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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Characterization of enterococci populations in livestock manure using BIOLOG

The BIOLOG system was used to generate knowledge of enterococci populations found in fresh and dry manure of livestock (cattle (Bos taurus), horse (Equus caballus), and sheep (Ovis aires)). Six-hundred and forty Enterococcus isolates from the host sources were observed as a combined fresh manure unit and a combined dry manure unit, E. casseliflavus and E. mundtii were predominant in fresh manure (36% and 35%, respectively) as well as in dry manure (51% and 28%, respectively). The other species were found at a frequency of less than 10%. A chi-square test of the two most predominant Enterococcus sp. indicated that there were some significant differences among the frequency of E. casseliflavus and E. mundtii in cattle and sheep, but not horse. Despite these differences, these two species were overwhelmingly predominant among all three livestock sources.     

Removal capacity of water plant alum sludge for phosphorus in aqueous solutions

Abstract

Alum sludge, which is a waste product from a potable water treatment process, was tested as an inexpensive alternate adsorbent for phosphorus in wastewater. The sludge was composed dominantly of sand size aggregates, and could remain stable in aqueous media. The majority of reactive Al in alum sludge was present as an amorphous phase, and seemed to be the major absorbent for P. The batch sorption test showed that the removal of P was influenced by the solubility of Al, Fe and organic carbon depending on pH condition. The acidic condition favored the removal of P, and there was a side effect in the P removal process such as dissolution of Al and organic C at acidic (pH < 4) and alkaline (pH < 8) conditions. The pH range from 4 to 6 was effective for all inorganic and organic phosphates with a low solubility of Al and organic C. The maximum adsorption capacity of alum sludge was calculated as 25,000 mg/kg for orthophosphate, and followed the order: orthophosphate > pyrophosphate > triphosphate > organic phosphate (adenosin). From the column test with a 30 mg/L orthophosphate solution at a flow rate of 3.0 ml/min, the alum sludge removed P to less than 1.0 mg/L over 250 pore volumes at initial pH 4, and 200 pore volumes at initial pH 5, respectively.     

Microbial populations and sludge characteristics in thermophilic aerobic sewage sludge digestion

Summary Estimates of bacterial numbers from raw sewage sludge and sludge treated by thermophilic aerobic digestion were compared with simple indicators of sludge quality and concentrations of potential substrates. Significant differences were found between sludge types for all but one of the variables examined (frequency of dividing cells). During a stable period of digestor operation, the average number of viable obligate thermophiles present in digested sludge (1.63 × 10⁶ ml^–1) was approximately 10²-fold greater than in feed sludge (1.10 × 10⁴ ml^–1). Total numbers of bacteria were slightly greater in digested sludge (3.24 × 10¹⁰ ml^–1) than in feed sludge (2.39 × 10 ml^–10), as were viable counts of bacteria at incubation temperatures of 37°C and 55°C. Significant correlation was found between viable counts of bacteria at 37°C and 55°C for digested sludge, and 65°C and 55°C for feed sludge. The numbers of obligate thermophiles present and the total of bacteria present were related to the temperature and pH of the digested sludge and inversely related to the numbers ofEscherichia coli and coliforms present, which were not detected at temperatures greater than 50°C.     

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.