1,720,999 research outputs found
Comparison of WDN segmentations based on modularity indexes
No full textWater distribution networks (WDNs) are divided into smaller districts for different technical purposes (e.g., pressure control, leakage management) relying heavily on the technician's experience. A recently developed approach based on modularity metric allow to quantify the degree of uniformity of a particular segmentation including information on network properties (e.g., pipe diameters, flow rates, pressures, leakages) as weights in the matrix representation of the WDN. This study compares different segmentation solutions obtained by maximizing modularity entailing different weights by using the mutual information index coming from the information theory. This study aims at providing insights on modularity formulations to find optimal WDN segmentation for different management purpose
Comparison of WDN segmentations based on modularity indexes
No full textWater distribution networks (WDNs) are divided into smaller districts for different technical purposes (e.g., pressure control, leakage management) relying heavily on the technician’s experience. A recently developed approach based on modularity metric allow to quantify the degree of uniformity of a particular segmentation including information on network properties (e.g., pipe diameters, flow rates, pressures, leakages) as weights in the matrix representation of the WDN. This study compares different segmentation solutions obtained by maximizing modularity entailing different weights by using the mutual information index coming from the information theory. This study aims at providing insights on modularity formulations to find optimal WDN segmentation for different management purposes
The Effect of Streamflow, Ambient Groundwater, and Sediment Anisotropy on Hyporheic Zone Characteristics in Alternate Bars
Full text linkThe hyporheic exchange is the main driver for the biogeochemical transformations of nutrients within a river bed. The current study addresses the variations in hyporheic zone (HZ) characteristics in alternate bars due to different streamflow, ambient groundwater, and sediment anisotropy. Several simulations, using a sequentially coupled surface water‐groundwater model of a synthetic reach with fully developed alternate bars morphology, were performed. Two HZs exist within the streambed; a shallow zone that is more linked to surface water, and a deep one that is more influenced by the groundwater variations. Increasing streamflow, and therefore bar submergence, decreases the hyporheic flow. The residence times distribution is bimodal, which implies the existence of two HZs . This bimodality is enhanced by anisotropic sediment conditions, while it is much milder in isotropic ones. The shallow zone residence times increase when streamflow value rises, while the residence times in the deep HZ are less affected. The mean and median residence times decrease by increasing streamflow in partially submerged case, and they are larger in fully submerged case. The hyporheic flow, area, residence times, and extent decrease by increasing groundwater fluxes. The deep zone is the most affected by the groundwater fluxes. Hyporheic flow and extent values are significantly larger in isotropic conditions than in anisotropic ones. The change in residence times values is different between the deep and shallow zones. A predictive model is driven to predict the hyporheic flux, residence times, and hyporheic depths dependence on bar submergence, ambient groundwater, and sediment anisotropy
Vertical greening systems for wastewater treatment
No full textThe utilization of decentralized water treatment using nature-based solutions (NBSs) has become an important topic. In densely populated urban settings, the integration of NBS into building designs, such as vertical greening systems (VGSs), has a high potential to implement the needed concept of water reuse in our cities. These systems not only require water for their operational needs but can also efficiently treat water, utilizing processes similar processes to those found in treatment wetlands. The main body of literature investiages the use of graywater for both irrigation and treatment within VGS. Variations are observed in the overall design, the types of plant growing media used, organic load, and the overall effectiveness of treatment across different studies. This chapter provides a comprehensive overview of the available research and discusses the necessary advancements required to promote the widespread implementation of VGS for graywater treatment
Comment on “Pore water flow due to near-bed turbulence and associated solute transfer in a stream or lake sediment bed" by M. Higashino et al.
No full textResilience to flow variability of an open-air green wall for greywater treatment
Full text linkWater management in urban areas is challenged by climate change and increasing population, and the reduction of water consumption in urban areas is becoming a major issue. Thus, domestic greywater (GW) can be a valuable water source for non-potable purposes, coupled with the benefits provided by a nature-based treatment approach. In this context, green walls have been proposed for GW treatment and local reuse, hence coupling the advantage of GW reuse with the benefits provided by a nature-based treatment approach. The amount of available GW is linked with the occupancy and habits of the inhabitants, but there is still limited knowledge on the impact of variations of GW flow rate on the treatment efficiency and on the health of the green wall. Therefore, this study aims to test the resilience of a modular green wall to variations in GW flow rate over 7 months. The experiments were performed on two configurations fed with synthetic GW: one was fed with a constant flow rate (equivalent to daily GW production per capita) as a reference, while the other received a variable flow schedule. The variable schedule included three phases: underload (−50 %), overload (+50 %) and maintenance flow. Input and output water were analysed to evaluate the treatment performances on fourteen physical-chemical parameters. Results showed that neither underload nor maintenance caused any detrimental effect on GW treatment efficiency or plants. Overload conditions caused a slight decrease in the treatment efficiency (e.g., 93.8 % for BOD5 compared to 100 % recorded in the control configuration), and plants exhibited visual signs of distress. However, these negative effects disappeared after re-establishing the standard flow rate. These findings demonstrated the resilience of green walls to inflow rate variations. The results provide useful indications for the application of green walls for GW treatment and provide important indications for design guidelines, in terms of maximum values of organic loading rate (∼20 gBOD5 m−2 d−1) and oxygen transfer rate (∼15 gO2 m−2 d−1), and focusing on building maximum capacity as driving parameter
Citizens’ perception and willingness to pay for green roofs and nature-based solutions in three Italian metropolitan cities
Full text linkNature-Based Solutions have been largely investigated and technically improved in the last decades. Thanks to their multiple benefits, these solutions can largely contribute to the sustainable urban development, especially if diffusely installed over large areas. A key point to support their implementation is to actively involve citizens, increasing interest and willingness to pay for installation and maintenance. Through an anonymous online survey distributed in three Italian metropolitan cities (i.e., Cagliari, Palermo and Torino), this study investigates citizens’ awareness of potential benefits provided by urban Nature-Based Solutions and their willingness to invest in different infrastructures, with a specific focus on green roofs. The aim of the study is to understand how different climatic and socio-demographic conditions could influence citizens’ interest in these tools, also exploring the potential impeding elements perceived by citizens. Results highlighted a higher interest for green roofs on public buildings than on private ones; most of the citizens are willing to financially contribute for green roofs and nature-based solutions in public spaces, with an average of 71€/year. Understanding citizens’ perception of environmental issues and willingness to pay for green solutions is essential for decision makers to properly define investments and incentivization policies, fostering the development of sustainable cities
Comportamento del dittero Simulium monticola (Simuliidae) in differenti condizioni idrologiche: uno studio in laboratorio
No full textExperimental study of greywater treatment through green walls
Full text linkAmong nature- based solutions (NBSs), green walls represent a key technology in the urban context because of the low energy demand and of the many ecological and social outcomes. This work presents the results of the experimental study at laboratory scale of the treatment of greywater (e.g. domestic wastewater excluding toilet flushes) through a green wall. It is made of two modular panels (1-set up for this study and 2-in use for 15 months), made of twelve pots arranged on four columns and three rows, and filled with a mix of coconut and perlite and different ornamental plant species. The green wall was fed discontinuously with 96 L/d of synthetic greywater for two months during the winter season. The treatment performances of the two panels were very high about total suspended solids (>87%), biological oxygen demand (>98%) and chemical oxygen demand (∼80%), in agreement with literature. Panel 1 exceeded the performances of panel 2 only about total suspended solids (96% vs 87%), probably because of a clogging phenomenon. This study proved the efficiency of green walls towards greywater treatment in challenging experimental conditions, as winter temperature and high hydraulic loading rate
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