Kenneth Carlson

Evolution of antibiotic occurrence in a river through pristine, urban and agricultural landscapes.

A river along the semi-arid Front Range of Colorado was monitored for antibiotics including five tetracycline and six sulfonamide compounds. Existing analytical methods were adapted to measure these compounds in a surface water matrix at environmentally relevant concentrations (0.05 microg/L). Natural organic matter present in surface waters was confirmed to significantly impact the low-level analysis of tetracyclines (TCs) necessitating the use of standard addition quantification techniques. Five sites along the Cache la Poudre River were monitored for antibiotics encompassing pristine areas without anthropogenic influence, urban areas impacted by wastewater discharges and agricultural areas susceptible to non-point source contaminant runoff. The only site at which no antibiotics were detected was the pristine site in the mountains before the river had encountered urban or agricultural landscapes. By the time the river had exited the urban area, 6 of the 11 antibiotic compounds that were monitored were found in the samples. At Site 5, which had both urban and agricultural influences all five of the TCs monitored were detected indicating both urban and agricultural influences. The concentration of TCs at Site 5 ranged from 0.08 to 0.30 microg/L.

Simulated rainfall study for transport of veterinary antibiotics-mass balance analysis.

Occurrence of human and veterinary antibiotics has been reported in various environmental compartments. Yet, there is a lack of information verifying the transport mechanisms from source to environment, particularly the transport of veterinary antibiotics as a non-point source pollutant. A rainfall simulation study was conducted to address surface runoff as a possible transport mechanism of veterinary antibiotics introduced in the field and mass balance was calculated with supplementary surface and depth soil measurement. Seven veterinary antibiotics that are the most abundantly used in agriculture for therapeutic and non-therapeutic (growth-promotion) purposes were examined in this study, including tetracycline (TC), chlortetracycline (CTC), sulfathiazole (STZ), sulfamethazine (SMZ), erythromycin (ETM), tylosin (TYL), and monensin (MNS). Runoff in aqueous and sediment phases was collected every 5 min for 1h with varied rainfall intensity and additional surface (0-2 cm) and depth (2-30 cm) soil samples were collected after rainfall simulation for mass balance analysis. Quantification of antibiotic concentration in all collected samples was based on solid phase extraction (SPE) followed by measurement with high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). MNS showed the highest concentration in runoff aqueous samples (0.22 mg plot(-1)), while ETM showed the highest concentration in runoff sediment samples (0.08 mg plot(-1)). The highest concentration of each applied antibiotic in surface soil samples occurred at different locations. This result might indicate the mobility of these compounds in surface soil varies due to different physicochemical properties among the antibiotics. Further, the analysis results showed that all of the subject antibiotics had penetrated into the subsurface; yet, no residuals were found for STZ, suggesting this compound might have penetrated even deeper into the soil. These results indicate that aqueous or sediment erosion control might reduce the transport of veterinary antibiotics in the environment.

The Formation of Filter-Removable Biodegradable Organic Matter During Ozonation

Abstract Biodegradable organic matter formed during the ozonation of natural waters was fractionated into rapidly and slowly degradable components based on measurements of biodegradable organic carbon (BDOC). The rapidly degradable fraction (BDOCrapid) was defined using the specific BDOC reactor incubation time that resulted in biodegradation similar to that in a pilot scale biofilter. Ozone dose was found to increase the formation of BDOCrapid up to a transferred dose of 1.0 to 1.5 mg O3/mg DOC. This fraction was insensitive to DOC quantity or character. The formation of BDOCslow was not sensitive to ozone dose but was sensitive to DOC quantity.

Distribution and Origin of Groundwater Methane in the Wattenberg Oil and Gas Field of Northern Colorado

Public concerns over potential environmental contamination associated with oil and gas well drilling and fracturing in the Wattenberg field in northeast Colorado are increasing. One of the issues of concern is the migration of oil, gas, or produced water to a groundwater aquifer resulting in contamination of drinking water. Since methane is the major component of natural gas and it can be dissolved and transported with groundwater, stray gas in aquifers has elicited attention. The initial step toward understanding the environmental impacts of oil and gas activities, such as well drilling and fracturing, is to determine the occurrence, where it is and where it came from. In this study, groundwater methane data that has been collected in response to a relatively new regulation in Colorado is analyzed. Dissolved methane was detected in 78% of groundwater wells with an average concentration of 4.0 mg/L and a range of 0-37.1 mg/L. Greater than 95% of the methane found in groundwater wells was classified as having a microbial origin, and there was minimal overlap between the C and H isotopic characterization of the produced gas and dissolved methane measured in the aquifer. Neither density of oil/gas wells nor distance to oil/gas wells had a significant impact on methane concentration suggesting other important factors were influencing methane generation and distribution. Thermogenic methane was detected in two aquifer wells indicating a potential contamination pathway from the producing formation, but microbial-origin gas was by far the predominant source of dissolved methane in the Wattenberg field.

The importance of soluble microbial products (SMPs) in biological drinking water treatment

Abstract The formation of soluble microbial products (SMPs) during a drinking water ozone-biofiltration process was estimated using two approaches. First, a model was developed that related the assimilation of biodegradable organic matter (BOM) to the accumulation of biomass on filter media. The model was calibrated with data from a regularly backwashed, pilot scale biofilter that approximated a steady-state plug flow reactor. The second approach was a direct measurement of SMP concentrations, accomplished by applying a synthetic water comprised of known compounds to a bio-acclimated filter. The SMP concentration was estimated by determining the difference between known-compound removal (on a carbon basis) and dissolved organic carbon (DOC) removal. Comparable results were obtained from both approaches. SMPs were found to be important relative to the carbon removal that is typically measured (DOC), indicating that this measurement can significantly underestimate the actual BOM removal (17–33% in this research). The concentration of SMPs was negligible relative to the filter effluent DOC pool.

The impact of ferrous ion reduction of chlorite ion on drinking water process performance.

The use of chlorine dioxide (ClO2) as a primary disinfectant and pre-oxidant in drinking water treatment is being explored as an alternative to chlorine for reducing disinfection by-product formation and to assure compliance with United States Environmental Protection Agencys Stage 1 Disinfection/ Disinfection By-Products Rule. However, the ClO2 by-product chlorite ion (ClO2-) is also regulated by the same regulation. Ferrous iron (Fe(II)) has been shown to effectively reduce chlorite ion to chloride ion (Cl-) and this study was conducted to evaluate the impact on overall treatment process performance due to the ferric hydroxide solids that form from the reaction. Ferrous iron application was explored at three different points in a pilot-scale water treatment system: pre-rapid mix. pre-settling and pre-filter. Chlorite ion concentrations were effectively reduced from 2mg/L to less than 0.3mg/L using an Fe(II) dose of approximately 6mg/L for all trials. Fe(II) addition at the rapid mix caused no adverse effects and, in fact, allowed for reduction of the alum dose due to the newly formed ferric hydroxide acting as a supplemental coagulant. An increase of 241 and 247% of total suspended solids influent to the filter process was observed when Fe(II) was applied at the pre-settling and pre-filter locations. Pilot-scale filter runs during these trials were less than 2 h and never obtained true steady state conditions. Jar testing was performed to better understand the nature of the ferric hydroxide solids that are formed when Fe(II) was oxidized to Fe(III) and to explore the effectiveness of Fe(II) addition at intermediate stages in the flocculation process.

Ozonation Of Dissolved Manganese In The Presence Of Natural Organic Matter

Abstract Oxidation of Mn2+ by ozone was studied with respect to.the effects of natural organic matter (NOM) and initial Mn2+ concentrations on post-ozonation dissolved Mn residuals. For an initial Mn2+ concentration of 200 ug/L, dissolved Mn residuals < 10 ug/L were attainable only in die absence of NOM. The presence of NOM complicates the use of ozone for Mn2+ removal by increasing dosage requirements, thus increasing the potential for the formation of permanganate ion, MnO4. For a constant TOC concentration of 3.4 mg/L, ozonation of natural water spiked with an initial Mn2+ concentration of 1000 ug/L produced dissolved Mn residuals < 10 ug/L. At lower initial Mn2+ concentrations (60-200 ug/L), dissolved Mn residuals following ozonation were consistently 20-30 ug/L.

Relative phosphorus load inputs from wastewater treatment plants in a northern colorado watershed.

Excess nutrients are among the leading sources of water quality impairment in the Unites States, and the USEPA has been working with state regulatory agencies to develop nutrient criteria for wastewater treatment plants (WWTPs). The Colorado Department of Public Health and Environment is scheduled to establish nutrient regulations in 2013, and stream total P (TP) concentration standards of 0.16 mg L in warm water and 0.11 mg L in cold water have been proposed for the rivers in the state. The objectives of this study were to monitor TP concentrations and loads along the Cache La Poudre River as it flows from the pristine upstream area through urban regions and finally through a mixture of agricultural and urban land uses. The study attempts to evaluate the sources and influences of TP under different hydrologic conditions. Twelve sampling events were completed from April 2010 to August 2011 to assess the influence of various flow and precipitation conditions on aqueous TP concentrations. During midrange flows and dry conditions, WWTPs were the major sources of TP, but other sources were more significant under high-flow and wet conditions according to a load analysis. The analysis indicates that reducing the TP load from WWTPs will only marginally affect the TP load in the river, and therefore it appears that other sources (e.g., stormwater and agricultural runoff) need to be addressed before the aquatic life-based stream standard can be achieved.

Measuring the Applicability of Biosensors to Detect Possible Terror Chemicals in Water Distribution Network

Instant and accurate detection of chemical contamination in a water distribution system is significant in protecting public health and water resource. Using water quality surrogates to signal a contamination occurrence offers the advantage of detecting a large number of chemicals. This article describes how the indigenous biofilm in a contaminated drinking water system may provide an effective indirect surrogate response with either turbidity or ultraviolet changes (UV254). Rotating annular bioreactors (RAB) and pipe loops were used to quantify biofilm along with turbidity and UV254 measurements. The number of biofilm cells on the polyvinyl chloride (PVC) analytical coupons was also enumerated, using automated fluorescence microscopy. Measuring the biosensing capacity, the analytical coupons were submersed into beakers with potential chemical contaminants such as aldicarb, cyanide, cycloheximide, nicotine, sodium arsenate, and sodium fluoroacetate. Resulting data indicated that turbidity was a useful surrogate for forensically monitoring chemical contaminants. Turbidity measurement can make an inexpensive biosensor for the security of a water distribution system.

Occurrence of β-lactam and polyether ionophore antibiotics in surface water, urban wastewater, and sediment

The occurrence and fate of antibiotic compounds in the aquatic environment has been recognized as an emerging area of interest in environmental chemistry. An analytical method was developed and validated for determining β-lactam and polyether ionophore antibiotics in surface water, urban wastewater, and sediment based on solid-phase extraction (SPE) and liquid chromatography–ion trap tandem mass spectrometry (LC-MS-MS). The average recovery of β-lactams and polyether ionophores from all the fortified samples was generally higher than 80% (except for amoxicillin and ampicillin). A total of 400 actual water and sediment samples were analysed using SPE-LC-MS-MS to evaluate the occurrence and fate of these antibiotic compounds in a river and a wastewater treatment plant in northern Colorado. Most samples were found to be negative for β-lactam compounds. In those samples with positive results, β-lactam compounds were found at 15–17 ng/L in influent wastewater samples, 9–11 ng/L in surface water samples, and 0.13–0.36 μg/kg in sediment samples. No β-lactam compounds were detected in any effluent wastewater samples. The β-lactams are expected to be easily eliminated in wastewater treatment plants due to the lability of the β-lactam ring towards chemical and microbial degradation. The average concentration of ionophores ranged 0.03–0.05 μg/L in surface water samples and 0.5–3.1 μg/kg in sediment samples. These results confirm that β-lactam and ionophore antibiotics are adsorbed by sediment.