Field-scale testing of a two-stage Bioreactor for removal of creosote and pentachlorophenol from ground water: Chemical and biological assessment

Abstract

A two-stage, field-scale bioreactor system was used to determine the efficacy of bioremediation of creosote- and pentachlorophenol (PCP)-contaminated ground water at the abandoned American Creosote Works (ACW) site in Pensacola, Florida. In separate 15-day runs of the field-scale (454L) system, bioreactor performance in the presence of specially-selected microbial inoculants was compared to that observed using non-specific biomass. In the first run, Bioreactor #1 was amended with nutrients, surfactants and microorganisms (strains CRE 1–13) that were isolated from soil at ACW and selectively cultured for their ability to biodegrade monitored creosote constituents. After 4 days of organism acclimation and degradation of organic contaminants, the batch system was converted to a flow-through regime. Effluent was transferred to Bioreactor #2 where Pseudomonas paucimobilis strain EPA 505 and Pseudomonas sp. strain SR 3 were introduced. A second 15-day bioreactor run was conducted using indigenous bacteria and microorganisms from a waste water treatment facility that was designed to treat effluents containing PAHs and phenolics.

Bioreactor performance was evaluated by chemical analysis of feed water initially pumped into Bioreactor #1 and clarified effluent from Bioreactor #2. These materials were also tested for toxic/teratogenic responses with developing embryonic Menidia beryllina, with Microtox^® 5-min EC₅₀ tests, and with Ceriodaphnia dubia 48-h LC₅₀ tests. Results obtained with specialty organisms in the first run of the field-scale bioreactor showed that, on average, 70.6% of polycyclic aromatic hydrocarbons (PAHs) and heterocycles were degraded. Only 36.9% of the pentachlorophenol (PCP) present was biodegraded, apparently because of low cell counts and incomplete induction of Pseudomonas sp. strain SR 3. A concomitant 67- to 74-fold decrease in toxicity was measured in Microtox^® 5-min EC₅₀ and Ceriodaphnia 48-h LC₅₀ values, respectively. No reduction in toxicity/teratogenicity was measurable in tests with embryonic M. beryllina.

In the second 15-day run of the bioreactor, microorganisms from an industrial waste water treatment facility averaged 51.0% biodegradation of PAHs and heterocycles. Degradation of PCP was 81.0%, a value substantially higher than in the first run. An 87-fold reduction in toxicity was measured with the Microtox^® 5-min EC₅₀, but only a 2.9-fold reduction in acute toxicity was measured in the Ceriodaphnia 48-L LC₅₀ test. In the second bioreactor run, samples taken from Bioreactors #1 and #2 indicated reduced embryo toxicity/teratogenicity. At the 1% test concentration most embryos developed normally and hatched. Larvae were also normal.