Quantifying the impact of the stream-aquifer interaction on the surface-subsurface exchange

The exchange of oxygen and nutrients between the well-aerated stream water and the subsurface water is crucial for the biochemical conditions of the hyporheic zone, i.e., the interface region between the stream and the deep aquifer. The hyporheic zone is extremely important for the ecology of the fluvial environment because of the rich microbial community that lives on the hyporheic sediments. The metabolic activity of these microrganisms controls the fate of nitrogen and phosphorus in the pore water, and influences the fate of these nutrients at the catchment scale. Unfortunately, the uncomplete knowledge of the complex hydrodynamics of the coupled surface-subsurface flow field often hinders the understanding of the ecological relevance of the hyporheic processes. A reasonable amount of information on these hydrodynamic conditions is required by biologists and ecologists in order to gain a deeper insight on these processes. This contribution analyses how the interaction between the groundwater table and the free-surface stream influences the hyporheic exchange induced by the bedforms through the streambed. The most representative characteristics of the hyporheic exchange - e.g., the depth of the hyporheic zone - have been parametrized in terms of a small number of easily measurable quantities. These information on the hyporheic flow field provide the fundamental basis for the study of the ecological functioning of the hyporeic zon

Community detection as a tool for DMA identification

Water losses, the portion of water introduced in a pipe network but not consumed by users, represent a significant problem in water distribution system (WDS) management. Modern guidelines suggest to divide the pipe network in clusters, in order to compute a water balance and measure water consumption by each group. These clusters are called district metered areas (DMAs). The division of a pipe network in DMAs is usually realized with a visual exam supported by technical experience. This approach, which is convenient for small WDSs, becomes dicult to apply to large WDSs characterized by thousands of user nodes and pipes. Therefore, it is necessary to have an automatic tool to recognize the affinity degree of neighbouring nodes and to decide how to assign a node to a particular DMA. We propose an automated approach to subdivide pipes, that only requires flow rates through the network. The method has been tested to a large WDS often used as benchmark. The approach successfully divides the pipe network in an acceptable number of DMAs. Each resulting DMA is characterized by a low number of external links and by a proper number of users

Resilience to flow rate variability in a green wall for greywater treatment

Green and blue infrastructures are an innovative solution to contrast climate changes (SDG 13 of UN 2030 Agenda) and increase cities resilience (SDG 11), using a smarter water management that transform wastewater into a new resource for non-potable reuses. Due to the lack of horizontal surfaces in urban areas, green walls are one of the most suitable nature-based solution to treat greywater (i.e. the portion of household wastewater that exclude toilet flush and kitchen sink). Green walls allow for a multidisciplinary approach, providing multiple benefits such as thermal and acoustic regulation, biodiversity preservation, decreasing heat islands effects and removing CO2, improving life quality and buildings value. Green walls have also been proposed for treating the large amount of greywater that is daily produced (e.g. around 100 L/PE/die in Italy), an approach that also provides urban green while reducing the need of irrigation water. Following previous work on a pilot system, this study aims to improve the green walls design and test its resilience to variations in the flow rate of greywater fed to the green wall. Two panels have been built in which synthetic greywater flows by gravity along three levels of pots with different plant species. The 18 pots (arranged in a 3x3 matrix in each panel) have been filled with a mix of coconut fibre and perlite (1:1 in volume) and fed with greywater, and output water samples have been collected almost weekly from June to December 2021. The control panel has been regularly fed with 24 L/die/col (standard flow rate), the other has been fed with different flow rates (standard, underflow, overflow and maintenance) that usually changed after three weeks. Different parameters (e.g. TSS, BOD5, COD, DO, TN, TP, MBAS), have been monitored in the outflow of each pot and average performances of each level has been evaluated. Results indicate a good efficiency of the green wall in removing contaminants even when the provided flow rate is not constant. The treatment performances increase along the columns in both panels and the first two levels guarantee a good compounds removal during standard flow and underflow rates. On the other hand, the overflow rate caused a performances decrease in the variable flow panel for many parameters, followed by a visible plant stress. However, one week of standard flow rate was sufficient to reduce the negative effects of the three- weeks-overflow. This demonstrated the resilience of the green wall facing flow variability, that can be caused by seasonal variation or system failure

REAL-TIME MEASUREMENT FAULT DETECTION AND REMOTE CONTROL IN A MOUNTAIN WATER SUPPLY SYSTEM

This work presents an algorithm for real-time fault detection in the SCADA system of a modern water supply system (WSS) in an Italian Alpine Valley. By means of both hardware and analytical redundancy, the proposed algorithm compares data and isolates faults on sensors through the residual analysis. Moreover, the algorithm performs a real- time selection of the most reliable measurements for the automated control of the WSS operations. A coupled model of the hydraulic and remote-control system was developed to test the effectiveness of the proposed algorithm. Simulations showed that error detection and measurement assessment are crucial for the safe operation of the WSS

Water Distribution System Modeling and Optimization: A Case Study

In the last years, the scientific literature has reported an increasing use of hydraulic models to describe water distribution systems (WDS). Hydraulic models represent tools for managing the complexity of WDSs, and a number of optimization methods have been proposed to improve the performance of these infrastructures. However, because of the lack of available data on WDSs many works have only considered synthetic WDS with idealized behaviour or small-sized WDSs with simple topology and limited complexity. This lack of complex case studies has often hindered the demonstration of the potential of hydraulic models and of the optimization approaches relying on their use. In this work, we present a case study about a real large WDS. The system is composed of approximately 3000 pipes (>170 km) and 3000 demand nodes (corresponding to 50,000 users) that are spread across a hilly area over a 200 m elevation gradient. Water is provided by ten wells and it is distributed by five pumping stations and four tanks at different elevations. Pump operation is partly automatically controlled by water levels in tanks and partly by a fixed temporal schedule. This complexity results in a nontrivial hydraulic behaviour that is well reproduced by our hydraulic model. The model is also used with a multi-objective genetic algorithm solver to identify different operational scenarios that lead to a reduction of energy consumption and water leakages

Biofilm-induced bioclogging produces sharp interfaces in hyporheic flow, redox conditions, and microbial community structure

Riverbed sediments host important biogeochemical processes that play a key role in nutrient dynamics. Sedimentary nutrient transformations are mediated by bacteria in the form of attached biofilms. The influence of microbial metabolic activity on the hydrochemical conditions within the hyporheic zone is poorly understood. We present a hydrobiogeochemical model to assess how the growth of heterotrophic and autotrophic biomass affects the transport and transformation of dissolved nitrogen compounds in bedform-induced hyporheic zones. Coupling between hyporheic exchange, nitrogen metabolism, and biomass growth leads to an equilibrium between permeability reduction and microbial metabolism that yields shallow hyporheic flows in a region with low permeability and high rates of microbial metabolism near the stream-sediment interface. The results show that the bioclogging caused by microbial growth can constrain rates and patterns of hyporheic fluxes and microbial transformation rate in many streams