Combined thermochemical and fermentative destruction of municipal biosolids: a comparison between thermal hydrolysis and wet oxidative pre-treatment

In this study the comparative destruction of municipal biosolids using thermal hydrolysis (140 or 165 °C) and wet oxidation (220 °C) was followed by biological degradation via mesophilic anaerobic digestion (36 °C). Wet oxidation (WO) destroyed more than 93% of the VSS, while thermal hydrolysis (TH) at 140 and 165 °C destroyed 9% and 22%, respectively. Combined TH and anaerobic digestion resulted in approximately 50% VSS destruction. The ultimate methane potential of the combined fractions from the thermal hydrolysis at 140 and 165 °C improved by 12-13% relative to the untreated control sample. Methane production from the WO material was 53% of the control yield and wholly attributable to soluble organic carbon in the liquid fraction, indicating that the WO destroyed all putrescible carbon from the solids fraction. Point sampling during the BMP assay revealed that methanogenic development, not solids hydrolysis, was the kinetic barrier during anaerobic digestion in this study.     

Minimally managed composting of beef manure at the pilot scale: Effect of manure pile construction on pile temperature profiles and on the fate of oxytetracycline and chlortetracycline

Oxytetracycline (OTC) and chlortetracycline (CTC) are broad-spectrum antibiotics used in livestock production. Although laboratory-scale studies have shown that extractable concentrations of these compounds decrease over time within treated and untreated manures and soils, there is relatively little information from farm-scale experiments. The objective of this study was to determine the effect of different levels of management on manure pile temperature profiles and on the fate of OTC and CTC in manure from therapeutically treated calves. Four treatments were designed to span a range of management options – from simply piling up the manure to amending it with straw to increase aeration and adding insulating layers of straw. Replicate samples of antibiotic-containing calf manure were held at ambient temperature or placed in three locations within replicate 3 m³ piles of beef manure. During the 28-day incubation period, concentrations of buffer-extractable OTC and CTC/ECTC (the summed concentrations of CTC and its epimer 4-epi-chlortetracycline (ECTC)) in manure samples incubated at ambient temperature (11–24 °C) decreased 75% (from 18 to 4.6 mg kg⁻¹ dry weight (DW)) and 90% (from 192 to 16 mg kg⁻¹ DW), respectively. Concentrations of the CTC metabolite iso-chlortetracycline (ICTC) decreased 90% (from 37 to 3 mg kg⁻¹ DW). OTC and CTC/ECTC concentrations in samples incubated for 28 days within a non-amended manure pile decreased 91% and >99%, respectively. During that period, the manure pile temperature ranged from 36 °C to 45 °C. Manure piles insulated with a blanket of straw and/or amended with straw (3:1, v/v) attained temperatures up to 70 °C and contained very low levels of OTC, CTC/ECTC, and ICTC (ranging from <0.1 to 0.4 mg kg⁻¹ DW) after 28 days.     

Characterization of compost produced from separated pig manure and a variety of bulking agents at low initial C/N ratios

The aim of this study was to investigate the composting of separated pig manure solids with or without a variety of bulking agents at a low initial C/N ratio (12.5-23.3). Compost stability was investigated using an oxygen uptake rate (OUR) test and compost maturity was investigated using a germination index test. All treatments showed typical patterns of compost temperature. Temperatures above 60 °C were achieved by Day 2, followed by a thermophilic phase (50-60 °C), which lasted for 1 to 2 weeks followed by a cooling phase. The stability of one of treatments which did not contain any bulking agent - OUR of 25 mmol O₂ kg⁻¹ OM hour⁻¹ - was negatively affected by its initial high water content (69%). The addition of a bulking agent and initial water content below 60% were necessary to compost the separated solid fraction of pig manure at a low initial C/N ratio.     

Methane recovery from the anaerobic codigestion of municipal sludge and FOG

The anaerobic biodegradability of a mix of municipal primary sludge (PS), thickened waste activated sludge (TWAS) and fat, oil, and grease (FOG) was assessed using semi-continuous feed, laboratory-scale anaerobic digesters operated at mesophilic (35 °C) and thermophilic (52 °C) temperature. Addition of a large FOG fraction (48% of the total VS load) to a PS + TWAS mix, resulted in 2.95 times larger methane yield, 152 vs. 449 mL methane @ STP/g VS added at 35 °C and 2.6 times larger methane yield, 197 vs. 512 mL methane @ STP/g VS added at 52 °C. The high FOG organic load fraction was not inhibitory to the process. The results of this study demonstrate the benefit of sludge and FOG codigestion.     

Influence of variables in the hydrothermal treatment of rice straw on the composition of the resulting fractions

The influence of the hydrothermal treatment conditions of rice straw (temperature – 150–190 °C , time – 0–20 min after reaching the operation temperature – and liquid/solid ratio – 6–8), on the composition of liquid and solid fractions was studied. Polynomial models were found for to reproduce the experimental results with errors less than 6%.     

The processes of methane production and oxidation in the soils of the Russian Arctic tundra

Methane emission from the following types of tundra soils was studied: coarse humic gleyey loamy cryo soil, peaty gleyey soil, and peaty gleyey midloamy cryo soil of the arctic tundra. All the soils studied were found to be potential sources of atmospheric methane. The highest values of methane emission were recorded in August at a soil temperature of 8–10°C. Flooded parcels were the sources of atmospheric methane throughout the observation period. The rates of methane production and oxidation in tundra soils of various types were studied by the radioisotope method at 5 and 15°C. Methane oxidation was found to occur in bog water, in the green part of peat moss, and in all the soil horizons studied. Methane production was recorded in the horizons of peat, in clay with plant roots, and in peaty moss dust of the bogey parcels. At both temperatures, the methane oxidation rate exceeded the rate of methane production in all the horizons of the mossy-lichen tundra and of the hillock tundra with flat-bottom depressions. Methanogenesis prevailed only in a sedge-peat moss bog at 15°C. Bacterial enrichment cultures oxidizing methane at 5 and 15°C were obtained. Different types of methanotrophic bacteria were shown to be responsible for methane oxidation under these conditions. A representative of type I methylotrophs oxidized methane at 5°C, and Methylocella tundrae, a psychroactive representative of an acidophilic methanotrophic genus Methylocella, at 15°C.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 261–270.Original Russian Text Copyright © 2005 by Berestovskaya, Rusanov, Vasileva, Pimenov.     

Multigenerational analysis of temperature and salinity variability affects on metabolic rate,generation time,and acute thermal and salinity tolerance in Daphnia pulex

Climate change, sea level rise, and human freshwater demands are predicted to result in elevated temperature and salinity variability in upper estuarine ecosystems. Increasing levels of environmental stresses are known to induce the cellular stress response (CSR). Energy for the CSR may be provided by an elevated overall metabolic rate. However, if metabolic rate is constant or lower under elevated stress, energy for the CSR is taken from other physiological processes, such as growth or reproduction. This study investigated the examined energetic responses to the combination of temperature and salinity variability during a multigenerational exposure of partheogenetically reproducing Daphnia pulex. We raised D. pulex in an orthogonal combination of daily fluctuations in temperature (15, 15–25, 15–30 °C) and salinity (0, 0–2, 0–5). Initially metabolic rates were lower under all variable temperature and variable salinity treatments. By the 6th generation there was little metabolic variation among low and intermediate temperature and salinity treatments, but metabolic suppression persisted at the most extreme salinity. When grown in the control condition for the 6th generation, metabolic suppression was only observed in D. pulex from the most extreme condition (15–30 °C, 0–5 salinity). Generation time was influenced by acclimation temperature but not salinity and was quickest in specimens reared at 15–25 °C, likely due to Q₁₀ effects at temperatures closer to the optima for D. pulex, and slowest in specimens reared at 15–30 °C, which may have reflected elevated CSR. Acute tolerance to temperature (LT₅₀) and salinity (LC₅₀) were both highest in D. pulex acclimated to 15–30 °C and salinity 0. LT₅₀ and LC₅₀ increased with increasing salinity in specimens raised at 15 °C and 15–25 °C, but decreased with increasing salinity in specimens raised at 15–30 °C. Thus, increasing temperature confers cross-tolerance to salinity stress, but the directionality of synergistic effects of temperature and salinity depend on the degree of environmental variability. Overall, the results of our study suggest that temperature is a stronger determinant of metabolism, growth, and tolerance thresholds, and assessment of the ecological impacts of environmental change requires explicit information regarding the degree of environmental variability.     

Fate of organic carbon in UAFB treating raw sewage: impact of moderate to low temperature

The anaerobic biological treatment of raw sewage under low ambient temperatures was investigated in an up-flow anaerobic fixed bed (UAFB) reactor, over a 220-day trial period. The operating temperature was lowered stepwisely from 35 to 25, 20 and 15 °C. Obvious accumulation of acetic acid was observed in the effluent as the temperature dropped, which almost tripled at 15 °C compared to that at 35 °C. An interesting psychrophilic-forward-shift trend of methane production rate following the decrease of temperature was discovered. The methane yield at each trial was 169, 201, 256 and 269 L_STP CH₄/kg COD_removed. For each temperature trial, about 32.6%, 28.3%, 34.4% and 34.9% were removed in form of methane. Based on PCR-DGGE results, the band corresponded to Methanosphaera spp. only showed up on 15 °C profile. Analysis of both methane production and DGGE results indicated that psychro-tolerant microorganisms dominated the archaeal populations in the UAFB under low-temperature.     

Effect of seed sludge and operation conditions on performance and archaeal community structure of low-temperature anaerobic solvent-degrading bioreactors

Two laboratory-scale expanded granular sludge bed (EGSB) anaerobic bioreactors (R1 and R2) were inoculated with biomass from different mesophilic (37 °C) treatment plants, and used for the treatment of an organic solvent-based wastewater at 9–14 °C at applied organic loading rates (OLRs) of 1.2–3.6 kg chemical oxygen demand (COD) m⁻³ d⁻¹. Replicated treatment performance was observed at 10–14 °C, which suggested the feasibility of the process at pilot-scale. Stable and efficient COD removal, along with high methane productivity, was demonstrated at 9 °C at an applied OLR of 2.4 kg COD m⁻³ d⁻¹. Clonal libraries and fluorescence in situ hybridization (FISH) indicated that the seed sludges were dominated (>60%) by acetoclastic Methanosaeta-like organisms. Specific methanogenic activity (SMA) profiles indicated shifts in the physiological profiles of R1 and R2 biomass, including the development of psychrotolerant methanogenic activity. Acetoclastic methanogenesis represented the primary route of methane production in R1 and R2, which is in contrast with several previous reports from low-temperature bioreactor trials. A reduction in the abundance of Methanosaeta-like clones (R2), along with the detection of hydrogenotrophic methanogenic species, coincided with altered granule (sludge) morphology and the development of hydrogenotrophic SMA after prolonged operation at 9 °C.     

Swine manure fermentation for hydrogen production

Biohydrogen fermentation using liquid swine manure as substrate supplemented with glucose was investigated in this project. Experiments were conducted using a semi-continuously-fed fermenter (8 L in total volume and 4 L in working volume) with varying pHs from 4.7 through 5.9 under controlled temperature (35 ± 1 °C). The hydraulic retention time (HRT) tested include 16, 20, and 24 h; however, in two pH conditions (5.0 and 5.3), an additional HRT of 12 h was also tried. The experimental design combining HRT and pH provided insight on the fermenter performance in terms of hydrogen generation. The results indicated that both HRT and pH had profound influences on fermentative hydrogen productivity. A rising HRT would lead to greater variation in hydrogen concentration in the offgas and the best HRT was found to be 16 h for the fermenter in this study. The best pH value in correspondence to the highest hydrogen generation was revealed to be 5.0 among all the pHs studied. There was no obvious inhibition on hydrogen production by methanogenesis when methane content in the offgas was lower than 2%. Otherwise, an inverse linear relationship between hydrogen and methane content was observed with a correlation coefficient of 0.9699. Therefore, to increase hydrogen content in the offgas, methane production has to be limited to below 2%.     

Methane emissions associated with a green manure amendment to flooded rice in California

The goals of sustainable food production and mitigation of greenhouse gas emissions may be in conflict when green manures are used in flooded rice systems. A field study was initiated in early spring 1992 near Sacramento, California to quantify the potential for enhanced methane emissions following a green manure amendment to rice. Replicate flux measurements were made twice a day every 3–4 days throughout the growing season in four treatment plots: burned rice straw, spring incorporated rice straw, burned straw plus purple vetch and spring incorporated straw plus vetch. Seasonal methane emissions ranged from 66–136 g CH₄ m⁻² and were 1.5 to 1.8 times higher from the straw plus vetch treatments relative to the straw only treatments. No significant differences in emissions were found between the two straw only treatments or the straw plus vetch treatments. Methane fluxes were exponentially related to soil temperature, but no effect of redox potential or floodwater depth were observed. The potential impact of these results on the global methane budget is discussed.     

Bioenergy potential of Ulva lactuca: biomass yield, methane production and combustion

The biomass production potential at temperate latitudes (56°N), and the quality of the biomass for energy production (anaerobic digestion to methane and direct combustion) were investigated for the green macroalgae, Ulva lactuca. The algae were cultivated in a land based facility demonstrating a production potential of 45 T (TS) ha⁻¹ y⁻¹. Biogas production from fresh and macerated U. lactuca yielded up to 271 ml CH₄ g⁻¹ VS, which is in the range of the methane production from cattle manure and land based energy crops, such as grass-clover. Drying of the biomass resulted in a 5-9-fold increase in weight specific methane production compared to wet biomass. Ash and alkali contents are the main challenges in the use of U. lactuca for direct combustion. Application of a bio-refinery concept could increase the economical value of the U. lactuca biomass as well as improve its suitability for production of bioenergy.     

Thermopreference,tolerance and metabolic rate of early stages juvenile Octopus maya acclimated to different temperatures

Thermopreference, tolerance and oxygen consumption rates of early juveniles Octopus maya (O. maya; weight range 0.38–0.78 g) were determined after acclimating the octopuses to temperatures (18, 22, 26, and 30 °C) for 20 days. The results indicated a direct relationship between preferred temperature (PT) and acclimated temperature, the PT was 23.4 °C. Critical Thermal Maxima, (CTMax; 31.8±1.2, 32.7±0.9, 34.8±1.4 and 36.5±1.0) and Critical Thermal Minima, (CTMin; 11.6±0.2, 12.8±0.6, 13.7±1.0, 19.00±0.9) increased significantly (P<0.05) with increasing acclimation temperatures. The endpoint for CTMax was ink release and for CTMin was tentacles curled, respectively. A thermal tolerance polygon over the range of 18–30 °C resulted in a calculated area of 210.0 °C². The oxygen consumption rate increased significantly α=0.05 with increasing acclimation temperatures between 18 and 30 °C. Maximum and minimum temperature quotients (Q₁₀) were observed between 26–30 °C and 22–26 °C as 3.03 and 1.71, respectively. These results suggest that O. maya has an increased capability for adapting to moderate temperatures, and suggest increased culture potential in subtropical regions southeast of México.     

Diurnal ammonia and urea excretion rates in European sea bass, Dicentrarchus labrax fed diets containing mixtures of canola and cotton seed oil at two different ambient temperature

The knowledge about the combined effects of higher temperature and dietary nutrient quality on the diurnal nitrogenous excretion rates is very limited in farmed fish species including European sea bass. Therefore this study investigated the combined effects of increasing levels (30 vs. 60 %) of dietary fish oil replacement by equal mixture of cotton seed oil (CSO) and canola oils (CO) and two different ambient temperature (24 vs. 30 °C) on diurnal total ammonia and Urea–N excretion rates in European sea bass (Dicentrarchus labrax). Experimental diets were fed to fish three times (08:30–13:30–18:30 h) at a fixed rate of 3 % BW.d⁻¹. The daily consumed nitrogen and energy intake of fish were similar during the investigation in different dietary treatments. However, the daily excretion rates of TAN, total nitrogen (TAN+Urea–N) and total nitrogen expressed as a proportion of consumed nitrogen by the European sea bass maintained at 30 °C were found to be significantly (P<0.001) higher (40 to 50%) than fish maintained at 24 °C in all the dietary treatments suggesting higher rates of deamination of ingested amino acids with increased temperature. Daily urea–nitrogen excretion of fish accounted for between 20–30 % of total ammonia–nitrogen excretion rates for each dietary treatment at 24 and 30 °C and appeared to be slightly increased by the temperature but neither the temperature nor the amount of plant oil mixture inclusion in diets or the interaction of these two factors had a significant effect on the urea nitrogen excretion rates of fish in different dietary treatments. However, Urea–N excretion rates in fish fed fish oil only (FO) diet were significantly higher (P<0.05) compared to that of fish fed diets containing increasing amount of plant oil mixture (VOM30 and VOM 60) during the light-on phase of the sampling period at 24 °C indicating periodic enhancement of permeability for urea at excretion sites. Further research is needed in order to elucidate the mechanism of nitrogenous excretion in European sea bass fed plant oil containing diets under extreme summer time temperatures employing total dietary fish oil replacement to reveal the possible effects of alteration in cell membrane phospholipid composition on enzymes responsible for nitrogenous excretion and/or detoxification.     

Optimization of biogas production from cattle manure by pre-treatment with ultrasound and co-digestion with crude glycerin

Biogas production by co-digestion of cattle manure with crude glycerin obtained from biodiesel production was studied after pre-treatment of the cattle manure or mixtures of cattle manure with different amounts of added glycerin with ultrasound. Batch experiments with 1750 mL of medium containing 1760 g of screened cattle manure or mixtures of cattle manure (screened or ground) and 70-140 mL or crude glycerin were incubated under mesophilic and thermophilic condition in stirred tank reactors. Under mesophilic conditions, the addition of 4% glycerin to screened manure increased biogas production by up to 400%. Application of sonication (20 kHz, 0.1 kW, and 4 min) to a mixture of manure + 4% glycerin increased production of biogas by up to 800% compared to untreated manure. The best results were obtained under thermophilic conditions using sonicated mixtures of ground cattle manure with 6% added glycerin (348 L methane/kg COD removed were obtained).     

Extrusion as a pretreatment to increase biogas production

Application of an extruder to increase the methane yield in a biogas production was examined, and large potential was proved. An extruder was tested on five agricultural biomass types, represented by 13 samples. The samples were analyzed for temperature, maximum particle size, biogas potential, and energy consumption. The extruder treatment increased biomass temperature by 5-35 °C. Large particles (>1 mm) were most affected by the extruder. Extrusion accelerated the degradation of slowly degradable organic compounds, and some otherwise nondegradable organic compounds were also degraded. The methane yield increased significantly: by 18-70% after 28 days, and by 9-28% after 90 days. The electrical energy equivalent of the extra methane, after subtracting the energy used by the extruder, resulted in energy surpluses of 6-68%. By day 90, the energy-efficiency of the extrusion process was ranked as follows: grass = straw = solids of flocculated manure < solids of screw-pressed manure < deep litter.     

Thermoregulatory behavior and oxygen consumption of Octopus mimus paralarvae: The effect of age

Octopus mimus is an important cephalopod species in the coastal zone of Peru and Chile that is exposed to temperature variations from time to time due to El Niño/Southern Oscillation (ENSO) episodes when surface temperatures can reach 24 °C, 6 °C above typical temperatures in their habitat. The relationships between temperature and food availability are important factors that determine the recruitment of juveniles into the O. mimus population. The present study was to evaluate the relationship between thermoregulatory behavior and the age of paralarvae (summer population) to determine whether changes in this behavior occur during internal yolk consumption, making larvae more vulnerable to environmental temperature change. Oxygen consumption of paralarvae when 1–4 d old was determined to establish if respiration could be used to monitor the physiological changes that occur during yolk consumption. Horizontal thermal selection (17–30 °C), critical thermal maxima (CTMax), minima (CTMin), and oxygen consumption experiments were conducted with fasting paralarvae 1–4 d old at 20 °C. Preferred temperatures were dependent on the age of O. mimus paralarvae. One day old paralarvae selected a temperature 1.1 °C (23·4 °C) higher than 2 – 4 d old paralarvae (22·3 °C). The CTMax of paralarvae increased with age with values of 31·9±1.1 °C in 1-d-olds and 33·4±0.3 to 4-d-olds. CTMin also changed with age with low values in 2-d-old paralarvae (9.1±1·3 °C) and 11·9±0·9 °C in 4-d-old animals. The temperature tolerance range of paralarvae was age-dependent (TTD=difference between CTMax and CTMin) with higher values in 2 and 3 d old paralarvae (25–26 °C) as compared to 1 d old (23·1 °C) and 4 d old animals (22.7 °C). Oxygen consumption was not affected by the age of paralarvae, suggesting that mechanisms exist that compensate their metabloism until at least 4 d of age. The temperature tolerance range of a planktonic paralarvae of octopus species is presented for the first time. This range was dependent on the age of paralarvae, and so rendered the paralarvae more vunerable to a combination of high temperature and food deprivation during first days of life. Results in the present study provide evidence that O. mimus could be under ecological pressure if a climate change causes increased or decreased temperatures into their distribution range.     

Different pressure–temperature behavior of the structured and unstructured regions of titin

Contrary to the classical view, according to which all proteins adopt a specific folded conformation necessary for their function, intrinsically unstructured proteins (IUPs) display random-coil-like conformation under physiological conditions. We compared the structured and unstructured domains from titin, a giant protein responsible for striated-muscle elasticity. A 171-residue-long fragment (polyE) of the disordered PEVK domain, and an Ig domain (I27) with ordered structure were investigated. FTIR (Fourier transform infrared) and fluorescence spectroscopy combined with a diamond anvil cell were used for investigation of the secondary structures under wide range of pressure and temperature. PolyE preserves its disordered characteristics across the entire range of investigated pressure (0–16 kbar), temperature (0–100 °C), pD (3–10.5) and different solvent conditions. The detailed temperature–pressure phase diagram of titin I27 was determined. At 30 °C, increasing pressure unfolds titin I27 in one step at 10.5 kbar. Increasing temperature at atmospheric pressure results in two transitions. At 50 °C the secondary structure is loosened and the protein transforms into a molten-globule state. At 65 °C the protein completely unfolds. Unfolding is followed by aggregation at ambient pressure. Moderate pressures (> 2 kbar), however, can prevent the protein from aggregation. Our experiments in wide range of physical parameters revealed four different structures for I27, while the unstructured character of the PEVK fragment is insensitive to these parameters.     

Combined effects of temperature and cadmium exposure on haemocyte apoptosis and cadmium accumulation in the eastern oyster Crassostrea virginica (Gmelin)

Combined effects of acclimation temperature (12, 20 and 28 °C) and exposure to a toxic metal cadmium (Cd, 50 μg L⁻¹) on haemolymph parameters related to immune defense and metal transport were studied in a model marine bivalve, Crassostrea virginica. Acclimation to elevated temperatures resulted in higher plasma protein concentrations and increased Cd levels in oyster haemolymph plasma and haemocytes. Cd accumulation in haemocytes was linear over the 45 days of Cd exposure and accumulation rates were 0.10, 0.53 and 0.56 μg Cd g⁻¹ dry mass at 12, 20 and 28 °C, respectively. Percentage of blood Cd burden associated with haemocytes increased with increasing temperatures from 13–20% at 12 °C to 26–47% at 20 and 28 °C suggesting a higher role for cellular Cd transport at elevated temperatures. Cd levels in gills and hepatopancreas were positively correlated with Cd concentration in haemocytes, but accumulation rates were considerably faster, so that after 45 days of exposure Cd levels in gills and hepatopancreas were >10–20 times higher than in haemocytes. As a result of slow Cd accumulation possibly reflecting fast haemocyte turnover rates and/or exocytosis of Cd-containing granules, haemocytes in Cd-exposed oysters did not reach threshold Cd burdens required to trigger apoptosis. This suggests that haemocyte viability is not likely to contribute to immunosuppression in the environmentally relevant Cd range. In contrast, elevated temperature (28 °C) resulted in a significant increase in the percentage of apoptotic haemocytes compared to 12 or 20 °C supporting the notion that 28 °C is physiologically stressful for C. virginica. Overall, our study demonstrates strong effects of environmental temperature on haemocyte viability and other important blood parameters such as plasma protein content and metal transport capability which may mask potential Cd effects at environmentally relevant exposure levels.