Optimization of High-Strength Hydrocarbon Biodegradation Using Respirometry

Laboratory respirometry experiments were conducted on mixtures of soil and oily sludge to estimate biodegradation rates by CO2 production rates and determine optimum conditions for biodegradation of high-strength hydrocarbon waste products. These experiments were used to determine a suitable range of total petroleum hydrocarbon (TPH) concentration for biological treatment and to optimize for nutrient addition and moisture content. CO2 production rates from biological respiration of hydrocarbon-contaminated soil were maximized at concentrations of 3-9% TPH (30,00090,000 mg/kg TPH). CO2 production rates decreased dramatically at concentrations above 9% TPH, indicating that either these concentrations are lethal to microbes present, or this high sludge content inhibits aeration of the soils. Addition of 120 mg/kg nitrogen, 40 mg/kg phosphorous, and 40 mg/kg potassium to the soils resulted in a three fold increase in CO2 production rates. No significant increase in CO2 production was observed when the nutrient addition was increased to 240 mg/kg nitrogen, 80 mg/kg phosphorous, and 80 mg/kg potassium. Maximum CO2 production rates were observed at 15-20% moisture content. CO2 production rates decreased significantly at and below 10% moisture and at and above 25% moisture. Maximum CO2 production rates observed for soil with 50,000 mg/kg TPH, with added nutrients at optimum moisture content, were 30-35 μL CO2/g/hr. Assuming all CO2 was generated from hydrocarbon degradation, this maximum CO2 production rate corresponds to a hydrocarbon biodegradation rate of approximately 500 mg TPH/kg/day (assuming 100% respiration for a conservative estimate). If ideal conditions are maintained and rates of respiration remain high, clay soil contaminated with 60,000 mg/kg TPH sludge could probably be remediated in 2 months

Methanotrophic Bacteria for Nutrient Removal from Wastewater: Attached Film System

It was hypothesized that nutrient removal from wastewater could be achieved by using methane oxidizing bacteria (methanotrophs). Because methane is inexpensive. it can be used as an energy source to encourage bacterial growth to assimilate nitrogen and phosphorus and other trace elements. This initial feasibility study used synthetic nutrient mixtures and secondary sewage effluent as feed to a laboratory-scale methanotrophic attached-film expanded bed (MAFEB) reactor operated at 35°C and 20°C. The MAFEB system operated successfully at low nutrient concentrations under a variety of nutrient-limited conditions. Using a synthetic nutrient mixture with a nitrogen:phosphorus feed ratio (w/w) of 9:1, phosphate concentrations were reduced from 1.3 mg P/ L to below 0.1 mg P/ L, and ammonia was reduced from 12 mg N/L to approximately 1 mg N/L on a continuous flow basis, with a bed hydraulic retention time of 4.8 hours. The average nutrient uptake rates from synthetic nutrient mixtures were 100 mg nitrogen and 10 mg phosphorus/L of expanded bed/d. Nutrient assimilation rates increased with increasing growth rate and with increasing temperature. Nitrogen/phosphorus uptake ratios varied from 8 to 13, and the observed yield varied from 0.11 to 0.16 g volatile solids (VS)/g chemical oxygen demand (COD). Nutrient removal from secondary sewage effluent was successfully demonstrated using sewage effluent from two local treatment plants. Nutrient concentrations of 10-15 mg N/L and 1.0-1.8 mg P/L were reduced consistently below 1 mg N/L and 0.1 mg P/L. No supplemental nutrients were added to the sewage to attain these removal efficiencies since the nutrient mass ratios were similar to that required by the methanotrophs. Removal rates were lower at 20°C than at 35°C, but high removal efficiencies were maintained at both temperatures. Effluent suspended solids concentrations ranged from 8 to 30 mg volatile suspended solids (VSS)/L, and the effluent soluble COD concentration averaged 30 mg/L

Microbial Activity of Soil Following Steam Treatment

The effect of steam treatment on subsurface aerobic and anaerobic microbial communities was investigated using multiple microbial assays. Soil samples were gathered and analyzed prior to, one month after, and eight months after a five-month field pilot test of steam injection and extraction. Aerobic soil samples were analyzed by respirometry, plate counts, and direct microscopic counts. Anaerobic microbial activity was examined by monitoring methane generation in anaerobic microcosms with gas chromatography. Respirometry showed pre-steam CO2 production was consistent with natural attenuation, post-steam (one month) CO2 production was below detection, and post-steam (eight months) CO2 production was about half of pre-steam. Post-steam (one and eight month) plate counts were one to four orders of magnitude lower than the pre-steam samples. Direct microscopic counts showed post-steam (one and eight month) cell numbers were higher than the pre-steam counts, but based on plate counts these cells were mostly non-viable. Significant amounts of methane and hydrogen were generated from pre-steam anaerobic microcosms, but post-steam microcosms had no detectable methane, and only trace amounts of hydrogen. Terminal restriction fragment (TRF) analysis was performed to determine the diversity of the microbial community before and after steam treatment. Pre-steam TRF analysis showed distinct differences in the microbial communities above and below the smear zone. Post-steam TRF analyses were not possible because insufficient DNA could be extracted from the soil

Many Labs 2: Investigating Variation in Replicability Across Samples and Settings

We conducted preregistered replications of 28 classic and contemporary published findings, with protocols that were peer reviewed in advance, to examine variation in effect magnitudes across samples and settings. Each protocol was administered to approximately half of 125 samples that comprised 15,305 participants from 36 countries and territories. Using the conventional criterion of statistical significance (p < .05), we found that 15 (54%) of the replications provided evidence of a statistically significant effect in the same direction as the original finding. With a strict significance criterion (p < .0001), 14 (50%) of the replications still provided such evidence, a reflection of the extremely highpowered design. Seven (25%) of the replications yielded effect sizes larger than the original ones, and 21 (75%) yielded effect sizes smaller than the original ones. The median comparable Cohen’s ds were 0.60 for the original findings and 0.15 for the replications. The effect sizes were small (< 0.20) in 16 of the replications (57%), and 9 effects (32%) were in the direction opposite the direction of the original effect. Across settings, the Q statistic indicated significant heterogeneity in 11 (39%) of the replication effects, and most of those were among the findings with the largest overall effect sizes; only 1 effect that was near zero in the aggregate showed significant heterogeneity according to this measure. Only 1 effect had a tau value greater than .20, an indication of moderate heterogeneity. Eight others had tau values near or slightly above .10, an indication of slight heterogeneity. Moderation tests indicated that very little heterogeneity was attributable to the order in which the tasks were performed or whether the tasks were administered in lab versus online. Exploratory comparisons revealed little heterogeneity between Western, educated, industrialized, rich, and democratic (WEIRD) cultures and less WEIRD cultures (i.e., cultures with relatively high and low WEIRDness scores, respectively). Cumulatively, variability in the observed effect sizes was attributable more to the effect being studied than to the sample or setting in which it was studied.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Instituto de Investigaciones Psicológicas (IIP

Biodegradation of Hydrocarbons Assisted by Arroyo Willows in Controlled Mesocosms Conducted at the Former Guadalupe Oil field

Abstract of paper presented at conference

Phytostimulation of Hydrocarbon Biodegradation By Arroyo Willows in Laboratory Microcosms

Controlled laboratory microcosms with and without Arroyo Willows (Salix lasiolepis) were used to elucidate potential mechanisms of phytoremediation of hydrocarbon-contaminated groundwater at a contaminated oil field near Guadalupe, CA. Laboratory control allows us to examine the synergistic effects between the plants themselves and the rhizobial bacteria associated with them. Laboratory microcosms were set up in triplicate with (1) sodium azide-inhibited soil, (2) soil with active bacteria, and (3) soil with active bacteria and willows. Hydrocarbon-contaminated groundwater was recirculated through the root zone for 105 days. Biodegradation rates were estimated by measuring total petroleum hydrocarbon (TPH) concentration and monitoring chemical oxygen demand (COD). TPH results showed a decrease in all chambers, the smallest decrease was for the sodium azide control chambers and the largest was for the willow chambers. For an initial TPH concentration of 3.6 ± 0.61 mg/L, the soil only chambers dropped to 0.40 ± 0.036 mg/L, and the soil and willow chambers dropped to 0.26± 0.080 mg/L. These results show a statistically significant effect of the willow trees compared to soil alone, suggesting the trees did contribute to bioremediation under these conditions, either directly via phytodegradation or indirectly via phytostimulation of bacterial biodegradation

Biodegradability and Toxicity of Hydrocarbon Leachate From Land Treatment Units

The biodegradability of leachate from the land treatment of hydrocarbon-contaminated soil was investigated in the laboratory using respirometry and toxicity testing in combination with total petroleum hydrocarbon (TPH) measurements. Soil in land treatment units (LTU) had been contaminated with a diesel-like hydrocarbon mixture formerly used as a diluent for crude oil at an oil field in California. Leachate was collected from two different LTUs for treatability testing in a respirometer under aerobic conditions. Only about 12% reduction in TPH concentration was observed after aeration for 161 days, indicating limited biodegradability of the hydrocarbon constituents in the leachate. Similarly, Microtox® toxicity did not change after 130 days. Leachate biodegradability was further tested by comparison to diluent-contaminated groundwater from the same site. Leachate diluted to the same TPH concentration as the contaminated groundwater was three times less toxic, but was much less biodegradable. The recalcitrance of the leachate hydrocarbons may be attributable to their high molecular weight, since the majority of the TPH was long-chained hydrocarbons of C20 or greater for leachate. In contrast, the diluent contaminated groundwater has a majority of its TPH concentration in short-chained hydrocarbons of C20 or less, which were more easily biodegraded. These short chain hydrocarbons are typically more toxic than the longer chain hydrocarbons, which would explain the observed decrease in toxicity of the diluent-contaminated groundwater during biodegradation

Biological Feasibility and Optimization of Biosparging at a Hydrocarbon-Contaminated Site

The purpose of this study was to identify any biological/chemical factors which may be limiting the biodegradation of total petroleum hydrocarbon (TPH) contaminants at a biosparge site located at a former oil field near Guadalupe, California. Laboratory experiments using a combination of respirometry and TPH analyses were conducted to determine if biodegradation of TPH at the site is limited by a lack of hydrocarbon-degrading microorganisms, depleted inorganic nutrient concentrations, insufficient dissolved oxygen supply, or the chemical composition of the partially biodegraded petroleum constituents in the groundwater. No increase in total CO2 production was observed in samples with added nutrients, inoculum, or both, over the 28-day experiment. No significant TPH biodegradation benefit could be attributed to the addition of nutrients or inoculum indicating both were sufficiently available at the site. Decreasing dissolved oxygen (DO) concentration decreased short-term CO2 production, but considerable CO2 production was observed even in samples with DO concentrations as low as 0.5 mg/L. In a long-term experiment, TPH degradation rates decreased significantly after initial observed biodegradation

Vinyl Chloride Biodegradation with Methanotrophic Attached Films

Methanotrophic degradation of vinyl chloride (VC) is investigated using a laboratory-scale methanotrophic attached-film expanded-bed (MAFEB) bioreactor. This study provides a basis for applying a microbial cometabolizing reaction to practical treatment of toxic chlorinated compounds. The MAFEB reactor was operated at 20°C with influent VC concentrations ranging from 1,800 to 9,600 µg/L and bed hydraulic retention times ranging from 3.7 to 7.6 h. VC effluent concentrations during steady continuous operation ranged from 3 to 140 µg/L, with most values less than 26 µg/L, resulting in removal efficiencies of 96.3% to 99.8%. The maximum continuous-flow VC degradation rate observed at 20°C was 2.5 mg VC per gram volatile solids (VS) per day [2.5 mg VC/(g VS d)] or 30 mg VC per liter expanded bed per day 30 mg VC/Leb d), under substrate-limited conditions. During semibatch runs at 35°C, vinyl chloride degradation rates up to 60 mg VC/ (g VS d) or 1 g/(Leb d) were observed. Degradation rates increased with temperature between 20°C and 35°C, approximately doubling every 10°C. Dissolved methane concentrations above 0.5 mg/L inhibited VC degradation, with no VC degradation observed with 8 mg/L dissolved methane. The methane consumed during VC degradation was about 40 g CH4/g VC. Toxic effects were observed after prolonged exposure of the methanotrophic culture to high concentrations of VC