Simultaneous microbial removal of carbon,nitrogen, and phosphorus in a modified anaerobic/aerobic (A/O) bioreactor with no phosphorus release

A modified anaerobic/aerobic (A/O) bioreactor that simultaneously removed carbon, nitrogen ( ‐N) and phosphorus ( ‐P) was continuously run and debugged. After 34 days of reactor operation, the removal efficiencies of ‐N, carbon (glucose) and ‐P reached 99.26, 95.81 and 94.35%, respectively. Notably, the ammonium removal with no accumulation of nitrite ( ‐N) and nitrate ( ‐N) in the anaerobic part supported the occurrence of simultaneous nitrification and denitrification and no ‐P was released during the removal process of phosphorus. Moreover, the principal component analysis and response surface methodology based on the Box–Behnken design were applied to determine the optimal removal conditions for volatile suspended solids (VSS) (335 mg/L), ‐N (60 mg/L), glucose (900 mg/L) and pH (7). Finally, phylogenetic analysis of the bacterial consortium was conducted by denaturing gradient gel electrophoresis, which demonstrated that Clostridium and Proteobacteria were the potential functional groups in the anaerobic tank of the A/O bioreactor.     

Improved dewaterability of sewage sludge by Fe(II)‐activated persulfate oxidation combined with polymers

The combination of Fe(II)‐activated persulfate oxidation with polymers potentially applied to enhance sludge dewaterability was investigated in this work. The experiments mainly concentrated on their efficacies and the optimization of the major operational parameters. The results showed that the combination was efficient, especially when polyaluminium chloride (PAC) and chitosan were used as polymers. The optimal conditions of this process under experimental conditions were at = 50 mg/g (dry solids), = 125 mg/g, reaction time = 20 min, PAC = 125 mg/g and chitosan = 100 mg/g, under which the specific resistance to filtration (SRF) with a reduction efficiency of 94.87% was achieved.     

Full‐scale maturation ponds working below a latitude of 43°S in a semiarid area: seasonal performance and removal mechanisms

Stabilisation ponds are the most frequently used wastewater treatment technology in Argentina. This study focuses on the performance of two maturation ponds (MPs) that are part of the full‐scale sewage treatment system of Puerto Madryn. Seventy‐seven shots of surface water were analysed for organic matter, inorganic nitrogen, phytoplankton dynamics and bacterial removal. The system presented a clear evolution with respect to oxygenation and phytoplankton development. The treated wastewater reached values above 8 mg‐O₂/L, an important organic matter removal, and this was accompanied by a strong increase in pH. removal and oxidation, was active even during winter in the MPs, with average concentrations below 10 mg ‐ /L. Bacteriological removal resulted in a liquid that approached the WHO recommendations for unrestricted irrigation. These results show that is possible to generate treated wastewater in stabilisation ponds working in a semiarid and temperate region, with bacterial content and conductivity suitable for irrigation.     

Environmental variables and benthic macroinvertebrate assemblage in the headwater streams of an Afro‐tropical reservoir

The assemblage of benthic macroinvertebrates in relation to some selected environmental variables of the two headwater streams of Aiba Reservoir was studied from May 2013 to March 2014. This was with a view to assessing the health status and water quality of the streams, and comparing their taxa richness with similar studies on the reservoir and its out‐flowing stream. A total of 23 taxa were recorded in the study. and showed indirect relationships (P < 0.05) with bioindicators of good water quality, while dissolved oxygen (DO) showed indirect relationship (P < 0.05) with bioindicators of poor water quality. The streams were of poor biological water quality, and diversity indices revealed that they were polluted and unstable in habitat structure. Anthropogenic impacts at the upper reaches need to be mitigated and regular biomonitoring of the streams is of the essence, in order to conserve the integrity of the downstream reservoir.     

Combining magnesium ammonium phosphate precipitation with membrane processes for ammonia removal from methanogenic leachates

Chemical precipitation of ammonia as magnesium ammonium phosphate (MAP) from methanogenic leachates can be a competitive alternative to biological ammonia removal. Potential for trading of the precipitate as a fertiliser defines the economics of the process. The precipitate from a landfill leachate often containing organics and heavy metals as impurities with unknown risks limits its possibility for agricultural use. This study combines MAP precipitation with membrane processes and investigates the influence of wastewater matrix, solution pH and dosage ratio of chemicals (Mg²⁺ : ) on the precipitate purity through lab scale semibatch experiments. Under similar experimental conditions (pH 8.5 and 1 : 1 Mg²⁺ : molar dosage), the precipitates from raw leachate and nanofiltration (NF) permeate showed MAP contents of 65 and 90%, respectively, correspondingly with about 8300 and 1600 mg TOC/kg_precipitate. For precipitation from NF permeate, precipitation at pH 8.0 with 1 : 1 dosage ratio and pH 8.5 with 1 : 0.9 dosage ratio gave precipitates each with about 97% purity.     

Sewage sludge conditioning by Fe(II)‐activated persulphate oxidation combined with skeleton builders for enhancing dewaterability

In this study, a joint application of Fe(II)‐activated persulphate oxidation and skeleton builders is used to condition sewage sludge for subsequent dewatering. The study mainly focuses on their efficacies and the optimization of the major operational parameters. The experimental results show that the joint application for conditioning sewage sludge is effective, especially using lime and ordinary Portland cement (OPC) as skeleton builders. Additionally, it is revealed that Fe(II)‐activated persulphate oxidation needs sufficient reaction time (20 min) to degrade organics in the sludge. The optimal conditions of this process are at Fe²⁺ = 47.6 mg g^?1 (dry solids), S₂ = 119.1 mg g^?1, lime = 446.4 mg g^?1, and OPC = 297.6 mg g^?1, under which the water content of dewatered sludge cake is 54.8% and the specific resistance to filtration (SRF) is 4.3 × 10¹¹ m kg^?1 with a reduction efficiency of 96.6%.     

A study of external mass transfer effect on biodegradation of phenol using low‐density polyethylene immobilized Bacillus flexus GS1 IIT (BHU) in a packed bed bioreactor

The impact of external mass transport on the biodegradation rate of phenol in a packed bed bioreactor (PBBR) was studied. A potential bacterial species, Bacillus flexus GS1 IIT (BHU), was isolated from the petroleum‐contaminated soil. Low‐density polyethylene (LDPE) immobilized with the B. flexus GS1 IIT (BHU) was used as packing material in the PBBR. The PBBR was operated by varying the inlet feed flow rate from 4 to 10 mL/min, and the corresponding degradation rate coefficients were found to be in the range of 0.119–0.157 L/g h. In addition, the highest removal rate of phenol was obtained to be 1.305 mg/g h at an inlet feed rate of 10 mL/min. The external mass transfer was studied using the model . A new empirical correlation for the biodegradation of phenol in the PBBR was developed after the evaluation at various values of K and n.     

Application of response surface methodology to optimize nitrate removal at low temperature by aerobic denitrificator Pseudomonas strain An‐1

Response surface methodology (RSM) was applied to optimize the conditions of nitrate removal by Pseudomonas strain AN‐1 at low temperature, which was isolated from aniline‐contaminated groundwater. A three‐factor, three‐level Box–Behnken experimental design and analysis of variance were combined with the obtained second‐order polynomial equation and applied for RSM optimization. By solving the second‐order polynomial equation and analysing the 3D response surface, a ‐N concentration of 65.29 mg/L, an initial pH of 6.65, and an initial DO of 7.53 were identified as the optimized conditions. These conditions achieved a removal percentage of 53.7485% after 48 h at 10°C, which was in good agreement with the predicted 53.8085%. This study showed the excellent ability of the Pseudomonas strain AN‐1 to degrade nitrate at low temperatures, which provided a solid foundation for the further application of this microorganism in the treatment of nitrate‐contaminated groundwater.     

Removal of endosulfan in a sequencing batch reactor: addition of granular activated carbon as improvement strategy

A granular activated carbon‐sequencing batch reactor (GAC‐SBR) was used to assess the removal of organochlorine endosulfan pesticide. The reactor operated in three stages: (I) starter and stabilization; (II) addition of 4 mg/L of endosulfan in feed; and (III) a single addition of 1 g/L of GAC to mixed liquor. During the 249 days of operation, the removal efficiency of COD was 96 ± 2%; for ‐N 72 ± 1%; and for PO₄^?3‐P 48 ± 13%. Was eliminated the 79% of endosulfan in stage II and 99% in stage III, not found its metabolite (endosulfan sulphate) in the reactor effluent. A consortium of eight bacterial strains was identified in the reactor stages, assessing five of them in the presence of 4 mg endosulfan/L by growth kinetics. According to the results, the joint action of the consortium and GAC addition is the responsible of eliminating the pesticide.     

Carbon dioxide emission and its regulation at land–water interface downstream of a point source at Ganga River (India)

The streams and rivers are considered hotspots of CO₂ exchange; and representative direct CO₂ emission measurements are essential for a correct regional estimate. We measured CO₂ emission flux at 15 sites at land–water interface downstream of a point source during low flow for three consecutive months for the year 2017. The general range of CO₂ efflux observed here was close to the results of regional studies, although values near the point source were disproportionately high (>350 mg/m²/h). CO₂ emission flux showed strong dependence on total organic carbon (TOC; R² = 0.96; P < 0.001), (R² = 0.88; P < 0.001), soluble reactive‐P (SRP; R² = 0.91; P < 0.001) and microbial activity measured in terms of fluorescein diacetate activity (FDAase; R² = 0.92; P < 0.001) and substrate induced respiration (SIR; R² = 0.96; P < 0.001). Because point source‐associated interfaces provide heterogeneous habitats, our study suggests the need for large scale monitoring of CO₂ emission at land–water interface of major rivers for more correctly presenting the regional scale CO₂ budget.     

A quantitative property‐property relationship for the internal diffusion coefficients of organic compounds in solid materials

Indoor releases of organic chemicals encapsulated in solid materials are major contributors to human exposures and are directly related to the internal diffusion coefficient in solid materials. Existing correlations to estimate the diffusion coefficient are only valid for a limited number of chemical‐material combinations. This paper develops and evaluates a quantitative property‐property relationship (QPPR) to predict diffusion coefficients for a wide range of organic chemicals and materials. We first compiled a training dataset of 1103 measured diffusion coefficients for 158 chemicals in 32 consolidated material types. Following a detailed analysis of the temperature influence, we developed a multiple linear regression model to predict diffusion coefficients as a function of chemical molecular weight (MW), temperature, and material type (adjusted R² of .93). The internal validations showed the model to be robust, stable and not a result of chance correlation. The external validation against two separate prediction datasets demonstrated the model has good predicting ability within its applicability domain (>.8), namely MW between 30 and 1178 g/mol and temperature between 4 and 180°C. By covering a much wider range of organic chemicals and materials, this QPPR facilitates high‐throughput estimates of human exposures for chemicals encapsulated in solid materials.     

A Modified Sliding Mode Fault Tolerant Control for Large‐Scale Civil Infrastructure

Adaptable active control strategies besides advance sensors and actuators technologies lead to higher performance of vibrational control in civil infrastructures under severe ground motions. These resilience control systems are robust against model uncertainties as well as being online recoverable from the malfunctioning of sensors and actuators. In this study, resilient control system based on sliding mode (SM) fault detection observer and SM fault tolerant control is improved for actuator fault in large‐scale systems. The SM fault detection observer is modified for eliminating the excessive chattering in estimating states and actuators’ fault, and the reconfigurable SM fault tolerant control is improved to minimizing input forces in control framework under seismic action. Design of observer and controller is performed using linear matrix inequalities. Numerical simulations on the cable‐stayed bridge benchmark demonstrate the effectiveness of the proposed fault‐tolerant system. Despite the high order of this large‐scale structure, the proposed fault detection and diagnosis method can effectively find the location and size of faults in actuators without performance degradation and computational costs. The fault‐tolerant controller maintains the performance of the structure at an acceptable level in the post‐fault case by redistribution of control signal to actuators.     

A mixing‐length‐scale‐based analytical model for predicting velocity profiles of open‐channel flows with submerged rigid vegetation

In open‐channel flows with submerged vegetation, the vertical velocity profile can often be described by two layers: the vegetation layer in the lower region and the surface layer in the upper non‐vegetated region. In this paper, a new mixing‐length scale of eddy is proposed for predicting the vertical velocity profile of flow in an open‐channel with submerged rigid vegetation. The analytical model of velocity profile is based on the momentum equation of flow where the turbulent eddy viscosity is assumed to have a linear relationship with the local velocity. The proposed model was tested against different datasets from the literature. The 22 datasets used cover a range of submergence [flow depth (H)/vegetation height (h) = 1.25 ~ 3.38], different vegetation densities of ah = 0.11 ~ 1.85 (a defined as the frontal area of the vegetation per unit volume) and bed slopes (S_o = 1.8 × 10^?6 ~4.0 × 10^?3). This study showed that the proposed model can predict the velocity profiles well against all datasets, and that the mixing length scale of eddies (λ) is well related with both vegetation height (h) and flow depth of surface layer (i.e. the height of non‐vegetation layer, H–h). Close examination of λ in the proposed model showed that when λ = 0.03, the model predicts vertical velocity profiles well for all datasets used except for very shallow submergence (i.e. H/h < 1.5).     

Skin squames contribute to ammonia and volatile fatty acid production from bacteria colonizing in air‐cooling units with odor complaints

One of the most notable Indoor Air Quality problems is odor emission. This study investigated the potential contribution of skin squames to the production of ammonia (NH₃) and volatile organic acids (VFAs) by 7 bacteria isolated from air‐cooling (AC) units with complaints of urine and body odors. Our previous study showed that keratinolytic activity is higher in AC units with odor complaints than those without. In the offices where these units are located, the most likely source of keratins is from human skin squames. Most bacteria can produce NH₃ and VFAs in the skin squame culture. Some correlations between the levels of NH₃, , VFAs, and keratinolytic activity were found. The odor production pathway with skin squames was proposed. Staphylococcus haemolyticus was abundant in the AC units with odor problems and had a high level of keratinolytic activity in addition to odor production. For long‐term odor control, it is important to reduce the level of skin squames entering the AC units.     

Research on a personalized targeted air supply device based on body movement capture

Unlike general ventilation, personalized ventilation can improve thermal comfort and conserve energy based on individual differences. It can also provide every individual the ability to control fresh air exposure and ensure good indoor air quality. However, determining how to improve air supply efficiency while avoiding a draft sensation is still a difficult question. This paper introduces a body movement-based personalized targeted air supply device. Two indices, size target value and velocity target value , are introduced to evaluate the degree to which the created flow field reaches the desired level. Additionally, the air supply effect of the device is compared with that of other devices. This research shows that the personalized targeted air supply device can successfully deliver air to the target area and improve air supply accessibility in the target area. The multinozzle coupling air supply mode produces a flow field air velocity of approximately 0.3 m/s, thus effectively avoiding a draft sensation. Compared with that of other personalized nozzles, the energy consumption is reduced significantly, by 88.2%, while the air supply accessibility can be increased by 48% with equivalent energy consumption.     

Strain gradient effects on flexural strength design of normal‐strength concrete beams

In the flexural strength design of normal‐strength concrete (NSC) beams, the resultant concrete force and its centroid within the compression zone is generally expressed in an equivalent rectangular stress block. The equivalent concrete stress is expressed as , where is the uni‐axial concrete cylinder strength. Currently, the value of α stipulated in various design codes for NSC is taken as 0.85. Nonetheless, in an experimental study conducted earlier by the authors on NSC columns subjected to concentric and eccentric axial loads, it was found that the value of α significantly depends on strain gradient, which generally increases as strain gradient increases until it reaches a maximum value. Therefore, strain gradient is a critical factor and should be considered in the flexural strength design of NSC members. In this paper, a new flexural strength design method that incorporates the effects of strain gradient is developed for NSC beams. An equivalent rectangular concrete stress block, which is strain‐gradient dependent, is proposed and applied to produce a set of equations for the flexural strength design of singly and doubly reinforced NSC beams with various concrete strengths. Lastly, these equations are converted into charts for practical design application. Copyright © 2010 John Wiley & Sons, Ltd.     

Erratum

Erratum: Wind and tall buildings: Negatives and positives The above‐mentioned article was published online on 3 November 2008 (DOI: 10.1002/tal.482). Some errors were subsequently identified within section 3·1 Wind turbines. Please find the corrected version below: […] The available power per square metre of approaching wind may be calculated from (3) where ρ is the air density (about 1·2 kg/m³), is the average of the cube of wind speed. Assuming the wind speed distribution is approximately Rayleigh in form, then may be estimated using . Therefore, the available power in the wind at turbine height is calculated to be (4) To calculate the energy extracted by the turbine, the available wind power P is multiplied by the turbine area and the turbine efficiency. Even an ideal turbine cannot exceed about 59% efficiency (the so‐called Betz limit) because much of the airflow tends to deflect around the turbine due to the turbine drag. Real turbines typically do not achieve overall efficiencies above about 40%. Assuming 40% efficiency, the 52‐m diameter turbine will therefore extract the following energy E from the wind (5) where 8766 is the number of hours per year. Assuming the building uses approximately 300 kWh/(year·m²) and that the used floor area is about 45000 m², its energy consumption will be 13·5 GWh/year. […]     

Modelling criteria for r/c elements constructed with ultra‐high‐strength concrete and subjected to cyclic loading

High‐strength concrete (HSC) has several benefits in high‐rise concrete buildings; however, its structural use in active seismic regions may be questioned due to the lower ductility of such concretes. In addition, seismic macro‐models being used currently are based on R/C elements constructed with normal‐strength concretes (f ≤ 40 MPa (5.8 ksi)). In this paper, the performance of plastic hinges in flexural elements constructed with a concrete strength up to 175 MPa (25.4 ksi) is investigated. In addition, other variables were studied such as the sectional reinforcement asymmetry, hinge shear strength and hinge shear demand. The seismic performance is presented in terms of stiffness deterioration, strength degradation, pinching phenomenon and displacement ductility. The requirements to implement the use of HSC in current macro‐models are examined. Current hysteretic models may be used to evaluate structural components constructed with higher concrete strength; however, the influence of concrete strength is controlled by the other test variables. Copyright © 2009 John Wiley & Sons, Ltd.     

The Capabilities and Limitations of Total Flooding, Water Mist Fire Suppression Systems in Machinery Space Applications

Water mist fire suppression systems are being seriously considered as replacements for Halon 1301 total flooding systems in machinery space applications. A total flooding water mist system is designed to discharge mist uniformly throughout the entire enclosure/compartment. The tests conducted to date form a substantial database for water mist systems installed in machinery spaces with volumes from 100 m³ to 1,000 m³ and varying degrees of ventilation. These tests have also identified the strengths and limitations of water mist in these applications. This report describes the capabilities of total flooding water mist fire suppression systems in machinery space applications.     

Plastic energy evaluation of bilinear SDOF systems with fluid viscous dampers

Current seismic practices are more concerned with dissipating a significant portion of seismic input energy than with lateral load resistance, as well as with determining seismic demands of structures using response spectra. This study aims to improve the knowledge of the plastic energy spectra ( $E_P$) of single-degree-of-freedom systems (SDOF) equipped with fluid viscous dampers (FVDs). This type of dampers is characterized by its supplemental damping ratio ${\xi }_{\mathit{add}}$ and velocity power $\alpha$. Using nonlinear dynamic analyses, the $E_P$ and its ratio to the input energy ( $E_P/E_I$) are determined using near-field-pulse, near-field-non-pulse and far-field ground motions. Parametric studies are conducted to investigate the effect of ground motion types, original system features and FVD characteristics on $E_P/E_I$ spectra. The results show that ground motion types have a considerable influence on the $E_P/E_I$ for systems with FVDs, while they are not effective for systems without FVDs. Increasing FVD nonlinearity (decreasing α) is more effective to reduce the $E_P/E_I$ under near-field-non-pulse and far-field motions than under near-field-pulse ground motions for structures with $T_n$ > 1 s. The paper further developed a prediction equation for estimating $E_P/E_I$for SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy-based seismic design.