How Can We Make Pump and Treat Systems More Energetically Sustainable?

Abstract

Pump and treat (P&T) systems are still widely employed for the hydraulic containment of contaminated groundwater despite the fact that their usage is decreasing due to their high operational costs. A way to partially mitigate such costs, both in monetary and environmental terms, is to perform heat exchange (directly or with a heat pump) on the groundwater extracted by these systems, thus providing low-carbon and low-cost heating and/or cooling to buildings or industrial processes. This opportunity should be carefully evaluated in view of preserving (or even improving) the removal efficiency of the remediation process. Therefore, the heat exchange should be placed upstream or downstream of all treatments, or in an intermediate position, depending on the effect of water temperature change on the removal efficiency of each treatment step. This article provides an overview of such effects and is meant to serve as a starting reference for a case-by-case evaluation. Finally, the potentiality of geothermal use of P&T systems is assessed in the Italian contaminated Sites of National Interest (SIN), i.e., the 41 priority contaminated sites in Italy. At least 29 of these sites use pumping wells as hydraulic barriers or P&T systems. The total discharge rate treated by these plants exceeds 7000 m3/h and can potentially provide about 33 MW of heating and/or cooling power.

Biochar from Pine Wood, Rice Husks and Iron-Eupatorium Shrubs for Remediation Applications: Surface Characterization and Experimental Tests for Trichloroethylene Removal

“…The oldest and most diffused system of groundwater treatment is the Pump and Treat, that uses wells for the extraction of the contaminated water and needs a successive treatment on external unit for the requalification of the liquid phase. In Italy, where PCE and TCE threshold limit (to be respected at the boundary of the site) are 1.1 and 1.5 µg L −1 , many of the SIN (National Interest Sites) are still treated with this approach [ 3 ]. However, it has been known for decades that this strategy has a high environmental and economic impact linked to the energy demand due to the treatment of high volumes of liquid phase [ 4 ].…”

Analytical and Numerical Methods for a Preliminary Assessment of the Remediation Time of Pump and Treat Systems

“…Subsequently, the total volume of water needed to be extracted was calculated by means of Equation (8) ( Table 7). Knowing the extension of the polluted area, the hydraulic conductivity of the aquifer (Table 2), and the hydraulic gradients, both the groundwater flow rates and the remediation times were evaluated by means of Equations (11) and (12) for the cases with (Model D2) and without (Model D1) the P&T system ( Table 7).…”

“…Such systems act as a hydraulic barrier for groundwater flow, avoiding the spreading of contamination outside the contaminated site boundaries (often considered as a constraint), while helping the aquifer remediation. Thanks to their versatility [8][9][10][11][12], many P&T applications can be found in Italy and worldwide. For instance, in many Italian SIN, more than one active hydraulic barrier operates.…”

Use of Fixed and Variable Speed Pumps in Water Distribution Networks with Different Control Strategies

“…These previous antecedents could incentivize researchers such as Casasso et al [3] and Candilejo et al [4] to develop strategies to improve energy efficiency in water infrastructures that include pumping stations. The Environmental Protection Agency (EPA) [5] defined several measures to save energy in pumping stations, such as reduced pressure service, managed pressure service, maximized efficiency of the system, and adequate pump and control modes selections.…”