In situbioremediation of trichloroethylene-contaminated water by a resting-cell methanotrophic microbial filter

Abstract

An in situ microbial filter technology is being tested and developed for remediating migrating subsurface plumes contaminated with low concentrations of trichloroethylene (TCE). The current focus is the establishment of a replenishable bioactive zone (catalytic filter) along expanding plume boundaries by the injection of a representative methanotrophic bacterium, Methylosinus trichosporium OB3b. This microbial filter strategy has been successfully demonstrated using emplaced, attached resting cells (no methane additions) in a 1.1 m flow-through test bed loaded with water-saturated sand. Two separate 24 h pulses of TCE (109 ppb and 85 ppb), one week apart, were pumped through the system at a flow velocity of 15 mm h" 1 ; no TCE ( < 0.5 ppb) was detected on the downstream side of the microbial filter. Subsequent excavation of the wet sand confirmed the existence of a TCE-bioactive zone 21 days after it had been created. An enhanced longevity of the cellular, soluble-form methane monooxygenase produced by this methanotroph is a result of the laboratory bioreactor culturing conditions. Additional experiments with cells in sealed vials and emplaced in the 1.1 m test bed yielded a high resting-cell finite TCE biotransformation capacity of about 0.25 mg per mg of bacteria; this is suitable for a planned sand-filled trench field demonstration at a Lawrence Livermore National Laboratory site.

Modeling the effects of systematic variation in ionic strength on the attachment kinetics of Pseudomonas fluorescens UPER‐1 in saturated sand columns

“…Effects of cell surface heterogeneity [Simoni et al, 1998] and motile/ nonmotile cells [Camesano and Logan, 1998] on cell attachment in column studies have been recently reported. Studies of microbial attachment in a two-dimensional (2-D) miniature sand-filled aquifer simulator [Shonnard et al, 1994] and a biofilter [Taylor et al, 1993] are reported. Harvey et al [1989] have reported field research on the transport of bacteria in a sandy aquifer.…”

An evaluation of in-situ bioremediation processes

“…The potential feasibility and effectiveness of an attached resting-cell filter strategy over extended periods of time has been demonstrated for degrading tirchloroethene flowing through a saturated homogeneous quartz sand (Oklahoma) by Taylor et al (1993), Shonnard et al(1994), , and Knapp et al(1995). This special method of allowing contaminants to flow through resting state microbial filters is, therefore, a great benefit in the technology.…”

“…In another unique approach, an in-situ microbial filter technology has been developed for remediating subsurface groundwater contaminated with trichloroethylene (Taylor et al 1993, Knapp et al 1995. This new technology eliminates problems associated with the common method of directly pumping a quantity of nutrients into the subsurface to stimulate growth of indigenous microbes.…”

Technical considerations for the implementation of subsurface microbial barriers for restoration of groundwater at UMTRA sites

“…These compounds were removed from a combination of air sparging and biodegradation. Taylor et al (1993) conducted research on the use of a resting-cell (Le., non-dividing) methanotrophic microbial fdter (biofilter) for remediating migrating subsurface plumes of trichloroethylene (TCE). In this system, methanotrophic microorganisms (Methylosinus trichosporium) were injected into a test bed ahead of an migrating TCE plume.…”