-DCA (32 mg L−1 ) in < 7 days was achieved with both bare and stabilized nPd (1 g L−1 ) particles and the reaction followed pseudo-first-order kinetics. No additional injections of borohydride or any other H2 source were needed. Ethane was the main reaction product indicating hydrogenolysis as the major dechlorination pathway. Different synthesis parameters were found to affect the oxidation state, elemental composition and the catalytic activity of nPd and consequently 1,2-DCA dechlorination. Detailed surface characterization including TEM, SEM/EDX, XPS and XRD of nPd particles was conducted. This study is an initial step to show that even recalcitrant COCs like 1,2-DCA can be successfully treated in the aqueous-phase via nPdborohydride
suspensions, and likely other nanocatalysts, without any  external/additional H2 source. However, further research is needed to provide more insight on how to transfer this technology from ideal laboratory conditions to real-field situations. The results also help provide clues on the development of a process level understanding of 1,2 DCA dechlorination via nanocatalysts.

Global research is moving forward in developing hydrogen as a renewable energy source in order to alleviate concerns related to carbon dioxide emissions and depleting fossil fuels resources. Biohydrogen has the potential to replace current hydrogen production technologies relying heavily on fossil fuels. Batch and continuous systems employing pure
mesophiles and thermophiles isolates and co-cultures of isolates have been investigated. The co-cultures of the isolates achieved better results than mono-cultures of the isolates with respect to different parameters. This paper presents a critical review of the literature reporting on fermentative biohydrogen production by pure cultures of bacteria in different systems. Synergies between different types of bacteria, i.e. strict and facultative, and a comparison between mono- and co-cultures, types of feedstocks, and preferred feedstocks for mono- and cultures are outlined.

1,2-Dichloroethane (1,2-DCA) is among the most prevalent groundwater chlorinated organic compounds (COCs) found at hazardous sites throughout the world. Given its pervasive contamination and adverse health effects, there is considerable interest in developing novel remediation technologies for successfully treating 1,2-DCA along with other COCs from water sources. Chemical reduction by nano zero valent iron (monometallic (nZVI) or bimetallic (Pd-nZVI)) has proven to be a successful field applicable technology, yet it has failed in degrading such a recalcitrant compound as 1,2-DCA. an effective remediation approach for multi-COCs contaminated groundwater depending upon site conditions.

Global research is moving forward in developing hydrogen as a renewable energy source in order to alleviate concerns related to carbon dioxide emissions and depleting fossil fuels resources. Biohydrogen has the potential to replace current hydrogen production technologies relying heavily on fossil fuels. Batch and continuous systems employing pure mesophiles and thermophiles isolates and co-cultures of isolates have been investigated. The co-cultures of the isolates achieved better results than mono-cultures of the isolates with respect to different parameters. This paper presents a critical review of the literature reporting on fermentative biohydrogen production by pure cultures of bacteria in different systems. Synergies between different types of bacteria, i.e. strict and facultative, and a comparison between mono-and co-cultures, types of feedstocks, and preferred feedstocks for mono-and cultures are outlined.

Per-and polyfluoroalkyl substances (PFAS) are manmade, fluorinated organic chemicals which have been identified as persistent organic pollutants. PFAS have surface active properties that have made them suitable for applications in oil-and water-resistant products, as well as many firefighting foams. No on-site remediation strategies exist to treat PFAS impacted soils. Mechanochemical remediation of PFOS-and PFOA-amended sand via a planetary ball mill was studied. The effect of sand mass, KOH as a co-milling reagent, and water saturation on the degradation of PFOA and PFOS was evaluated. By 4 h of milling concentrations were reduced by up to 98% for PFOS-amended dry sand and 99% for PFOA-amended dry sand without the addition of a co-milling reagent. Water saturation was determined to be a significant hindrance on the mechanochemical destruction of PFOS and PFOA. A maximum of 89% of fluoride was recovered from PFOS-amended sand when KOH was used as a co-milling reagent. It is hypothesized that reactive particles generated from the fracture of sand grains react with PFAS molecules to initiate destruction, which can result in full defluorination. Milling experiments were also conducted on soils from a Canadian firefighting training area (FFTA), demonstrating that PFOS concentrations can be reduced by up to 96% in site soils. For the first time, ball milling for the remediation of PFAS in environmental media has been demonstrated using amended sand and legacy soils from a FFTA.

Aqueous-phase catalyzed reduction of organic contaminants via zerovalent copper nanoparticles (nCu0), coupled with borohydride (hydrogen donor), has shown promising results. So far, the research on nCu0 as a remedial treatment has focused mainly on contaminant removal efficiencies and degradation mechanisms. Our study has examined the effects of Cu0/Cun+ ratio, surface poisoning (presence of chloride, sulfides, humic acid (HA)), and regeneration of Cu0 sites on catalytic dechlorination of aqueous-phase 1,2-dichloroethane (1,2-DCA) via nCu0-borohydride. Scanning electron microscopy confirmed the nano size and quasi-spherical shape of nCu0 particles. X-ray diffraction confirmed the presence of Cu0 and Cu2O and x-ray photoelectron spectroscopy also provided the Cu0/Cun+ ratios. Reactivity experiments showed that nCu0 was incapable of utilizing H2 from borohydride left over during nCu0 synthesis and, hence, additional borohydride was essential for 1,2-DCA dechlorination. Washing the nCu...

1,2-Dichloroethane (1,2-DCA) is among the most prevalent groundwater chlorinated organic compounds (COCs) found at hazardous sites throughout the world. Given its pervasive contamination and adverse health effects, there is considerable interest in developing novel remediation technologies for successfully treating 1,2-DCA along with other COCs from water sources. Chemical reduction by nano zero valent iron (monometallic (nZVI) or bimetallic (Pd-nZVI)) has proven to be a successful field applicable technology, yet it has failed in degrading such a recalcitrant compound as 1,2-DCA. an effective remediation approach for multi-COCs contaminated groundwater depending upon site conditions.

Per-and polyfluoroalkyl substances (PFAS) are manmade, fluorinated organic chemicals which have been identified as persistent organic pollutants. PFAS have surface active properties that have made them suitable for applications in oil-and water-resistant products, as well as many firefighting foams. No on-site remediation strategies exist to treat PFAS impacted soils. Mechanochemical remediation of PFOS-and PFOA-amended sand via a planetary ball mill was studied. The effect of sand mass, KOH as a co-milling reagent, and water saturation on the degradation of PFOA and PFOS was evaluated. By 4 h of milling concentrations were reduced by up to 98% for PFOS-amended dry sand and 99% for PFOA-amended dry sand without the addition of a co-milling reagent. Water saturation was determined to be a significant hindrance on the mechanochemical destruction of PFOS and PFOA. A maximum of 89% of fluoride was recovered from PFOS-amended sand when KOH was used as a co-milling reagent. It is hypothesized that reactive particles generated from the fracture of sand grains react with PFAS molecules to initiate destruction, which can result in full defluorination. Milling experiments were also conducted on soils from a Canadian firefighting training area (FFTA), demonstrating that PFOS concentrations can be reduced by up to 96% in site soils. For the first time, ball milling for the remediation of PFAS in environmental media has been demonstrated using amended sand and legacy soils from a FFTA.

Water that seeps through the bed and sides the canal are very significant. The ultimate purpose of performance assessment of an irrigation system is to achieve an efficient and effective use of available water resources. The present study was conducted to estimate the transmission losses in the Sathanur Left Bank canal and one of its distributory. The transmission losses was estimated using inflow—outflow method. The performance of the system is assessed by applying indicators. The transmission losses in the head reach of the canal is found to be higher than that of middle and tail reaches. The performance indicators showed that there was excess supply of water in the distributory.

Deriving the optimal operational rules for a multi-reservoir system serving various purposes like irrigation, multiple hydropower plants and flood control are complex. In the present study, such a multi-reservoir system with multiple hydropower plants are optimized for maximizing the hydropower production and satisfying the irrigation demands using a Non-linear Programming (NLP) technique. The developed NLP model has been applied to Koyna Hydro-Electric Project (KHEP) for maximizing the hydropower production and solved for three different dependable inflow scenarios under various operating policies. The complexity of the problem is such that the power releases and irrigation releases are in opposite direction and are non-commensurate. The total annual power production, monthly power production and the end of the month storage plots are compared for different inflows and operating policies. From the study, it is found that hydropower production can be increased to a minimum of 22% by slightly relaxing the tribunal constraint on releases towards the western side. The optimal releases from Policy 3 are further evaluated using a simulation model. The simulation result shows that the optimal releases have performed satisfactorily over long period of operation.

The purpose of this study is to efficiently improve biological sequencing batch reactor (SBR) system of high-concentrated nitrate nitrogen in reverse osmosis (RO) concentrates by total dissolved solids (TDS) regulation. Since a laboratory-scale SBR system had been operated, we had analyzed specific denitrification rate (SDNR) and specific oxygen uptake rate (SOUR) for microbial activity in according to various injection concentration of TDS. As a result, higher injection concentration of TDS decreased SDNR, and delayed denitrification within denitrification process. Moreover, the higher injection concentration of TDS was, the lower microbial activity was during operation of laboratory-scale SBR system. Therefore, the regulation of TDS injection concentration is necessary to improve efficiency of nitrate nitrogen in the biological SBR system, and treatment of calcium ion (Ca 2+ ) is also specifically focused to remove nitrate nitrogen. Moreover, analytical data of SDNR and SOUR can be the effective kinetic design parameters to application of biological treatment of RO concentrate by aerobic granular sludge (AGS).

Wastewater reclamation is becoming an important alternative for sustainable water resources management and building climate change resiliency in many regions around the world. The purpose of this research was to investigate the polishing of secondary effluents and Combine Sewer Overflows (CSOs) by a laboratory scale Soil Aquifer Treatment (SAT) considering local sub-surface geology and wastewater characteristics. Results show that characteristic soils of southwestern Ontario can effectively polish secondary effluents in terms of BOD5 (64.9% to 100%), e-coli (100%) and total coliforms (100%). However, low removals of DOC (22.81%) and Nitrate (15.17 %) were achieved. Furthermore, low to moderate improvements of CSOs quality were observed with maximum removals of 54.26 % for BOD5, 36.67% for e-coli, 58.15% for total coliforms and 44.83 % for Total Nitrogen. Additionally, de-nitrification of secondary effluents was greatly improved (46.1 % to 100%) by the addition of readily available o...

Wastewater reclamation is becoming an important alternative for sustainable water resources management and building climate change resiliency in many regions around the world. This research investigated the polishing of secondary effluents and combined sewer overflows (CSOs) by a laboratory-scale soil aquifer treatment considering local soils and wastewater characteristics of southwestern Ontario. Results show that high permeability soils of southwestern Ontario, have the ability to polish secondary effluents in terms of dissolved organic carbon, Escherichia coli, and total coliforms. Regarding the simulated CSOs, low to moderate improvements of wastewater quality were observed. Denitrification of secondary effluents improved significantly by the addition of readily available organic matter, which supports the importance of protecting recharge wetlands for groundwater quality protection. Soil aquifer treatment in southwestern Ontario is a feasible alternative for the recharge of non...

Convective heat transfer coefficient (CHTC) is known to play an important role in the evaluation of heat exchange between a building and its surroundings. There are several correlations suggested for the estimation of CHTC from the external surfaces of a building. However, there is a marked difference between values obtained from these correlations under similar set of conditions. Therefore, there is a need for an extensive correlation addressing the discrepancies in some of the existing correlations. In the current study, the impact of built morphology, associated with different land-use classes (e.g., industrial, residential, or downtown, etc.), on the convective heat transfer from buildings is numerically investigated. CFD simulations are conducted in a Navier-Stokes solver with Reynolds stress turbulence model as a closure method. The surrounding buildings are expected to influence the local microclimate (wind speed and turbulence), which in turn will affect the CHTC of the stud...

In this paper, the measurement of friction factor in gas with slip at the wall is presented; these are made to encompass the following aspects: change in pipe material, pipe wall roughness, and channel geometry, for various gases. Two different wall materials (stainless steel and copper), three different grades of roughness, and two wall geometries (circular and square) are considered in this study. The gases employed in this investigation are nitrogen, oxygen and argon. The ranges of Knudsen number and Reynolds numbers covered in this study are 0.0022-0.024 and 0.54-13.2 respectively. The experimental setup is validated by comparing the friction factor close to the continuum and slip flow regimes for nitrogen against available results in the literature. The experimental results suggest that the friction factor is affected by the wall roughness and geometry of cross-section, in addition to the amount of rarefaction. However, the effect of changing the gas or pipe material is minimal. A correlation for slip flow in square duct is also proposed. This is one of the first such detailed studies and has implications for both gas flow in microchannels and rarefied gas in large pipes.

This article focuses on determining the friction factor from experimental results available in literature for gas flow in a smooth tube. The friction factor ͑f͒, Reynolds number ͑Re͒, and Knudsen number ͑Kn͒ are calculated from the reported pressure drop and mass flow rate. The variation in friction factor with Knudsen number and Reynolds number is analyzed in the Kn range of 0.0004-2.77 and Re range of 0.001-227. It is found that f Re is independent of gas and surface material and can be estimated by a simple semiempirical correlation within Ϯ20% and a mean absolute error of 8%. The correlation gives friction factor for a particular value of Knudsen number and Reynolds number, irrespective of the type of gas or surface material.

Wind-driven ventilation is one of the primary methods used to control the environment within commercial greenhouses. Greenhouse ventilation is difficult to study in either full-scale or in wind tunnel simulations, due to the many scales involved in the problem and the difficulty of collecting measurements. Study of wind-driven greenhouse ventilation is difficult in full scale. Computational fluid dynamics (CFD) simulations can give insight into aspects of the flow field that are difficult or impossible to measure in full-scale or wind tunnel. Past greenhouse CFD studies have relied almost exclusively on Reynolds-Averaged Navier-Stokes (RANS) solvers with k-ε turbulence closure. This study presents RANS CFD simulations of external flow over a greenhouse, and interior ventilation flow through a hollow box with openings. These studies provide insight into appropriate CFD simulation methods for predicting wind-driven ventilation within greenhouses. The results of the simulations are discussed, and recommendations are given for RANS simulation of greenhouse ventilation. Full scale measurements of ventilation in Venlo-type greenhouses are limited. De Jong [5] conducted a

Urban building arrangements such as packing density, orientation and size are known to influence the microclimate surrounding each building. Studies on the impact of urban microclimatic changes on convective heat transfer coefficient (CHTC) from a stock of buildings, however, have been rare in surveyed literature. The present study focusses on numerical and analytical investigation of CHTC from building-like models with homogeneous and quasi-heterogeneous arrangement of obstacles. Consequently, the study discusses the CHTC response in relation to broader changes in the urban surface form. Part of the process involves the development of a simplified one-dimensional semi-analytical CHTC model based on a simplified analytical mean wind velocity flow profile for urban canopies. The remaining portion consists of performing sets of CFD simulations to obtain CHTC values for a broader range of packing densities. Analysis and results of the study reveal that CHTC is affected both by changes in planar as well as frontal densities. These changes might lead to up to 2.5 times higher or approximately an order lower CHTC compared to the conventional u10 formulations (based on upstream reference conditions at 10 m from the ground), which are mostly done without considering packing density effects. It is observed that the least CHTC values lie at higher planar densities, whereas the highest CHTC corresponds to the combination of the lowest planar and highest frontal densities for the windward and leeward surfaces. An increase in planar area density increases the CHTC at smaller frontal densities for top and lateral surfaces. The study reveals the CHTC estimate from conventional models may have mostly been overestimated compared with iii the values for buildings in city neighborhoods. New correlations for estimating CHTC for three canopy flow regimes are proposed. A relationship is also recognized between CHTC and the land-use class assignment of an urban neighborhood. The simplified analytical model, proposed correlations and the semi-analytical model are expected to enable estimation of CHTC for buildings located in urban neighborhoods based on the built area density or land-use class.