Variation in hydraulic conductivity with decreasing pH in a biologically-clogged porous medium

Abstract

a b s t r a c tMicrobial biomass can clog porous media and ultimately affect both structural and mineral trapping of CO 2 in geological carbon storage reservoirs. Whether biomass can remain intact following a sudden decrease in groundwater pH, a geochemical change associated with CO 2 injection, is unclear. We examined this question using twelve biologically-active and three control column-reactor experiments. Cell abundance and distribution was monitored using confocal microscopy, plating, and direct counting. Hydraulic conductivity (K) was monitored using pressure sensors. Growth occurred for four days at neutral pH. During that time, K within the clogged portion of the reactors decreased from 0.013 to 0.0006 cm s −1 on average, a 1.47 log reduction. Next, the pH of the inflowing aqueous medium was lowered to pH 4 in six experiments and pH 5.7 in six experiments. As a result, K increased in five of the pH 4 experiments and two of the pH 5.7 experiments. Despite this increase, however, the columns remained largely clogged. Compared to pre-inoculation K values, log reductions averaged 1.13 and 1.44 in pH 4 and pH 5.7 experiments, respectively. Our findings show that biomass can largely remain intact following acidification and continue to reduce K, even when considerable cell stress and death occurs.

Effects of bacterial cells and two types of extracellular polymers on bioclogging of sand columns

“…2). This result was consistent with the findings of Kirk et al (2012), in which the concentration of bacterial cells increased to approximately 8 log 10 CFU/mL in the first few days as the hydraulic conductivity decreased. At the early stage, it seemed that cell accumulation could cause significant clogging.…”

Pore-Scale Process Coupling and Effective Surface Reaction Rates in Heterogeneous Subsurface Materials

“…For example, the reaction rate at the molecular scale can be heterogeneous, even on a single mineral phase (Piana et al 2006;Spagnoli et al 2006;Boily and Rosso 2011;Lüttge et al 2013); the rates of reactions occurring in nano-pores can be infl uenced by water ordering, surface curvature, and overlapping double layers Liu 2009, 2012;Argyris et al 2010;Bourg and Steefel 2012); and mineral surface reactivity can be modifi ed as reactions proceed (Alekseyev et al 1997;Benner et al 2002;White and Brantley 2003;Bernard 2005;Noiriel et al 2005;Luquot and Gouze 2009). The pore geometry and connectivity can also be changed by mineral precipitation (Steefel and Lichtner 1994;Davis et al 2006;Zhang et al 2010a;Yoon et al 2012;Fanizza et al 2013;Boyd et al 2014) and dissolution (Noiriel et al 2004(Noiriel et al , 2005(Noiriel et al , 2009Bernard 2005;Flukiger and Bernard 2009;Luquot and Gouze 2009;Kang et al 2010), microbial growth (Taylor and Jaffe 1990;Nambi et al 2003;Thullner et al 2004Thullner et al , 2007Knutson et al 2005;Engesgaard 2007, 2012;Brovelli et al 2009;Zhang et al 2010b;Kirk et al 2012;Tang et al 2013) and biomineralization (Zhang and Klapper 2010;…”

Interplay between microorganisms and geochemistry in geological carbon storage

“…We used pure-culture batch reactor experiments to test the influence of mineralogy on the ability of cells to survive exposure to high-pressure CO 2 (Santillan et al, 2013). We considered how decreasing pH, a geochemical change caused by CO 2 injection, will affect the stability of bioclogging in porous media (Kirk et al, 2012). And, we used bioenergetics and mixed-community bioreactor experiments to assess potential changes in the relative significance of different microbial processes in response to increasing CO 2 abundance (Kirk, 2011;Kirk et al, 2013).…”