Search

Abstract Algal-bacteria high-rate ponds represent an energy-efficient wastewater treatment approach and a source for affordable and sustainable biomass feedstock for production of renewable energy through anaerobic digestion (AD). However, there is still a need for more data on wastewater treatment efficiency, biomass productivity and settleability from outdoor treatment facilities, as well as on impact of variability in biomass composition and digestibility on methane yield and energy output. Hydraulic retention time (HRT) and wastewater quality fed into 30 m2 raceway ponds had a major effect on algal-bacteria polyculture productivity, settleability, phylogenetic and biochemical compositions, digestibility and methane yield. While Micractinium , Scenedesmus , Chlorella , and pennate diatoms were always among the key species observed, the gross productivity and 2-hour settleability during summer cultivation varied in the first-stage ponds treating primary wastewater from 29 ± 5 to 54 ± 12 g AFDW /m2/d and from 88 ± 8 to 94 ± 4% for HRT of 3 and 2 days, respectively. For these conditions, the effluent had csBOD of 3.4 or 3.3 mg/L and N total (mostly NO 3 −-N) of 9.2 or 8.2 mg/L, respectively. The second-stage algal ponds (HRT 3 days) showed lower productivity of 16 ± 6 g AFDW /m2/d, settleability of 84 ± 11%, and effluent csBOD 3.7 mg/L and N total 0.8 mg/L. Biomass composition from different ponds was 34–38% protein, 18–28% total lipids and 6–14% FAME. The methane yield varied about 30% with largest value of 0.34 ± 0.01 L/gVS and showed a positive correlation with biomass lipid content (R2 = 0.93). First-order and pseudo-parallel first-order rate kinetic models exhibited a better fit for methane production (most R2 > 0.993) than the modified Gompertz model. The variation in biomass composition led to significant differences in energy output (varied by about 60%), Net Energy Ratios (ranged from 1.6 to 2.2) and Net Energy Efficiency (from 60% to 70%) when projecting the energy balance for a large-scale continuous AD process with an optimal HRT of 20–30 days. Graphical abstract Unlabelled Image Highlights • Pond residence time (HRT) and water quality affected productivity and settleability. • 2 days HRT provided superior biomass productivity and settleability than 3 days HRT. • 1-Stage pond system provided same organic C but lower N removal than 2-stage ponds. • CH 4 yield from biomass from different ponds varied ~30% (max value 0.34 ± 0.01 L/gVS). • Net Energy Output varied by 60% and Net Energy Ration ranged from 1.6 to 2.5. [ABSTRACT FROM AUTHOR]

Scale-up of microalgal biofuel technology is challenged by availability of nitrogen and phosphorus fertilizers and the potential negative impact vast increases in chemical fertilizer demand would have on conventional agriculture. The current study investigated replacement of chemical fertilizers with nutrients sourced from primary and secondary wastewater effluents and anaerobic digestion centrate (ADC). Although primary wastewater effluent possessed a high optical density (OD) and bacterial contamination, it was a superior growth medium for microalgal cultivation than nutrient-scarce secondary effluent. Chlorella sorokiniana and Scenedesmus acutus f. alternans showed higher growth rates, productivities, and robustness than other species or poly-cultures of five species. While supplementing with 5–10% nutrient-rich ADC increased wastewater OD, it also enhanced microalgal growth rates from 0.2–0.3 d − 1 to 0.7–0.9 d − 1 and biomass productivity from 10 to 20 mg L − 1 d to 40–60 mg L − 1 d with greater improvements for secondary effluents. Supplementation with ADC also increased nutrient concentrations (N, P, Mn, B, Zn, Co by > 100% and S, Mg, Ca, Mo by 20–60%) and improved the nitrogen to phosphorus (N:P) ratio. Higher ADC dose of 20% inhibited microalgae growth potentially due to ammonia toxicity. Elevation of inoculum doses and light intensity increased final biomass density and productivity, with intensities < 140 μmol photon m − 2 s − 1 limiting algal growth rates. Inoculum doses of ≥ 2.5 × 10 5 cell mL − 1 were most favorable for cultivation of all tested microalgae and for FAME content and composition for a newly characterized strain of Chlorella sorokiniana . Overall, ADC represents an economical fertilizer substitute providing various nutrients needed for microalgal growth and enhancing biofuel sustainability. [ABSTRACT FROM AUTHOR]

The modern world is highly dependent on energy. Biodiesel is recognized as a green and alternative renewable diesel fuel, and Brazil is the world׳s third largest producer of biodiesel, which in this country is mainly produced from soybeans. As the demand for biodiesel is increasing due to the increasing use of transportation fuel, it is advisable to look for other sources that would not need a vast cropland. Recently, microalgae have emerged as a source than can play the dual role of bioremediation of wastewater and generation of biomass for biodiesel production. This paper focuses on the feasibility of utilizing wastewater to cultivate algae for the production of biodiesel in Brazil. By using only domestic wastewater from 40% of Brazilian municipalities, the production of biodiesel would increase by 21.4%. Moreover, the use of wastewater treatment becomes an economically attractive alternative as the revenue from selling biodiesel overcomes the production costs by at least 10%. As a result, Brazil could easily increase its current biodiesel production and simultaneously amazingly improve its index of sanitation. [ABSTRACT FROM AUTHOR]

Traveling bacterial waves are capable of improving contaminant remediation in the subsurface. It is fairly well understood how bacterial chemotaxis and growth separately affect the formation and propagation of such waves. However, their interaction is not well understood. We therefore perform a modeling study to investigate the coupled effects of chemotaxis and growth on bacterial migration, and examine their effects on contaminant remediation. We study the waves by using different initial electron acceptor concentrations for different bacteria and substrate systems. Three types of traveling waves can occur: a chemotactic wave due to the biased movement of chemotactic bacteria resulting from metabolism-generated substrate concentration gradients; a growth/decay/motility wave due to a dynamic equilibrium between bacterial growth, decay and random motility; and an integrated wave due to the interaction between bacterial chemotaxis and growth. Chemotaxis hardly enhances the bacterial propagation if it is too weak to form a chemotactic wave or its wave speed is less than half of the growth/decay/motility wave speed. However, chemotaxis significantly accelerates bacterial propagation once its wave speed exceeds the growth/decay/motility wave speed. When convection occurs, it speeds up the growth/decay/motility wave but slows down or even eliminates the chemotactic wave due to the dispersion. Bacterial survival proves particularly important for bacterial propagation. Therefore we develop a conceptual model to estimate the speed of growth/decay/motility waves. [ABSTRACT FROM AUTHOR]

Abstract: Pharmaceuticals and personal care products (PPCPs) have been detected in bodies of water worldwide, yet their effects on the environment are not fully understood. Recent toxicity studies suggest that mixtures of PPCPs at low concentrations may be detrimental to exposed organisms, highlighting the need to remove PPCPs from wastewater treatment plant effluent before it is discharged to the environment. In this study, the utility of biofilm-based PPCP removal as a means to prevent environmental PPCP contamination was investigated. The removal of 14 PPCPs, each at an initial concentration of 10 μg/L, was studied in laboratory sand columns inoculated with wastewater treatment plant effluent. The examined PPCPs included biosol, biphenylol, p-chloro-m-cresol, p-chloro-m-xylenol, chlorophene, sodium diclofenac, gabapentin, gemfibrozil, 5-fluorouracil, ibuprofen, ketoprofen, naproxen, triclosan, and valproic acid. Ten of the PPCPs were removed by greater than 95% during column passage, while the four other compounds proved more recalcitrant. The effect of the concentration (either 50 or 1000 μg/L) of an easily degradable primary substrate (acetate) supplied along with the mixture of PPCPs was examined. Most of the tested PPCPs were removed consistently by the biofilms regardless of the concentration of acetate, although the extent of removal for three compounds showed dependence on acetate concentration, and two behaved with no reproducible pattern over time. Biofilm protein measurements indicated that the mixture of PPCPs supplied to columns suppressed biofilm growth, suggesting toxicity of the PPCPs to the biofilm communities. This laboratory-scale experiment suggests that biofilm-based water treatment strategies, such as soil aquifer treatment and slow sand filtration, may be well-suited for the removal of many PPCPs from impacted water. [Copyright &y& Elsevier]

Abstract: In-situ reduction of toxic Cr(VI) to nontoxic Cr(III) represents an important natural attenuation process for Cr(VI)-impacted environments. This study investigates the stoichiometry and kinetics of Cr(VI) reduction by pyrite, a reduced iron–sulfur mineral ubiquitous in recent estuarine and marine sediments. Pyrite suspensions at surface loadings of 0.28–2.10m2/L (typical of estuarine or marine sediments) were capable of completely reducing 7–120μM Cr(VI) on the timescale of minutes to days, with the time to reaction completion decreasing with increasing pyrite loading, decreasing initial Cr(VI) concentration, and decreasing suspension pH. Analysis of metal species (Cr and Fe) and sulfur species in solution and at the mineral surface indicated that Cr(VI) oxidatively dissolved the pyrite surface, releasing ferrous iron and sulfate into solution as the reaction progressed. Surface disulfide groups were postulated as the Cr(VI)-reactive surface entity. Net production or consumption of aqueous Fe(II) was shown to depend upon the relative rates of proton-promoted Fe(II) release, Fe(II) release due to oxidative dissolution of pyrite in the presence of Cr(VI), and Fe(II) consumption due to homogeneous reaction with Cr(VI). Kinetics of Cr(VI) reduction by pyrite displayed a biphasic pattern, and the time to reaction completion increased dramatically with increasing initial Cr(VI) concentration. Rapid Cr(VI) removal occurred early in the reaction progress, attributable to Cr(VI) loss under an adsorption-limited regime. Slow, approximately zero-order, Cr(VI) removal occurred over the bulk of the time courses, and corresponded to Cr(VI) removal under surface site saturation conditions. Stoichiometric Cr(VI) reduction was able to proceed under surface site limited conditions owing to regeneration of reactive surface sites following desorption/dissolution of oxidized surface products, as demonstrated in repeat Cr(VI)-spiking experiments. The role of surface passivation was evaluated by comparing rates of Cr(VI) reduction in the presence and absence of the Cr(III)-complexing agent citrate. While citrate addition significantly enhanced Cr(III) solubility, rates of Cr(VI) reduction were only marginally accelerated, suggesting that Cr(OH)3(s) coatings did not completely block access of Cr(VI) to reactive surface sites on pyrite. Given the rapid rates of Cr(VI) reduction with pyrite under pH and surface coverage conditions typical of natural environments, we propose that Cr(VI) reduction by pyrite be considered in fate and transport models for Cr in contaminated sediments. [Copyright &y& Elsevier]

Abstract: Treated drinking water samples from 12 water utilities in the Midwestern United States were collected during Fall 2003 and Spring 2004 and were analyzed for selected neutral degradates of chloroacetamide herbicides, along with related compounds. Target analytes included 20 neutral chloroacetamide degradates, six ionic chloroacetamide degradates, four parent chloroacetamide herbicides, three triazine herbicides, and two neutral triazine degradates. In the fall samples, 17 of 20 neutral chloroacetamide degradates were detected in the finished drinking water, while 19 of 20 neutral chloroacetamide degradates were detected in the spring. Median concentrations for the neutral chloroacetamide degradates were ∼2–60ng/L during both sampling periods. Concentrations measured in the fall samples of treated water were nearly the same as those measured in source waters, despite the variety of treatment trains employed. Significant removals (average of 40% for all compounds) were only found in the spring samples at those utilities that employed activated carbon. [Copyright &y& Elsevier]

Abstract: Recent studies have revealed the presence of neutral degradates of chloroacetamide herbicides in the Chesapeake Bay at concentrations greatly in excess of the parent compounds. As some degradates are being considered for regulation in drinking water, exposure of human populations to such micropollutants is of interest. Here we report the results of a survey of source waters used by 12 drinking water utilities in the Midwestern United States. Analytes included 20 neutral and six ionic chloroacetamide degradates, four parent chloroacetamide herbicides, three triazine herbicides, and two triazine degradates. Samples were collected during Fall 2003 and Spring 2004. In the fall samples, 16 of 20 neutral chloroacetamide degradates were detected, while 18 of 20 neutral chloroacetamide degradates were detected in the spring samples. Concentrations of most parent chloroacetamides and neutral degradates were somewhat to substantially higher in the spring than in the fall, with median concentrations of ∼10–100 ng/L. Groundwater sources tended to have lower concentrations of parents and neutral degradates than surface water sources in the fall, although concentrations of parents and degradates in groundwater were similar to those in surface water in the spring. [Copyright &y& Elsevier]

Abstract: It is important to determine the behavior of constituents in treated sewage during soil aquifer treatment for water recycling. A collaborative project with Herman Bouwer published in 1984 documented the fate and occurrence of Priority Pollutants during groundwater recharge using wastewater with application to water reuse and agricultural systems. New compounds are continually being manufactured and released to the environment. The interest today has shifted to the behavior of emerging contaminants. One important class of emerging contaminants is pharmaceuticals and personal care products (PPCPs). The hazards to the environment and human health of trace levels of PPCPs in water supplies are poorly understood. A multi compound method using solid phase extraction and chemical derivatization with pentafluorobenzylbromide, followed by analysis via gas chromatography/mass spectrometry was used to study the occurrence and removals of 18 PPCPs in a local wastewater treatment plant (WWTP). Overall, 16 out of the 18 selected PPCPs, which span a range of therapeutic classes and some commonly used personal care products, were detected in raw sewage samples collected from the Baltimore Back River WWTP. Ten of the 18 selected PPCPs were detected in the treated sewage effluent, signifying incomplete removal for the majority of the PPCPs during the wastewater treatment processes. The majority of the target analytes were detected in both the influent and effluent WWTP samples at μg/L levels, although some PPCPs (e.g., naproxen and ibuprofen) were encountered at μg/L levels. Biodegradation is an important process for wastewater and soil aquifer treatment. Aerobic batch biodegradation (using activated sludge as microbial inocula) experiments were conducted to gain insight into the biodegradation behavior of our target PPCPs at initial concentrations of 50, 10, and 1μg/L. Sterile control studies showed no loss of our target PPCPs during the entire incubation period, and sorption to the biomass was found to be negligible for all testing conditions. Biodegradation results were not sensitive to the initial concentration and showed that 13 of the 18 PPCPs tested exhibited biotransformations greater than 80% after 50 days of incubation. Phenytoin, 5-fluorouracil, and diclofenac were the only three compounds with removals less than 60%. The occurrence study revealed the presence of PPCPs in sewage effluents, and the biodegradation study suggests that biotransformation is a possible removal mechanism for PPCPs during groundwater recharge or soil aquifer treatment for water recycling. [Copyright &y& Elsevier]

Abstract: Directly adjacent to the Chesapeake Bay lies the Aberdeen Proving Ground, a U.S. Army facility where testing of armor-piercing ammunitions has resulted in the deposition of >70,000kg of depleted uranium (DU) to local soils and sediments. Results of previous environmental monitoring suggested limited mobilization in the impact area and no transport of DU into the nation''s largest estuary. To determine if physical and biological reactions constitute mechanisms involved in limiting contaminant transport, the sorption and biotransformation behavior of the radionuclide was studied using geochemical modeling and laboratory microcosms (500ppb U(VI) initially). An immediate decline in dissolved U(VI) concentrations was observed under both sterile and non-sterile conditions due to rapid association of U(VI) with natural organic matter in the sediment. Reduction of U(VI) to U(IV) occurred only in non-sterile microcosms. In the non-sterile samples, intrinsic bioreduction of uranium involved bacteria of the order Clostridiales and was only moderately enhanced by the addition of acetate (41% vs. 56% in 121 days). Overall, this study demonstrates that the migration of depleted uranium from the APG site into the Chesapeake Bay may be limited by a combination of processes that include rapid sorption of U(VI) species to natural organic matter, followed by slow, intrinsic bioreduction to U(IV). [Copyright &y& Elsevier]

Abstract: Eighteen models with different levels of complexity for representing sorption, mass transfer, and biodegradation are used to simulate the biodegradation of toluene (primary substrate) and TCE (cometabolic substrate). The simulations are conducted for hypothetical completely mixed systems of various scenarios with regard to sorbent, microbial composition, and solute concentrations. The purpose of the suite of simulations is to investigate the sensitivity of different modeling approaches in simulating the bio-attenuation of co-existing solutes in sorbent-water systems. The sensitivity of results to the modeling approach depends on the biogeochemical conditions of the system. For example, the results are insensitive to the type of sorption model in systems with low sorption strength and slow biodegradation rates, and insensitive to the biodegradation rate model if mass transfer controlled. Differences among model results are generally greater when evaluated in terms of total mass removal rather than aqueous phase concentration reduction. The fate of the cometabolite is more sensitive to the proper consideration of co-solute effects than is the fate of the primary substrate. For a given system, graphical comparison of a characteristic mass transfer rate coefficient (α mt) versus a characteristic biodegradation rate coefficient (α bio) provides an indication of how sensitivity to the different processes may be expected to change with time and can guide the selection of an appropriate level of model complexity. [Copyright &y& Elsevier]

Abstract: Microbial monitoring was conducted over a period of more than 1year at three full-scale riverbank filtration (RBF) facilities, located in the United States along the Ohio, Missouri, and Wabash Rivers. Results of this study demonstrated the potential for RBF to provide substantial reductions in microorganism concentrations relative to the raw water sources. Cryptosporidium and Giardia were detected occasionally in the river waters but never in any of the well waters. Average concentrations and log reductions of Cryptosporidium and Giardia could not be accurately determined due to the low and variable concentrations in the river waters and the lack of detectible concentrations in the well waters. Average concentrations of aerobic and anaerobic spore-forming bacteria, which have both been proposed as potential surrogates for the protozoans, were reduced at the three facilities by 0.8 to >3.1 logs and 0.4 to >4.9 logs, respectively. Average concentrations of male-specific and somatic bacteriophage were reduced by >2.1 logs and ⩾3.2 logs, respectively. Total coliforms were rarely detected in the well waters, with 5.5 and 6.1 log reductions in average concentrations at the two wells at one of the sites relative to the river water. Average turbidity reductions upon RBF at the three sites were between 2.2 and 3.3 logs. Turbidity and microbial concentrations in the river waters generally tracked the river discharge; a similar relationship between the well water concentrations and river discharge was not observed, due to the low, relatively constant well water turbidities and lack of a significant number of detections of microorganisms in the well waters. Further research is needed to better understand the relationships among transport of pathogens (e.g., Cryptosporidium, Giardia, viruses) and potential surrogate parameters (including bacterial spores and bacteriophage) during RBF and the effects of water and sediment characteristics on removal efficiency. [Copyright &y& Elsevier]

Effects of H2O2 dosage (0, 10, 50, 100 and 300 mg/l), reaction pH (11.9, 6.5 and 2.5) and initial color intensity (85, 80 and 60 color unit) on decolorization of alkaline 2,4,6-trinitrotoluene (TNT) hydrolysis effluents were investigated at a fixed UV strength (40 W/m2). Results indicated that UV/H2O2 oxidation could efficiently achieve decolorization and further mineralization. Pseudo first-order decolorization rate constants, k, ranged between 2.9 and 5.4 h−1 with higher values for lower H2O2 dosage (i.e., 10 mg/l H2O2) when the decolorization occurred at the reaction pH of 11.9, whereas a faster decolorization was achieved with increase in H2O2 dosage at both pH 6.5 and 2.5, resulting in the values of k as fast as 15.4 and 26.6 h−1 with 300 mg/l H2O2 at pH 6.5 and 2.5, respectively. Difference in decolorization rates was attributed to the reaction pH rather than to the initial color intensity, resulting from the scavenging of hydroxyl radical by carbonate ion. About 40% of spontaneous mineralization was achieved with addition of 10 mg/l H2O2 at pH 6.5. Efficient decolorization and extension of H2O2 longevity were observed at pH 6.5 conditions. It is recommended that the colored effluents from alkaline TNT hydrolysis be neutralized prior to a decolorization step. [Copyright &y& Elsevier]

Inactivation of Klebsiella pneumoniae cultures by chlorine and chloramine was evaluated under different growth conditions by varying nutrient media dilution, concentrations of essential inorganic nutrients (FeCl3, MgSO4, phosphate, and ammonium salts), and temperature. All inactivation assays were performed at room temperature (22–23°C) and near neutral pH (7.2–7.5). C*T99.9 values for chlorine increased >20-fold and for chloramine increased 2.6-fold when cells were grown in 100-fold diluted nutrient broth (2NB) solutions (final TOC of 35–40 mg/L). Background levels of Mg: 6.75×10−2 mM and Fe: 3.58×10−5 mM or high levels of FeCl3 (0.01 mM) and MgSO4 (1 mM) during growth resulted in the highest resistances to chlorine with C*T99.9 values of 13.06 (±0.91) and 13.78 (±1.97) mg-min/L, respectively. Addition of low levels of FeCl3 (0.001 mM) and MgSO4 (0.1 mM) to K. pneumoniae cultures during growth resulted in the lowest bacterial resistances to inactivation; C*T99.9 values ranged from 0.28 (±0.06) to 1.88 (±0.53) mg-min/L in these cultures. Increase in growth temperature from 22.5°C to 35°C for unamended 2NB cultures resulted in a 42-fold decrease in C*T99.9 values for chlorine. A similar change in temperature resulted in no significant change in C*T99.9 values for chloramine. These results indicate that inactivation of K. pneumoniae cultures by chlorine was highly sensitive to changes in growth conditions unlike inactivation by chloramine. [Copyright &y& Elsevier]

Highlights: [•] Anaerobic digestion of microalgae can be hampered by low biodegradability. [•] We examined the effect of pretreatment on algal solubilization and methane yields. [•] Chemical or thermal pretreatments were ineffective on methane yield. [•] Thermochemical pretreatment improved methane yield by 30–40% from specific species. [•] Algal type and the cell-wall nature strongly impacts on biogas and methane yields. [ABSTRACT FROM AUTHOR]

Abstract: Four chloroacetamide herbicides and 20 neutral chloroacetamide derivatives (known to occur as their environmental degradates) were subjected to simulated drinking water treatment (coagulation, oxidation and adsorption). Coagulation with alum and ferric chloride, at doses for optimum turbidity removal, provided little to no (<10%) removal of parent herbicides or neutral degradates. Chlorination with 6mg/L applied free chlorine for 6h was able to achieve 100% removal of those degradates lacking an acetanilide substituent; compounds possessing this functional group exhibited low (0–16%) removal efficiencies. Products were generally not identified, except in the case of dimethenamid and its deschloro degradate, both of which formed a single ring-chlorination product on their ready reaction (84% and 96% removal, respectively) with aqueous chlorine species. Treatment with ozone at an applied dose of 3mg/L for 30min proved effective (60–100%) at transforming all of the compounds under investigation to unidentified products. The parent herbicides and neutral degradates underwent adsorption by powdered activated carbon (PAC). Adsorption capacities (Freundlich K constants) correlated with K ow values. [Copyright &y& Elsevier]

Abstract: This study was conducted to assess the applicability of alkaline hydrolysis as an alternative ex situ technology for remediating 2,4,6-trinitrotoluene (TNT)-contaminated water. TNT reactivity had a strong dependence on the reaction pH (11–12) and initial TNT (5–25mgL−1) in batch systems, resulting in pseudo first-order transformation rate, k ranging between 1.9×10−3 and 9.3×10−5 min−1. In continuous flow stirred-tank reactor (CFSTR) systems with initial TNT of 1mgL−1, the highest 74% of TNT reduction was achieved at the reaction pH of 11.9 and 2-day hydraulic retention time under steady-state condition. Oxalate was produced as the major hydrolysate in the CFSTRs, indicating a ring cleavage during alkaline hydrolysis. It was also believed that TNT alkaline hydrolysis occurred through the production of color-forming intermediates via dimerization. It is concluded that alkaline hydrolysis can be an alternative treatment technology for remediation of TNT-contaminated water. [Copyright &y& Elsevier]

Abstract The feasibility of generating a lipid-containing algal-bacterial polyculture biomass in municipal primary wastewater and enhancing biomethanation of lipid-extracted algal residues (LEA) through hydrothermal pretreatment and co-digestion with sewage sludge (SS) was investigated. In high-rate algal ponds, the polyculture of native algal and bacteria species demonstrated a monthly average net and gross biomass productivity of 30 ± 3 and 36 ± 3 g AFDW m−2 day−1 (summer season). The algal community was dominated by Micractinium sp. followed by Scenedesmus sp., Chlorella sp., pennate diatoms and Chlamydomonas sp. The polyculture metabolic activities resulted in average reductions of wastewater volatile suspended solids (VSS), carbonaceous soluble biochemical oxygen demand (csBOD 5) and total nitrogen (N total) of 63 ± 18%, 98 ± 1% and 76 ± 21%, respectively. Harvested biomass contained nearly 23% lipid content and an extracted blend of fatty acid methyl esters satisfied the ASTM D6751 standard for biodiesel. Anaerobic digestion of lipid extracted algal residues (LEA) demonstrated long lag-phase in methane production of 17 days and ultimate methane yield of 296 ± 2 mL/gVS (or ~50% of theoretical), likely because to its limited biodegradability and toxicity due to presence of the residual solvent (hexane). Hydrothermal pretreatment increased the ultimate methane yield and production rate by 15–30% but did not mitigate solvent toxicity effects completely leading to less substantial improvement in energy output of 5–20% and diminished Net Energy Ratio (NER < 1). In contrast, co-digestion of LEA with sewage sludge (10% to 90% ratio) was found to minimize solvent toxicity and improve methane yield enhancing the energy output ~4-fold, compared to using LEA as a single substrate, and advancing NER to 4.2. Graphical abstract Unlabelled Image Highlights • Average net and gross algal biomass productivity reached 30 ± 3 and 36 ± 3 g AFDW m-2 day-1. • Ultimate methane yield from LEA reached 296 ± 2 mL gVS-1 with lag-phase of 17 days. • Hexane solvent residue was responsible for LEA toxicity and methanogens inhibition. • HydroThermal treatment increased methane yield but did not mitigate solvent toxicity. • Co-digestion LEA with sewage sludge alleviated inhibition and enhance methane yield. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Optimal algae to cellulose ratios were 35%:65% and 20%:80% (volatile solids based). • Synergy resulted in enhancing the ten days cumulative methane yield up to 100%. • Co-digestion reduced time-lag by 50% and increased methane production rate by 35%. • Modified Gompertz kinetic model offered superior methane production description. • Co-digestion boosted the Energy Output and NER by 30–45% depending on the HRT. Abstract This study investigated enhancing methane production from algal-bacteria biomass by adjusting the C/N ratio through co-digestion with a nitrogen-poor co-substrate – cellulose. A biomethane potential test was used to determine cumulative biogas and methane production for pure and co-digested substrates. Four kinetic models were evaluated for their accuracy describing experimental data. These models were used to estimate the total energy output and net energy ratio (NER) for a scaled AD system. Increasing the algal C/N ratio from 5.7 to 20–30 (optimal algae:cellulose feedstock ratios of 35%:65% and 20%:80%) improved the ultimate methane yield by >10% and the first ten days production by >100%. The modified Gompertz kinetic model demonstrated highest accuracy, predicting that co-digestion improved methane production by reducing the time-lag by ∼50% and increasing rate by ∼35%. The synergistic effects increase the AD system energy efficiency and NER by 30–45%, suggesting potential for substantial enhancements from co-digestion at scale. [ABSTRACT FROM AUTHOR]

The properties and commercial viability of biodegradable polymers can be significantly enhanced by the incorporation of carbon nanotubes (CNTs). The environmental impact and persistence of these carbon nanotube/polymer nanocomposites (CNT/PNCs) after disposal will be strongly influenced by their microbial interactions, including their biodegradation rates. At the end of consumer use, CNT/PNCs will encounter diverse communities of microorganisms in landfills, surface waters, and wastewater treatment plants. To explore CNT/PNC biodegradation under realistic environmental conditions, the effect of multi-wall CNT (MWCNT) incorporation on the biodegradation of polyhydroxyalkanoates (PHA) was investigated using a mixed culture of microorganisms from wastewater. Relative to unfilled PHA (0% w/w), the MWCNT loading (0.5–10% w/w) had no statistically significant effect on the rate of PHA matrix biodegradation. Independent of the MWCNT loading, the extent of CNT/PNC mass remaining closely corresponded to the initial mass of CNTs in the matrix suggesting a lack of CNT release. CNT/PNC biodegradation was complete in approximately 20 days and resulted in the formation of a compressed CNT mat that retained the shape of the initial CNT/PNC. This study suggests that although CNTs have been shown to be cytotoxic towards a range of different microorganisms, this does not necessarily impact the biodegradation of the surrounding polymer matrix in mixed culture, particularly in situations where the polymer type and/or microbial population favor rapid polymer biodegradation. [ABSTRACT FROM AUTHOR]

An integrated system was implemented for water phytoremediation and biofuel production through sequential cultivation of filamentous algae followed by cultivation of lipid-producing microalgae Chlorella sorokiniana . Natural poly-culture of filamentous algae was grown in agricultural stormwater using the Algal Turf Scrubber®, harvested and subjected for lipid extraction and/or methane production using anaerobic digestion (AD). While filamentous algae lipid content was too low for feasible biodiesel production (<2%), both whole biomass and lipid-extracted algal residues (LEA) yielded ∼0.2 L methane per gVS at loading rates up to 5 g VS/L-day. Importantly, essential macro-nutrients and trace elements captured from stormwater were released into the AD effluent as soluble nutrients and were successfully tested as fertilizer replacement for cultivation of lipid-accumulating C. sorokiniana in a subsequent stage. Accordingly, filamentous algae poly-culture was exploited for waste nutrient capturing and biofuel feedstock generation. These nutrients were recovered and reused as a concentrated supplement for potentially high-value microalgae. [ABSTRACT FROM AUTHOR]

Sustainable mass production of algal biofuels requires a reduction in nutrient demand and efficient conversion into fuels of all biomass including lipid-extracted algal residues (LEA). This study evaluated methane production, nutrient recovery and recycling from untreated and enzymatically pretreated Nannochloropsis LEA using semi-continuous anaerobic digestion (AD). Additionally, this process was compared to methane generation from whole Nannochloropsis alga (WA) and thermally pretreated WA. The methane production from untreated LEA and WA reached up to 0.22 L and 0.24 L per gram of biomass volatile solids (VS), respectively, corresponding to only 36–38% of the theoretical potential. Additionally, observed VS reduction was only 40–50% confirming biomass recalcitrance to biodegradation. While enzymatic treatment hydrolyzed up to 65% of the LEA polysaccharides, the methane production increased by only 15%. Alternatively, WA thermal pretreatment at 150–170 °C enhanced methane production up to 40%. Overall, an integrated process of lipid conversion into biodiesel coupled with LEA conversion into methane generates nearly 40% more energy compared to methane production from WA, and about 100% more energy than from biodiesel alone. Additionally, the AD effluent contained up to 60–70% of the LEA phosphorus content, 30–50% of the nitrogen, sulfur, calcium and boron, 20% of the iron and cobalt, and 10% of manganese, zinc and copper, which can partially replace chemical fertilizers during algal cultivation. Consequently, supplementation of Nannochloropsis cultures with 5% AD effluent was optimal for a high algal growth rate. Therefore, coupling biodiesel and methane production provides significant energy advantages along with sustainability and economic benefits from nutrient recycling. [ABSTRACT FROM AUTHOR]

This study evaluated methane production and nutrient recovery from industrially produced, lipid extracted algal biomass (LEA) of Auxenochlorella protothecoides using semi-continuous anaerobic digestion (AD) at different organic loading rates (OLRs) and hydraulic retention times (HRTs). It was shown, that AD can improve biofuel production efficiency and sustainability, especially for scaled processes, through up to 30% increase in energy generation (up to 0.25 L of methane per g of LEA volatile solids) and partial nutrient recovery and recycling. The nutrient recycling with the AD effluent may reduce the cost of the supplied fertilizers by up to 45%. However, methane production was limited to nearly 50% of theoretical maxima potentially due to biomass recalcitrance and inhibition effects from the residual solvent in the LEA. Therefore, further AD optimization is required to maximize methane yield and nutrient recovery as well as investigation and elimination of inhibition from solvent residues. [ABSTRACT FROM AUTHOR]

Abstract: Concentrations of total mercury (Hg) and selenium (Se) were determined in diet fish and whole blood and tissue samples from seven bottlenose dolphins (Tursiops truncatus) housed at the National Aquarium Baltimore (NAB). In addition, concentrations of monomethylmercury (CH3Hg+) were determined in diet fish and dolphins'' tissue samples. The data were compared with the values found in wild populations to better understand how the dietary Hg and Se uptake rates affect the Hg and Se levels in dolphins. The diet fish total Hg concentrations ranged between 14 and 47ngg−1 and were markedly lower than for similar fish found in Florida, South Carolina, and other aquaria. CH3Hg+ accounted for 85 to 91% of the total Hg found in diet fish. The diet fish Se concentrations ranged between 270 and 800ngg−1, indicating excess molar concentrations of Se over Hg. The Hg concentration range in the blood of NAB dolphins was 27–117ngg−1 and the concentrations were about one order of magnitude and several factors lower than the concentrations found in the blood of wild bottlenose dolphins in Florida and in South Carolina, respectively. The total Hg and CH3Hg+ in tissue samples were also significantly lower than the reported values obtained from wild populations of bottlenose dolphins. The differences in the Hg concentrations in the dolphins'' blood may be due to the different levels of Hg atmospheric deposition in the area where the dolphins'' diet fish were found. The Se concentration range in the blood of NAB dolphins was 221–297ngg−1 which was two factors lower than the values found in wild populations. The lower Hg levels, as well as higher Se:Hg molar ratios in the blood of NAB dolphins, suggest that NAB dolphins may be less susceptible to the potential neurotoxicity from the CH3Hg+ in their blood. [Copyright &y& Elsevier]

The interaction of anaerobic microorganisms with carbon nanotube/polymer nanocomposites (CNT/PNC) will play a major role in determining their persistence and environmental fate at the end of consumer use when these nano-enabled materials enter landfills and encounter wastewater. Motivated by the need to understand how different parameters (i. e., polymer type, microbial phenotype, CNT characteristics) influence CNT/PNC biodegradation rates, we have used volumetric biogas measurements and kinetic modeling to study biodegradation as a function of polymer type and CNT properties. In one set of experiments, oxidized multiwall carbon nanotubes (O-MWCNTs) with a range of CNT loadings 0–5% w/w were incorporated into poly-ε-caprolactone (PCL) and polyhydroxyalkanoates (PHA) matrices and subjected to biodegradation by an anaerobic microbial community. For each CNT/PNC, complete polymer biodegradation was ultimately observed, although the rate of biodegradation was inhibited above certain critical CNT loadings dependent upon the polymer type. Higher loadings of pristine MWCNTs were needed to decrease the rate of polymer biodegradation compared to O-MWCNTs, an effect ascribed principally to differences in CNT dispersion within the polymer matrices. Above certain CNT loadings, a CNT mat of similar shape to the initial PNC was formed after polymer biodegradation, while below this threshold, CNT aggregates fragmented in the media. In situations where biodegradation was rapid, methanogen growth was disproportionately inhibited compared to the overall microbial community. Analysis of the results obtained from this study indicates that the inhibitory effect of CNTs on polymer biodegradation rate is greatest under conditions (i. e., polymer type, microbial phenotype, CNT dispersion) where biodegradation of the neat polymer is slowest. This new insight provides a means to predict the environmental fate, persistence, and transformations of CNT-enabled polymer materials. Unlabelled Image • Polymer matrices of MWCNT polymer nanocomposites (PNC) were biodegraded using an anaerobic microbial community • Mineralization of polymer is slowed by CNT inclusion in polyhydroxyalkanoates and polycaprolactone but is not prevented • Oxidation improves dispersion of CNTs in polymer but decreases rate of polymer loss at lower loadings than pristine CNTs • For polymers with high CNT loadings a residual CNT mat exists after polymer biodegradation reducing CNT transport • Methanogenic microbes are particularly affected by CNTs incorporated into rapidly biodegraded polymer • Influence of CNTs on polymer biodegradation is greatest when polymer loss is slow [ABSTRACT FROM AUTHOR]

• Heavy metals in water accumulate within sediments that alter their behavior. • Manganese is a watershed contaminant associated with Parkinsonism in mammals. • Manganese sediment interaction does not alter total manganese in drinking water. • Manganese sediment interaction reduced motor impairment in mice exposed via drinking water. Heavy metals enter the aquatic environment and accumulate within water sediments, but these metal-sediment interactions remain to be explored within toxicity studies. We developed an exposure model in mice that encapsulates the aquatic microenvironment of metals before exposure. Male and female C57/BL6 mice were exposed via their drinking water to manganese contaminated sediment (Sed_Mn) or to manganese without sediment interaction (Mn) for six weeks. Sediment interaction did not alter weekly manganese ingestion from water in males or females. We analyzed motor impairment, a common feature in manganese-induced Parkinsonism, using the beam traversal, cylinder, and accelerating rotarod tests. Sed_Mn mice performed better overall compared to Mn mice and males were more sensitive to manganese than females in both Sed_Mn and Mn treatment groups. Our study indicates that metal-sediment interactions may alter metal toxicity in mammals and introduces a new exposure model to test the toxicity of metal contaminants of drinking water. [ABSTRACT FROM AUTHOR]