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At least 181 records · Page 10Linked to original sources
PubMed1995

Survival of E. coli and Salmonella populations in aerobic thermophilic composts as measured with DNA gene probes.

Aerobic, thermophilic composting is a widely practiced method for disposal of organic wastes. The wastes which are composted include biosolids from waste water treatment plants (WWTP), and biowastes (food scraps and yardwaste). Important hygiene issues are involved in composting since many potential pathogens may be present in the fresh wastes. In this study, the survival of Salmonella and Escherichia coli is examined during aerobic composting of municipal solid wastes, municipal wastewater sludge and biowastes. A laboratory compost was prepared by inoculating with 10(7) Salmonella typhimurium Q and Escherichia coli B. In both industrial and laboratory trials, gene probes were used to determine at what time during the composting and at what temperature these bacteria became undetectable. It was observed that Salmonella and E. coli survived for 59 days at about 60 degrees C in an industrial compost. The bacteria became undetectable after the temperature decreased from 62 degrees C to about 40 degrees C in the compost curing. The bench scale trials showed that E. coli B survived for at least 9 days at 60-70 degrees C in a biowaste (food waste) compost or a waste water sludge compost. Salmonella typhimurium Q survived for at least 9 days over 60 degrees C in the food biowaste compost and at least 5 days in the waste water sludge compost. Data collected show that the temperature or the time of high temperature is difficult to correlate to the destruction of the pathogen, Salmonella, or the pathogen indicator, E. coli. These results suggest that the mechanism for removal of these microorganisms during aerobic composting is complex and not simply the result of a thermal physical environment.

Aerobiosis↗
PubMed1995

[Composition and ways of reusing activated carbon sludge from surface water treatment plants].

By using activated carbon (PAC) or by other water treatment procedures remarkable amounts of sludges are produced that have normally to be discharged as wastes outside the plant site. The research objective of this study is to get basic information about the quality of PAC sludges to characterise these materials in order to decide between depositing or re-use/recycling. On four water works with artificial ground water recharge and PAC treatment plants to eliminate pesticides from surface waters detailed analyses and experiments were carried out. The determination of carbon, nitrogen, other nutrient elements, heavy-metals and organic pollutants reveal greatly differing amounts within the water works and during the year. The treatment techniques had an important influence on the chemical composition of the sludges. Mixing of PAC sludges with other sludges strongly reduced the amount of carbon. Heavy metals were present only in small quantities. Sludge from one plant, however, contained elevated concentrations of arsenic. PAC sludges from plants treating river water had considerably high amounts of adsorbable organohalogen. Leaching experiments performed with the sludges demonstrated that only small quantities of pollutants are extractable. For most sludges a deposition on domestic refuse dumps is possible. An alternative way is to discharge the liquid sludges into municipal sewage treatment plants. Addition to the biological treatment tank significantly reduced the concentration of AOX in the sewage effluent. Laboratory experiments and field studies on heavily polluted dump leachates showed a remarkable remaining adsorption capacity of the PAC. As a consequence, PAC sludges have to be considered not exclusively as wastes, but rather as valuable materials for purification processes treating waste waters with high loads of organic, especially organohalogen, substances.

Adsorption↗
PubMed1996

[The sat4 streptothricin acetyltransferase gene of Campylobacter coli: its distribution in the environment and use as epidemiological marker].

The main of this study is to give evidence about the spread of streptothricin resistance within Campylobacters which were isolated from animals, men and environmental sources. Streptothricin resistant Campylobacters were isolated over a five years period, when the use of streptothricin for ergotropic purposes was not allowed, from slurry of swine, slurry of cattle, waste water of a goose farm and waste water of a communal sewage treatment plant. The streptothricin resistance was found to be connected with resistances to kanamycin and streptomycin (MIC > 1024 micrograms/ml). For DNA-DNA-hybridisation we used a gene probe derived from the streptothricin acetyltransferase determinant sat4 from Campylobacter coli to find out epidemiological associations between Campylobacters of different origin. The hybridisation experiments show that all streptothricin resistant strains, which were isolated from one ecosystem or where an epidemiological link seems given, have sat4 positive signals at identical positions of the digested and blotted chromosomal DNA. The detection of the sat4 gene seems to be a good tool to discriminate clonal diversities within multiple antibiotic resistant Campylobacters.

Acetyltransferases↗
PubMedDate not supplied

Specific resistance to filtration of biomass from membrane bioreactor reactor and activated sludge: effects of exocellular polymeric substances and dispersed microorganisms.

This study investigates the effect of dispersed microorganisms and exocellular polymeric substances on biomass dewaterability. Specific resistance to filtration (SRF) was measured for biomass from a membrane bioreactor and a completely mixed activated sludge system. Both laboratory-scale reactors were fed with synthetic wastewater and operated at a high food-to-microorganism ratio (F/M) (1 to 11 kilograms chemical oxygen demand per kilogram mixed liquor volatile suspended solids per day [kgCOD/(kg MLVSS.d)]) and short solids retention times (0.25 to 5 d). The SRF values were affected by strong interactions of three parameters: (1) the mixed liquor suspended solids concentration, (2) the amount of dispersed microorganisms, and (3) the exocellular polymeric substances (EPS) concentration. At F/M smaller than 2 kg COD/(kg MLSS.d) and mixed liquor suspended solids (MLSS) concentration higher than 2000 mg/L, increasing amount of dispersed microorganisms in the biomass yielded higher SRF values. However, at high F/M (> 5 kg COD/kg MLSS.d) and low MLSS concentrations (< 600 mg/L), lower EPS concentrations resulted in slightly smaller SRF values, even though the amount of dispersed microorganisms in the biomass was much higher. Thus, at low MLSS concentrations, EPS concentrations rather than the amount of dispersed microorganisms tend to control SRF.

Bacteria↗
PubMed2004

[Effects of Mn2+, Mo6+ and Zn2+ on the components change of extracellular polymeric substances in activated sludge].

By specific oxygen uptake rate, (SOUR) measurements of activated sludge with different metal ion concentration, the optimal stimulation concentrations of Mn2+, Mo6+ and Zn2+ were determined. Then within each metal ion stimulation concentration range, extracellular polymeric substances (EPS) were extracted from activated sludge and its components (protein, polysaccharide and nucleic acid) contents changes were investigated. The results showed that the optimal stimulation concentration of each metal ion is 1mg x L(-1). EPS components of activated sludge vary obviously with Mn2+ and Zn2+ concentration change but not with Mo6+. After storage at low temperature, EPS quantities in activated sludge are reduced with polysaccharide reduction is the most.

Bacterial Adhesion↗
PubMed2005

Quantitative analysis of biological effect on membrane fouling in submerged membrane bioreactor.

The objective of this study is to investigate solids concentration and extracellular polymeric substance (EPS) effects on the membrane fouling in the submerged membrane bioreactor. The relationship between the solids retention time (SRT) and the amount of EPS is observed in three lab-scale MBRs. Additionally, the EPS effect on membrane fouling is quantified by calculating the specific cake resistance (alpha) using an unstirred batch cell test. By observing the sludge over a long period under various SRT scenarios, a wide range of EPS and membrane fouling data is obtained. These observations provide sufficient evidence of the functional relationship between SRT, EPS and alpha. As SRT decreases, the amount of EPS bound in sludge floc becomes higher in the high MLSS condition (> 5,000 mg/L). The amount of EPS in the sludge floc has positive influence on alpha. A sigmoid trend between EPS and alpha is observed and the functional relationship obtained by dimensional analysis is consistent with the experimental results.

Bacteria, Aerobic↗