The Use of Silica Encapsulated DNA Particles with a Supermagnetic Iron Core (Sidnamag) in Sand Filtration System: Effect of Water Chemistry

Abstract

Sand filtration systems (SF) are a well-established approach in ensuring the availability of clean water. Understanding the hydraulic properties inherent in SF systems is of paramount importance for optimizing their performance. This study investigates the potential utilization of silica-encapsulated DNA particles, equipped with a magnetic core to enhance particle separation and quantification efficiency (SiDNAMag), as tracers for determining particulate fate in sand filtration units. We focused on exploring the sensitivity of SiDNAMag to solution chemistry, while elucidating the underlying mechanisms governing their transport and retention in sand filtration systems. We employed laboratory columns and HYDRUS-1D modeling to analyze a range of water chemistry solutions, encompassing NaCl, NaHCO3, CaCl2, and MgCl2, with ionic strengths ranging from 0.1 mM to 20 mM. We found that the transport of DNA-tagged silica particles could be described by a first-order kinetic attachment and detachment rate coefficient. Intriguingly, higher ionic strength enhanced particle attachment and reduced detachment rates regardless of the chemical composition of the feedwater. The sticking efficiencies of SiDNAMag particles exhibited a range of 0.7 to 1. This notable sticking efficiency can be attributed to the relatively low negative charge of SiDNAMag particles, resulting in the formation of unstable colloids and promoting the aggregation of the colloidal particles. This work underscored the potential of SiDNAMag as effective tracers for identifying key hydrological characteristics in SF systems. However, further research is warranted to investigate strategies for reducing the interaction between these particles and sand, particularly in response to the chemistry of the infiltrated water.

Keywords: sand filtration system, tracer, DNA-tagged silica particles, solution chemistry, transport