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.     

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.     

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.     

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.     

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.     

Growth and disparities in Europe: Insights from a spatial growth model*

This paper provides a spatial neoclassical growth model for a system of N regional economies. Regional output growth is determined by interregional fixed capital relocations which depend on initial factor endowments as well as a region's relative location in space. The dynamics of the model are captured by a Taylor approximation, which provides a testable spatial econometric model specification that is applied for European regions on the NUTS 2 level. Both theoretical and empirical results show how relatively high human capital endowments are beneficial to growth if found within one region, but disadvantageous if found in neighbouring regions. Este artículo proporciona un modelo de crecimiento neo‐clásico espacial para un sistema de N economías regionales. El crecimiento del producto regional viene determinado por deslocalizaciones interregionales de capital fijo que dependen de la dotación de factores inicial, así como de la relativa localización espacial de una región. Las dinámicas del modelo son capturadas mediante una aproximación de Taylor, que proporciona una especificación comprobable de modelo econométrico espacial que se aplica a regiones europeas a nivel NUTS 2. Tanto los resultados teoréticos como los empíricos muestran como las dotaciones relativamente elevadas de capital humano son ventajosas para el crecimiento cuando se concentran en una región, pero una desventaja si se encuentran en regiones vecinas.      

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. […]     

The sources of metropolitan unemployment fluctuations in the Greater Taipei metropolitan area*

While past macroeconomic studies based on the natural rate hypothesis have tended to limit their discussions to cyclical unemployment, this paper applies shift‐share analysis to additionally consider both frictional and structural unemployment, which is composed of sectoral shifts and geographic mismatches. The results of the estimation confirm that the recent high unemployment in the Taipei metropolitan area mainly stems from both sectoral shifts and frictional unemployment. Therefore, how to smooth the industrial transformation and more flexible turnovers should be critical in reducing the pressure brought about by such unemployment today. Resumen Mientras que los estudios macroeconómicos previos basados en la hipótesis de la tasa natural han tendido a limitar sus discusiones al desempleo cíclico, este artículo aplica un análisis shift‐share para considerar adicionalmente tanto el desempleo friccional como el estructural, formado este por cambios sectoriales y desajustes geográficos. Los resultados de esta estimación confirman que el elevado desempleo sufrido recientemente en el área metropolitana de Taipei proviene principalmente tanto de cambios sectoriales como del desempleo friccional. Por ello, tanto la manera de suavizar la transformación industrial como una renovación del personal más flexible deberían ser críticos para reducir la presión provocada por el desempleo actual.      

Spatial monopoly of multi‐establishment firms: An empirical study for supermarkets in the Netherlands

Multi‐establishment firms can create local spatial monopolies in the form of clusters of own establishments without competition. This paper examines the existence of spatial monopolies for Dutch supermarkets in 2009. It is found that 23 percent of consumers can be qualified as being locked‐in in a spatial monopoly of a specific supermarket brand. Resumen. Las empresas con múltiples establecimientos pueden crear monopolios espaciales locales en forma de conglomerados de sus propios establecimientos sin que haya competencia. Este artículo examina la existencia de monopolios espaciales de supermercados en los Países Bajos en 2009. Se encontró que el 23 por ciento de consumidores pueden clasificarse como cautivos de un monopolio espacial de alguna marca de supermercado específica.      

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.     

Composite beam composed of steel and pre‐cast concrete. (Modularized Hybrid System,MHS) Part II: analytical investigation

This paper introduces the concept of a wide flange steel beam with the bottom flange encased in pre‐cast concrete. These composite beams utilize the merits of both steel and concrete materials. The effective interaction between the two materials can reduce the size of the steel beams. The reinforcement and the concrete are pre‐integrated with the bottom flange of the steel beam at a manufacturing plant. In this paper, the analytical investigation of the flexural moment strength of the composite beams at both the yield limit state and the maximum load limit state is performed and compared with the experimental results. The depth of the equivalent rectangular stress block of the beams is obtained using an equilibrium equation when both the compression steel reinforcements are present. The post‐yield behaviour of the composite beams is also investigated based on the normalized effective stiffness versus the normalized drift ratio . The stiffness of the composite beams degrades gradually with sufficient ductility and dissipating energy capability. A six‐step procedure provides a fast, effective and accurate way of investigating the post‐yield behaviour of the composite beams. Copyright © 2008 John Wiley & Sons, Ltd.     

Crime and social sanction*

In this paper we provide evidence that social sanctions represent a very strong deterrent of property crime. We present a formal model relating crime and social sanction to social interaction density. Consistently with our theoretical framework and the literature on network closure and social interactions, we resort to demographic and geomorphological information to develop an exogenous and reliable measure for the density of social interactions based on town dimension and isolation. We estimate a spatial panel model by means of a GMM procedure and we find that areas with denser social interactions display significantly and substantially lower rates of property crime. Resumen. En este artículo aportamos pruebas de que las sanciones sociales constituyen un elemento disuasorio muy poderoso para el crimen contra la propiedad. Presentamos un modelo formal que relaciona el crimen y la sanción social con la densidad de interacción social. De manera consecuente con nuestro marco teórico y la literatura sobre exclusión de redes e interacciones sociales, acudimos a información demográfica y geomorfológica para desarrollar una medida exógena y fiable de la densidad de las interacciones sociales, basada en el tamaño y aislamiento de la ciudad. Estimamos un modelo de panel espacial por medio de un procedimiento de método generalizado de momentos (MGM) y hallamos que las áreas con interacciones sociales más densas muestran significativa y substancialmente tasas menores en crímenes contra la propiedad.      

Production technology and agglomeration for Japanese prefectures during 1991–2000*

We analyse the seemingly unrelated regression (SUR) models with spatial dependencies from a Bayesian point of view and estimate the parameters of the models using a Markov chain Monte Carlo (MCMC) method. Further, we analyse the production technology and the economics of agglomeration in Japanese prefectures from 1991 to 2000, simultaneously taking into account spatial and serial correlation. Model comparison is done via log‐marginal likelihoods, and it is found that the spatial error SUR model is the best model and that the economics of agglomeration and spatial heterogeneity decreased over this decade. Resumen. Analizamos modelos de ecuaciones aparentemente no relacionadas (SUR, siglas en inglés) con dependencias espaciales desde un punto de vista bayesiano y estimamos los parámetros de los modelos utilizando el método de Monte Carlo basado en cadenas de Markov (MCMC). Además, analizamos la tecnología de la producción y las economías de aglomeración en prefecturas japonesas desde 1991 a 2000, teniendo en cuenta simultáneamente la correlación espacial y serial. La comparación de modelos se realiza mediante verosimilitud log‐marginal, y se encontró que el error espacial del modelo SUR es el mejor modelo y que las economías de aglomeración y la heterogeneidad espacial disminuyeron durante esta década.      

Employment,income, migration and public services: A simultaneous spatial panel data model of regional growth*

We estimate a regional spatial panel simultaneous‐equations growth model, using a five‐step new estimation strategy that generalizes an approach outlined in Kelejian and Prucha. The study region consists of the 418 Appalachian counties 1980?2000. Estimates show feedback simultaneities among the endogenous variables, conditional convergence with respect to the respective endogenous variables, and spatial autoregressive lag and spatial cross‐regressive lag effects with respect to the endogenous variables. A key policy conclusion is that sector‐specific programs should be integrated and harmonized and that regionally differentiated development policies may yield greater returns than treating all locations the same. Estimamos un modelo de crecimiento de panel espacial regional por ecuaciones simultaneas, utilizando una nueva estrategia de estimación de cinco pasos que generaliza una enfoque descrito en Kelejian y Prucha. La región de estudio comprende los 418 condados Apalaches 1980‐2000. Las estimaciones muestran simultaneidades de retroalimentación entre las variables endógenas, convergencia condicional con respecto a las variables endógenas respectivas, y un retardo espacial autorregresivo y efectos de retardo regresivos cruzados espaciales con respecto a las variables endógenas. Una conclusión clave sobre políticas es que los programas sectoriales específicos deberían estar integrados y armonizados, y que las políticas de desarrollo diferenciadas regionalmente podrían producir mejores retornos que si se tratasen todas las localizaciones del mismo modo.      

The core‐periphery model with three regions and more*

We determine the properties of the core‐periphery model with three regions and compare our results with those of the standard 2‐region model. The conditions for the stability of dispersion and concentration are established. As in the 2‐region model, dispersion and concentration can be simultaneously stable. We show that the 3‐region (2‐region) model favours the concentration (dispersion) of economic activity. Furthermore, we provide some results for the n‐region model. We show that the stability of concentration of the 2‐region model implies that of any model with an even number of regions. Determinamos las propiedades de un modelo núcleo‐periferia de tres regiones y comparamos nuestros resultados con los del modelo estándar de dos regiones. Se establecen las condiciones para la estabilidad de la dispersión y la concentración. Al igual que en el modelo de dos regiones, la dispersión y la concentración pueden ser estables simultáneamente. Mostramos que el modelo de tres regiones (dos regiones) favorece la concentración (dispersión) de la actividad económica. Además, aportamos algunos resultados para un modelo n‐regional. Mostramos que la estabilidad de la concentración del modelo bi‐regional implica eso mismo de cualquier modelo con un número par de regiones.      

Structural and spatial characteristics of personal actor networks: The case of industries for the elderly in Korea*

This paper studies the relationship between geography and dynamics of network in the evolutionary process of a newly emerging industry. Core actors are well connected with one another through policy‐related project networks, as well as temporary clusters, such as trade fairs, conventions, and seminars. Although geographical proximity is not significantly related to the occurrence of co‐operation between individuals, position of an actor in the network is significantly related to his/her geographical reach. Despite the importance of other industrial network in the Capital Region, actors in non‐Capital Regions played important positions in the networks and assumed key roles in institutional‐building processes. Resumen. Este artículo estudia la relación entre la geografía y las dinámicas de red en el proceso evolutivo de una nueva industria emergente. Los actores esenciales están bien conectados entre sí mediante redes de proyectos relacionados con políticas, así como por conglomerados temporales como ferias de exposiciones, convenciones y seminarios. Aunque no hay una relación significativa entre la proximidad geográfica y la aparición de una cooperación entre individuos, la posición de un actor en la red está relacionada significativamente con su alcance geográfico. A pesar de la importancia de otras redes industriales en la región capital, los actores del resto de regiones ocuparon posiciones importantes en las redes y asumieron papeles clave en procesos de desarrollo institucional.      

Estimating the demand for public open space: Evidence from North Carolina municipalities*

This paper empirically identifies socio‐economic, physical, and geographic factors of the demand for open space in the state of North Carolina in the United States. Estimated coefficients suggest that spatial dependency exists in open space demand and that open space is a normal good. The paper provides the first empirical investigation of how open space demand is affected by local weather conditions. It is found that the demand has a statistically significant substitution relationship with nice weather. We discuss the socio‐economic rationale for the estimated demand models within the regional context of North Carolina and point to some relevant policy implications. Resumen. Este artículo identifica empíricamente los factores socioeconómicos, físicos y geográficos de la demanda de espacios al aire libre en el estado de Carolina del Norte en los Estados Unidos. Los coeficientes estimados sugieren que existe una dependencia espacial en la demanda de espacios al aire libre y que los espacios al aire libre son un bien normal. El artículo ofrece la primera investigación empírica sobre como se ve afectada la demanda de espacios al aire libre por las condiciones meteorológicas locales. Se ha encontrado que la demanda tiene una relación de substitución estadísticamente significativa con una meteorología benigna. Discutimos el fundamento socioeconómico de los modelos de demanda estimados dentro del contexto regional de Carolina del Norte e indicamos varias implicaciones relevantes para la formulación de políticas.      

Modelling spatial externalities in panel data: The Spatial Durbin model revisited*

The purpose of this paper is twofold. First, it extends the spatial Durbin model to panel data allowing for non‐spherical disturbances and proposes two alternative estimators based on ML techniques. While one of the estimators exhibits more degrees of freedom, the other is computationally less burdensome. Results from a Monte Carlo study reveal that both estimators have satisfactory small sample properties also in cases when the error structure is in effect spherical. Second, the paper demonstrates that conventional testing procedures may wrongly reject the existence of spatial externalities. In particular, it shows that the incidence of a type II error increases as the spatial weight matrix becomes denser. Este artículo tiene un doble objetivo. Primero, amplia el modelo espacial de Durbin a datos de panel, permitiendo perturbaciones no esféricas y propone dos estimadores alternativos basados en técnicas de aprendizaje automático (ML). Mientras que uno de los estimadores exhibe un mayor número de grados de libertad, el otro es menos problemático en cuanto a su cómputo. Los resultados de un estudio de Monte Carlo mostraron que ambos estimadores poseen propiedades satisfactorias en cuanto a pequeños muestreos, incluso en casos en los que la estructura del error es de hecho esférica. Segundo, el artículo demuestra que los procedimientos convencionales de ensayo podrían rechazar erróneamente la existencia de externalidades espaciales. En particular, se muestra que la incidencia en un error de tipo II aumenta a medida que la matriz ponderada espacial se vuelve más densa.      

Proximity,accessibility and choice: A matter of taste or condition?*

Drawing on a combination of register data and travel survey data, this research explores changes in the accessibility to different amenities for the Swedish population between 1995 and 2005, as well as the reasons behind the changes: redistribution of either amenities or the population. Overall, proximity has increased concerning most of the amenities during the period. However, despite decreasing ‘potential’ distances, actual travel distances are growing longer due to, for example, an increasing selectivity in preferences. An analysis of the accessibility development for service amenities shows that restructuring within the service sector is the main cause of the changes, and to a lesser extent population redistribution. Resumen. Haciendo uso de una combinación de datos de registros y encuestas de viajes, este estudio explora cambios en la accesibilidad de diferentes servicios y lugares de recreo para la población sueca entre 1995 y 2005, así como las razones detrás de dichos cambios: una redistribución de los servicios o de la población. En conjunto, la proximidad ha aumentado con respecto a la mayoría de los servicios durante el periodo estudiado. Sin embargo, a pesar de las reducciones en distancias “potenciales”, las distancias de viaje están aumentando debido a por ejemplo una mayor selectividad en las preferencias. Un análisis del desarrollo de la accesibilidad de servicios y ocio muestra que la reestructuración dentro del sector servicios es la causa principal de los cambios y, en menor medida, la redistribución de la población.