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PubMedDate not supplied

Fate and toxicity of aircraft deicing fluid additives through anaerobic digestion.

Benzotriazole derivatives are widely used corrosion inhibitors and their fate during wastewater treatment processes is unknown. The purpose of this research was to study the toxic effects and fate of the two commercially significant benzotriazole isomers used in aircraft deicing fluids (4-, and 5-, methylbenzotriazole [MeBT]) during anaerobic digestion. Experiments were executed in microcosms using mesophilic anaerobic biomass co-digesting wastewater sludge and propylene glycol. Sorption of MeBT to digesting solids could be approximated with a Freundlich model, and no anaerobic breakdown of either MeBT isomer was detected. Digesters fed more than 300 mg/L MeBT responded with a significant decrease in methanogenic microbial activity and volatile solids production and a concomitant increase in accumulation of volatile fatty acids. Direct microscopic measurements using fluorescent phylogenetic probes applied to digesting biomass revealed that members of both Archaea and Bacteria domains were sensitive to MeBT. Granular activated carbon (GAC) (volatile solids: GAC = 10%) reduced the apparent toxic effects of MeBT; GAC addition nearly restored the baseline activity of digesters fed MeBT (500 to 1000 mg/L).

Aircraft↗
PubMedDate not supplied

Changing mesophilic wastewater sludge digestion into thermophilic operation at Terminal Island Treatment Plant.

This paper describes the progress up to June 2000 for thermophilic digestion of wastewater sludge at the Los Angeles, California, Bureau of Sanitation's Terminal Island Treatment Plant. The development of the microorganism culture has followed a course similar to that seen at other successful plants for establishment of a stable, well-balanced thermophilic culture in a large digester, but at an accelerated pace. This study began with rapid heating, increasing the temperature of the 4500 m3 (1.2 mil. gal) digester to the target temperature of 55 degrees C at approximately 3 degrees C/d. A method of feeding to maximize the rate of culture development was used as feeding accelerated to approximately 400 m3/d (0.1 mgd). An initial rise of acid concentration (primarily acetate) was seen. Within two weeks, acid concentration declined and stabilized, indicating that acidogenic and methanogenic microbial communities came into balance. Coliform data indicate that digester disinfection was stably effective from the middle of April. The salmonella tests done to date satisfy the U.S. Environmental Protection Agency (U.S. EPA) class A specification. Testing with helminth ova and enteric viruses before and after the digester shows satisfaction of class A standard for those organisms. The present combination of low volatile fatty acids and low hydrogen sulfide is good news for odor control. The data show increases in volatile solids destruction and estimated gas production, compared with the previous mesophilic operation; however, large uncertainties have been calculated from the data. As the digester is now operating successfully at the current feed rate, there seems to be no barriers to processing the entire sludge production of the plant. Other results indicate that the U.S. EPA requirements for exceptional quality class A biosolids are likely to be achieved.

Animals↗
PubMed2006

Thermophilic-anaerobic digestion to produce class A biosolids: initial full-scale studies at Hyperion Treatment Plant.

The highest quality of biosolids is called exceptional quality. To qualify for this classification, biosolids must comply with three criteria: (1) metal concentrations, (2) vector-attraction reduction, and (3) the Class A pathogen-density requirements. The City of Los Angeles Bureau of Sanitation Hyperion Treatment Plant (HTP) (Playa del Rey, California) meets the first two requirements. Thus, the objective of this study was to ensure that HTP's biosolids production would meet the Class A pathogen-reduction requirements following the time-temperature regimen for batch processing (U.S. EPA, 1993; Subsection 32, Alternative 1). Because regulations require the pathogen limits to be met at the last point of plant control, biosolids sampling was not limited to immediately after the digesters, i.e., the digester outflows. The sampling extended to several locations in HTP's postdigestion train, in particular, the last points of plant control, i.e., the truck loading facility and the farm for land application. A two-stage, thermophilic-continuous-batch process, consisting of a battery of six egg-shaped digesters, was established in late 2001 for phase I of this study and modified in early 2002 for phase II. As the biosolids were discharged from the second-stage digesters, the Salmonella sp. (pathogen) and fecal-coliform (indicator) densities were well below the limits for Class A biosolids, even though the second-stage-digester temperatures were a few degrees below the temperature required by Alternative 1. Salmonella sp. densities remained below the Class A limit at all postdigestion sampling locations. Fecal-coliform densities were also below the Class A limit at postdigestion-sampling locations, except the truck-loading facility (phases I and II) and the farm for final use of the biosolids (phase II). Although federal regulations require one of the limits for either fecal coliforms or Salmonella sp. to be met, local regulations in Kern County, California, where the biosolids are land-applied, require compliance with both bacterial limits. Additional work identified dewatering, cooling of biosolids after the dewatering centrifuges, and contamination as possible factors in the rise in density of fecal coliforms. These results provided the basis for the full conversion of HTP to the Los Angeles continuous-batch, thermophilic-anaerobic-digestion process. During later phases of testing, this process was demonstrated to produce fully disinfected biosolids at the farm for land application.

Anaerobiosis↗
PubMed1993

Effect of the protein matrix on the digestion of cereal grains by ruminal microorganisms.

Experiments were conducted to investigate the role of the protein matrix in the digestion of barley and corn by ruminal microorganisms. Grains, ground and collected on sieves as two particle fractions .25 to .89 mm (small particles) and 2.00 to 3.00 mm (large particles), as well as isolated barley and corn starch granules, were incubated with ruminal inocula. For both grains, digestion of starch in small particles was greater (P < .001) than that of large particles. At 16 and 24 h starch digestion was greater (P < .01) in barley than in corn, for small and large particles. Digestion of barley starch granules did not differ (P > .05) from that of corn starch granules at any incubation time. A 4-h preincubation of small-particle corn and barley with protease increased (P < .001) microbial digestion of starch in corn at 16 h but did not affect digestion of barley. When four ruminally cannulated steers were fed diets containing 80% barley, corn, or wheat or 100% alfalfa hay in a 4 x 4 Latin square experiment, amylolytic activity of ruminal inoculum was higher for steers fed grains than for those fed alfalfa. However, when standardized for total viable counts of bacteria, ruminal amylolytic activity did not differ (P > .05) among diet treatments, but proteolytic activity of ruminal inoculum for steers fed alfalfa was higher (P < .01) than that for steers fed cereal grains. Activity of serine proteases in ruminal inoculum was higher (P < .05) for steers fed alfalfa than for steers fed grains.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed2005

Increasing dietary pectin level reduces utilization of digestible threonine intake, but not lysine intake, for body protein deposition in growing pigs.

Two N balance studies were conducted to investigate the effects of feeding graded levels of pectin (a soluble nonstarch polysaccharide, NSP) on the utilization of ileal digestible threonine (Thr; Thr study) and lysine (Lys; Lys study) intake for body protein deposition (PD) in growing pigs. In each study, eight Yorkshire barrows with an average initial BW of 17.2 +/- 1.3 (Thr study) and 14.3 +/- 1.4 kg (Lys study) were fed each of five experimental diets during five subsequent experimental periods, according to a crossover design. Pigs were fed twice daily at 2.6 times maintenance energy requirements. The soybean- and cornstarch-based diets, in which either Thr or Lys was the first-limiting nutrient, were formulated to contain (as-fed basis) 0, 4, 8, or 12% pectin or 8% cellulose (water-insoluble NSP), respectively, and with NSP substituting cornstarch. Across treatments, the mean daily Thr and Lys intake were 5.42 +/- 0.04 g/d (Thr study) and 7.98 +/- 0.12 g/d (Lys study), respectively. Apparent and standardized ileal digestibilities of Thr and Lys were determined in a separate study. Mean PD was 93.4, 90.2, 82.1, 76.7, and 87.9 g/d (SEM = 1.3; Thr study) and 90.7, 88.6, 87.8, 85.3, and 88.1 g/d (SEM = 1.1; Lys study) for the five respective treatments. Utilization of ileal digestible Thr intake, but not of ileal digestible Lys intake, for PD decreased linearly with dietary pectin level, and was not influenced by diet cellulose level. The current study indicates that apparent and standardized ileal digestibility values do not provide an accurate predictor of dietary effects on the utilization of ileal digestible Thr intake for protein deposition in growing pigs fed diets containing soluble NSP.

Animal Feed↗
PubMed1982

Comparison of N,N-dimethyldodecanamine with antibiotics on in vitro cellulose digestion and volatile fatty acid production by ruminal microorganisms.

Eleven antibiotic compounds used in animal production, were compared with N,N-dimethyldodecanamine for their effects on in vitro cellulose digestibility and VFA production. Dose-response data were analyzed statistically to determine the concentration for each compound which would inhibit cellulose digestion of VFA production by 50%, thereby providing a convenient reference point for evaluation of the amine with respect to the antibiotics. Chlortetracycline, oxytetracycline and penicillin inhibited cellulose digestion by 17 to 35% and VFA production by 18 to 26% at concentrations of 2.5 micrograms/ml, while N,N-dimethyldodecanamine and dihydrostreptomycin at concentrations of 10 micrograms/ml inhibited cellulose digestion and VFA production by 5 to 19%. For similar inhibitive effects, bacitracin, chloramphenicol, kanamycin, sulfanilamide and sulfathiazole were required in concentrations of 25 micrograms/ml. Tylosin at a concentration of 1 microgram/ml inhibited cellulose digestion and VFA production by about 80 and 50%, respectively, and monensin was effective at 5 micrograms/ml. In general, compounds of lesser importance for growth promotion in ruminants (sulfathiazole, sulfanilamide and kanamycin) had a less inhibitory effect on cellular digestion and VFA production in vitro. N,N-dimethyldodecanamine was more effective than these compounds but repressed cellulolytic activity less than those antibiotics (chlortetracycline, oxytetraxycline and monensin) that are most effective in improving feed efficiency.

Amines↗
PubMed1985

Digestibility of modified milk proteins: nutritional implications.

Chemical changes in the structure of several milk proteins were quantitated and the effects on digestibility evaluated using a number of in vitro techniques developed in our laboratory. An assay for digestibility was developed and standardized incorporating immobilized gastric, pancreatic, and intestinal mucosal proteinases and peptidases and thereby simulating in vivo digestion. The method displayed a direct relationship to digestibilities determined in human feeding studies. Various degrees of racemization were induced in a number of proteins and quantitated with the aid of a bioreactor containing coimmobilized D-amino acid oxidase and catalase. Digestibility values were directly related to the degree of racemization and to the amount of lysinoalanine. In a separate study of these proteins, various degrees of Maillard reaction were induced, and the available lysine was quantitated using the fluorometric o-phthalaldehyde method. Digestibility values determined for these modified proteins were also directly related to the amount of available lysine. A bioreactor containing various immobilized proteinases and peptidases catalyzed complete hydrolysis of a number of proteins including beta-lactoglobulin. Because this method does not degrade residues such as tryptophan and methionine nor hydrolyze aldosyl lysine to give unmodified lysine, analysis of these hydrolysates yields more nutritionally meaningful chemical scores. In summary, these techniques appear to be useful for quantitating and monitoring changes in the structures of proteins resulting from processing and storage, which affect their nutritional quality.

Amino Acids↗
PubMed2001

Size and structure effects on centrifugal dewatering of digested sewage sludge.

The application of light scattering over small angles for the determination of digested sludge floc size and structure and its relationship with dewaterability is investigated. It appears that improved dewatering corresponds with lower floc fractal dimension (a more open structure) and a smaller proportion of fine particles. The initial increase in fractal dimension with increasing polymer dose for the digested sludge is most likely due to more efficient aggregation of the finer particles and the resulting formation of denser particle aggregates. A large colloidal fractal of the digested sludge (< 10 microm) appears to be less negative than the bulk digested sludge. This suggests that the fine particles will react differently and possibly less aggressively to the cationic polymer than the larger and more negative particles. The higher negative charge associated with the larger particles might be related to greater levels of highly negatively charged extracellular polysaccharides (EPS) adsorbed to the flocs or could result from the association of FeS with the finer fraction. The appearance of much greater levels of fine particles after digestion suggests that the flocs have undergone disintegration. Whether this is due to reduced biological efficiency within the digestor or iron reduction under the anaerobic conditions is not known for certain, although no indication of prolonged stress in the digesters could be found from plant performance data.

Centrifugation↗
PubMed2001

Removal of fecal indicator organisms and parasites (fecal coliforms and helminth eggs) from municipal biologic sludge by anaerobic mesophilic and thermophilic digestion.

In this work, two egg-shaped, 5L-volume, anaerobic sludge digesters were used, one under mesophilic conditions (35 degrees C, M1), and the other under thermophilic conditions (55 degrees C, T1). Both digesters were fed with the purged sludge from an anaerobic treatment plant (start-up period) and from an activated sludge plant (stabilization period), treating municipal wastewaters. The purpose of the study was to establish the technical feasibility of the anaerobic thermophilic sludge treatment comparatively, during the stages of start-up and stabilization of the process, for removing pathogenic microorganisms and parasites efficiently. The results show that, in both stages, the anaerobic thermophilic digester presents higher efficiency on the removal of pathogens and parasites, than the mesophilic digester. Anaerobic thermophilic digestion is close to complying with the EPA (1998) limits for "Class A" type biosolids, referring to the number of parasitic helminth eggs (0.25 HELarval/gTS), and to the pathogen indicator fecal coliforms (< 1000 MPN/gTS). Therefore, the results show that thermophilic anaerobic digestion of biologic sludge may be considered as a suitable technology for the production of Class A biosolids, for further use in agriculture without restrictions.

Agriculture↗
PubMed2002

Removal of helminth eggs and fecal coliforms by anaerobic thermophilic sludge digestion.

Anaerobic digestion of two types of waste sludge was applied in order to assess the suitability of thermophilic conditions for the stabilization of organic matter and removal of fecal coliforms and helminth eggs. Feeding sludge was taken from an activated sludge municipal facility (BS) and from an enhanced primary treatment municipal plant (EPT). As an accompanying experiment, mesophilic digesters were also operated. The four digesters (M1, M2, T1, T2) had a 5 litre volume and an egg shape. A highly stabilized material was obtained at both temperatures with BS type of sludge, taking the reduction of volatile fraction of suspended solids (%Rvss) as indicator (84% for M1 and 74% for T1). In general, EPT sludge was a more difficult substrate, if compared with BS sludge; thermophilic condition was better adapted than mesophilic for this kind of sludge. Satisfactory reductions on counts of fecal coliforms and helminth eggs were achieved under thermophilic digestion for both types of feeding sludge. T1 digester, fed with biological sludge, removed fecal coliforms below 1000 MPN/gTS and helminth eggs down to 0.28 HELarval/gTS, at an HRT of 20 days. As a general conclusion, anaerobic thermophilic digestion may be an appropriate option for sludge stabilization, in order to meet EPA Class A biosolids final disposal regulations. However, further research is needed in order to consistently remove helminth eggs and fecal coliforms from waste sludge at shorter hydraulic retention times.

Animals↗
PubMed2002

Thermochemical pretreatment in the anaerobic digestion of waste activated sludge.

Effects of a thermochemical pretreatment on the anaerobic digestion of waste activated sludge (WAS) was investigated by semicontinuously-fed digesters operated at 37 degrees C. WAS from a return sludge line of a municipal sewage treatment plant was pretreated by autoclaving at 130 degrees C for 5 minutes after adding 0.3g NaOH/g VSS. Solids of WAS were thermochemically solubilized to one half and then 60% or more were in totality solubilized in anaerobic digesters fed with pretreated WAS at 2-8 days of hydraulic retention times (HRT), while only 16-36% were solubilized in digesters fed with raw WAS. The adverse effect of the set temperature (130 degrees C) on the biodegradability of protein was not found. As a result, removal rates of COD in digestion was increased from 38% to 57% at 8 days HRT by the pretreatment. A specific methane production rate in the pretreated process was three times as high as the normal process. The thermochemical pretreatment was found to be very effective to enhance biodegradability as well as solubilization of WAS in anaerobic digestion.

Bacteria, Anaerobic↗
PubMed2002

Biological nutrient removal wastewater treatments and sewage sludge anaerobic mesophilic digestion performances.

The paper deals with the performances of the mesophilic anaerobic digestion treatment of sewage sludge from a full scale BNR process without primary settling (nominally 300,000 PE). A relation between the activated sludge observed yields, Y(obs), and the anaerobic digester performance was preliminarily found: for values of Y(obs) of 0.25 kgVSS/kgCOD the anaerobic digester specific gas production showed the best performances (0.22 m3/kgVS(fad)). This has to be confirmed with wider future studies. It was also shown the level of sludge pre-thickening to be reached for the self-sustaining warming of the digester also in wintertime. According to the energetic balance and to a comparison with an aerobic stabilisation process, it was pointed out as when a co-generation unit for heat and energy production was introduced about 3.4 kWh/PE y of energy were produced in the anaerobic digestion process. On the other hand, 4.3 kWh/PE y were spent if an aerobic stabilisation process was applied. The economic assessment, carried out on the basis of the energy balances, showed that the anaerobic digestion is always economically advantageous if compared to aerobic stabilisation processes, also for small WWTPs. According to the energetic evaluations an environmental balance was assessed, in terms of CO2 emissions. The difference between anaerobic and aerobic processes was about 5.3 kgCO2/PE y in favour of anaerobic processes application.

Bacteria, Anaerobic↗
PubMedDate not supplied

[Disorders affecting the digestive system during sleep].

AIMS: In this work we review the major publications dealing with disorders that affect the digestive system and how they are related to sleep. Development. Sleep disorders occur in 12-25% of the general population and a large percentage of these pathologies are related to disorders of the digestive system. We review the different pathologies and symptoms linked to the digestive tract that give rise to sleep disorders. The study first examined the upper digestive tract, that is, the teeth and teeth grinding, and we then went on to look at gastroesophageal reflux, esophageal motility disorders, peptic ulcer disease, cholelithiasis, gastric ulcer, irritable bowel, proctalgia, the extent to which the disorders are related to pregnancy, disorders at the paediatric age and eating disorders. CONCLUSIONS: Digestive pains during sleep form a heterogeneous clinical picture that disrupts patients' sleep and exerts an influence on their quality of daily living, which in turn may affect sleep and favour the appearance of pains. To date these symptoms have received relatively little attention, but in the few studies that have been carried out, it has not been possible to establish with any degree of accuracy whether sleep and the digestive system share common control mechanisms or not. Research into this type of disorders could help to prevent the appearance of the complications that appear in these clinical pictures.

Abdominal Pain↗
PubMed2004

Application of Methanobrevibacter acididurans in anaerobic digestion.

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.

Acetates↗
PubMedDate not supplied

The Protein Digestibility-Corrected Amino Acid Score (PDCAAS)--a concept for describing protein quality in foods and food ingredients: a critical review.

Protein Digestibility-Corrected Amino Score (PDCAAS) is discussed. PDCAAS is now widely used as a routine assay for protein quality evaluation, replacing the more traditional biological methods [e.g., measurement of the Protein Efficiency Ratio (PER) in rats]. PDCAAS is based on comparison of the essential amino acid content of a test protein with that of a reference essential amino acid pattern and a correction for differences in protein digestibility as determined using a rat assay. Although PDCAAS is a rapid and useful method, it often shows discrepancies when compared to PER values. These discrepancies relate to the following issues: uncertainty about the validity of reference patterns, invalidity of correction for fecal (versus ileal) digestibility, truncation of PDCAAS values to 100%, failure to obtain full biological response after supplementation of the limiting essential amino acid, discrepancies between protein and amino acid digestibility, effects of processing on protein quality, and effects of the presence of antinutritional factors in the matrix containing the protein. Part of the discrepancy between PDCAAS and PER can be overcome by modifications of PDCAAS. This article describes some proposed modifications and puts forward the suggestion that the rat protein fecal digestibility assay be replaced by an in vitro ileal amino acid digestibility assay based on a computer-controlled gastrointestinal model.

Amino Acids↗
PubMed2005

Thermal pre-treatment of primary and secondary sludge at 70 degrees C prior to anaerobic digestion.

In general, mesophilic anaerobic digestion of sewage sludge is more widely used compared to thermophilic digestion, mainly because of the lower energy requirements and higher stability of the process. However, the thermophilic anaerobic digestion process is usually characterised by accelerated biochemical reactions and higher growth rate of microorganisms resulting in an increased methanogenic potential at lower hydraulic retention times. Furthermore, thermal pre-treatment is suitable for the improvement of stabilization and could be realized at relatively low cost especially at low temperatures. The present study investigates the effect of the pre-treatment at 70 degrees C on thermophilic (55 degrees C) anaerobic digestion of primary and secondary sludge in continuously operated digesters. Thermal pre-treatment of primary and secondary sludge at 70 degrees C enhanced the removal of organic matter and the methane production during the subsequent anaerobic digestion step at 55 degrees C. It also greatly contributed to the destruction of pathogens present in primary sludge. Finally it results in enhanced microbial activities of the subsequent anaerobic step suggesting that the same efficiencies in organic matter removal and methane recovery could be obtained at lower HRTs.

Acetates↗
PubMed2005

Anaerobic digestion of slaughterhouse waste with UF-membrane separation and recycling of permeate after free ammonia stripping.

Anaerobic digestion can adapt to free ammonia to a certain extent. During the anaerobic digestion of slaughterhouse waste, however, an ammonia concentration of up to 15 g Nl(-1) can be reached in the sludge liquid and this will even inhibit adapted sludge. To lower this concentration, a fraction of the digester liquid must therefore be continuously separated from the digested sludge and the free ammonia stripped before the liquid is recycled to the digester. A mesophilic laboratory digester was successfully operated with an ammonium concentration of 4-5g l(-1) and a pH of 8.0-8.4. After free ammonia stripping, the excess liquid was treated in a laboratory SBR for nitrogen and phosphorus removal before being added to the receiving water. The effluent had no toxic effect on daphnia and algae.

Abattoirs↗
PubMed2005

Flow pattern visualization in a mimic anaerobic digester: experimental and computational studies.

Advanced non-invasive experiments like computer automated radioactive particle tracking and computed tomography along with computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have appreciable effect on the flow pattern of the digesters.

Bacteria, Anaerobic↗