Optimal Sensor Placement in a Partitioned Water Distribution Network for the Water Protection from Contamination

Water network protection from accidental and intentional contamination is one of the most critical issues for preserving the citizen health. Recently, some techniques have been proposed in the literature to define the optimal sensor placement. On the other hand, through the definition of permanent DMAs (District Meter Areas), water network partitioning allows significant reduction in the number of exposed users through the full isolation of DMA. In this paper, the optimal sensor placement is coupled with water network partitioning in order to define the best location of isolation valves and control stations, to be closed and installed respectively. The proposed procedure is based on different procedures, and it was tested on a real water network, showing that it is possible both to mitigate the impact of a water contamination and simplify the sensor placement through the water network partitioning

Discontinuous permeable adsorptive barrier design and cost analysis: a methodological approach to optimisation

The following paper presents a method to optimise a discontinuous permeable adsorptive barrier (PAB-D). This method is based on the comparison of different PAB-D configurations obtained by changing some of the main PAB-D design parameters. In particular, the well diameters, the distance between two consecutive passive wells and the distance between two consecutive well lines were varied, and a cost analysis for each configuration was carried out in order to define the best performing and most cost-effective PAB-D configuration. As a case study, a benzene-contaminated aquifer located in an urban area in the north of Naples (Italy) was considered. The PAB-D configuration with a well diameter of 0.8 m resulted the best optimised layout in terms of performance and cost-effectiveness. Moreover, in order to identify the best configuration for the remediation of the aquifer studied, a comparison with a continuous permeable adsorptive barrier (PAB-C) was added. In particular, this showed a 40% reduction of the total remediation costs by using the optimised PAB-D

Influence of Autogenerative Final Pressure on the Specific Methanogenic Yield in a High-pressure Anaerobic Digestion Process

In recent years, the development of renewable energy and the improvement of technologies for its production has aroused particular interest. In this perspective, pressurised anaerobic digestion (PAD), i.e. the anaerobic digestion process occurring at a pressure higher than the atmospheric one, has attracted significant attention. PAD enables the production of pressurised biogas, reducing energy costs required for biogas upgrading and injection into the distribution grid. In addition, PAD presents the advantage that by increasing pressure, the solubilisation of CO2, as compared to CH4, increases, resulting in the production of biogas with a high content of CH4 (v/v% CH4 = 90%). Furthermore, results in the literature reported the potential of the autogenerative PAD, in which biogas accumulates in the headspace of the reactor and leads to a gradual increase in autogenerated pressure. In this research, the effect of autogenerated final pressure on the specific methanogenic yield (SMY) was investigated by simulating an autogenerative PAD process of sodium acetate and using a modified ADM1 (Anaerobic Digestion Model No 1) model in batch mode; moreover, the kinetic parameters of the process were assessed. Simulation results showed a good agreement with experimental results and highlighted that SMY increases by increasing the autogenerated final pressure

Pump-and-treat configurations with vertical and horizontal wells to remediate an aquifer contaminated by hexavalent chromium

Pump-and-treat technology is among the most used technologies for groundwater remediation. While conventional, vertical wells (VRWs) are well-known and used from long time, horizontal wells (HRWs) have been explored for remediation technologies only in last few decades. HRWs have shown to outperform vertical wells in terms of versatility, productivity and clean-up times under certain conditions. In this paper, the efficacy of an innovative pump-and-treat (P&T) configuration for groundwater remediation obtained by adopting either VRWs or HRWs technology is comparatively tested. A 3D transient finite element model of an unconfined aquifer containing a hexavalent chromium (Cr(VI)) contamination plume is considered to compare a single horizontal well configuration vs a range of spatially-optimised arrays containing vertical wells. A sensitivity analysis aimed at finding the best configuration to minimise the remediation time and the related cost is carried out by comparing different well diameters, D, pumping rates, Q, and position of wells. A comparative cost analysis demonstrates that, for the examined case-study, a single HRW achieves the clean-up goals in the same time span as for a greater number of vertical wells, but at higher price due to the excavation costs

Extraction of astaxanthin from microalga Haematococcus pluvialis in red phase by using generally recognized as safe solvents and accelerated extraction

Abstract Solvent Extraction was tested to extract astaxanthin from Haematococcus pluvialis in red phase (HPR), by investigating effects of solvents, extraction pressure and temperature. Astaxanthin isomers were identified and quantified in the extract. The performances of acetone and ethanol, Generally Recognized As Safe (GRAS) solvents, were explored. Negligible effect of pressure was found, while with increasing extraction temperature astaxanthin recovery increased till a maximum value, beyond which thermal degradation seemed to be greater than the positive effect of temperature on extraction. Furthermore, to maximize the extraction yield of astaxanthin, mechanical pre-treatment of HPR biomass was carried out and several extraction runs were consecutively performed. Experimental results showed that after the mechanical pre-treatment the astaxanthin recovery strongly increased while a single extraction run of 20 min was sufficient to extract more than 99% of total astaxanthin extracted. After pre-treatment, maximum recovery of about 87% was found for acetone (pressure = 100 bar; temperature = 40 °C; total time = 60 min)

Optimal Design Of Network Partitioning For Water Distribution System Protection From Intentional Contamination

The intentional contamination of water distribution systems represents one of the major risks for citizens, consequently after 11th September 2001 many international organizations have been concerned about it. The availability at low cost of new monitoring and management devices, controlled by a remote system, allows to define different layouts of the water network in a new paradigm of dynamic layouts of water distribution systems in which an important role is played by water network partitioning and sectorization. Recently the advantages of these techniques have been investigated to analyse their application to the problem of water network protection from the contamination. The possibility of designing districts and sectors reduces the risk of affecting many people because several points of contaminant introduction would be needed to produce a wide negative impact on the network. Furthermore, the closure of the sectors, in which the contamination occurs, allows to protect significantly a part of the users. This way the water network partitioning respects the criteria of dual-use value because districts and sectors, in addition to protect the network from contamination, are essentially defined for other aims (water balance, pressure management, etc.) optimizing the costs. The design of the water network partitioning is essentially based only on the reduction of the negative effects on hydraulic performance due to the insertion of gate valves in the network, but not on the minimization of the negative effects of a possible contamination. In this study a novel methodology is proposed that allows to optimize the design of water network partitioning both for compliance of hydraulic performance and for water protection. The methodology is based on heuristic optimization techniques that optimize a costrained multiobjective fuction. The analysis was carried out with different contaminant and sectorization scenarios on a real multiple source water distribution network in Mexico

An optimized configuration of adsorptive wells for the remediation of an aquifer contaminated by multiple aromatic hydrocarbon pollutants

Adsorptive wells arrays are an innovative outline of Permeable Reactive Barrier (PRBs) made of a definite number of passive deep wells opportunely distributed in the aquifer, known as PAB-D (Discontinuous Permeable Adsorptive Barrier). They are generally located downstream the contaminated groundwater flow and perpendicularly to the groundwater flow direction. Being PAB-D wells filled with adsorbing media, whose hydraulic permeability is higher than the surrounding media, the array will create a targeted capture zone, which will force the contaminated water to pass through the whole PAB-D, allowing for both the interception of the contaminant plume and its treatment. In this work, an optimized configuration of PAB-D is presented, for the in situ-remediation of an aquifer simultaneously contaminated by benzene and toluene. The design optimization of the PAB-D was performed by using COMSOL Multiphysics®, in which numerical simulations reproduced the transport and the adsorptive phenomena occurring inside the aquifer and the barrier itself. The proposed technique was applied to the remediation of an aquifer located in an urban area in the north of Naples (Italy), in proximity of numerous landfills, where the contamination was spread over an area of 0.10 km2. Simulation results confirm the effectiveness of the PAB-D, being both pollutant plumes intercepted and their concentrations reduced below their correspondent Italian regulatory threshold values. The best array configuration of PAB-D resulted made of 741 wells, each having a diameter of 0.6 m, which was also compared with a continuous barrier (PAB-C) showing a reduction of about 49% of the volume and 35% of the overall remediation cost