Abstract
Abstract. Trenchless Technology of Forming Horizontal Insulating Barriers (TFHB) can be considered a method of groundwater protection against inflow of pollutants. In TFHB technology, the working fluid (sodium silicate solution) and the gelling agent (CO2) are injected separately, using one tool, to different zones of the aquifer profile. Carbon dioxide injected into the saturation zone rises due to buoyancy forces and reaches the silicate which was injected at the water table level. This initiates the process of silicate gelation, resulting in the formation of an insulating barrier. For technological purposes, the gelation time must be controlled, and the resulting gel must have certain mechanical properties. In order to apply THFB in real conditions it was necessary to identify important technological and technical parameters, as well as to define interactions between the injected fluid and the aquifer rocks. Geochemical modelling (equilibrium, reaction path and reactive transport) was used to identify potential geochemical effects of the application of TFHB in sandy aquifers. Certain petrophysical parameters and mineralogical assemblages of aquifers were addressed, taking into account both low and strongly mineralized groundwater. The simulations revealed that TFHB does not have a negative impact on the chemistry of rock-water systems described in this work.
Highlights
Protection of groundwater resources is a key challenge in the 21st century
One advantage of the developed Technology of Forming Horizontal Insulating Barriers (TFHB) technology in shallow groundwater aquifers is the injection of a non-toxic, environmentally friendly modified water solution of sodium silicate
An important element of TFHB technology is the treatment fluid, which is based on sodium silicate water solution and characterized by low viscosity
Summary
New technologies are crucial in order to prevent pollution close to urban settings with highly congested infrastructure, and in the case of demanding topographical relief. Trenchless Technology of Forming Horizontal Insulating Barriers (TFHB) can be considered an emergency form of immediate groundwater protection against inflow of pollutants, e.g. from hazardous landfill; so far there is no approved insulating technology which does not require the displacement of waste. One advantage of the developed TFHB technology in shallow groundwater aquifers is the injection of a non-toxic, environmentally friendly modified water solution of sodium silicate. The set of additives which enable hybrid gelation mechanisms are determined by the composition and properties of the applied sodium silicate gels and the complex chemical reactions which cause reduced hydraulic conductivity
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