Anaerobic digestion of pig manure mixed with sewage sludge

This experiment explored the possibility of treating pig manure plus sewage sludge by anaerobic digestion, using batch fermentation at 37°C.The results indicated that the digested materials contained a lower level of putrescible matter when compared to the raw materials. Co-digestion of pig manure and sewage sludge at the ratio of 2:1 seemed to give the best results in terms of reducing the organic load and yielding a higher volume of methane.The experiment should be repeated in digestion tanks of a sewage treatment plant, especially for treating pig manure which has been recognized as the major source of water pollution in Hong Kong.     

Modelling N mineralization from bovine manure and sewage sludge composts

Nitrogen mineralization kinetics were compared in three different soils (pH values: 5.2, 7.1 and 8.6) when treated with bovine manure (BM) and sewage sludge (SS) composts. The soil-compost mixtures were kept at a controlled moisture content of 60% of their water holding capacity (WHC) and were incubated in the dark at 25 °C for 2 years. Five mathematical models were compared (simple exponential, double exponential, special model, hyperbolic and parabolic), using as experimental data the mineralized N accumulated during 360 and 720 days of incubation. The results showed that the best fit for describing the mineralization of organic N from the compost after 1 year of experimentation was obtained with the simple exponential model. However, the special model showed the best fit for data from 2 years of incubation and thus better reflected organic N mineralization over a longer time-span. This suggested that the organic N in the two composts was made up of two organic pools of different degrees of stability.     

Influence of peptone,ammonia water and urea supplements on keratinolytic and associated non-keratinolytic fungi in sewage sludge

A hair-baiting method was used in laboratory study of the influence on the composition of the keratinolytic and non-keratinolytic mycobiota in sewage of adding the ammonium nitrogen sources, peptone, ammonia water and urea. It was demonstrated that, independent of the nitrogen source, the ammonium nitrogen concentration was the critical factor affecting the fungal composition. Ammonium prevented or markedly inhibited the growth of Trichophyton terrestre, with its teleomorph Arthroderma quadrifidum; other geophilic dermatophytes and non-keratinolytic fungi. It also favoured growth of Chrysosporium keratinophilum and some other species, mainly in the genus Chrysosporium. The composition of the keratinolytic mycobiota can be an indicator of sludge organic matter stabilization, and used in relation to sewage sludge at wastewater treatment plants and in reclamation practice.     

Characterizing and modeling hydrogen sulfide production in anaerobic digestion of livestock manure,agro-industrial wastes,and wastewater sludge

Hydrogen sulfide (H₂S) is the most undesirable inorganic gas in biogas from anaerobic digestion (AD). However, H₂S production in AD is complex and understanding of its processes is still limited. This study performed six controlled batch anaerobic co-digestion experiments to investigate H₂S production. Materials were obtained from four field anaerobic digester systems and co-digestion feedstocks from agroindustry. An additional precipitation experiment was conducted to further examine H₂S production dynamics. Digesters containing highly soluble, carbohydrate-based wastes had a high H₂S final specific production (FSP) value. Additionally, the FSP values were negatively correlated with the initial Fe(II):S ratios in the digester liquid of the batch tests. The precipitation experiment indicated that iron sulfide precipitation was preferred in the presence of an anaerobic community. The H₂S production as a time series was successfully modeled using a generalized additive model (R² > 0.82). This study revealed that sulfate, phosphorus, and iron concentrations are important predictors and potential inhibitors of H₂S production in AD. Further examination of real-time H₂S modeling in AD is warranted.     

Vancomycin resistant enterococci (VRE) in Swedish sewage sludge

Background  

Antimicrobial resistance is a serious threat in veterinary medicine and human healthcare. Resistance genes can spread from animals, through the food-chain, and back to humans. Sewage sludge may act as the link back from humans to animals. The main aims of this study were to investigate the occurrence of vancomycin resistant enterococci (VRE) in treated sewage sludge, in a Swedish waste water treatment plant (WWTP), and to compare VRE isolates from sewage sludge with isolates from humans and chickens.     

抗生素耐药基因在畜禽粪便-土壤系统中的分布、扩散及检测方法

抗生素耐药基因作为一种新型的环境污染物已引起研究者的高度关注。畜禽养殖业长期将抗生素添加到饲料中,在促进动物生长、预防和治疗动物疾病等方面起了重要作用。这些抗生素大多数不能被动物完全吸收,在动物肠道中诱导出耐抗生素细菌和抗生素耐药基因,并随着粪便排出体外。畜禽粪便作为重要的抗生素、耐抗生素细菌和抗生素耐药基因储存库,通过堆粪、施肥等农业活动进入土壤环境中,可刺激土壤中耐抗生素细菌和抗生素耐药基因的富集。耐药基因借助于基因水平转移等方式在土壤介质中进一步传播扩散,甚至进入植物中随食物链传播,对生态环境和人类健康造成极大的威胁。为了正确评估抗生素耐药基因的生态风险,本文结合国内外相关研究,系统阐述了畜禽粪便-土壤系统中抗生素耐药基因的来源、分布及扩散机制,同时探讨了细菌耐药性的主要研究方法,指出堆肥化处理仍是目前去除抗生素耐药基因的主要手段,并对今后的研究方向进行展望。     

Codigestion of olive oil mill wastewaters with manure, household waste or sewage sludge

Combined anaerobic digestion of oil mill effluent(OME) together with manure, household waste (HHW) orsewage sludge was investigated. In batch experimentsit was shown that OME could be degraded into biogaswhen codigested with manure. In codigestion with HHWor sewage sludge, OME dilution with water (1:5) wasrequired in order to degrade it. Using continuouslystirred lab-scale reactors it was shown thatcodigestion of OME with manure (50:50 and 75:25 OMEto manure ratios) was successful with a theoreticalOME utilization of 75% and with approx. 87%reduction of the lipids content in OME. An OMEutilization of approx. 55%, and lipid reduction of73% was reached in codigestion with HHW (50:50 and75:25 OME to HHW ratios). The results showed thatthe high buffering capacity contained in manure,together with the content of several essentialnutrients, make it possible to degrade OME withoutprevious dilution, without addition of externalalkalinity and without addition of external nitrogensource.     

Prevalence of verotoxin-producing Escherichia coli (VTEC) in slurry,farmyard manure and sewage sludge in France

AIMS: The aims of the present study were to determine VTEC prevalence in manure, slurry and sewage sludge in France and to characterize the VTEC strains isolated (virulence genes and serotype). METHODS AND RESULTS: Seven hundred and fifty-two samples from 55 farmyard manures, 136 bovine and porcine faeces, 114 slurries, 10 composts, and 437 samples from outflows of sewage wastewater treatment plants were analysed. Twenty-four percent contained isolates which were PCR positive for stx gene. Twenty-one VTEC strains were recovered from positive samples by colony hybridization: 76% of them were positive for stx(2) gene, 33% for stx(1) gene,and 19% for eae gene. One strain belonged to serotype O157:H7 and two others to serogroups O26 and O55, respectively. CONCLUSIONS: Some of the VTEC strains isolated from environments in France should be considered as potentially pathogenic for humans. SIGNIFICANCE AND IMPACT OF THE STUDY: Appropriate handling or use of manure, slurry and sewage sludge is necessary so that contamination of the environment and food by VTEC can be prevented.     

Multivariate analysis of vegetational changes in permanent woodland plots with different sewage sludge treatments

Vegetation data from an experiment on the impact of sewage sludge on woodland vegetation dynamics are analysed by ordination to examine the reaction of a forest community to sludge disturbance. Two different kinds of vegetational response are discussed in relation to horizontal patchiness of vegetation. It is suggested that the species-poor component of the vegetation mosaic observed reveals quicker recovery from sludge disturbance than the species-rich component, which is characterized by a more complicated network of interspecific relations. A high correlation between plot-scores on the first ordination axis and sludge dose is found, indicating that in the altered community the main vegetational gradient reflects the intensity of disturbance. An attempt is made to interpret the main gradients of vegetational variation in terms of ecological indicator values of species. It is concluded that the modified competitive ability of species in a changed environment plays the most important role in building up a new community structure.     

畜禽粪便中抗生素抗性基因的分布特征及消减技术研究进展

随着集约化畜禽养殖业的不断发展,兽用抗生素的长期使用导致畜禽粪便抗生素抗性基因污染日益严重,对生态环境和人类健康造成严重危害。如何有效消减畜禽粪便中的抗生素抗性基因成为当前研究热点。本文系统总结了畜禽粪便中抗生素抗性基因的产生途径、分布和影响因素,并阐述了好氧堆肥、厌氧消化及其强化工艺消减畜禽粪便抗生素抗性基因的研究进展,根据现有工艺研究存在的问题展望了今后的重点研究方向,为畜禽粪便中抗生素抗性基因的消减提供理论基础和技术支撑。     

Occurrence, fate, and biodegradation of estrogens in sewage and manure

The estrogens estrone (E1), 17α-estradiol (E2α), 17β-estradiol (E2β), and estriol (E3) are natural sex hormones produced by humans and animals. In addition, there are some synthetic estrogens, such as 17α-ethinylestradiol (EE2), used for contraception purposes. These compounds are able to produce endocrine disruption in living organisms at nanogram-per-liter levels. In both humans and animals, estrogens are excreted in urine and feces, reaching the natural environment through discharge from sewage treatment plants (STP) and manure disposal units. In STPs, hormone removal depends on the type of treatment process and on different parameters such as the hydraulic and sludge retention times. Thus, hormone elimination rates vary from 0% to 90% in different STPs. Animals are also an important source of estrogens in the environment. Indeed, animals produce high concentrations of hormones which will end up in manure which is typically spread on land. Hence, waste-borne animal hormones may transfer these pollutants to the soil. The purpose of this review is to highlight the significance for both health and the environment of pollution by estrogens and critically review the existing knowledge on their fate and removal in different treatment processes. Relevant information on the microbial degradation of hormones and metabolic pathways is also included.     

Human enteropathogen load in activated sewage sludge and corresponding sewage sludge end products

This study demonstrated a significant reduction in the concentrations of Cryptosporidium parvum and Cryptosporidium hominis oocysts, Giardia lamblia cysts, and spores of human-virulent microsporidia in dewatered and biologically stabilized sewage sludge cake end products compared to those of the respective pathogens in the corresponding samples collected during the sludge activation process.     

Development and application of real-time PCR assays for quantification of erm genes conferring resistance to macrolides-lincosamides-streptogramin B in livestock manure and manure management systems

Erythromycin and tylosin are commonly used in animal production, and such use is perceived to contribute to the overall antimicrobial resistance (AR) reservoirs. Quantitative measurements of this type of AR reservoir in microbial communities are required to understand AR ecology (e.g., emergence, persistence, and dissemination). We report here the development, validation, and use of six real-time PCR assays for quantifying six classes of erm genes (classes A through C, F, T, and X) that encode the major mechanism of resistance to macrolides-lincosamides-streptogramin B (MLS(B)). These real-time PCR assays were validated and used in quantifying the six erm classes in five types of samples, including those from bovine manure, swine manure, compost of swine manure, swine waste lagoons, and an Ekokan upflow biofilter system treating hog house effluents. The bovine manure samples were found to contain much smaller reservoirs of each of the six erm classes than the swine manure samples. Compared to the swine manure samples, the composted swine manure samples had substantially reduced erm gene abundances (by up to 7.3 logs), whereas the lagoon or the biofilter samples had similar erm gene abundances. These preliminary results suggest that the methods of manure storage and treatment probably have a substantial impact on the persistence and decline of MLS(B) resistance originating from food animals, thus likely affecting the dissemination of such resistance genes into the environment. The abundances of these erm genes appeared to be positively correlated with those of the tet genes determined previously among these samples. These real-time PCR assays provide a rapid, quantitative, and cultivation-independent measurement of six major classes of erm genes, which should be useful for ecological studies of AR.     

Characterization of the combined effects of enzyme,pH and temperature treatments for removal of pathogens from sewage sludge

The combined effects of enzyme, pH and temperature treatments for removal of pathogens from sewage sludge were investigated. An adjustment to pH 10 for 24-h at 23 °C or a 3-h hold at 50 °C resulted in a 100% kill of coliforms but a significant count of Salmonella species still survived. However, pH adjustment to 12 with a hold of 48-h at 23 °C or pH adjustment to 10 or 12 and a 3-h hold at 60 °C was required to achieve a 100% kill of Salmonella species. Although protease enzyme treatment at 40 °C with or without alkali treatment eliminated coliforms completely, Salmonella counts were reduced by two to three orders of magnitude. However, complete elimination of pathogens was observed when enzymatic treatment was provided at 50 °C. Application of alkaline protease, through its combined beneficial effects in pathogen reduction, solids reduction and improved solids settling, has potential as an effective procedure for processing of sewage sludge.     

柠檬酸、草酸和乙酸对污泥中镉、铅、铜和锌的去除效果

研究了柠檬酸、草酸和乙酸对污泥中Cd、Pb、Cu和Zn等重金属的去除效果,并分析了污泥中重金属的形态变化和生物有效性.结果表明,随着反应时间和酸浓度的增加,污泥中重金属（Cu除外）的去除率也相应增加.污泥加入柠檬酸溶液反应7 h即可去除污泥中52.0%的Pb和74.2％的Zn, 24 h后可去除76.0%的Pb和92.5%的Zn,草酸和乙酸对重金属的去除率较低.柠檬酸去除的Pb和Zn主要以稳定态存在,并导致污泥中不稳定态重金属的比例上升,其中可交换态重金属浓度有不同程度的增加.虽然有机酸对Cd和Cu的去除率较低,但反应后可交换态Cd和Cu的浓度仍有小幅增加.     

Efficient,high-speed methane fermentation for sewage sludge using subcritical water hydrolysis as pretreatment

A novel biomass-energy process for the production of methane from sewage sludge using a subcritical water (sub-CW) hydrolysis reaction as pretreatment is proposed. The main substances of sewage sludge hydrolyzed by sub-CW at 513 K for 10 min were acetic acid, formic acid, pyroglutamic acid, alanine, and glycine. Fermentation experiments were conducted in an anaerobic-sludge reactor for two different samples: real sewage sludge and a model solution containing components typically produced by the sub-CW pretreatment of sewage sludge. In the experiment for the sub-CW pretreatment of sewage sludge, methane generation was twice that for non-pretreatment after 3 days of incubation. In the model experiment, the methane conversion was about 40% with the application of mixture of organic acids and amino acids after 5 days of incubation. Furthermore, the methane conversion was about 60% for 2 days when only organic acids, such as acetic acid and formic acid, were applied. Because acetic acid is the key intermediate and main precursor of the methanogenesis step, fermentation experiments were conducted in an anaerobic-sludge reactor with high concentrations of acetic acid (0.01–0.1 M). Nearly 100% of acetic acid was converted to methane and carbon dioxide in 1–3 days.     

Characterization of anaerobic non-spore-forming bacteria in municipal sewage sludge and integrated paper-mill waste water

Summary Forty-three isolates of Gram-negative, mesophilic, non-spore-forming anaerobic cellulolytic bacteria were obtained from (i) an anaerobic reactor treating waste water from an integrated paper mill and (ii) an anaerobic sewage-sludge digestor. These isolates were studied for carbohydrate fermentation and fermentation products. By numerical techniques, 22 isolates could be placed in two groups: group A (10 isolates) and group B (12 isolates). The isolates belonging to group A showed degradation of filter paper in 2–7 days. They were slightly-curved long rods and similar toBacteroides cellulosolvens andAcetivibrio cellulolyticus. Acetic acid was produced as major product. The bacteria also produced ethanol, isobutanol, pyruvic and lactic acids. Group B strains degraded filter paper in 4–5 weeks. They were short rods and produced propionic, lactic, succinic and acetic acids as fermentation products. The remaining 21 isolates could disintegrate filter paper in 2–5 weeks. They showed variable fermentation patterns, both as to fermentable carbohydrates and end products. Except for one isolate, which showed obvious similarity toButyrivibrio fibrisolvens, the isolate differed distinctly from reference strains of ruminai origin.

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Caractérisation des bactéries anaérobies non-sporulantes dans la boue résiduaire de station d'épuration des eaux domestiques (boues d'égout) et dans l'eau résiduaire d'une usine intégrale de pâte à papier

Résumé 43 souches de bactéries cellulolytiques Gram-négatives, mésophiles, non-sporulantes, et anaérobies ont été isolées à partir (A) d'un réacteur anaérobie traitant l'eau résiduaire d'une usine intégrale de pâte à papier et (B) de digesteurs anaérobies de boues d'égout. Ces souches ont été étudiées quant à leurs propriétés de fermenter les hydrates de carbone et quant à leurs produits de fermentation. Des techniques numériques ont permis de classer 22 de ces souches dans deux groupes: le groupe A (10 souches) et le groupe B (12 souches). Les souches appartenant au groupe A dégradaient le papier filtre en 2 à 7 jours. Elles se présentaient sous la forme de longs bâtonnets curvilignes et ressemblaient àBacteroides cellulosolvens et àAcetivibrio cellulolyticus. Le metabolite majeur était l'acide acétique. Elles produisaient aussi de l'éthanol, de l'iso-butanol, et des acides pyruvique et lactique. Les souches appartenant au groupe B dégradaient le papier filtre en 4 à 5 semaines. Elles se présentaient sous la forme de bâtonnets courts et produisaient, comme métabolites, les acides propionique, lactique, succinique et acétique. Les 21 souches restantes dégradaient le papier filtre en 2 à 5 semaines. Elles présentaient des profils de fermentation variables tant en ce qui concernait les hydrates de carbone fermentés que les produits finaux. A part une souche qui présentait une similitude évidente avecButyrivibrio fibrisolvens, ces souches différaient de façon marquée d'avec les souches de référence du rumen.

     

Occurrence, growth, and suppression of salmonellae in composted sewage sludge

Composted sewage sludge may be used to improve soil quality, but there remains some doubt concerning the microbiological safety of the product. Sewage sludge composts from 30 municipalities were sampled, and four samples (12%) contained salmonellae (two contained fewer than 0.3/g, and the other two had 21/g and 1.7 X 10(4)/g). All 30 composts were inoculated with salmonellae; the populations decreased at a specific death rate of about 0.15 h-1 over 24 h at 36 degrees C. In irradiation-sterilized composts inoculated with salmonellae, the salmonellae grew at a rate of 0.65 doublings per h for over 24 h. Growth and death rates were found to be moisture and flora associated. The growth or death rates for antibiotic-resistant salmonellae were not different from those of nonresistant strains. It was concluded that the active indigenous flora of compost establishes a homeostatic barrier to colonization by salmonellae, and in the absence of competing flora, reinoculated salmonellae may grow to potentially hazardous densities. The active microflora of moist composts eliminated contaminating salmonellae (10(5)/g) after 6 weeks.     

Transformations of water soluble organic materials during thermophilic composting of sewage sludge

Sewage sludge was composted by adding wood chips as a bulking agent. The decomposition of the cellulosic material was ascertained by measuring the transient concentrations of water soluble sugars. The concentrations were found to increase in accordance with the decomposition of the cellulosic material, provided the operating temperature was kept at a level appropriate for the activity of microorganisms.Two kinds of concentrations of water soluble sugars were measured. One was on the concentration of the total sugars determined by the calorimetric method of Dubois. The other was on the concentration of the reducing sugars determined by the Somogyi-Nelson method. The pattern of HPLC (High Pressure Liquid Chromatogram) was determined utilizing a wave length of 280 nm. Time courses of the sugars concentrations and the HPLC pattern enabled us to detect two sources of cellulosic materials: one from the sewage sludge and the other from the wood chips. The former appears to be decomposed by thermophilic bacteria and thermophilic actinomycetes, whereas the latter is decomposed by thermophilic fungi.