Carlo Modica

Probabilistic prediction of urban water consumption using the SCEM-UA algorithm

Prediction of urban water consumption can help to improve the performance of water distribution systems. Despite the obvious presence of uncertainty in measurements and in assumed model types/structures, most of the existing water consumption prediction models are developed and used in a deterministic context. Methods for more realistic assessment of parameter and model prediction uncertainties have begun to appear in literature only recently. A novel application of the Shuffled Complex Evolution Metropolis algorithm (SCEM-UA) for the calibration of a water consumption prediction model is proposed here. The model is applied to a case study of the city of Catania (Italy) with the aim to predict daily water consumption. The SCEM-UA algorithm is used to calibrate the parameters of the artificial neural network based prediction model and in turn to determine the associated parameter and model prediction uncertainties. The results obtained using the SCEM-UA ANN approach were compared to the corresponding results obtained using other predictive models developed recently by the authors of the paper. When compared to the these models, the SCEM-UA ANN based water consumption prediction model shows similar predictive capability but also the ability to identify simultaneously the prediction uncertainty bounds associated with the posterior distribution of the parameter estimates.

Calibration of Proportional Controllers for the RTC of Pressures to Reduce Leakage in Water Distribution Networks

AbstractPressure control is a key issue for the reduction of water loss through leakage in municipal water distribution networks (WDNs). The paper presents a general method to calibrate the proportional controllers for the real time control (RTC) of motorized pressure valves in WDNs to reduce leakage during ordinary operation. The method is based on the comprehensive dimensionless analysis of the behavior of simplified hydraulic systems under RTC scenarios. A numerical approach was used to derive a simple regressive relationship to tune the controller on the basis of the system dimensionless variables involved in the control process. The method was validated by application to a well-known bench-test water distribution network and compared with an existing literature calibration procedure. Results show that the proposed method allows for effective controller tuning and leads to performing leakage reduction-oriented real time control of pressures.

Designing domestic rainwater harvesting systems under different climatic regimes in Italy.

Nowadays domestic rainwater harvesting practices are recognized as effective tools to improve the sustainability of drainage systems within the urban environment, by contributing to limiting the demand for potable water and, at the same time, by mitigating the generation of storm water runoff at the source. The final objective of this paper is to define regression curves to size domestic rainwater harvesting (DRWH) systems in the main Italian climatic regions. For this purpose, the Köppen-Geiger climatic classification is used and, furthermore, suitable precipitation sites are selected for each climatic region. A behavioural model is implemented to assess inflow, outflow and change in storage volume of a rainwater harvesting system according to daily mass balance simulations based on historical rainfall observations. The performance of the DRWH system under various climate and operational conditions is examined as a function of two non-dimensional parameters, namely the demand fraction (d) and the modified storage fraction (sm). This last parameter allowed the evaluation of the effects of the rainfall intra-annual variability on the system performance.

Experimental investigation on water saving by the reuse of washbasin grey water for toilet flushing

The paper presents the results of an experimental investigation aimed at estimating the water saving obtained by reusing washbasin grey waters for toilet flushing in domestic bathrooms. Six Italian households characterised by different number of users largely heterogeneous in age, gender, occupation and customs were selected for the experimental campaign. Washbasin and toilet uses for each selected household were monitored recording chronological series of time instants of washbasin tap opening/closure and of toilet flushing operations. On the basis of water balances on a short time scale, acquired data enabled the evaluation of water saving and unused grey water deriving by the adoption of a simple grey water reuse scheme. Specific dimensionless variables were adopted to present the results and to enable their use within the ranges of practical applications.

Laboratory investigation on the effects of flushes on cohesive sediment beds

Hydraulic flushing gates have recently been successfully adopted for the removal of sewer sediments. A large number of researches are aimed at the evaluation of the performances of these devices in the case of granular sediment deposits, but little information exists about the effectiveness of flushes on cohesive sediments as yet in literature. The current paper reports the results of an experimental investigation on the erosive performances of flushing waves on cohesive sediment beds. Experiments were performed in a laboratory flume adopting two flushing hydraulic conditions and comparing the erosive effects on cohesive and granular sediment beds. Different behaviours of cohesive sediments were observed during flushing operations: in particular, erosive effects in cohesive sediment beds were observed to be smaller than in granular sediments during initial flushes whereas erosion in cohesive sediments proved to be higher during subsequent flushes.

Field-Oriented Methodology for Real-Time Pressure Control to Reduce Leakage in Water Distribution Networks

AbstractIn this paper, a novel field-oriented methodology to setup real-time control (RTC) for leakage reduction by pressure control valves in water distribution networks is presented. The paper introduces modalities to address the selection of proper RTC system architecture based on the network connectivity at the valve sites. Criteria for target node identification and RTC strategy selection in case of single-control (one valve–one target node) and multiple-control (multiple valve–one target node) architectures are developed. The impact on the control performance of controller calibration and communication protocol selection procedures, and of background noise in pressure signals is also explored. Then, developed criteria and procedures are applied to a Norwegian water distribution network in which a future field-pilot RTC system will be installed. Benefits in terms of pressure control effectiveness and water leakage reduction are evaluated by simulation under different control scenarios as a basic step...

Regional scale analysis for the design of storage tanks for domestic rainwater harvesting systems

A regional scale analysis for the design of storage tanks for domestic rain water harvesting systems is presented. The analysis is based on the daily water balance simulation of the storage tank by the yield-after-spillage algorithm as tank release rule. Water balances are applied to 17 rainfall gauging stations in Sicily (Italy). Compared with literature existing methods, a novel dimensionless parameter is proposed to better describe the intra-annual character of the rainfall patterns. As a result, easy-to-use regional regressive models to evaluate the water saving performance and the overflow discharges from the tank are provided along with a stepwise procedure for practical application. The regional models demonstrate good fits between model predictions and simulated values of both water savings and overflows from the tank.

P controller calibration for the real time control of moveable weirs in (proportional) sewer channels

In this paper, a detailed study on the local real time control of moveable sharp-crested weirs in sewer channels is presented. Firstly, an experimental analysis aimed at determining the hydraulic behaviour of the regulator under both free flow and submerged flow conditions was carried out. Then, a numerical investigation into the calibration of proportional (P) controllers for the weir control was performed. In particular, suitable values were evaluated for the controller proportional parameter in order to obtain quick regulations and avoid the occurrence of permanent water level oscillations behind the weir. A dimensionless approach was adopted for the generalisation of the results.

Unsteady flow modeling of pressure real-time control in water distribution networks

AbstractThis paper investigates the potential of unsteady flow modelling for the simulation of remote real-time control (RTC) of pressure in water distribution networks. The developed model combine...

Modelling the erosive effects of sewer flushing using different sediment transport formulae

A numerical investigation to simulate the cleaning effects of successive flushes over sediment beds in prismatic channels is presented in this paper. The 1D De Saint Venant-Exner equations were used to describe the temporal evolution of the sediment bed after each flush. The predictive capacity of two sediment transport formulae was explored against experimental results from laboratory tests. Results show that the adopted model can successfully describe the evolution of the sediment bed due to the flushes exerted during the experiments, with differences between the used transport formulae depending on the channel invert slope and on the flush energy.