Joseph P. Salanitro

Temporal ecological assessment of oil contaminated soils before and after bioremediation

Ecotoxicity methods were used to assess different soil and oil combinations before, during and after laboratory bioremediation with associated hydrocarbon analysis. Heavy, medium and light crude oil (API gravity 14, 30, and 55) was spiked (ca. 5% w/w) into two sandy soils in the laboratory having organic carbon concentrations of 0.3 (Norwood) and 4.7% (Norwood/Baccto). The earthworm (Eisenia fetida) 14-d lethality assay, the modified Microbics Microtox Solid-Phase assay, and the 14-d plant seed germination and growth assays using corn, wheat and oats, were spiked and tested during a 360-d laboratory remediation. Eisenia was the most sensitive of the three methods utilized with survival increasing throughout bioremediation with fastest toxicity reduction in the high carbon Norwood/Baccto soils where LC50s were 100% or greater at the end of 90-d whereas, > 150-d were required to achieve a similar result in the low carbon soil. Analysis of the undiluted treatments with oily soil alone showed that earthworm survival was high after 90-d in all high organic carbon soils, and after eight months in the low carbon soils, except for the Norwood soil-light oil treatment, which required 360-d to achieve 100% survival. The Microtox assay was less sensitive with EC50s 100% or greater observed after 90-d in high carbon soils and after 240-d for all low carbon soils. After bioremediation, no effects on seed germination were observed, although some plant growth inhibition effects remained. There was no direct correlation between total petroleum hydrocarbon concentrations and toxicity.

Assessment of the acute toxicity of crude oils in soils using earthworms, microtox®, and plants

The assessment of soil quality resulting from a chemical or oil spill and/or remediation effort may be obtained by evaluating the toxicity to soil organisms. To enhance our understanding of the soil quality resulting from laboratory and field oil spill remediation, we have assessed three soil toxicity test methods. Heavy, medium and light crude oils (API gravity 16–18, 30 and 53) were spiked into two soils in the laboratory. The earthworm (Eisenia foetida) 14-d lethality assay, the modified Microbics Microtox® Solid-Phase assay, and the 14-d plant seed germination and growth assays were tested with combinations of crude oils and soils. Earthworms were 1.4 to 14 times more sensitive than Microtox and 1.3 to >77 times more sensitive than plants to the oily soils. Light oil in the silty low organic carbon soil was generally the most toxic, while heavy oil in the sandy high organic carbon soil was least toxic. The bioassay techniques were demonstrated to be sensitive indicators of soil quality and may be used to evaluate the quality of remediated oily soils.

Bioaugmentation for MTBE Remediation

Bioaugmentation to treat methyl tert-butyl ether (MTBE) in groundwater was considered a promising technique for several years, with several researchers involved in developing and testing MTBE-degrading bacteria. Although the effort yielded important insights into the biodegradation of MTBE and its daughter product tert-butyl alcohol (TBA), bioaugmentation for these contaminants is not used currently, and it is likely to remain a minor field of endeavor. The costs and time required to generate enough biomass to seed a barrier system has proven to be prohibitive for most applications, and generally not necessary for effective aerobic treatment. Although MTBE and TBA were originally considered to be highly recalcitrant, indigenous microorganisms have proven capable of effective aerobic treatment, given sufficient oxygen, and it also has proven possible to create stable and robust zones of oxygenation even in relatively complex lithologic systems. Lessons learned in the course of the research on MTBE/TBA bioremediation include: (1) sufficient delineation is critical, (2) sufficient oxygen delivery is a common limitation, (3) biostimulation is typically sufficient, though a time lag may be experienced, (4) bioaugmentation activity can persist for years in situ, (5) typical cocontaminants must be considered, (6) effective treatment typically requires a minimum of 6–12 months, and (7) large numbers of bacteria may be needed for effective treatment.

Anaerobic biodegradability testing of surfactants

Anionic and nonionic surfactants (5-50 mg C/g solids/L medium) were screened for anaerobic microbial decomposition to methane in an automated pressure transducer serum bottle assay system at 35C using municipal digester solids as a source of anaerobic bacteria. Analysis of the headspace gas recovered from tests with linear primary alcohol sulfates (A45S and A24S) and a linear alcohol ethoxylate (LAE-8) showed that these compounds were readily degraded (60-85% of the theoretical methane, TM) after a 15-30 day lag period at 50 ppm C. The extent of degradation of a branched alkyl phenol ethoxylate (NPE-9) was lower (30-40% TM). A survey of intact nonionic and anionic surfactants present in municipal digester sludges in the U.S. showed that these materials were present at levels of 0.5-8 mg CTAS or MBAS/g dry solids. A surfactant which was slower to biodegrade (NPE-9) at 50 ppm C was readily metabolized to methane when tested at 5 and 10 mg C/g solids/L. The pressure transducer serum bottle method described may be used to test biodegradability and inhibitory effects on methanogenesis at surfactant concentrations (e.g. 5 ppm C/g solids) typically present in digesters.

Influence of hydrophobe type and extent of branching on environmental response factors of nonionic surfactants

A number of ethoxylated nonionic surfactants differing in hydrophobe branching and chainlengths have been evaluated for environmental responses. Screening biodegradation tests show that those nonionics having more than one methyl group per hydrophobe degrade considerably slower than those having less extensive branching. Continuous flow-through activated sludge tests, simulating actual waste treatment, show that the more highly branched nonionics biodegrade more slowly and less extensively than those with less hydrophobe branching. In addition, treated effluents originating from influents containing the more highly branched nonionics tend to be more surface active and more toxic to aquatic species than those originating from influents containing surfactants with less hydrophobe branching. Under conditions simulating plant stress, such as high surfactant concentrations in the influent or low temperature, biodegradation of the highly branched nonionics was considerably less extensive, while biodegradation of the linear nonionics was not affected to any measurable degree compared to more normal operating conditions.

Understanding the limitations of microbial metabolism of ethers used as fuel octane enhancers

Abstract Recent reports on the microbial degradation of alkyl ether octane enhancers indicate that the metabolism of these compounds in soils and biosludges is uncommon and relatively slow under aerobic and anaerobic conditions. A mixed bacterial culture has now been isolated that can completely mineralize the branched alkyl ether methyl tertiary butyl ether, and the ether-cleaving activity of this culture appears to be subject to feedback regulation by metabolites. In addition, this type of alkyl ether degradation appears to be different from both alkyl-aryl ether cleaving and aromatic hydrocarbon oxygenase activities reported in other microbial systems.

Analysis of nonionic surfactants in bench-scale biotreater samples

The effluents and activated sludges used in benchscale biotreater units have been analyzed for nonionic alcohol ethoxylates and their residues. Separate bench-scale units were fed linear alcohol ethoxylates (AE), highly branched and branched nonylphenol ethoxylates. Effluents and sludges were first pretreated by a foam sublation technique to provide a gross separation of surfactants from the environmental matrix. This step was followed by normal-phase high-performance liquid chromatography (HPLC) with either fluorescence detection (FD) or evaporative light-scattering detection (ESLD). The AEs were derivatized with phenylisocyanate and analyzed by normal-phase HPLC coupled with FD. At extremely low surfactant levels, pretreatment of large sample volumes resulted in interferences on derivatization. Hence, a normal-phase HPLC method with ELSD was developed. Although some interferences do appear using ELSD, this method appears to be a more viable alternative to derivatization/FD for very low levels of AE. HPLC with FD and ELSD detection methods are more quantitative and provide information on the polyoxyethylene chain than is possible with traditional methods like cobalt-thiocyanate active substance.

Aerobic biodegradability of surfactants at low concentrations using an automated pressure transducer system

Abstract We have developed a simple and reliable automated pressure transducer system (APTS) to evaluate the ready and ultimate aerobic biodegradability of surfactants in 28 days at low concentrations (5 mg C/L) using modifications of existing CO 2 evolution assays (Sturm & Gledhill). Pressure transducers (PT) are fitted to Gledhill-type flasks containing Sturm minerals solution, dilute (50 mg/L) unacclimated activated sludge microbial seed and test compound. PT monitor microbial respiration through oxygen consumption from the headspace and CO 2 from metabolism is absorbed in a 1M KOH solution within the flask. Results with nonionic ethoxylate (AE-7) and anionic sulfate (AS) surfactants prepared from linear or 2-alkyl branched C 14−15 alcohol moieties show that sewage bacteria readily consumed 02 (70–140% ThO 2 ) and degraded these compounds to C02 (65–75% ThCO 2 ) in 12 days at 25C. However, when a more branched alcohol ethoxylate (NPE-9) was tested in the APTS, only 50% of both the ThO 2 was consumed and ThCO 2 was produced. Glucose and benzoic acid were biodegraded to CO 2 similarly to the AE-7 and AS surfactants. Comparison of alcohol ethoxylate degradation data in the APTS with those published from traditional Sturm test methods demonstrated that the C0 2 recovery results were the same for readily metabolized compounds. Our experience with the APTS indicate that the method is reliable, less cumbersome and requires less manipulation than the Sturm and Gledhill assays. Furthermore, the method can be adapted to screen the ready biodegradability of volatile, insoluble and other organic compounds for which radiolabelled material is not available to study microbial degradation.