Mechanisms of Virus Mitigation and Suitability of Bacteriophages as Surrogates in Drinking Water Treatment by Iron Electrocoagulation

Emerging water treatment technologies using ferrous and zero-valent iron show promising virus mitigation by both inactivation and adsorption. In this study, iron electrocoagulation was investigated for virus mitigation in drinking water via bench-scale batch experiments. Relative contributions of physical removal and inactivation, as determined by recovery via pH 9.5 beef broth elution, were investigated for three mammalian viruses (adenovirus, echovirus, and feline calicivirus) and four bacteriophage surrogates (fr, MS2, P22, and ΦX174). Though no one bacteriophage exactly represented mitigation of the mammalian viruses in all water matrices, bacteriophage ΦX174 was the only surrogate that showed overall removal comparable to that of the mammalian viruses. Bacteriophages fr, MS2, and P22 were all more susceptible to inactivation than the three mammalian viruses, raising concerns about the suitability of these common surrogates as indicators of virus mitigation. To determine why some bacteriophages were particularly susceptible to inactivation, mechanisms of bacteriophage mitigation due to electrocoagulation were investigated. Physical removal was primarily due to inclusion in flocs, while inactivation was primarily due to ferrous iron oxidation. Greater electrostatic attraction, virus aggregation, and capsid durability were proposed as reasons for virus susceptibility to ferrous-based inactivation. Results suggest that overall treatment claims based on bacteriophage mitigation for any iron-based technology should be critically considered due to higher susceptibility of bacteriophages to inactivation via ferrous oxidation

Removal of Estrogenic Compounds from Water Via Energy Efficient Sequential Electrocoagulation-Electrooxidation

The purpose of this study was to investigate energy reduction using electrocoagulation (EC) followed by electrooxidation (EO) targeting initial removal of dissolved organic carbon (DOC) during EC and subsequent removal of estrogenic compounds in EO. EC offers benefits over conventional coagulation such as in situ generation of coagulant but is not practical for removing estrogenic compounds. Advanced oxidation processes, including EO, can effectively remove micropollutants such as estrogenic compounds but are hindered by the presence of bulk organic matter. This study investigated four estrogenic compounds from the U.S. EPA\u27s Contaminant Candidate List: estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2). First, EC (iron electrodes) was employed to remove humic acid and improve downstream removal of estrogenic compounds while reducing overall energy consumption in EO (boron-doped diamond electrodes). The sequential EC and EO system effectively reduced overall electrical energy per order (EEO) by more than half compared with EO alone for each estrogenic compound. The system also effectively removed humic acid and estrogenic compounds. An EC current density of 8.88 mA/cm2 and electrolysis time of 8 min with a flocculation stir rate of 40 rpm (G = 23 s−1) achieved the greatest DOC and UV-VIS254 removal. EO treatment achieved the highest estrogenic compound removal at a current density of 22.2 mA/cm2. Initial humic acid sodium salt concentration (0–60 mg/L C) had an effect on EC iron dose and estrogenic compound removal. The EEO for EC-EO treatments was lower than EC alone, EO alone, UV photolysis, UV photocatalysis, and ozone but was higher than a photocatalytic reactor membrane and UV/H2O2. Overall, the EC-EO system was effective at removing bulk organic matter during EC and estrogenic compounds during EO. EC-EO reduced overall energy demand, indicating that this system should be developed further as an advanced technology that could efficiently remove micropollutants

From Micro to Macro-Contaminants: The Impact of Low-Energy Titanium Dioxide Photocatalysis Followed by Filtration on The Mitigation of Drinking Water Organics

This study evaluated strategies targeting macro- and micro-organic contaminant mitigation using low-energy titanium dioxide photocatalysis. Energy inputs of 1, 2, and 5 kWh m−3 resulted in incomplete oxidation of macro-organic natural organic matter, signified by greater reductions of UV254 and specific ultraviolet UV absorbance (SUVA) in comparison to dissolved organic carbon (DOC). The rate of UV254 removal was 3 orders of magnitude greater than the rate of DOC degradation. Incomplete oxidation improved operation of downstream filtration processes. Photocatalysis at 2 kWh m−3 increased the bed life of downstream granular activated carbon (GAC) filtration by 340% relative to direct filtration pretreatment. Likewise, photocatalysis operated ahead of microfiltration decreased fouling, resulting in longer filter run times. Using 2 kWh m−3 photocatalysis increased filter run time by 36 times in comparison to direct filtration. Furthermore, levels of DOC and UV254 in the membrane permeate improved (with no change in removal across the membrane) using low-energy photocatalysis pretreatments. While high-energy UV inputs provided high levels of removal of the estrogenic micro-organics estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynlestradiol (EE2), low-energy photocatalysis did not enhance removal of estrogens beyond levels achieved by photolysis alone. In the cases of E1 and E3, the addition of TiO2 as a photocatalyst reduced degradation rates of estrogens compared to UV photolysis. Overall, process electrical energy per order magnitude reductions (EEOs) greatly improved using photocatalysis, versus photolysis, for the macro-organics DOC, UV254, and SUVA; however, energy required for removal of estrogens was similar between photolysis and photocatalysis

Varied effects of algal symbionts on transcription factor NF-κB in a sea anemone and a coral: possible roles in symbiosis and thermotolerance

Many cnidarians, including the reef-building corals, undergo symbiotic mutualisms with photosynthetic dinoflagellate algae of the family Symbiodiniaceae. These partnerships are sensitive to temperature extremes, which cause symbiont loss and increased coral mortality. Previous studies have implicated host immunity and specifically immunity transcription factor NF-κB as having a role in the maintenance of the cnidarian-algal symbiosis. Here we have further investigated a possible role for NF-κB in establishment and loss of symbiosis in various strains of the anemone Exaiptasia (Aiptasia) and in the coral Pocillopora damicornis. Our results show that NF-κB expression is reduced in Aiptasia larvae and adults that host certain algae strains. Treatment of Aiptasia larvae with a known symbiosis-promoting cytokine, transforming growth factor β, also led to decreased NF-κB expression. We also show that aposymbiotic Aiptasia (with high NF-κB expression) have increased survival following infection with the pathogenic bacterium Serratia marcescens as compared to symbiotic Aiptasia (low NF-κB expression). Furthermore, a P. damicornis coral colony hosting Durusdinium spp. (formerly clade D) symbionts had higher basal NF-κB expression and decreased heat-induced bleaching as compared to two individuals hosting Cladocopium spp. (formerly clade C) symbionts. Lastly, genome-wide gene expression profiling and genomic promoter analysis identified putative NF-κB target genes that may be involved in thermal bleaching, symbiont maintenance, and/or immune protection in P. damicornis. Our results provide further support for the hypothesis that modulation of NF-κB and immunity plays a role in some, but perhaps not all, cnidarian-Symbiodiniaceae partnerships as well as in resistance to pathogens and bleaching.Accepted manuscrip

Analysis of operational parameters, reactor kinetics, and floc characterization for the removal of estrogens via electrocoagulation

Estrogenic compounds can cause human and ecological health issues and have been detected in surface and drinking water. In this research a reactor analysis determined the impact of operational parameters, the best fit kinetic model for the removal of estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2) using a bench-top iron electrocoagulation reactor, and characterized the floc generated in-situ. The parameters investigated were current density, conductivity, stir rate, and polarity reversal. Estrogen removal correlated well with an increase in current density, while conductivity did not impact removal but did reduce potentials. High stir rates and frequent polarity reversal demonstrated greater removal. The operating parameters that achieved the greatest estrogen removal were a current density of 16.7 mA cm−2, conductivity of 1000 μS cm−1, stir rate of 500 rpm, and a polarity reversal time of 30 s. These parameters led to average removal efficiencies of 81%, 87%, 85%, and 97% for E1, E2, E3, and EE2, respectively. The removal data for all estrogenic compounds best fit a pseudo-first order relationship with kinetic rate constants of 0.015 min−1 for E1 and E2, 0.016 min−1 for E3 and 0.040 min−1 for EE2. The floc formed in-situ were characterized by determining the crystalline phases with X-ray diffraction, the size and zeta potential, and the shape and major components using scanning electron microscope with energy-dispersive X-ray spectrometer. The iron coagulant generated during electrocoagulation was lepidocrocite with a point of zero charge of 5.67 and an average floc diameter of 2255 nm

Restrictive Breathing Mask Reduces Total Repetitions in Resistance-Trained Males: An Ongoing Study

Recently a popular exercise training device has been developed, which has been promoted by companies as a training aid, known as a restrictive breathing mask (RBM).The RBM is designed to simulate training at higher altitudes and has become commonplace for individuals to utilize during resistance-training sessions. PURPOSE: The purpose of this study was to examine the impact of a RBM on muscle performance and perceptual measures in resistance-trained males. METHODS: A cross-over study design was utilized in 9 resistance-trained males with performance trials separated by 7 days. A baseline strength testing session was completed for 12RM for squat, leg press, and leg extension. Participants completed the lower body workout with no mask or RBM. After the initial warm up, participants completed 4 sets of reps to failure of squats, leg press, and leg extension with 2 minutes rest between sets and 3 minutes between exercises. Heart rate was collected immediately post set. Participants completed a 10cm visual stress scale immediately post resistance training session and Session RPE (SRPE) was collected 10 minutes post. Paired T-tests were utilized to analyze total session reps, SRPE, average post set session heart rate, and session stress scale. RESULTS: There was a significant reduction in total session reps during the RBM trial compared to the no mask trial (p\u3c 0.001). SRPE was significantly higher during the RBM trial compared to the no mask trial (p= 0.003). There was a significant elevation in perceived stress during the RBM trial (p= 0.01). Finally, there was a statistically significant increase in post set heart rate during the RBM session (p=0.04) CONCLUSION: Based on the performance variables, it appears that a RBM reduces the total repetitions that an individual can complete during an acute bout of resistance training, while also increasing the perceived difficulty and stressfulness of the bout. Subsequently, a reduction in mechanical stimuli could result in a diminished hypertrophic response over time

Enabling Surgical Placement of Hydrogels through Achieving Paste-Like Rheological Behavior in Hydrogel Precursor Solutions

Hydrogels are a promising class of materials for tissue regeneration, but they lack the ability to be molded into a defect site by a surgeon because hydrogel precursors are liquid solutions that are prone to leaking during placement. Therefore, although the main focus of hydrogel technology and developments are on hydrogels in their crosslinked form, our primary focus is on improving the fluid behavior of hydrogel precursor solutions. In this work, we introduce a method to achieve paste-like hydrogel precursor solutions by combining hyaluronic acid nanoparticles with traditional crosslinked hyaluronic acid hydrogels. Prior to crosslinking, the samples underwent rheological testing to assess yield stress and recovery using linear hyaluronic acid as a control. The experimental groups containing nanoparticles were the only solutions that exhibited a yield stress, demonstrating that the nanoparticulate rather than the linear form of hyaluronic acid was necessary to achieve paste-like behavior. The gels were also photocrosslinked and further characterized as solids, where it was demonstrated that the inclusion of nanoparticles did not adversely affect the compressive modulus and that encapsulated bone marrow-derived mesenchymal stem cells remained viable. Overall, this nanoparticle-based approach provides a platform hydrogel system that exhibits a yield stress prior to crosslinking, and can then be crosslinked into a hydrogel that is capable of encapsulating cells that remain viable. This behavior may hold significant impact for hydrogel applications where a paste-like behavior is desired in the hydrogel precursor solution

Interactive effects of temperature and nitrogen on the physiology of kelps (Nereocystis luetkeana and Saccharina latissima)

Kelp forest declines have been linked to warming ocean temperatures worldwide. Ocean warming rarely occurs in isolation, so multiple stressor studies are necessary to understand the physiological responses of kelp to climate change. The canopy-forming bull kelp, Nereocystis luetkeana, is going locally extinct in areas of the Salish Sea that are seasonally warm and nutrient poor, while the understory kelp, Saccharina latissima, persists at those sites. Further, nitrogen availability can alter physiological responses of kelps to temperature stress, including alleviating warming stress. We compared the physiological responses of kelp sporophytes to high temperature stress and nitrogen limitation between two populations of N. luetkeana with different environmental histories (warm and nutrient poor vs. cold and nutrient rich) and between two species, N. luetkeana and S. latissima. Using laboratory mesocosms, we tested the interactive effects of short term (8-9 day) exposure of kelp blades to different temperatures: low (9, 13°C), moderate (15, 16°C), and warm (21°C) at two different nitrogen concentrations: low (1-3 μM) vs. high (>10 μM). We examined a wide array of physiological responses: blade growth, photosynthesis, respiration, photosynthetic yield, nutrient uptake, and tissue C:N. Both kelp species responded negatively to elevated temperatures, but not to low nitrogen levels. Blades of both species showed signs of metabolic stress and reduced growth in the warmest temperature treatment (21°C), at both high and low nitrogen levels, suggesting that N. luetkeana and S. latissima are susceptible to thermal stress over short time periods. Populations of N. luetkeana from warm, nutrient poor and cool, nutrient rich areas were equally susceptible to the effects of ocean warming. Our results suggest that nutrient additions may actually reduce kelp performance at supra-optimal temperatures, and a thorough understanding of kelp responses to coastal temperature and nutrient dynamics is needed to guide conservation and restoration actions

Importance of the Active Site "Canopy" Residues in an O_2-Tolerant [NiFe]-Hydrogenase

The active site of Hyd-1, an oxygen-tolerant membrane-bound [NiFe]-hydrogenase from Escherichia coli, contains four highly conserved residues that form a “canopy” above the bimetallic center, closest to the site at which exogenous agents CO and O_2 interact, substrate H_2 binds, and a hydrido intermediate is stabilized. Genetic modification of the Hyd-1 canopy has allowed the first systematic and detailed kinetic and structural investigation of the influence of the immediate outer coordination shell on H_2 activation. The central canopy residue, arginine 509, suspends a guanidine/guanidinium side chain at close range above the open coordination site lying between the Ni and Fe atoms (N–metal distance of 4.4 Å): its replacement with lysine lowers the H_2 oxidation rate by nearly 2 orders of magnitude and markedly decreases the H_2/D_2 kinetic isotope effect. Importantly, this collapse in rate constant can now be ascribed to a very unfavorable activation entropy (easily overriding the more favorable activation enthalpy of the R509K variant). The second most important canopy residue for H_2 oxidation is aspartate 118, which forms a salt bridge to the arginine 509 headgroup: its mutation to alanine greatly decreases the H_2 oxidation efficiency, observed as a 10-fold increase in the potential-dependent Michaelis constant. Mutations of aspartate 574 (also salt-bridged to R509) to asparagine and proline 508 to alanine have much smaller effects on kinetic properties. None of the mutations significantly increase sensitivity to CO, but neutralizing the expected negative charges from D118 and D574 decreases O_2 tolerance by stabilizing the oxidized resting Ni^(III)–OH state (“Ni-B”). An extensive model of the catalytic importance of residues close to the active site now emerges, whereby a conserved gas channel culminates in the arginine headgroup suspended above the Ni and Fe

Restoring Rivers One Reach at a Time: Results from a Survey of U.S. River Restoration Practitioners

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72915/1/j.1526-100X.2007.00244.x.pd