The rates of mineralization of nitrilotriacetic acid (NTA), 2,4-dichlorophenoxyacetic acid (2,4-D), p-nitrophenol, aniline, and isopropyl N-phenylcarbamate (IPC) at one or more concentrations ranging from 100 pg/ml to 1.0 microgram/ml were proportional to chemical concentrations in samples of three lakes. The rates at 100 pg of NTA, 2,4-D, p-nitrophenol, and aniline per ml in samples of one or more lakes were less than predicted, assuming the rates were linearly related to the concentration. Neither NTA nor 2,4-dichlorophenol at 2.0 ng/ml was mineralized in some lake waters, but higher levels of the two chemicals were converted to CO2 in samples of the same waters. In samples from two lakes, little or no mineralization of IPC or 2,4-D occurred at 1.0 microgram/ml, but 10 ng/ml or lower levels of the herbicides were mineralized. The mineralization in sewage of 1.0 microgram of NTA per ml was biphasic; about 20% of the substrate was mineralized in 20 h, and mineralization was only reinitiated after a period of 130 h. The biphasic transformation was not a result of the accumulation of organic products, and it was still evident if protozoan activity was inhibited. NTA also underwent a biphasic mineralization in lake waters, and the biphasic pattern was not altered by additions of growth factors and inorganic nutrients. From 40 to 60% of the carbon of aniline added to lake water at levels of 100 pg/ml to 1.0 microgram/ml was mineralized, but more than 90% of the carbon of NTA, 2,4-D, or p-nitrophenol added to lake water at 10 ng/ml or 1.0 microgram/ml was mineralized.(ABSTRACT TRUNCATED AT 250 WORDS)
A 75 liter immobilized microbe biological reactor with a bed retention time of 20.5 hours was used in a continuous flow mde to remediate contaminated groundwater containing ethylene dichloride (EDC), tetrachloroethylene, and trichloroethylene, with EDC being the predominant contaminant. The reactor was initially seeded with Xanthobacter autotrophicus, a demonstrated halogenated aliphatic substrate utilizer. The reactor was operated fin-forty-two days. Material balance determinations for primary volatile aliphatics of concern indicated an acerage of 90.2% mineralization of EDC, 81.7% of the trkhlorethylene (TCE) and 64.0% of the tetrachlorethylene (TeCE). In addition to Xan thobacter autotrophicus, four indigenous bacterial species from the groundwater had successfuUy acclimated to the reactor bed.
Well‐recovery networks coupled to immobilized microbe bioreactors (IMBRs) were installed at a 172‐acre former wood preserving facility for the bioremediation of organic wood preservatives present in site groundwater. Free‐phase creosote from the hardpan and soluble preservative fractions contained in subsurface groundwater were pumped separately to different holding tanks. Trace creosote fractions contained in the subsurface groundwater were further gravity separated in the holding tank. Immobilized microbial isolates evaluated in earlier laboratory and field pilot tests were established into two 40, 000‐liter bioreactors for the biodegradation of all targeted consitituents. Microbial growth, dissolved oxygen, pH, nutrients, flow rate, and temperature were monitored in this in situ/ex situ bioremediation system. The process was used to remove the polycyclic aromatic hydrocarbon (PAH) and phenolic components of creosote and pentachlorophenol from contaminated groundwater. Data generated during the past 2 1/2 years indicate that 26 target compounds consistently are reduced to levels acceptable for discharge. Currently operating in Baldwin, Florida, this full‐scale prototype is remediating the former wood preserving facility and is being used as a model system for the design and construction of new bioreactor systems needed at similar industrial sites in the United States and abroad.
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