Search results for "environmental engineering"

Waste activated sludge dewaterability: comparative evaluation of sludge derived from CAS and MBR systems

2016

Nowadays, sludge dewatering is one of the greatest operational cost to wastewater treatment cycle. Specifically, 1t of fresh sludge to be disposed is composed, on average, by 0.25 - 0.30t of suspended solids, with an average cost for treatment and disposal around 280 - 470 €/t of suspended solids. Despite several technologies have been developed with the focus to reduce also the specific sludge production, still mechanical dewatering represents a crucial step to limit the amount of sludge to be disposed. Many physical–chemical parameters influence the sludge dewaterability: floc structure, particle size, bound water content, surface charge and hydrophobicity, Extracellular Polymeric Substan…

Closure to “Extraction of the Flow Rate Equation under Free and Submerged Flow Conditions in Pivot Weirs with Different Side Contractions” by N. Shei…

2018

Financial winners and losers since the privatization of the English and Welsh water and sewerage industry: a profit decomposition approach

2020

Evaluating changes in profit, price and productivity over time can be of great importance for regulated water industries. We investigate the drivers of profit, price (capital, labour and other inputs) and productivity change (cost efficiency change, technical change and scale effect) and the recipients of productivity change (consumers, the business itself, employees and other resource suppliers) of the English and Welsh water and sewerage companies over the period of 1995–2016. The results indicate that the profit decreased over time due to the negative quantity effect, which offset the positive price effect. A further decomposition of the quantity effect illustrates the negative impact of…

A Systematic Review of the Hydrological, Environmental and Durability Performance of Permeable Pavement Systems

2021

Due to urbanization, large portions of vegetated territory have been replaced by waterproof surfaces. The consequences are greater outflows, lower infiltration, and lower evapotranspiration. Pavement systems made with permeable surfaces allow the infiltration of water, ensuring reduction of runoff volume. In this paper, the methods of analysis of the hydrological and environmental performance of the pavement systems are reviewed in the context of urban drainage and regarding their durability. The purpose is to present an overview of the studies published during the last decade in the field. The Pubmed and Web Science Core Collection electronic databases were used to conduct the scientific l…

The role of extracellular polymeric substances on aerobic granulation with stepwise increase of salinity

2018

Abstract A granular sequencing batch reactor (GSBR) worked for 164 days to study the effect of salinity on aerobic granulation. The feeding had an organic loading rate (OLR) of 1.6 kg COD⋅m −3 ⋅d −1 and a gradual increase of salinity (from 0.30 to 38 g NaCl − ⋅L −1 ) to promote a biological salt-adaptation. First aggregates (average diameter ≈ 0.4 mm) appeared after 14 days. Extracellular polymeric substances (EPSs) analyses revealed that proteins were mainly higher than polysaccharides, and microorganisms metabolized EPSs as additional carbon source, mostly in feast phase, to face the energy demand for salinity adaptation. No significant worsening of organic matter removal was observed. Th…

Assessing Urban System Vulnerabilities to Flooding to Improve Resilience and Adaptation in Spatial Planning

2018

Fluvial, pluvial and coastal flooding are the most frequent and costly natural hazard. Cities are social hubs and life in cities is reliant on a number of services and functions such as housing, healthcare, education and other key daily facilities. Urban flooding can cause significant disruption to these services and wider impacts on the population. These impacts may be short or long with a variably spatial scale: urban systems are spatially distributed and the nature of this can have significant effects on flood impacts. From an urban-planning perspective, measuring this disruption and its consequences is fundamental in order to develop more resilient cities. Whereas the assessment of phys…

Improvement of lateral connectivity in a sector of River Hârtibaciu (Olt/Danube Basin)

2017

Abstract The Hârtibaciu River in the Alţâna area has a disturbed lateral connectivity owing to its lateral embankments, as a result of which fish communities in this river sector are negatively influenced. The method of obtaining the water supply for a new proposed wetland is by gravitation, and any excessive water supply to the wetland will be controled and directed to the Hârtibaciu River in a natural manner. A state-of-the-art man-made wetland should increase the quality of the habitat for local fish communities, especially for the Rhodeus sericeus population, which is a species of conservation interest.

The role of urban growth, climate change, and their interplay in altering runoff extremes

2018

Changes in climate and urban growth are the most influential factors affecting hydrological characteristics in urban and extra-urban contexts. The assessment of the impacts of these changes on the extreme rainfall–runoff events may have important implications on urban and extra-urban management policies against severe events, such as floods, and on the design of hydraulic infrastructures. Understanding the effects of the interaction between climate change and urban growth on the generation of runoff extremes is the main aim of this paper. We carried out a synthetic experiment on a river catchment of 64 km2to generate hourly runoff time series under different hypothetical scenarios. We impos…

Comparing two applicative criteria of the soil erosion physical model concept

2017

The physical model represented by a replicated plot has been suggested to be the best possible, unbiased, real world model to predict plot soil erosion. The aim of this investigation was to compare the original applicative criterion of the physical model concept proposed by Nearing with that later suggested by Bagarello et al. The comparison was performed by using three empirical soil erosion models (the Universal Soil Loss Equation [USLE], a modified USLE [USLE-MM], and the Central and Southern Italy [CSI] model) and plot soil loss data collected at the experimental station of Sparacia, in Sicily (southern Italy). The investigation showed that (i) the new criterion was generally more restr…

Analytical approach extending the Granier method to radial sap flow patterns

2020

Abstract The Granier thermal dissipation (TD) method is probably the most applied method to compute the transpiration flux of trees, due to its simplicity and effective compromise between theory and data availability. Starting from the heat transfer equations at the basis of Granier’s method, the objective of this paper is to derive an analytical solution for the transpiration flux to extend the sap flow equations to the radial domain. We adopted a flexible approach to cope with the differences in radial sapflow density (SFD) profile shapes that are known to occur in relation to wood anatomy (diffuse porous vs. ring- or non-porous xylem). With this purpose, we investigated the robustness of…