Optimal design of active spreading systems to remediate sorbing groundwater contaminants in situ

Abstract

The effectiveness of in situ remediation to treat contaminated aquifers is limited by the degree of contact between the injected treatment chemical and the groundwater contaminant. In this study, candidate designs that actively spread the treatment chemical into the contaminant are generated using a multi-objective evolutionary algorithm. Design parameters pertaining to the amount of treatment chemical and the duration and rate of its injection are optimized according to objectives established for the remediation - maximizing contaminant degradation while minimizing energy and material requirements. Because groundwater contaminants have different reaction and sorption properties that influence their ability to be degraded with in situ remediation, optimization was conducted for six different combinations of reaction rate coefficients and sorption rates constants to represent remediation of the common groundwater contaminants, trichloroethene, tetrachloroethene, and toluene, using the treatment chemical, permanganate. Results indicate that active spreading for contaminants with low reaction rate coefficients should be conducted by using greater amounts of treatment chemical mass and longer injection durations relative to contaminants with high reaction rate coefficients. For contaminants with slow sorption or contaminants in heterogeneous aquifers, two different design strategies are acceptable - one that injects high concentrations of treatment chemical mass over a short duration or one that injects lower concentrations of treatment chemical mass over a long duration. Thus, decision-makers can select a strategy according to their preference for material or energy use. Finally, for scenarios with high ambient groundwater velocities, the injection rate used for active spreading should be high enough for the groundwater divide to encompass the entire contaminant plume.

A bilevel groundwater management model with minimization of stochastic health risks at the leader level and remediation cost at the follower level

“…However, in general, the groundwater remediation will last for a long time (over 5 years), but the sorption process is instantaneous compared to the long remediation time. Previous sensitivity analysis has shown that the sorption process would have a slight effect on the benzene concentration over the entire remediation period, i.e., the benzene concentration will not change obviously with variation of sorption coefficients (He et al 2012;Yoo et al 2016;Piscopo et al 2016;Majumder and Eldho 2016;EEP 2005). Therefore, influences of rate-limited sorption were neglected by assuming the sorption process to be instantaneous equilibrium.…”

Experiments and Simulations on Plume Spreading by Engineered Injection and Extraction in Refractive Index Matched Porous Media

“…Each of these studies used the same 12‐step pumping sequence, but subsequent work showed that sorbing contaminants require different pumping sequences (Neupauer & Mays, 2015). Notably, multi‐objective evolutionary algorithms identified that the optimal pumping sequence for non‐sorbing contaminants (Piscopo et al., 2015) and sorbing contaminants (Piscopo et al., 2016) were generally not those that imposed chaotic advection. Importantly, these works were theoretical, not experimental.…”

Improving the Efficiency of 3‐D Hydrogeological Mixers: Dilution Enhancement Via Coupled Engineering‐Induced Transient Flows and Spatial Heterogeneity

“…Neupauer et al (2014) systematically quantified the efficiency of remediation as a function of the coupled effect of aquifer heterogeneity and engineering-induced velocity oscillations. The injection-extraction scheme proposed by Mays and Neupauer (2012), and used in the subsequent studies (e.g., Neupauer et al, 2014;Piscopo et al, 2013Piscopo et al, , 2015, can be cast within an optimization framework (Piscopo et al, 2015(Piscopo et al, , 2016. A system of engineering alternate pumping was applied also by Rodr ıguez-Escales et al (2017) to develop a reactive transport model for improving degradation of organic compound.…”