Experimental and numerical analyses about the efficiency of flow through devices for the sediment controll in urban runoff

As land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, particle size distribution and specific gravity). The efficiency in terms of particles retained has been evaluated as a function of influent flow rate and particles characteristics; results have been compared to efficiency evaluated applying an overflow rate model. Furthermore the role of particles settling velocity in efficiency determination has been investigated. After the experimental runs on the gully pot, a standard full-scale model of an hydrodynamic separator (HS) has been tested under unsteady influent flow rate condition, and constant solid concentration at the input. The results presented in this study illustrate that particle separation efficiency of the unit is predominately influenced by operating flow rate, which strongly affects the particles and hydraulic residence time of the system. The efficiency data have been compared to results obtained from a modified overflow rate model; moreover the residence time distribution has been experimentally determined through tracer analyses for several steady flow rates. Finally three testing experiments have been performed for two different configurations of a full-scale model of a clarifier (linear and crenulated) under unsteady influent flow rate condition, and constant solid concentration at the input. The results illustrate that particle separation efficiency of the unit is predominately influenced by the configuration of the unit itself. Turbidity measures have been used to compare turbidity with the suspended sediments concentration, in order to find a correlation between these two values, which can allow to have a measure of the sediments concentration simply installing a turbidity probe.

Biohydrogen production from food industry waste by suspended and immobilized thermophylic bacteria

This work describes hydrogen production by anaerobic digestion of glucose, molasses and milk whey by 4 thermophilic Thermotoga strains. In the attached-cell tests, the biofilm support characterized by the highest specific surface resulted in the best H2 rate. All the Thermotoga strains examined (T. neapolitana, T. maritima, T. naphtophila, T. petrophila) could produce H2 from glucose, molasses and milk whey, both in suspended- and attached-cell tests. With all the three substrates, the best performances were obtained with T. neapolitana. Some tests were conducted out to select the optimal carrier for the attached-cell conditions. 4 types of carrier were tested: 3 sintered glass carriers and a ceramic one; the chosen carrier was Biomax.

Stream sediments analysis for geochemical mapping of Romagna Apennines (Northern Italy): monitoring and management tool of environmental resources at various scales

Geochemical mapping is a valuable tool for the control of territory that can be used not only in the identification of mineral resources and geological, agricultural and forestry studies but also in the monitoring of natural resources by giving solutions to environmental and economic problems. Stream sediments are widely used in the sampling campaigns carried out by the world's governments and research groups for their characteristics of broad representativeness of rocks and soils, for ease of sampling and for the possibility to conduct very detailed sampling In this context, the environmental role of stream sediments provides a good basis for the implementation of environmental management measures, in fact the composition of river sediments is an important factor in understanding the complex dynamics that develop within catchment basins therefore they represent a critical environmental compartment: they can persistently incorporate pollutants after a process of contamination and release into the biosphere if the environmental conditions change. It is essential to determine whether the concentrations of certain elements, in particular heavy metals, can be the result of natural erosion of rocks containing high concentrations of specific elements or are generated as residues of human activities related to a certain study area. This PhD thesis aims to extract from an extensive database on stream sediments of the Romagna rivers the widest spectrum of informations. The study involved low and high order stream in the mountain and hilly area, but also the sediments of the floodplain area, where intensive agriculture is active. The geochemical signals recorded by the stream sediments will be interpreted in order to reconstruct the natural variability related to bedrock and soil contribution, the effects of the river dynamics, the anomalous sites, and with the calculation of background values be able to evaluate their level of degradation and predict the environmental risk.

Bioremediation of PCB-contaminated marine sediments: From identification of indigenous dehalorespirers to enhancement of microbial reductive dechlorination

Marine sediments are the main accumulation reservoir of organic recalcitrant pollutants such as polychlorinated biphenyls (PCBs). In the anoxic conditions typical of these sediments, anaerobic bacteria of the phylum Chloroflexi are able to attack these compounds in a process called microbial reductive dechlorination. Such activity and members of this phylum were detected in PCB-impacted sediments of the Venice Lagoon. The aim of this work was to investigate microbial reductive dechlorination and design bioremediation approaches for marine sediments of the area. Three out of six sediment cultures from different sampling areas exhibited dechlorination activities in the same conditions of the site and two phylotypes (VLD-1 and VLD-2) were detected and correlated to this metabolism. Biostimulation was tested on enriched dechlorinating sediment cultures from the same site using five different electron donors, of which lactate was the best biostimulating agent; complementation of microbial and chemical dechlorination catalyzed by biogenic zerovalent Pd nanoparticles was not effective due to sulfide poisoning of the catalyst. A new biosurfactant-producing strain of Shewanella frigidimarina was concomitantly obtained from hydrocarbon-degrading marine cultures and selected because of the low toxicity of its product. All these findings were then exploited to develop bioremediation lab-scale tests in shaken reactors and static microcosms on real sediments and water of the Venice lagoon, testing i) a bioaugmentation approach, with a selected enriched sediment culture from the same area, ii) a biostimulation approach with lactate as electron donor, iii) a bioavailability enhancement with the supplementation of the newly-discovered biosurfactant, and iv) all possible combinations of the afore-mentioned approaches. The best bioremediation approach resulted to be a combination of bioaugmentation and bioremediation and it could be a starting point to design bioremediation process for actual marine sediments of the Venice Lagoon area.