How the Clogging Behavior of Reactive Mats Influences Contaminant Transport

摘要

Reactive capping mats are increasingly being used to remediate contaminatedsediments. The mats are composed of two geotextiles embedding a reactivematerial to bind the contaminants. In this research, a nonwoven geotextile provides filterand separation requirements, while the other is a woven geotextile providing the strengthrequired for installation and recovery. Typically, the reactive mat is protected by 0.3 m ofclean sand/silt. The cap system is permeable to allow transport of contaminants to thereactive material. Fine-grained sediment provides a challenge in terms of short- and longtermclogging behavior of the system because prevention of sediment transport into themater must be balanced against prevention of clogging. This study presents a numericalstudy of geotextile clogging after mat deployment, and how it affects the groundwaterflow and contaminant transport. Results from 2-D finite element models indicate there isno significant change on contaminant transport conditions when the geotextile clogs,reducing flow by one order of magnitude. Furthermore, the possible reduction of geotextilepermeability contributes to the isolation and separation of the contaminants, butheavily clogged (almost impermeable) caps must be avoided.