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Low-pressure membranes provide high-quality water through physical removal of bacteria, cysts, and particles. Bacteria can attach to the membrane surface and form biofilms that reduce energy efficiency and increase the frequency of membrane replacement. Modifying membranes with polydopamine, a chemical mimic of the adhesive proteins that mussels release, has the potential to delay biofilm formation. Dopamine polymerizes under mild conditions, forming a coating that is of interest in membrane applications due to its hydrophilic and reactive nature. Compared with hydrophobic base membranes, hydrophilic surfaces are resistant to bacterial attachment. Additionally, when polydopamine is exposed to silver nitrate, a reduction reaction takes place that embeds antimicrobial silver nanoparticles into the polydopamine layer. This study paired short-term deposition experiments with longer-term filtration experiments to determine the efficacy of this modification when challenged with Pseudomonas aeruginosa. Modification with polydopamine resulted in an average 48% reduction in the initial deposition rate of P. aeruginosa. However, hydrophilicity of the polydopamine layer did not have a significant impact on membrane performance over 3 days of bacterial filtration. Only the combination of both polydopamine and silver nanoparticles improved the rate of water production, with an average flux 1.7 times greater than that of the unmodified membrane. Confocal microscopy revealed heterogeneous bacterial growth on all membrane types with a lack of association between membrane performance and biofilm structure. Modifying membranes with polydopamine and silver nanoparticles has the potential to ameliorate the effects of biofouling, thereby increasing the efficiency of membrane water treatment. [ABSTRACT FROM AUTHOR]

To examine rates of Shigella infections in household contacts of pediatric shigellosis patients, we followed contacts and controls prospectively for 1 week after the index patient obtained care. Household contacts of patients were 44 times more likely to develop a Shigella infection than were control contacts (odds ratio 44.7, 95% CI 5.5-361.6); 29 (94%) household contacts of shigellosis patients were infected with the same species and serotype as the index patient's. Pulsed-field gel electrophoresis showed that 14 (88%) of 16 with infected contacts had strains that were indistinguishable from or closely related to the index patient's strain. Latrine area fly counts were higher in patient households compared with control households, and 2 patient household water samples were positive for Shigella. We show high susceptibility of household contacts of shigellosis patients to Shigella infections and found environmental risk factors to be targeted in future interventions. [ABSTRACT FROM AUTHOR]

Eighteen microalgae, including two local isolates, were evaluated for their ability to grow and remove nutrients from unsterilized primary or secondary wastewater effluents as well as wastewater supplemented with nutrient-rich anaerobic digester centrate (ADC). Most of the tested species except several phylogenetically clustered Chlorella sorokiniana including local isolates and Scenedesmus strains were unable to grow efficiently. This may reflect the presence of certain genetic traits important for robust growth in the unsterilized wastewater. The maximum algal-specific growth rates and biomass density obtained in these bacterial-contaminated cultures were in the range of 0.8-1 day and 250-350 mg L, respectively. ADC supplementation was especially helpful to biologically treated secondary effluent with its lower initial macronutrient and micronutrient content. As a result of algal growth, total nitrogen and orthophosphate levels were reduced by as much as 90 and 70 %, respectively. Biological assimilation was estimated to be the main mechanism of nitrogen removal in primary and secondary effluents with ammonia volatilization and bacterial nitrification-denitrification contributing for cultures supplemented with ADC. Assimilation by algae served as the principal mechanism of orthophosphate remediation in secondary wastewater cultures, while chemical precipitation appeared also to be important for orthophosphate removal in primary wastewater. Overall, cultivation of microalgae in primary and primary + 5 % ADC may be more favorable from an economical and sustainability perspective due to elimination of the costly and energy-intensive biological treatment step. These findings demonstrate that unsterilized wastewater and ADC can serve as critical nutrient sources for biomass generation and that robust microalgae can be potent players in wastewater phytoremediation. [ABSTRACT FROM AUTHOR]

Economically feasible and sustainable energy production from microalgae requires optimization of algal growth, maximization of lipid content, and enhancement of biomass conversion into energy. An innovative, mixed trophic state process with high productivity was implemented to generate microalgae with high lipid content for generating biodiesel and biogas. Auxenochlorella protothecoides, a unicellular green alga, was grown phototrophically to 0.28 dry weight per L (gdw/L) then concentrated to 36 gdw/L for use as an inoculum for a subsequent heterotrophic cultivation to a final density of nearly 120 gdw/L. Simultaneous nitrogen deprivation and glucose supplementation during the heterotrophic stage increased the total lipid content from 16 to 57 % while the triacylglycerol (TAG) fraction of total lipids advanced from 2 to 79 %. Productivity peaked at 4.9 g of biomass/L-h and 1.7 g TAGs/L-h. The extracted lipids, including high levels of oleic, linoleic, and palmitic acids, were converted into biodiesel with a predicted cetane number of 56.4 and low concentrations of long-chain saturated and polyunsaturated fatty acid methyl esters. Both intact microalgal biomass and lipid-extracted algal residues (LEA) were good substrates for anaerobic digestion (AD) with methane yields of 0.6 and 0.4 L/g volatile solids (VS), respectively. These yields represented nearly 80 % of theoretical methane potential. LEA, with a favorable carbon to nitrogen ratio (C:N) of approximately 19:1, is an appropriate substrate for anaerobic microorganisms, most likely because it contains essential nutrients required for microbial digestion. The biochemical composition of the biomass, especially its lipid content, is the major contributor for energy output. As a result, coupling biodiesel production with AD of LEA to generate methane can increase the overall process' energy output up to 40 %. [ABSTRACT FROM AUTHOR]

A critical factor in implementing microalgal biofuels for mass production is the nutrient requirements. The current study investigated the fate of macro- and micronutrients and their availability in a sequential phototrophic-heterotrophic production process for the lipid rich microalga Auxenochlorella protothecoides. More than 99 % (by weight) of overall process nutrients were supplied during the initial photoautotrophic stage reflecting its significantly larger volume. Under photoautotrophic growth conditions only 9-35 % of supplied Mn, S, Fe, N, Mg, and Cu and less than 5 % of P, Mo, Co, B, Zn, and Ca were consumed by the algae. The rest of these nutrients remain in the spent growth media during the culture concentration-down from an 800 L phototrophic pond to a 5 L heterotrophic fermenter. In contrast, Zn, Mo, Mn, Mg, Ca, and N were exhausted (90-99 % removal) during the first 25 h of the heterotrophic growth stage. The depletion of these key nutrients may have ultimately limited the final biomass density and/or lipid productivity achieved. Approximately 10-20 % of the total supplied S, Mn, Fe, N, and Cu and 5 % of Ca and Zn were assimilated into algal biomass. Several elements including N, P, Mn, B, Cu, Ca, Mg, S, and Fe were released back into the liquid phase by anaerobic digestion (AD) of the residual biomass after lipid extraction. The nutrients recovered from the AD effluent and remaining in the spent medium should be recycled or their initial concentration to the phototrophic stage decreased to enhance process economics and sustainability for future commercialization of algal-derived biofuels. [ABSTRACT FROM AUTHOR]

Conversion of CH3Hg+ concentrations in water to CH3Hg+ concentrations in fish tissue is critically important in characterizing Hg health risks to humans and biota in aquatic ecosystems. However, this is a challenging task due to complex biogeochemical CH3Hg+ processes that are replete with uncertainty. In the present study, the uncertainty was reduced by employing the Spreadsheet-based Ecological Risk Assessment for the Fate of Mercury (SERAFM) model and a linear relationship between logarithmic Hg concentrations and stable isotope ratios of nitrogen (δ15N) in biota. By using this approach, the fate, transport, and bioaccumulation of CH3Hg+ in Sarasota Bay, FL, was modeled. Modeling results suggest that ∼60% of the total Hg loading (8.7 kg/year) to the Sarasota Bay in 2011 originated from atmospheric Hg deposition to the watershed with subsequent transport to the waterbody via stormwater runoff. This indicated that watershed runoff could be an important source of Hg to a bay adjacent to highly urbanized areas. In addition, our modeling results suggested that Hg runoff reduction (90%) from impervious surfaces together with lowering atmospheric Hg deposition (21→10 μg/m/year) would be a practical approach to lower current Hg levels and associated risks to the Sarasota Bay ecosystem. Since future Hg loadings to the Bay are likely to rise from increases of atmospheric Hg deposition and watershed urbanization, it will be necessary to reduce various Hg loadings by employing appropriate implementation plans for the management of this urbanized watershed. [ABSTRACT FROM AUTHOR]

The bioaccumulation and biomagnification of Hg and Se were investigated in Sarasota Bay, Florida, USA, to characterize the Hg exposure risks to wild bottlenose dolphins in the bay. Concentrations of total mercury (THg), monomethylmercury (MMHg), and total selenium (TSe) were monitored in the bay, the latter of which might reduce Hg toxicity. The food web structure and dolphins' trophic level-specific consumption rates were evaluated using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). Regressions developed for Hg biomagnification in the food chain were log10 CTHg (nanograms per gram) = 0.27 × δ15N (‰) - 0.42, R2 = 0.87, for THg and log10 CMMHg = 0.33 × δ15N (‰) - 1.0, R2 = 0.93, for MMHg. Unlike Hg, nearly constant TSe concentrations were observed at 248 ± 179 ng g−1 in the food web, and the TSe-to-THg molar ratio was predicted by log10( CTSe/ CTHg) = −0.10 × δ15N (‰) + 2.8, R2 = 0.60. The THg-uptake rates of Sarasota bottlenose dolphins are estimated to vary between 2.1 and 4.9 µg kg−1 d−1; however, the estimated TSe-uptake rates (15.1 µg kg−1 d−1) were higher than those for THg, and the Hg-exposure risks of the Sarasota Bay resident bottlenose dolphins are considered to be low. Approaches employed in the present study can be extended to other environments to characterize Hg contamination in aquatic systems and Hg exposure risks in top predators. Environ. Toxicol. Chem. 2013;32:1143-1152. © 2013 SETAC [ABSTRACT FROM AUTHOR]

A sensitive yet robust analytical method is presented for the simultaneous determination of 12 human pharmaceuticals (valproic acid, phenytoin, ibuprofen, gabapentin, acetaminophen, gemfibrozil, naproxen, ketoprofen, secobarbital, phenobarbital, 5-fluorouracil, and diclofenac) and 6 antiseptics (biosol, biphenylol, p-chloro- m-cresol, p-chloro- m-xylenol, chlorophene, and triclosan). The method employs solid-phase extraction (SPE) followed by a novel pentafluorobenzylation using a mixture of acetontrile/water (1/1, v/ v). The method is simple to perform (derivatization can be completed in a single test tube) and eliminates the need for any solvent/SPE cartridge drying or blow-down. It affords excellent resolution, high sensitivity and reproducibility, and freedom from interference even for matrices as complex as untreated sewage. The method was applied to the analysis of sewage samples using 15 isotopically labeled surrogates, which resulted in the detection of 10 of the 12 pharmaceuticals and all of the antiseptics sought. Ten of 15 surrogates were synthesized from pure analytes by a simple H-D exchange reaction employing DO and DSO. Measured recoveries were sensitive to matrix effects and varied substantially among analytes, indicative of the limitations associated with using a single surrogate standard. [ABSTRACT FROM AUTHOR]

Use of landfill gas as a fuel often requires pretreatment for removal of contaminants that damage energy-recovery equipment. Because these contaminants are present in trace levels, biofiltration may be a suitable treatment option. However, the high carbon dioxide (CO2) concentrations in the gas could encourage autotrophic growth in place of consumption of the trace organics, or decrease the pH of the biofilter material. Xanthobacter autotrophicus GJ10 has broad ability to transform halogenated hydrocarbons, and is also known to grow on CO2 as a sole carbon source. Microcosms of this bacterium, grown on CO2, were spiked with 1,2-dichloroethane (1,2-DCA) to monitor the bacterium's ability to switch from autotrophic to heterotrophic transformation at moderate pH. Additional cultures of X. autotrophicus GJ10 were established over a range of pH from 4 to 8, values that might result from media exposure to landfill gas. Growth on a nonchlorinated organic carbon source was monitored under these conditions. Also, dechlorination of 1,2-DCA was correlated to high, moderate, or low pH microcosms. Results demonstrated no effect on transformation of 1,2-DCA under high CO2 concentrations when pH remained near 6. On the other hand, pH conditions lower than 5.5 impeded growth of the organism. No growth was observed when pH was less than 4.6. Within the range of good growth (pH between 5.5 and 8.1), low pH influenced transformation rates. Conditions of pH less than 6 reduced the transformation rate coefficient by 25%. Therefore, pH control in a biofilter unit for treatment of 1,2-DCA will be an important consideration. [ABSTRACT FROM AUTHOR]

Pharmaceuticals and personal care products (PPCPs) have been the focus of much recent research as concerns rise about their occurrence in bodies of water worldwide. In an effort to characterize the risk and determine the prevalence of these micropollutants in lakes and rivers, many researchers are examining PPCP removal from impaired water during wastewater treatment and water recycling (soil passage) processes. Biodegradation studies and projects considering combinations of biodegradation and other removal processes have been conducted over a wide range of compound categories and therapeutic classes, as well as across different systems and scales of study. This review summarizes the extent of PPCP removal observed in these various systems. [ABSTRACT FROM AUTHOR]

Industrial activities in the Baltimore Harbor, Baltimore, Maryland, USA, have resulted in widespread chromium contamination of sediments. A comprehensive analysis of Cr speciation in sediment and porewater collected from 22 locations in the Baltimore Harbor was completed to understand Cr bioavailability and probability of toxicity due to Cr in sediments. The analysis employed a reverse-phase ion-pair high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLCICP- MS) method. Sub-microgram-per-liter determination of Cr(III) and Cr(VI) in environmental samples was found, with method validation revealing broad method applicability of HPLC-ICP-MS to a wide range of sample types. The major limitation of the method was poor Cr species separation in high ionic strength solutions (greater than 0.1 M NaCl). Total Cr concentrations in Baltimore Harbor sediments ranged from 2.5 to 1,050 mg/kg with 11 of the 22 sites containing total Cr in excess of the 370 mg/ kg effects range-median (ER-M) sediment quality guideline. The Cr(VI) concentrations in sediments, however, were markedly lower, ranging from 0.10 to 0.38 mg/kg with Cr(VI) not detected in 14 of the 22 stations. Porewater concentrations, both for total Cr and Cr(VI), were quite low, with total Cr ranging from 0.20 to 2.16 μg/L and Cr(VI) ranging from 0.73 to 1.17μg/L. The Cr(VI)-reducing capacity of the sediments, based on a sediment-spiking experiment, was found to be strongly correlated with the acid volatile sulfides content of the sediment. Overall, our results provide field validation of the hypothesis that Cr(VI) will not persist in sediments with excess acid volatile sulfides. Given the low concentrations of Cr(VI) in sediment and porewater, it appears unlikely that Cr in Baltimore Harbor sediments contributes appreciably to previously observed sediment toxicity. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the effectiveness of alkaline hydrolysis as an alternative ex situ technology for remediating groundwater contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Treatment in both batch reactor and continuous stirred tank reactor (CSTR) was investigated. RDX reactivity was strongly dependent on the reaction pH investigated (11–13). The batch system achieved pseudo-first-order RDX reaction rates in the range of (0.8–27.7)×10-3 min-1, corresponding to half-life periods of 17.9 to 0.5 h, respectively. In the CSTR system operated at the initial RDX concentration of 4.5×10-3 mM, 99% RDX removal was achieved with the hydraulic retention time of 2 days and the reaction pH of 11.9. Formate and nitrite were produced as the major hydrolysates in the CSTR system, indicating a simultaneous reaction mechanism involving RDX ring cleavage and elimination of the ring nitrogen. The net OH- demand used only for RDX removal in the CSTR was found to be 1.5, 390, and 130 MOH-/MRDXremoved at pH values of 11.9, 11.5, and 11.0, respectively. A conceptual cost analysis indicated that the expense of alkaline treatment may be comparable to the expense of granular activated carbon treatment for long treatment periods (30 years or more), due to the potentially lower annual operational cost of alkali treatment. [ABSTRACT FROM AUTHOR]

For systems of sediments, soils, and subsurface solids that involve aggregations of fine-grained materials and zones of immobile water, the desorption of organic contaminants is often controlled by aqueous diffusion within the immobile water of a sorption domain. Accurate modeling in such systems requires not only a rational conceptual model for rates, but also good understanding of the equilibrium condition and of the initial conditions that existed at the onset of desorption. In this work, numerical modeling was used to obtain synthetic experimental results with a hypothetical (yet realistic) system in which rates were controlled by sorption-retarded diffusion. Batch sorption and desorption experiments are simulated at a variety of time scales and the results interpreted through modeling. Results show that even 50 days can be far too short to obtain equilibrium isotherms, and that the associated isotherm interpretations cause incorrect kinetic interpretations and predictions. In particular, 4- week batch sorption/desorption rate experiments could be well described using any of the presumed isotherms, but these results lead to greatly overpredicted rates of desorption under longer term conditions more relevant to field remediation. Additional results were also generated to quantitatively illustrate how misunderstanding of sorption equilibrium and diffusion rate will lead to incorrect suppositions of desorption hysteresis. [ABSTRACT FROM AUTHOR]

For aerobic co-metabolism of chlorinated solvents to occur, it isnecessary that oxygen, a primary substrate, and the chlorinated compound all be available to an appropriate microorganism – that is, a microorganism capable of producing the nonspecific enzyme that will promote degradation of the ontaminant while the primary substrate is aerobically metabolized. Thus, the transport processes that serve to mix the reactants are crucial in determining the rate and extent of biodegradation, particularly when considering in situ biodegradation. These transport processes intersect, at a range of scales, with the biochemical reactions. This paper reviews how the important processes contributing to aerobic co-metabolism of chlorinated solvents at different scales can be integrated into mathematical models. The application of these models to field-scale bioremediation is critically examined. It is demonstrated that modeling can be a useful tool in gaining insight into the physical, chemical, and biological processes relevant to aerobic co-metabolism, designing aerobic co-metabolic bioremediation systems, and predicting system performance. Research needs are identified that primarily relate to gaps in our current knowledge of inter-scale interactions. [ABSTRACT FROM AUTHOR]

Discusses results from several studies that investigated biofiltration and ozone-biofiltration for use in water treatment. Batch experiments to evaluate the effect of natural organic matter (NOM) source and ozone dose on NOM biodegration.

The low bioavailability of hydrophobic organic compounds (HOCs) is one of the key sources of uncertainty in the implementation of in situbioremediation. Bioavailability of HOCs in the subsurface is affected by sorption/desorption processes in two important ways. First, sorption causes high organic concentrations in microporous regions and impermeable zones to which bacterial access is obstructed. Second, because desorption and immobile zone diffusion must occur before biodegradation can proceed, the overall rate of bioremediation can be limitedor even controlled by these mass transfer processes, not by the activity of the degrading microorganisms. Rate models that couple sorption/desorption--related mass transfer processes and biodegradation havebeen successfully applied to laboratory results and are beginning tooffer some insight into the problem. Specifically, the influence of sorption on biodegradation is quantified here by defining a bioavailability factor, Bf. However, many questions remain and predictive modeling is elusive, especially in the context of complicated heterogeneous natural systems. Challenges facing environmental engineers are to develop a better understanding of these processes at both laboratory and field scales and ultimately to use such understanding toward the development of more effective and economical remediation technologies. [ABSTRACT FROM AUTHOR]

Aerobic biodegradation of benzene, toluene and naphthalene was studied in pre-equilibrated soil-water slurry microcosms. The experiments were designed to simulate biodegradation at waste sites where sorption reaches equilibrium before biodegradation becomes important. Rates of biodegradation were reduced by the presence of soil. For example, nearly complete naphthalene biodegradation (1.28 mg/L) by indigenous soil bacteria occurred within 60 hours in aqueous solution (soil-free) while it took two weeks to degrade the same amount in the presence of 0.47 kg soil/L of water. The rate of biodegradation was observed to decrease with increasing organic compound hydrophobicity, soil/water ratio, soil particle size, and soil organic carbon content. These results clearly indicate that the rate of biodegradation is affected by both the extent and rate of sorption. Further analysis suggests that mass transfer could control the performance of in situ bioremediation for highly hydrophobic organic contaminants which exhibit a large extent of sorption and slow rate of desorption. [ABSTRACT FROM AUTHOR]

The feasibility of aerobic in situ bioremediation is being investigated for use in a strategy to control subsurface coal tar contamination at the site of a former manufactured gas plant. As part of this investigation, anoxic aquifer sands collected between 11 and 25 m below ground surface were assayed in batch microcosms to measure the singular and combined effects of O2, NO3-,and PO43- on 14C-naphthalene mineralization. The influence of these additives varied considerably between sediments. A high initial concentration of O2 (21 mg/L) promoted the greatest extent of mineralization in the majority of active sediments. NO3- (85 mg/L) was observed to enhance, inhibit, or have no effect on the rate of naphthalene mineralization, although significant denitrification was observed in nearly all the active sediments. Data suggest that PO43- complexation and/or precipitation with sediment cations limited P bioavailability. The sediments that were incapable of mineralizing naphthalene were characterized by low pH (< 4.1), high SO42- (>500 mg/L), and moderate to high dissolved Fe(II) (30-265 mg/L) when equilibrated aerobically with water. Fe(II) likely exerted a significant O2 demand that reduced the O2 available as an electron acceptor for biodegradation. These experiments demonstrate that while aeration/oxygenation can be an effective strategy for enhancing subsurface bioremediation of aromatic hydrocarbons, the biodegradation response to aeration/oxygenation and nutrient addition may vary considerably within an aquifer. [ABSTRACT FROM AUTHOR]