焦化废水COD氨氮降解技术

焦化废水含有机废水,用活性污泥法处理对含氮化合物及构成COD难生物降解的污染物却很难奏效。本文研究采用缺氧——压氧——好氧(即A/A/o)处理工艺,不仅可使COD、氨氮达标排放,对其它污染物处理效果优于活性污泥法。     

Using the Kinetics of Biological Flocculation and the Limiting Flux Theory for the Preliminary Design of Activated Sludge Systems. I: Model Development

Current activated sludge models consider that the removal of biodegradable organics by suspended growth includes rapid enmeshment of the organic particles in the microbial floc, hydrolysis of the complex organic molecules into readily biodegradable organic substances, and oxidation of dissolved organic substances. All of the models assume hydrolysis is the rate-limiting step, but none consider the role that the kinetics of biological flocculation and the sludge settling characteristics may play in defining the activated sludge operating parameters. Several researchers have studied the kinetic of biological flocculation, and have analyzed its role on the removal of particulate COD in suspended growth reactors. It has been demonstrated that a large proportion of the organic matter present in sewage can be removed by biological flocculation using short hydraulic retention times and subsequent settling. This paper demonstrates that the one-dimensional limiting flux theory may be useful for coupling the sludge settling properties with the aeration tank behavior, and is a reasonable first approximation that can be used for activated sludge system design and operation.     

Activated Carbon Addition to an Activated Sludge Model Reactor for Color Removal from a Cotton Textile Processing Wastewater

Color removal from cotton textile processing wastewater by addition of powdered activated carbon (PAC) into a lab-scale activated sludge system was examined. The activated sludge system was continuously operated in different sludge ages (SRTs) and hydraulic retention times (HRTs). SRT = 30?d and HRT = 1.6?d operation resulted in up to 36% color removal and 94% COD removal. PAC was added 100, 200, and 400 mg/L into the activated sludge system under these operating conditions. The results indicated that 100 mg/L PAC was sufficient to remove the maximum color measured (up to 50 m?1) from the wastewater. The addition of PAC did not affect chemical oxygen demand (COD) removal significantly. Oxygen uptake rate (OUR) tests were also performed to investigate the microbial activities controlling the system performance. The average OUR was 74.1 mg/L/h without PAC addition while it was 70 mg/L/h with PAC addition. Adsorbable organic halogens of the effluent wastewater decreased from 400 to 50 μg/L with the addition of PAC. Toxicity dilution factor decreased from 2 to 1.5 with the PAC addition into the activated sludge system.     

Using the Kinetics of Biological Flocculation and the Limiting Flux Theory for the Preliminary Design of Activated Sludge Systems. II: Experimental Verification

Current activated sludge models consider that the removal of biodegradable organics by suspended growth includes: rapid enmeshment of the organic particles in the microbial floc, hydrolysis of the complex organic molecules into readily biodegradable organic substances, and oxidation of dissolved organic substances. All of the models assume that hydrolysis is the rate-limiting step, but none considers the role that the kinetics of biological flocculation and the sludge-settling characteristics may play in defining the activated sludge operating parameters. Several researchers have studied the kinetics of biological flocculation, and have analyzed its role on the removal of particulate chemical oxygen demand in suspended growth reactors. It has been demonstrated that a large proportion of the organic matter present in sewage can be removed by biological flocculation using short hydraulic retention times and subsequent settling. The first paper demonstrates that the one-dimensional limiting flux theory may be useful for coupling the sludge-settling properties with the aeration tank behavior, and the second paper presents experimental evidence that the proposed model is a reasonable first approximation that can be used for activated sludge system design and operation.     

ACE inhibitor-induced angioedema. Incidence, prevention and management

Increased consumer awareness and concern about microbial foodborne diseases has resulted in intensified efforts to reduce contamination of raw meat, as evidenced by new meat and poultry inspection regulations being implemented in the United States. In addition to requiring operation of meat and poultry slaughtering and processing plants under the principles of the hazard analysis critical control point (HACCP) system, the new regulations have established microbiological testing criteria for Escherichia coli and Salmonella, as a means of evaluating plant performance. These developments have renewed and intensified interest in the development and commercial application of meat and poultry decontamination procedures. Technologies developed and evaluated for decontamination include live animal cleaning/washing, chemical dehairing, carcass knife-trimming to remove physical contaminants, steam/hot water-vacuuming for spot-cleaning/decontamination of carcasses, spray washing/rinsing of carcasses with water of low or high pressures and temperatures or chemical solutions, and exposure of carcass sides to pressurized steam. Under appropriate conditions, the technologies applied to carcasses may reduce mean microbiological counts by approximately one-three log colony forming units (cfu)/cm2, and some of them have been approved and are employed in commercial applications (i.e., steam-vacuuming; carcass spray-washing with water, chlorine, organic acid or trisodium phosphate solutions; hot water deluging/spraying/rinsing, and pressurized steam). The contribution of these decontamination technologies to the enhancement of food safety will be determined over the long term, as surveillance data on microbial foodborne illness are collected. This review examines carcass decontamination technologies, other than organic acids, with emphasis placed on recent advances and commercial applications.     

United front--veterinary and medical collaboration

Four cases of concomitant animal and human Salmonellosis were investigated. Liaison took place between veterinary, public health medical and environmental health professionals. An epidemiological association between veterinary and medical disease outbreaks was established following cases in a dairy unit, a poultry unit, a calf rearing unit and one pig and dairy unit (on the same farm). In three cases clinical disease in animals preceded clinical disease in humans while in the fourth case, the poultry unit, salmonella isolations from poultry carcasses coincided with clinical salmonellosis in a human working with the live poultry. Important epidemiological factors are identified. The problems of delay in seeking veterinary advice, compartmentalisation of veterinary and medical practices, and the benefits of direct collaboration between veterinary and medical professionals in the event of a diagnosis of salmonellosis in animals and/or humans are highlighted. A collaborative reporting and liaison model is proposed.     

Lactate and pyruvate changes in the cerebral gray and white matter during posthypoxic seizures in newborn pigs

Cerebral lactate rises after chemically induced seizures, but it is not known if this occurs with posthypoxic seizures. We examined changes in lactate and pyruvate in gray and white matter in the newborn pig brain after a hypoxic insult known to produce seizures and permanent brain damage. Fourteen halothane-anesthetized piglets aged 24-49 h, were instrumented with a two-channel scalp EEG and microdialysis probes positioned in white and gray matter. Forty-five minutes of hypoxia were induced by reducing the fraction of inspired O2 to the maximum concentration at which EEG amplitude was < 7 microV. Postinsult EEG was classified as electroconvulsive activity (ECA) (n = 4) or burst suppression (n = 2), persistently low amplitude (n = 2), or intermittent spikes on normal background activity (n = 6). Six hours after the insult the brains were perfusion fixed for histologic probe localization. Plasma lactate and brain lactate had different time courses with brain having a persistently elevated lactate/pyruvate (L/P) ratio. The highest L/P ratios in gray and white matter were in the two pigs with persistently low amplitude EEG. There was no association between onset of electroconvulsive activity and an increase in lactate or L/P ratio. Posthypoxic energy metabolism is disturbed in both gray and white matter probably because of mitochondrial dysfunction. Seizure activity does not increase cerebral lactate or L/P ratio above the already raised levels found in posthypoxic encephalopathy. These findings cast further doubt on the hypothesis that such seizures are, in themselves, damaging.     

Insight into the lipophilicity of the aromatic N-oxide moiety

PURPOSE: A systematic study to assess the influence of N-oxygenation on the lipophilicity of aromatic weak bases was performed. METHODS: The methods used were experimental (CPC and shake-flask techniques) and computational (AMI semi-empirical method). RESULTS: The intrinsic increment in the log P(oct) system for an oxygen atom added to form an aromatic N-oxide, designated as diff(log PN(O) -N), was -1.91, but the presence of para-substituents markedly affected this value. The good linear relationship (r2 = 0.92) between diff(log PN(O) - N), and the electronic density on the oxygen atom suggests that H-bond acceptor basicity is the main structural factor responsible for the variations in lipophilicity of aromatic N-oxides. Partition coefficients of aromatic N-oxides in dodecane/buffer and chloroform/buffer systems also support this hypothesis. CONCLUSIONS: The solvent-dependent polarity of the N-oxide moiety is mainly due to its marked H-bond acceptor basicity.     

Isolation and characterization of verocytotoxin-producing Escherichia coli O157 strains from Dutch cattle and sheep

In the periods from July to November 1995 and 1996, fecal samples from Dutch cattle and sheep were collected at the main slaughterhouses of The Netherlands, located at different geographic sites. The samples were examined for the presence of verocytotoxin (VT)-producing Escherichia coli (VTEC) of serogroup 0157. E. coli O157 strains could be isolated from 57 (10.6%) of 540 adult cattle, 2 (0.5%) of 397 veal calves, 2 (3.8%) of 52 ewes, and 2 (4.1%) of 49 lambs. Immunomagnetic separation with O157-specific-antibody-coated beads appeared to be significantly more sensitive than conventional plating for detection of the organism in feces. With the exception of two isolates from adult cattle which appeared to be negative for VT genes, all animal isolates were positive for both VT (VT1 and/or VT2) and E. coli attaching-and-effacing gene sequences, and therefore, they were regarded as potential human pathogens. Although genomic typing by pulsed-field gel electrophoresis revealed a wide variety of distinct restriction patterns, comparison of the 63 animal isolates with 33 fecal O157 VTEC strains previously isolated from humans with the diarrhea-associated form of the hemolytic-uremic syndrome by their phage types and VT genotypes showed a marked similarity between animal and human isolates: 30 (90.9%) of the 33 human isolates appeared to be of E. coli O157 strain types also isolated from cattle and sheep. It was concluded that Dutch cattle and sheep are an important reservoir of E. coli O157 strains that are potentially pathogenic for humans.     

Adsorption of Perfluorinated Compounds onto Activated Carbon and Activated Sludge

The adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was investigated in the presence and absence of effluent organic matter (EfOM) at an environmentally relevant concentration range (0.1–500??μg/L). Adsorption of PFOS and PFOA to PAC fitted the Freundlich model well (r2>0.98), and adsorption capacity of PFOS (KF = 17.48) and PFOA (KF = 10.03) in the absence of EfOM was more than one order of magnitude higher than that in the presence of EfOM (KF = 0.66 for PFOS, KF = 0.20 for PFOA), indicating that EfOM greatly reduces the adsorption capacity of PAC. Moreover, EfOM was characterized by ultrafiltration, and fractions of nominal molecular weights were obtained to investigate their effect on the PFOS and PFOA adsorption. The fraction of <1??kDa had greater effect on adsorption than the fraction of >30??kDa, indicating that the similar molecular size of target compounds was the major contributor to adsorption competition. Additionally, biosorption of PFOS and PFOA to activated sludge fitted the linear isotherm (r2>0.9) within a concentration range of 50–400??μg/L. On the basis of our data, the estimated partition coefficient, Kd, was 729??L/kg for PFOS and 154??L/kg for PFOA, respectively, suggesting that PFOS and especially PFOA have a low tendency to partition onto sludge.     

The anesthetic effect of oxygen

Low pressures of O2 (3 to 5 atm) cause convulsions in mice but higher pressures produce a state very similar to anesthesia. The authors estimated the anesthetic potency of O2 in mice which were exposed to either N2O alone, N2O + NaBr, or O2 + NaBr. From the dose-response curves, ED50S were derived for the gases. The ED50 for N5O alone was 1.50 +/- 0.036 atm (n = 12) and 1.11 +/- 0.041 atm (n = 12) in the presence of NaBr, a reduction of 25 percent. The O2 ED50 with NaBr was 3.91 +/- 0.077 atm (n = 12). After correction for the NaBr, the ED50 of O2 is estimated at 5.3 atm. This is lower than predicted from the lipid solubility of O2.     

Nature and amount of aerial pollutants from livestock buildings

The air in animal housing contains gases, odours, dust particles and microorganisms which are discharged by way of the ventilation system into the environment. There is increasing concern within parts of the population that these compounds may affect the respiratory health of people living close to livestock enterprises. A brief survey is presented on airborne emissions from livestock buildings. About 136 gaseous compounds are analysed in animal house air of which only 22 are quantified. The most environment-related compounds are ammonia and methane. It is assumed that German animal husbandry emits up to 750,000 Mg ammonia per year. The concentrations of airborne microorganisms in livestock buildings are between some 100 and several 1000 per liter. Staphylococcae, streptococcae, colilike bacteria, fungi, moulds and yeasts are regularly found. The 24 h average concentrations of dust in animal barns vary considerably. In poultry houses the highest inhalable resp. respirable dust concentrations (up to 10 mg/m3 resp. 1.2 mg/m3) were found, followed by pig houses (5.5 mg/m3) and cattle barns (1.22 mg/m3 resp. 0.17 mg/m3). The concentrations of endotoxins in the airborne dust can range from 0.6 ng/m3 (cattle, respirable dust) to 860 ng/m3 (laying hens, inhalable dust). The presently discussed occupational health threshold at the workplace is around 5 ng/m3 (50 EU/m3). The emission rate for respirable dust from piggeries is at about 60 mg/h, from poultry houses nearly 300 mg/h and from cattle barns at 20 mg/h, related to 500 kg liveweight of the animals. Little is known about the distances these particles are transported through the air outside the animal buildings.     

Research notes: Prevalence of selected microbial pathogens in processed poultry waste used as dairy cattle feed

Processed poultry litter intended for dairy cattle feed was collected on 13 dairy ranches in the San Joaquin Valley of California and analyzed for the presence of significant bacterial pathogens associated with clinical disease in cattle or foodborne disease in humans. Litter samples were collected from the surface and interior of the litter piles upon arrival on the dairies and 2 to 4 wk later. Litter samples were cultured for Salmonella, Escherichia coli, Campylobacter, and other bacteria. The temperature of the litter piles was obtained on the surface and interior at each sampling. Dry matter was determined for each sample. No Salmonella, E. coli O157, or Campylobacter was identified (n = 104). Other E. coli strains were found in 8 out of 52 samples on arrival and 4 out of 52 samples at 2 to 4 wk after arrival. Although the surface and interior temperatures of the litter pile were different (23 C vs 50 C, respectively), the mean temperatures did not significantly change with time on the ranches. Average dry matter content did not differ between samples. In conclusion, the pathogens under investigation were not detected in processed poultry litter on these California dairy ranches upon arrival at the dairy or 2 to 4 wk later.     

Determining the Volatile Fatty Acid Equivalent in Thermophilic Aerobically Digested Sludge Supernatant

Thermophilic aerobically digested (TAD) sludge supernatant has been found to be a potential carbon alternative for biological nutrient removal (BNR) enhancement in wastewater treatment plants. Carbonaceous substrates, other than the volatile fatty acids (VFAs) in TAD supernatant, were also found to be utilizable in BNR enhancement; however, these carbon compounds could not be detected by conventional chemical analyses (e.g., gas chromatography). A headspace carbon dioxide (CO2) monitoring method was tested in this study to estimate the overall available carbon source, or the VFAs accumulated in a microaerated TAD operation. This on-line method uses real activated sludge and TAD supernatant samples to determine the available carbon equivalent in real time. In comparison to the gas chromatography (GC) analyses of the TAD supernatant samples, the headspace CO2 monitoring method resulted in “overestimation” of VFA concentrations, in both the phosphorus release and denitrification reactions. Operating results suggested that the CO2 monitoring approach was capable of revealing the overall VFA equivalent that could be available for the main BNR reactions.     

Fate of Anionic Surfactants in a 38?ML/Day UASB-Based Municipal Wastewater Treatment Plant: Case Study

The outcome of a 15-month monitoring study (August 2004–October 2005) on the anionic surfactants (AS), at the 38?ML/day up-flow anaerobic sludge blanket (UASB)-based sewage treatment plant (STP) is described. The average removal of AS was only around 57%. Appreciable concentration of AS was being discharged to the watercourse (average 2.41?mg/L; range 0.63–5.16?mg/L). On an average dried sludge contained 1,560?mg?AS?kg?1 dry weight. Mass balance indicated that, AS load of the orders of 23 and 33% is removed by adsorption in UASB reactors and polishing ponds (PP), respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation ( ≈ 70%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100?units, than 43 and 7?units are discharged with treated effluent and dried sludge, respectively, whereas 33 and 16?units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds, respectively.     

SSPRSD Using a Filamentous Fungal Strain Penicillium expansum BS30 Isolated from Wastewater Sludge

A filamentous fungal strain (Penicillium expansum BS30) isolated from a municipal wastewater treatment plant was used in this study to simultaneously reduce sludge solids, pathogens, and improve the sludge settling and dewaterability [simultaneous solids and pathogens reduction, settling and dewatering (SSPRSD)] in shake flask and 10-L bioreactor experiments. The fungal strain role in the SSPRSD process was evaluated at different temperatures and inoculum (spores) concentrations. The best performance of the process was achieved at incubation temperature of 25°C and inoculum concentration of 106?spores/mL. At these optimal conditions, suspended solids (SS) and volatile SS were degraded >50 and >53%, respectively. The capillary suction time value recorded (<13?s) was lower than that required for sludge dewaterability (<20?s). The populations of total coliforms and Salmonella (pathogen indicators) were reduced by two and four log cycles, respectively. A study on molecular screening of penicillin biosynthesis gene cluster and toxic organic compounds degrading machinery of the fungal strain was also conducted. It was found that the fungal strain possessed the penicillin-producing gene and toxic organic compounds degrading genes, and therefore may be helpful in degrading these compounds.     

Anesthetics and cerebral edema

Localized edema follows the freezing of a small area of cerebral cortex. Effects of five subsequent hours of anesthesia on this edema were studied in six groups of six dogs each. Six anesthetic techniques were studied. In six additional "awake" dogs, anesthesia (halothane) was discontinued immediately after the lesion was made. Eight control dogs received neither anesthesia nor cryogenic injury. Control white matter contained 67.4 +/- .4 (mean +/- SE) per cent water by weight. Twenty-four hous after the cryogenic injury, water accounted for the following percentages of total weight of white matter adjacent to the lesion: 60 mg/kg pentobarbital, 73.2 +/-.9; 70 per cent N2O/Innovar, 73.6 +/- .9; "awake", 77.9 +/- .9; 1.95 per cent enflurane, 78.2 +/- .9; 1.33 per cent isoflurane, 78.6 +/- .8; 0.86 per cent halothane, 78.2 +/- .6; 1.89 per cent halothane, 79.7 +/- .6. Peak intracranial pressures (ICP) were 15.4 +/- 1.3 torr with pentobarbital, 21.6 +/- 1.8 torr with N2O/Innovar, and 31.1 +/- 2.6 to 38.3 +/- 4.5 torr with the halogenated anesthetics. The water content of white matter and ICP were significantly lower (P less than 0.05) in animals receiving pentobarbital or N2O/Innovar anesthesia than in animals receiving inhalation anesthetics. The authors conclude that pentobarbital and fentanyl-droperidol (Innovar) limit the extent of cerebral edema, but that inhaled anesthetics do not.     

Pyridyloxobutyl adduct O6-[4-oxo-4-(3-pyridyl)butyl]guanine is present in 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone-treated DNA and is a substrate for O6-alkylguanine-DNA alkyltransferase

The lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is activated to reactive metabolites that methylate or pyridyloxobutylate DNA. Previous studies demonstrated that pyridyloxobutylated DNA interferes with the repair of O6-methylguanine (O6-mG) by O6-alkylguanine-DNA alkyltransferase (AGT). The AGT reactivity of pyridyloxobutylated DNA was attributed to (pyridyloxobutyl)guanine adducts. One potential AGT substrate adduct, 2'-deoxy-O6-[4-oxo-4-(3-pyridyl)butyl]guanosine (O6-pobdG), was prepared. This adduct was stable at pH 7.0 for greater than 13 days and to neutral thermal hydrolysis conditions (pH 7.0, 100 degrees C, 30 min). Under mild acid hydrolysis conditions (0.1 N HCl, 80 degrees C), O6-pobdG was depurinated to yield O6-[4-oxo-4-(3-pyridyl)butyl]guanine (O6-pobG). O6-pobdG was hydrolyzed to 4-hydroxy-1-(3-pyridyl)-1-butanone and guanine under strong acid hydrolysis conditions (0.8 N HCl, 80 degrees C). O6-pobG was detected in 0.1 N HCl hydrolysates of DNA alkylated with the model pyridyloxobutylating agent 4-(acetoxymethylnitrosamino)-1-(3-[5-3H]pyridyl)-1-butanone ([5-3H]NNKOAc). When [5-3H]NNKOAc-treated DNA was incubated with either rat liver or recombinant human AGT, O6-pobG was removed, presumably a result of transfer of the pyridyloxobutyl group from the O6-position of guanine to AGT's active site.     

Biological treatment of dye wastewaters using an anaerobic-oxic system

Three dye solutions, namely, C.I. Acid Yellow 17, C.I. Basic Blue 3, and C.I. Basic Red 2, were treated in an upflow anaerobic sludge blanket (UASB) reactor followed by a semi-continuous aerobic activated sludge tank. When hydraulic retention time was about 12 hours, no significant color removal was observed in the aerobic stage. In the anaerobic stage, Acid Yellow 17, Basic Blue 3, and Basic Red 2 were removed by 20%, 72%, and 78%, respectively. To treat wastewater from a dye manufacturing factor with COD concentration of 1200 mg/l and Color of 500 degrees (dilution factor), an UASB reactor (4.5 liters) and an activated sludge tank (5 liters, adjustable), COD and color were removed by more than 83% and 90% at a COD loading rate of 5.3 kg COD/m3-day in the anaerobic stage, and at the hydraulic retention time of 6-10 hours for the anaerobic stage and 6.5 for the aerobic stage. The anaerobic stage of the A/O system removes both color and COD. In addition, it also improves biodegradability of dyes for further aeroic treatment.     

Lime-Soda Softening Process Modifications for Enhanced NOM Removal

In this research, a number of process modifications to the lime-soda softening process were examined, including utilization of high Mg-content lime, addition of MgCl2, and the recycling of softening sludge, in order to improve the removal of natural organic matter (NOM) and reduce the formation of disinfection byproducts (DBPs). Jar test results showed that dissolved organic carbon (DOC) removal increased and trihalomethane (THM) formation was reduced as the magnesium in hydrated lime increased, and was directly correlated with the amount of magnesium removed from the system. However, a dolomitic quick lime hydrated under atmospheric conditions resulted in less effective DOC removal due to a lack of available Mg, and subsequently, less co-precipitation of Mg(OH)2-NOM complexes. The addition of MgCl2 to the raw water also increased DOC removal and reduced THM formation in both the presence and absence of softening sludge, with DOC removal increasing as softening sludge and magnesium dosages increased. As high as 43% removal of DOC was achieved at the stoichoimetric lime-soda ash dose in the presence of 457 mg/L sludge and 7.5 mg/L MgCl2, as compared to only 13% removal in the absence of sludge and MgCl2. The recycling of softening sludge had little or no effect on the hardness and the level of inorganic elements in treated water. The results presented here provide new approaches for improving DBP precursor removal during lime-soda softening without significantly increasing lime and soda ash dosage or the generation of waste sludge.