Temperature, inocula and substrate: Contrasting electroactive consortia, diversity and performance in microbial fuel cells.

The factors that affect microbial community assembly and its effects on the performance of bioelectrochemical systems are poorly understood. Sixteen microbial fuel cell (MFC) reactors were set up to test the importance of inoculum, temperature and substrate: Arctic soil versus wastewater as inoculum; warm (26.5°C) versus cold (7.5°C) temperature; and acetate versus wastewater as substrate. Substrate was the dominant factor in determining performance and diversity: unexpectedly the simple electrogenic substrate delivered a higher diversity than a complex wastewater. Furthermore, in acetate fed reactors, diversity did not correlate with performance, yet in wastewater fed ones it did, with greater diversity sustaining higher power densities and coulombic efficiencies. Temperature had only a minor effect on power density, (Q10: 2 and 1.2 for acetate and wastewater respectively): this is surprising given the well-known temperature sensitivity of anaerobic bioreactors. Reactors were able to operate at low temperature with real wastewater without the need for specialised inocula; it is speculated that MFC biofilms may have a self-heating effect. Importantly, the warm acetate fed reactors in this study did not act as direct model for cold wastewater fed systems. Application of this technology will encompass use of real wastewater at ambient temperatures.

Emergent behaviour in a chlorophenol-mineralising three-tiered microbial 'food web'.

Anaerobic digestion enables the water industry to treat wastewater as a resource for generating energy and recovering valuable by-products. The complexity of the anaerobic digestion process has motivated the development of complex models. However, this complexity makes it intractable to pin-point stability and emergent behaviour. Here, the widely used Anaerobic Digestion Model No. 1 (ADM1) has been reduced to its very backbone, a syntrophic two-tiered microbial 'food chain' and a slightly more complex three-tiered microbial 'food web', with their stability analysed as a function of the inflowing substrate concentration and dilution rate. Parameterised for phenol and chlorophenol degradation, steady-states were always stable and non-oscillatory. Low input concentrations of chlorophenol were sufficient to maintain chlorophenol- and phenol-degrading populations but resulted in poor conversion and a hydrogen flux that was too low to sustain hydrogenotrophic methanogens. The addition of hydrogen and phenol boosted the populations of all three organisms, resulting in the counterintuitive phenomena that (i) the phenol degraders were stimulated by adding hydrogen, even though hydrogen inhibits phenol degradation, and (ii) the dechlorinators indirectly benefitted from measures that stimulated their hydrogenotrophic competitors; both phenomena hint at emergent behaviour.

Anaerobic-aerobic sequencing bioreactors improve energy efficiency for treatment of personal care product industry wastes.

Personal care product (PCP) industry liquid wastes contain shampoo residues, which are usually treated by aerobic activated sludge (AS). Unfortunately, AS is expensive for PCP wastes because of high aeration and energy demands, whereas potentially energy-positive anaerobic designs cannot meet effluent targets. Therefore, combined anaerobic-aerobic systems may be the best solution. Seven treatment systems were assessed in terms of energy and treatment performance for shampoo wastes, including one aerobic, three anaerobic (HUASB, AHR and AnCSTR) and three anaerobic-aerobic reactor designs. COD removals were highest in the HUASB-aerobic (87.9 ± 0.4%) and AHR-aerobic (86.8±0.5%) systems, which used 69.2% and 62.5% less energy than aerobic AS. However, actual methane production rates were low relative to theoretical in the UASB and AHR units (∼10% methane/COD removed) compared with the AnCSTR unit (∼70%). Anaerobic-aerobic sequence reactors show promise for treating shampoo wastes, but optimal designs depend upon whether methane production or COD removal is most important to operations.

Low-energy treatment of colourant wastes using sponge biofilters for the personal care product industry.

Four trickling biofilter designs were assessed as low-energy alternatives to aerobic activated sludge (AS) for the treatment of personal care product industry wastes. The designs included partially submerged packed-media and sponge reactors with and without active aeration. Partial submergence was used to reduce active aeration needs. Simulated colourant wastes (up to COD=12,480 mg/L, TN=128 mg/L) were treated for 201 days, including wastes with elevated oxidant levels. COD and TN removal efficiencies were always >79% and >30% (even without aeration). However, aerated sponge reactors consistently had the highest removal efficiencies, especially for TN (∼60%), and were most tolerant of elevated oxidants. This study shows sponge biofilters have great potential for treating colourant wastes because they achieve high treatment efficiencies and reduce energy use by >40% relative to AS systems.

Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell.

Addressing the need to recover energy from the treatment of domestic wastewater, a 120-L microbial electrolysis cell was operated on site in Northern England, using raw domestic wastewater to produce virtually pure hydrogen gas (100 ± 6.4 %) for a period of over 3 months. The volumetric loading rate was 0.14 kg of chemical oxygen demand (COD) per cubic metre per day, just below the typical loading rates for activated sludge of 0.2-2 kg COD m(-3) day(-1), at an energetic cost of 2.3 kJ/g COD, which is below the values for activated sludge 2.5-7.2 kJ/g COD. The reactor produced an equivalent of 0.015 LH(2)L(-1) day(-1), and recovered around 70 % of the electrical energy input with a coulombic efficiency of 55 %. Although the reactor did not reach the breakeven point of 100 % electrical energy recovery and COD removal was limited, improved hydrogen capture and reactor design could increase the performance levels substantially. Importantly, for the first time, a 'proof of concept' has been made, showing that this technology is capable of energy capture as hydrogen gas from low strength domestic wastewaters at ambient temperatures.

Feasibility tests for treating shampoo and hair colorant wastewaters using anaerobic processes.

Wastes from the personal care product (PCP) industry are often high in biodegradable carbon, which makes them amenable to aerobic biological treatment, although process costs are usually high due to aeration inefficiencies, high electricity demand and production of large amounts of sludge. As such, anaerobic treatment technologies are being considered to lower net energy costs by reducing air use and increasing methane production. To assess the amenability of PCP wastes to anaerobic treatment, methane yields and rates were quantified in different anaerobic reactors treating typical PCP wastes, including wastes from shampoo and hair colorant products. Overall, shampoo wastes were more amenable to methanogenesis with almost double the methane yields compared with colour wastes. To assess relevant microbial guilds, qPCR was performed on reactor biomass samples. Methanosaetaceae abundances were always significantly higher than Methanosarcinaceae and Methanomicrobiales abundances (P < 0.05), and did not differ significantly between waste types. Although colour wastes were less amenable to anaerobic treatment than shampoo wastes, differences cannot be explained by relative microbial abundances and probably result from the presence of inhibiting compounds in hair colorants (e.g., oxidants) at higher levels. Results showed that anaerobic technologies have great potential for treating PCP wastes, but additional work is needed to establish the basis of elevated methane yields and inhibition, especially when colorant wastes are present.

Determination of the internal chemical energy of wastewater.

The wastewater industry is facing a paradigm shift, learning to view domestic wastewater not as a waste stream which needs to be disposed of but as a resource from which to generate energy. The extent of that resource is a strategically important question. The only previous published measurement of the internal chemical energy of wastewater measured 6.3 kJ/L. It has long been assumed that the energy content in wastewater relates directly to chemical oxygen demand (COD). However there is no standard relationship between COD and energy content. In this study a new methodology of preparing samples for measuring the internal chemical energy in wastewater is developed, and an analysis is made between this and the COD measurements taken. The mixed wastewater examined, using freeze-drying of samples to minimize loss of volatiles, had 16.8 kJ/L, while the domestic wastewater tested had 7.6 kJ/L nearly 20% higher than previously estimated. The size of the resource that wastewater presents is clearly both complex and variable but is likely to be significantly greater than previously thought. A systematic evaluation of the energy contained in wastewaters is warranted.

Methanogenic degradation of petroleum hydrocarbons in subsurface environments remediation, heavy oil formation, and energy recovery.

Hydrocarbons are common constituents of surface, shallow, and deep-subsurface environments. Under anaerobic conditions, hydrocarbons can be degraded to methane by methanogenic microbial consortia. This degradation process is widespread in the geosphere. In comparison with other anaerobic processes, methanogenic hydrocarbon degradation is more sustainable over geological time scales because replenishment of an exogenous electron acceptor is not required. As a consequence, this process has been responsible for the formation of the world's vast deposits of heavy oil, which far exceed conventional oil assets such as those found in the Middle East. Methanogenic degradation is also a potentially important component of attenuation in hydrocarbon contamination plumes. Studies of the organisms, syntrophic partnerships, mechanisms, and geochemical signatures associated with methanogenic hydrocarbon degradation have identified common themes and diagnostic markers for this process in the subsurface. These studies have also identified the potential to engineer methanogenic processes to enhance the recovery of energy assets as biogenic methane from residual oils stranded in petroleum systems.

Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO3- and N2O: a review.

Stable isotope analysis of oxygen (O) is increasingly used to determine the origin of nitrate (NO(3)-) and nitrous oxide (N(2)O) in the environment. The assumption underlying these studies is that the (18)O signature of NO(3)- and N(2)O provides information on the different O sources (O(2) and H(2)O) during the production of these compounds by various biochemical pathways. However, exchange of O atoms between H(2)O and intermediates of the (de)nitrification pathways may change the isotopic signal and thereby bias its interpretation for source determination. Chemical exchange of O between H(2)O and various nitrogenous oxides has been reported, but the probability and extent of its occurrence in terrestrial ecosystems remain unclear. Biochemical O exchange between H(2)O and nitrogenous oxides, NO(2)- in particular, has been reported for monocultures of many nitrifiers and denitrifiers that are abundant in nature, with exchange rates of up to 100%. Therefore, biochemical O exchange is likely to be important in most soil ecosystems, and should be taken into account in source determination studies. Failing to do so might lead to (i) an overestimation of nitrification as NO(3)- source, and (ii) an overestimation of nitrifier denitrification and nitrification-coupled denitrification as N(2)O production pathways. A method to quantify the rate and controls of biochemical O exchange in ecosystems is needed, and we argue this can only be done reliably with artificially enriched (18)O compounds. We conclude that in N source determination studies, the O isotopic signature of especially N(2)O should only be used with extreme caution.

Phosphorus availability for plant uptake in a phosphorus-enriched noncalcareous sandy soil.

Mining soil phosphorus (i.e., harvesting P taken up from the soil by a crop grown without external P addition) has been proposed as a possible management strategy for P-enriched soils to decrease the risk of P leaching. We performed a pot experiment in a greenhouse where grass was cropped on a P-enriched noncalcareous sandy soil at zero P application over a period of 978 d. We determined the long-term availability of soil P and evaluated the effectiveness of mining soil P to decrease P in different pools. There were two treatments: soil layers in the pots of either 5 or 10 cm thickness. Soils were analyzed at various stages of the experiment. Phosphorus in soil solution and the total pool of sorbed P were estimated using 1:10 (w/v) 0.01 M CaCl2 extracts and acid ammonium oxalate (P(ox)), respectively. A desorption isotherm was constructed, which described the relationship between P in soil solution and the total pool of sorbed P for the soils of the 5- and 10-cm treatments. The Langmuir equation gave a very good description of the isotherm. In the long-term, 65% of P(ox) in the initial soil can be removed by plant uptake, as was calculated from the Langmuir equation and a critical P concentration in soil solution at which P uptake can just be maintained. Thus, P(ox) may be largely plant available. From the strong nonlinearity of the desorption isotherm, it can be understood why the relative decrease of the P concentration in the CaCl2 extracts was much larger than the relative decrease of P(ox). Mining soil P decreased the P concentration in soil solution effectively and, therefore, risk of P leaching from our P-enriched soil.

Health-related quality of life in relation to gender and age in couples planning IVF treatment.

BACKGROUND: Specific subgroups of people planning IVF might be at risk of having more psychological or health-related problems. Identification of subgroups at risk may better enable allocation of appropriate counselling. METHODS: A group of 425 men and 447 women planning to undergo IVF treatment filled out a questionnaire. Four domains of health-related quality of life were measured, namely perceived emotional, physical, cognitive and social functioning. RESULTS: Young men and women (aged 21-30 years) planning IVF had more short-term social and emotional problems than people of the same age group in the general population. No substantial differences were found in cognitive and physical functioning for all age groups of men nor women planning IVF compared with the general population. A high level of irrational parenthood cognitions substantially accounted for a less optimal score on all the different domains of quality of life. These cognitions ('needing a child in order to live a happy life') were especially prevalent among younger women. CONCLUSIONS: Patients with high levels of irrational parenthood cognitions are at risk of a less optimal quality of life. A short cognitive counselling therapy is advised for patients with high levels of these cognitions.

Potential for anaerobic conversion of xenobiotics.

This review covers the latest research on the anaerobic biodegradation of aromatic xenobiotic compounds, with emphasis on surfactants, polycyclic aromatic hydrocarbons, phthalate esters, polychlorinated biphenyls, halogenated phenols, and pesticides. The versatility of anaerobic reactor systems regarding the treatment of xenobiotics is shown with the focus on the UASB reactor, but the applicability of other reactor designs for treatment of hazardous waste is also included. Bioaugmentation has proved to be a viable technique to enhance a specific activity in anaerobic reactors and recent research on reactor and in situ bioaugmentation is reported.

Low 11-deoxycortisol to cortisol conversion reflects extra-adrenal factors in the majority of women with normo-gonadotrophic normo-estrogenic infertility.

BACKGROUND: Women with normogonadotrophic normo-estrogenic oligomenorrhoea often disclose a variety of clinical symptoms. Many of these individuals are obese with features of pseudo-hypercortisolism. In the current study, 11-deoxycortisol and cortisol concentrations were determined in this group and compared with ovulatory controls. METHODS AND RESULTS: Twenty-six women with clomiphene citrate-resistant infertility, 12 lean and 11 obese ovulatory controls were studied. Women with infertility had the highest 11-deoxycortisol concentrations (mean +/- SD: 4.1 +/- 1.5 ng/ml) compared with obese and lean controls (3.1 +/- 1.4 and 2.4 +/- 0.9 ng/ml) (P < 0.01), but similar morning cortisol concentrations (0.47 +/- 0.15, 0.45 +/- 0.16 and 0.47 +/- 0.18 nmol/l). Baseline 11-deoxycortisol/cortisol ratios (>90th percentile of ovulatory controls) were elevated in 23/26 infertile women (88%), and in 3/26 women (12%) after adrenocorticotrophic hormone (ACTH) stimulation. Three out of six lean infertile women had elevated baseline 11-deoxycortisol/cortisol ratios, but none of these women had elevated ratios after ACTH stimulation. Stepwise regression analysis, after exclusion of testosterone, revealed significant correlations between the groups (lean controls, obese controls, infertility) and ACTH-stimulated 11-deoxycortisol/cortisol ratio (P < 0.05), but not with fasting glucose, insulin, cortisol, 11-deoxycortisol and baseline 11-deoxycortisol/cortisol ratios. CONCLUSIONS: Congenital adrenal hyperplasia was not observed in the majority of infertile women. The data indicate that extra-adrenal factors were involved in most of the infertility syndromes that were studied.

Wet chemical and phosphorus-31 nuclear magnetic resonance analysis of phosphorus speciation in a sandy soil receiving long-term fertilizer or animal manure applications.

In areas under intensive livestock farming and with high application rates of animal manure, inorganic and organic phosphorus (P) may be leached from soils. Since the contribution of these P compounds to P leaching may differ, it is important to determine the speciation of P in these soils. We determined the effect of various fertilization regimes on the P speciation in NaOH-Na2EDTA (ethylenediaminetetraacetic acid) and water extracts of acidic sandy soil samples from the top 5 cm of grassland with wet chemical analysis and 31P nuclear magnetic resonance (NMR) spectroscopy. These soils had been treated for a period of 11 years with no fertilizer (control), N (no P application), N-P-K, or different animal manures. Inorganic P was highly elevated in the NaOH-Na2EDTA extracts of the soils amended with N-P-K or animal manures, while organic P increased only in the soil treated with pig slurry. Water-extractable P showed a similar trend. As indicated by 31P NMR, orthophosphate monoesters were the main organic P compounds in all soils. Our results suggest that long-term applications of large amounts of P fertilizer and animal manures caused an accumulation of inorganic P, resulting in an increase of the potential risk related to mobilization of inorganic P in the top 5 cm of these soils.

Soil phosphorus quantity-intensity relationships to predict increased soil phosphorus loss to overland and subsurface flow.

Soil phosphorus (P) quantity-intensity (q-i) relationships, based on common extraction methods, may potentially be used to estimate the risk of P loss in overland flow and subsurface drainage water. Some workers have used nonlinear q-i relationships to derive thresholds in soil test P (STP; a quantity factor) above which the risk of P loss increases, while others find linear relationships and no threshold. We present here a simple modelling exercise (based on Langmuir adsorption theory) along with data from literature to explain the behaviour of q-i relationships, and to give an explanation for this apparent discrepancy. The data indicate that q-i relationships are dependent upon the soil to solution ratio of the P intensity parameter, adsorption capacity (Qmax) and strength (K) of the soil, and the total range in STP. In turn, this affects the calculation of a threshold in STP. The q-i relationship tends towards linearity under conditions of a narrow total range of STP and/or when using a wide soil to solution ratio for estimating the P intensity parameter. Under such conditions, a threshold is difficult to detect, and uncertain. We conclude that the sensitivity of thresholds to experimental conditions and soils needs to be considered if thresholds are to be successful in environmental management to decrease P loss to surface waters.

Cadmium uptake by earthworms as related to the availability in the soil and the intestine.

The free metal concentration in the soil solution is often considered a key parameter for metal uptake by and toxicity to soft-bodied soil organisms. The equilibrium partitioning theory, which assumes a relationship between the contaminant concentration in pore water and the contaminant concentration in the body tissue, can be used to describe uptake by earthworms. This theory has proved useful for organic chemicals, but its applicability is less clear for metals. In this study, the Cd concentration in soil pore water (pw) was varied by increasing the soil pH by the addition of lime (Ca(OH)2) and by adding manganese oxide (MnO2), which has a high metal binding capacity. Both lime (0.135% w/w) and MnO2 (1% w/w) decreased [Cd2+]pw by a factor of 25, while Cdworm was reduced only by a factor of 1.3 in lime-treated soils and 2.5 in MnO2-treated soils. Cadmium uptake was weakly related to the free metal concentration (R2adj = 0.66). Adding pH as an explanatory variable increased R2adj to 0.89, indicating that Cd uptake from pore water is pH dependent, which might be attributed to competition of protons and Cd at the surface of the earthwororm body. However, previous earthworm experiments in reconstituted groundwater showed a conspicuously smaller pH dependency of Cd uptake. The differences in metal uptake between earthworms in lime- and MnO2-treated soils are therefore more likely to reflect the predominance of pH-independent intestinal uptake of Cd. Equilibrating the soil with a solution of 0.01 M CaCl2 and 0.1 M triethanolamine (buffered at pH 7.2), simulating the conditions prevailing in the worm intestine, yielded free Cd concentrations that were closely (R2adj = 0.83) and linearly related to the Cd concentration in the earthworm tissue.

Effect of beringite on cadmium and zinc uptake by plants and earthworms: more than a liming effect?

Metal-contaminated soils are potentially harmful to plants, animals, and humans. Harmful effects are often related to the free-metal concentration in the soil solution. Immobilization is a potentially useful method to improve the quality of metal-contaminated soils by transforming free-metal ions into species that are less mobile and less toxic. The effect of many immobilizing products can be attributed to sorption on the surface of the material. Alkaline materials also enhance adsorption to soil particles by decreasing proton competition. Immobilization should preferably be evaluated independently of soil pH to discriminate between these processes. In this study, the immobilizing effect of beringite, an alkaline alumino silicate, was compared with that of lime. Plants (Swiss chard [Beta vulgaris L. var. cicla]) were grown on a soil contaminated with cadmium and zinc and treated with graded amounts of beringite or lime. Metal availability, as determined by a 0.01 M CaCl2 extraction, and metal uptake by plants strongly decreased in all treated soils. Beringite did not reduce metal availability more than liming when the obtained pH levels were similar. The effect of beringite can, therefore, be explained as a liming effect, at least for the duration of our experiment (10 weeks). The effect of beringite and lime on metal accumulation by earthworms (Eisenia veneta and Lumbricus rubellus) was small or not significant, although the CaCl2-extractable metal concentration in treated soils decreased by more than 90%. We conclude that immobilizing agents based on a liming effect can decrease metal uptake by plants, but they will hardly affect metal uptake by earthworms. Hence, these materials can reduce negative ecological effects of metal contamination on plants and herbivores, but not on earthworm predators.

The Microbial Logic behind the Prevalence of Incomplete Oxidation of Organic Compounds by Acetogenic Bacteria in Methanogenic Environments.

Microbial degradation of organic material in methanogenic ecosystems is a multistep process in which subsequent groups use the products of the first groups of organisms in the chain as substrates. The acetogenic bacteria in these systems produce both H2 and acetate. In the present minireview a thermodynamic approach is taken to evaluate the logic behind this duality. The evaluation shows that at the H2 partial pressures that usually occur in methanogenic ecosystems the acetogenic oxidation of known acetogenic substrates such as propionate, butyrate, and benzoate yields more energy than their complete oxidation to H2/CO2. Also, H2 partial pressures needed to achieve complete hydrogenogenic oxidation of these acetogenic substrates would have to be so low that H2 would be virtually unavailable to the hydrogenotrophic bacteria, in casu the methanogens.

Energetics of anaerobic degradation pathways of chlorinated aliphatic compounds.

This minireview explores the energetics of the (anaerobic) oxidative and fermentative degradation of halogenated ethenes and ethanes. It is shown that these pathways are viable alternatives to the traditional routes that start with one or more reductive dechlorination steps. In contrast to reductive dehalogenation, oxidative and fermentative degradation pathways do not require an external source of reducing equivalents. This suggests that organisms that use these pathways are most likely to be found at high redox potentials, i.e, under conditions where competition for reducing equivalents is great.