Search results for "Water science"

Evaluation of biomass activity and wastewater characterization in a UCT-MBR pilot plant by means of respirometric techniques

2011

Abstract Over the last two decades, Membrane Bioreactors (MBRs) emerged even more for wastewater treatment, ensuring high removal efficiencies as well as very small footprint requirements. Indeed, in this kind of process, a modification in biomass activity and viability can exist compared to that of a CAS process. In this context, respirometric analysis represents a reliable tool in order to evaluate the actual biomass kinetic parameters, to insert in mathematical models in the design phase, as well as to monitor the biomass viability, especially when these processes are operated with high SRT values. The paper presents some results of respirometric techniques applied for the characterisati…

Detection and prevention of enhanced biological phosphorus removal deterioration caused by Zoogloea overabundance.

2008

A sequencing batch reactor was operated in the conventional anaerobic-aerobic mode for enhanced biological phosphorus removal using acetate as the sole substrate. Despite the nutrients concentrations in the influent being high enough to satisfy the biological requirements, Zoogloea ramigera managed to grow in the system until it had negative effects on the process performance. The excess of exocellular polymeric material produced by this microorganism contributed to a viscous bulking phenomenon and caused important settling problems. The examination of the sludge under the microscope was a valuable tool to diagnose the cause of the imbalance in the process. The strategy adopted to avoid the…

The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink

2022

We assessed the potential of dead seagrass Posidonia oceanica matte to act as a biogeochemical sink and provide a coherent archive of environmental change in a degraded area of the Mediterranean Sea (Augusta Bay, Italy). Change in sediment properties (dry bulk density, grain size), concentration of elements (Corg, Cinorg, N, Hg) and stable isotope ratios (δ13C, δ 15N) with sediment depth were measured in dead P. oceanica matte and unvegetated (bare) sediments in the polluted area, and an adjacent P. oceanica meadow. Principal Component Analysis (PCA) revealed a clear clustering by habitat, which explained 72% of variability in our samples and was driven mainly by the accumulation of N and H…

Overland flow generation on hillslopes of complex topography: analytical Solutions

2007

The analytical solution of the overland flow equations developed by Agnese et al. (2001; Hydrological Processes15: 3225–3238) for rectangular straight hillslopes was extended to convergent and divergent surfaces and to concave and convex profiles. Towards this aim, the conical convergent and divergent surfaces are approximated by a trapezoidal shape, and the overland flow is assumed to be always one-dimensional. A simple ‘shape factor’ accounting for both planform geometry and profile shape was introduced: for each planform geometry, a brachistochrone profile was obtained by minimizing a functional containing a slope function of the profile. Minima shape factors are associated with brachist…

High Order Textural Classification of Two SAR ERS Images on Mount Cameroon

2006

Abstract Many researchers have demonstrated that textural data increase the precision of a classification when they are combined with level of grey information. However, the calculation of textural parameters of order two is often too long in a computer. The problem is more complex when one must compute higher order textural parameters, which however can considerably improve the precision of a classification. This work is based on statistical methods of order two and three for the calculation of textural parameters [Akono et al., 2003]. In this work, we suggest a new method of calculation of textural parameters, which is more general, not limiting itself only on order two or three, but whic…

Assessing performance in the management of the urban water cycle

2011

This paper proposes the use of directional distance functions and Data Envelopment Analysis techniques to assess technical efficiency in the provision of the different stages of the urban water cycle in Andalusia, a Southern European region. Evaluating performance in the management of specific stages of the urban water cycle provides utility managers and regulating authorities with relevant information that may not be detected by more conventional approaches based on assessing performance at utility level. We find that Andalusian water and sewage utilities could achieve significant increases in the volume of water delivered without diminishing the output of their other services and using th…

Assessment of a pilot system for seawater desalination based on vacuum multi-effect membrane distillation with enhanced heat recovery

2018

Abstract This work presents the evaluation of an innovative system based on vacuum multi-effect membrane distillation modules (V-MEMD) for seawater desalination at pilot scale. This four-effect unit introduces a remarkable modification from previous V-MEMD systems, consisting of the use of the seawater feed flow as cooling in the condenser, rather than a separate circuit. Preheating the feed in the condenser improved heat efficiency (maximum gained output ratio obtained for seawater was 3.2). Maximum distillate fluxes reached 8.5 l h−1 m−2 for hot feed temperature 75 °C and feed flow rate 150 l h−1. Increasing both parameters to raise the productivity was hindered by the inability of the co…

Discussion of “Free Overfall in Inverted Semicircular Channels” by Subhasih Dey

2004

Improving drinking water treatment without tariff impact: the Spanish case study

2017

Abstract Water is essential for our lives and activities. Everyone can drink good quality water, the question is whether they have access to it in the first place. Water quality and its treatment depend on the water source. This treatment has costs that users have to pay in the water tariff. It is very important to establish a water tariff that permits the best water treatment and has a low impact on the users. Cost functions are a useful tool to predict costs before an implementation or improvement. This article, using three easy steps (analysis, obtaining costs and modification of the water tariff) proposes improving water purification treatment using cost functions in order to find the b…

A particle based simulation model for glacier dynamics

2013

This publication is contribution number 22 of the Nordic Centre of Excellence SVALI, “Stability and Variations of Arctic Land Ice”, funded by the Nordic Top-level Research Initiative (TRI). The work has been supported by the SVALI project through the University of Lapland, Arctic Centre, and through the University Centre in Svalbard. Funding was also provided by the Conoco-Phillips and Lunding High North Research Program (CRIOS: Calving Rates and Impact on Society). A particle-based computer simulation model was developed for investigating the dynamics of glaciers. In the model, large ice bodies are made of discrete elastic particles which are bound together by massless elastic beams. These…