Effects of temperature,storage time and pH on survival of Escherichia coli in source‐separated yellowwater

Laboratory‐scale experiments on the survival of Escherichia coli in raw, undiluted, freshly collected, source‐separated yellowwater were performed. Concentrations of E. coli and its survival at different temperature regimes and storage times were measured in yellowwater originally cross‐contaminated with faeces and yellowwater purposely contaminated (deliberately spiked) with faecal material. The temperature regimes of cold (4°C), mild (10°C) and warm (22°C) were the limited factors, whereas the storage time of the contaminated yellowwater was unlimited and lasted until the E. coli concentrations reached the limit of detection of < 1 Most Probable Number (MPN)/100 mL. Temperature and pH played the main role in the inactivation and longevity of E. coli in source‐separated yellowwater. The mild storage conditions were the most favourable for the persistence of E. coli, which reached 40 days with a concentration of 2.0 E+03 MPN in 100 mL of undiluted yellowwater.     

Effects of temperature and pH on the growth of heterotrophic bacteria in waste stabilization ponds

This paper presents the effects of temperature and pH on the growth of heterotrophic bacteria in Chlorella vulgaris-heterotrophic bacteria culture. The growth of heterotrophic bacteria was studied at 10, 15, 20 and 30°C, and pH was controlled from 3.0 to 11.5 in a series of fed-batch chemostat reactors supplied with glucose as the sole source of carbon. Samples were analyzed for heterotrophic bacteria by tryptone glucose extract agar in triplicate. The agar pH of 7.0 was the best for enumeration of heterotrophic bacteria. The bacteria grown at pH near neutral were more sensitive to the variation of agar pH than those grown at very alkaline pH. No significant difference in the number of cells capable of forming colonies was noted for incubation temperature of 20 and 35°C, but the lag time for colony formation was longer at 20°C. Samples for enumeration of heterotrophic bacteria collected from algal-bacterial systems such as waste stabilization ponds are recommended to be incubated at 35°C for 72 h. Depending on the pH of the culture, about 86–98% of the cells capable of forming colonies will be visible to the naked eyes after incubation at 35°C for 72 h. At the steady state conditions, heterotrophic bacteria were not sensitive to temperature in the range of 10–20°C. However, at 30°C, a notable competition for glucose between Chlorella vulgaris and heterotrophic bacteria was observed. This competition was responsible for the low bacterial density near neutral pH. No evidence was found to support the view that the discharge of bactericidal substances from Chlorella vulgaris was responsible for reduction of heterotrophic bacteria at high pH.     

Factors affecting the vermistabilization process: Temperature,moisture content and polyculture

Vermistabilization is the stabilization of organic wastes using earthworms. The worms maintain aerobic conditions in the wastes and accelerate and enhance the biological decomposition of the wastes. This study evaluated several fundamental factors that affect the performance of the process such as temperature, moisture content of the waste material and the combined use of several earthworm species (polyculture).The earthworms Dendrobaena veneta, Eisenia fetida, Eudrilus eugeniae, Perionyx excavatus and Pheretima hawayana were used in one or more of the studies. The best growth and reproduction of these species occurred at temperatures of 20–25°C. Growth of all five species was reduced at 30°C and death occurred at 35°C. Of the five species, E. fetida produced the largest number of young in a 20 week study. The growth of E. fetida occurred optimally in media with a total solids content, wet basis, of between 9–16%. Polyculture did not have any obvious advantages over monoculture.     

Inactivation mechanisms of bacterial pathogen indicators during electro-dewatering of activated sludge biosolids

Electro-dewatering is an energy-efficient technology in which an electric field can increase the dryness of biosolids from secondary wastewater treatment from 15% w/w to 30-50% w/w. Here, we address bacterial pathogen indicators inactivation (total coliforms, Escherichia coli and aerobic endospores) during electro-dewatering, investigating the roles of electrochemically generated oxidants, extreme pH, and high temperature (from Joule heating). Our results demonstrate that temperature is the primary factor affecting total coliforms and E. coli inactivation. First, several electro-dewatering cycles were used to increase sludge temperature to about 100 °C after 6 min, during which time the average pH decreased from 7 to 3.6 after 10 min. Total coliforms and E. coli MPNs reached their detection limits after 6 min (with 4-5 logs of inactivation for total coliforms and 3-4 logs for E. coli). In contrast, aerobic endospores were not inactivated under these conditions; rather, their germination appeared to be stimulated by 6-8 min of electro-dewatering. Second, the dewatering cake was separated into four horizontal layers. After 8 min of electro-dewatering, the pH in the top layers decreased to 3, whereas the pH in the bottom layers increased to 8. Inactivation of total coliforms and E. coli in the sludge cake was similar in all layers, increasing with time, suggesting that oxidants and extreme pH are secondary inactivation factors. Finally, electrodes were cooled to maintain a temperature less than 34 °C. Although pH decreased significantly after 12 min of electro-dewatering, there was no significant bacterial pathogen indicator inactivation at low temperature.     

A simple technique for the differentiation of Escherichia coli in water examination

New media for the demonstration of gas and indole production in a single tube were compared with media recommended by Report 71 for use in the 44°C confirmatory test for E. coli. The results demonstrate that the use of mannitol can reduce the numbers of false positive and false negative gas reactions. Indole-production tests may be performed in the same tube as the mannitol fermentation test by including tryptone in the medium. Tryptone mannitol ricinoleate broth and tryptone mannitol broth were found to be most suitable for the confirmation of E. coli in coliform presumptive tubes and membrane filter colonies respectively. The results of the mannitol fermentation and indole-production tests are available within 24 h at 44°C. The media are inexpensive and simple to prepare.     

Comparative studies of methods for the enumeration of coli aerogenes bacteria and E. coli in surface water

In a comparative study of four enrichment media for the detection of bacteria of the coli aerogenes group, formate glutamate medium was found to be the best one. No significant differences were assessed between the three confirmation media used in this study.For the detection of E. coli, the use of Eijkman lactose broth, incubated in an air incubator at 44°C, was found to be better than the use of Eijkman glucose broth. When this method was applied, no significant differences could be observed between the results obtained upon immediate testing of the samples, and when the same samples were examined after 24 h storage at 4–6°C, as is often inevitable in practice.For the combined detection of E. coli and the coli aerogenes group, which may be required in practice, the formate glutamate medium proved again to be the best one. No evidence was found that use of this procedure may result in a low E. coli counts. On the contrary, this technique gave even slightly higher results than the direct Eijkman 44°C-procedure. Suitable confirmation tests on gassing tubes are required when this 37°C-procedure is used.     

Disinfection by in-duct ultraviolet lamps under different environmental conditions in turbulent airflows

In this study, we investigated the effects of environmental factors such as airflow velocity, relative humidity (RH), temperature, and duct reflectance on the performance of in-duct UVC lamps. Staphylococcus epidermidis, Pseudomonas alcaligenes, and Escherichia coli were used as the test bacteria. The UV irradiance, disinfection efficacy, and UV susceptibility constant (Z value) of the test bacteria were experimentally determined. The results showed that the UV disinfection efficacy decreased as the airflow velocity and RH increased. The maximum UV disinfection efficacy was obtained at temperature of 20-21°C compared with the performance at lower temperature (15-16°C) and higher temperature (25-26°C). When the RH increased from 50% to 90%, the Z values of airborne bacteria reduced by 40%, 60%, and 38% for S epidermidis, P alcaligenes, and E coli, respectively. Besides, susceptibility constants had lower values under both cooling temperature (15-16°C) and heating temperature (25-26°C) compared with that under the temperature of 20-21°C. It was observed that S epidermidis generally had the highest resistance to the UV irradiance. The results also showed that the UV disinfection efficacy was lower in the duct with a black surface than in the clean duct.     

Fate of Escherichia coli experimentally injected in a drinking water distribution pilot system

Detection of coliforms and E. coli in drinking water distribution systems can be explained by accidental contaminations and/or growth of these bacteria in the network. This last point still remaining debatable, an experiment was carried out with two E. coli strains (E. coli O126:B16 and one isolated from a drinking water distribution system) separately injected in a drinking water distribution pilot plant continuously fed with drinking water. The work aimed to study (i) the partition of the injected bacteria between the water phase and the indigenous biofilm phase and (ii) the kinetic of disappearance or growth of these bacteria.Depending on the strain, 1–50% of injected bacteria adsorbed within a few hours to the indigenous bacterial biofilm. During the first 5–7 days, both E. coli populations behaved similarly: the total number of injected bacteria decreased more quickly than the theoretical washout (death, lysis, predation, ...). Then the number of these bacteria slowly increased and at day 9–12, the number of recoverable injected bacteria became higher than the predictable number calculated from the theoretical washout. This result clearly proves that both E. coli strains are able to grow at 20°C in the absence of residual chlorine in a distribution network system largely colonized with an autochthonous population. However, colonization of the network by E. coli strains was only partial and transient.     

In situ persistence of indicator bacteria in streams polluted with acid mine drainage

Persistence of indicator organisms (total coliforms, fecal coliforms, and fecal streptococci) associated with natural samples of raw sewage was studied following in situ exposure to five aquatic environments. Three of these streams contained significant amounts of acid mine water (AMW) while the other two were relatively uncontaminated. Indicator organisms were rapidly killed upon exposure to the acid mine systems, whereas little reduction in numbers was observed in the uncontaminated streams. Seasonal changes affected survival of indicators as reflected by prolonged persistence at colder in situ water temperatures. The fecal coliform group was most susceptible to the AMW stress, while the fecal streptococci were most persistent. An enrichment technique resulted in substantially enhanced recovery of certain species of sublethally injured survivors of acid stress. Enrichment was particularly beneficial for recovery of AMW-injured fecal coliforms. Relatively little improvement in recovery of fecal streptococci was afforded by the enrichment technique.     

A modified method for removal and stabilization of cesium metal in the vitrified matrix

Laboratory experiments were designed to investigate the separation and stabilization of cesium metal. Cesium was removed from simulated waste through sorption under certain physicochemical conditions. Silica sand (locally purchased) was used to remove cesium from simulated liquid waste. The range of pH and temperature was optimized and maximum removal (94–98%) of cesium was achieved with pH 10 at the temperature 36°C. Under optimized conditions with a temperature range of 301–315K ΔH, ΔSand ΔG _{309 K} for 150 ppm solution are ?27.22 ± 0.18 KJ/mol, ?74.1 ± 0.96 J/mol and ?3071 ± 2.1 KJ/mol respectively, and for 200 ppm solution thermodynamic entities are ΔH = ?20.2 ± 0.20 KJ/mol, ΔS = ?47.86 ± 0.66 J/mol and ΔG _{301 K} = ?4344 ± 3.7 KJ/mol. The sorbed metal ion has chances of desorption under changed physicochemical conditions in final disposal. To overcome this problem the final “secondary waste (metals on sorbents)” was stabilized by converting it into a stable vitreous borosilicate matrix through the vitrification process to prevent leaching. It was found that the sorbed cesium was evaporated during heating at 1250°C. The evaporation of cesium during vitrification was overcome by modifying the process. This modified vitrification process is found excellent to immobilize the sorbed cesium. Stability was tested by desorption attempts at different pH.     

A national field survey of house temperatures

Information about temperatures in houses is of importance in assesing the value of various energy conservation measures and gives an indication of the standards of thermal comfort enjoyed by the occupants. In the present paper results are discussed of the most extensive survey of domestic dwelling temperatures to have been taken in the U.K. During February and March 1978, when the outside temperature was close to the average for the heating season, spot measurements of the wet- and dry-bulb temperatures were made in each room of 1000 homes nationwide. On the same occasion, an interview was conducted with an adult member of the household to obtain information on thermal comfort conditions and heating patterns. The globe temperature was measured in the room where the interview took place (usually the living-room). Interviews were conducted both during the daytime and in evenings, and at weekends as well as on weekdays. The mean of the living-room temperatures recorded was 18.3°C, mean kitchen temperature 16.7°C and mean temperature of the warmest bedroom 15.2°C. The average dwelling temperature was 15.8°C. The major sources of variance in temperature were the type and operation of the heating system, the dwelling age, household income, the time of day and geographical location. Household composition was a minor factor. The living-room temperature was relatively insensitive to the above-mentioned factors and had the appearance of being held at a level more or less independent of that in the rest of the dwelling. Centrally-heated houses ran 3°C warmer on average than non-centrally-heated houses. However, the difference in mean temperatures in the living-rooms between the two categories was only 1.5°C dry-bulb and 0.9°C globe temperature. Although strong correlations between a number of the explanatory variables, such as dwelling age and heating system type, means that a deeper analysis is required before a firm causal model can be proposed, the results provide an important new basis for assessing energy conservation options in domestic space heating.     

Thermal effects on bacterial bioaerosols in continuous air flow

Exposure to bacterial bioaerosols can have adverse effects on health, such as infectious diseases, acute toxic effects, and allergies. The search for ways of preventing and curing the harmful effects of bacterial bioaerosols has created a strong demand for the study and development of an efficient method of controlling bioaerosols. We investigated the thermal effects on bacterial bioaerosols of Escherichia coli and Bacillus subtilis by using a thermal electric heating system in continuous air flow. The bacterial bioaerosols were exposed to a surrounding temperature that ranged from 20 °C to 700 °C for about 0.3 s. Both E. coli and B. subtilis vegetative cells were rendered more than 99.9% inactive at 160 °C and 350 °C of wall temperature of the quartz tube, respectively. Although the data on bacterial injury showed that the bacteria tended to sustain greater damage as the surrounding temperature increased, Gram-negative E. coli was highly sensitive to structural injury but Gram-positive B. subtilis was slightly more sensitive to metabolic injury. In addition, the inactivation of E. coli endotoxins was found to range from 9.2% (at 200 °C) to 82.0% (at 700 °C). However, the particle size distribution and morphology of both bacterial bioaerosols were maintained, despite exposure to a surrounding temperature of 700 °C. Our results show that thermal heating in a continuous air flow can be used with short exposure time to control bacterial bioaerosols by rendering the bacteria and endotoxins to a large extent inactive. This result could also be useful for developing more effective thermal treatment strategies for use in air purification or sterilization systems to control bioaerosols.     

Patient comfort and radiant ceiling heating in a hospital ward

An experimental survey of the limitations placed by patient comfort considerations on the size and surface temperature of infra-red ceiling heating panels in a hospital ward is described.It was found that at ceiling surface temperatures of up to 50°C patients suffered no additional discomfort with angle factors, based on a parallel planes measure, of up to 0.31 to the heated surface, and that at ceiling surface temperatures of up to 60°C angle factors of up to 0.12, where the air temperature was limited to 23°C, and of up to 0.31, where the air temperature was limited to 21°C, were permissible.     

Teepol and triton media for the enumeration of Escherichia coli by membrane filtration

Previous reports have indicated a very high incidence (ca. 25%) of false positive reactions on membrane enriched Teepol broth when used at 44°C for the enumeration of Escherichia coli in water and sewage. By reducing the concentration of Teepol 610 from 0.4% to 0.2% the incidence of false positives was reduced to 8.9%. Membrane enriched Triton agar, a modification of an MPN broth used to count E. coli in estuarine waters and containing 0.2% Triton X-100, was found to be a satisfactory alternative medium for the enumeration of E. coli by membrane filtration at 44°; the incidence of false positive results on this medium was 6.8%.     

Effects of primary sludge particulate (PSP) entrapment on ultrasonic (20 kHz) disinfection of Escherichia coli

The role of primary sludge particulates (PSPs) in ultrasonic disinfection of Escherichia coli (E. coli) was investigated. Entrapment of E. coli by PSP was directly observed through scanning electron microscope (SEM) after E. coli and PSP were incubated together in water for 24 h at 35 °C. Entrapment coefficient was proposed for the first time to reflect the ability of PSP to entrap E. coli and was estimated as 1.4 × 10³ CFU/mg PSP under our experimental conditions. Ultrasonication (20 kHz) of different E. coli-PSPs solutions showed that the entrapped E. coli cells were protected by PSP from ultrasonication and the unentrapped cells were not. However, the protection of entrapped E. coli cells gradually decreased as ultrasonication proceeded, suggesting the ability of power ultrasonication to deprotect the entrapped E. coli cells. SEM studies suggested a two-step mechanism for ultrasonic (20 kHz) disinfection of entrapped E. coli: breakdown of the protective PSP refugia and disinfection of the exposed E. coli cells. This research will enable more informed decisions about disinfection of aqueous samples where porous PSP are present.     

Nitrification in porous media during rapid,unsaturated water flow

A substantial nitrification in rapid infiltration (RI) systems for wastewater treatment is a prerequisite for obtaining good N removal by denitrification. The purpose of this study is to investigate nitrification in porous media at conditions corresponding to RI treatment systems. Nitrification in six 50-cm porous media columns (98% weathered granite or sand and 2% field soil) during unsaturated leaching at constant flow rates of synthetic wastewater was investigated. Concentrations of NH₄-N between 20 and 60 mg l⁻¹ were applied and vertical concentration profiles of NO₃-N, NO₂-N and NH₄-N were measured for 54 d at 30°C (three columns) and for 140 d at 10°C (three columns). A time lag in nitrification of 20 d was found at 10°C. Complete nitrification was obtained after 3–5 at 30°C and after approximately 50 d at 10°C. Assuming first-order nitrification at steady-state, the corresponding first order reaction rate coefficients (k₁) for NO₃ production in the columns were estimated to be between 0.4 and 1 h⁻¹ at 10°C and between 6 and 9 h⁻¹ at 30°C. Steady-state NO₃ profiles were obtained between 1.5 and up to 9 weeks after the experiments were started. At the actual soil-air contents (0.10 cm³ air phase cm⁻³ soil), oxygen limitations were not observed during the experiments. Nitrogen loadings (water flow times N concentration) above 100 mg N 1⁻¹ cm h⁻¹ (1 g N m⁻² h⁻¹) caused NH₄ accumulation in the columns at 10°C and should probably be avoided during operation of RI system.     

Pollution levels in some nigerian rivers

Surveys of five rivers in a hot-humid zone of a tropical country (Nigeria) were carried out over 3 years by obtaining samples for physical, chemical and bacteriological analyses. The main characteristics monitored were temperature, turbidity, total, dissolved and suspended solids, pH, dissolved oxygen, BOD, ammonia-nitrogen and the coliform counts. In addition, the main characteristics of the liquid waste being discharged into the rivers were determined.During the dry season, the highest mean temperature is 29°C with a range of 5°C and the lowest is 26°C with a range of 3°C. In the wet season, the highest mean temperature is 27.3°C with a range of 2°C while the lowest is 24.5°C with a range of 1°C. The other characteristics vary more widely with seasons. The high temperature in these rivers all the year round encourages pollution by human activities. During the dry season, pollution causes prolific algae boom, which causes oxygen supersaturation during periods of high temperature and abundant sunlight. The physical, chemical and biological characteristics of the rivers deteriorate sharply as they flow through towns and other human communities.     

Survival of manure-borne E. coli in streambed sediment: Effects of temperature and sediment properties

Escherichia coli bacteria are commonly used as indicator organisms to designate of impaired surface waters and to guide the design of management practices to prevent fecal contamination of water. Stream sediments are known to serve as a reservoir and potential source of fecal bacteria (E. coli) for stream water. In agricultural watersheds, substantial numbers of E. coli may reach surface waters, and subsequently be deposited into sediments, along with fecal material in runoff from land-applied manures, grazing lands, or wildlife excreta. The objectives of this work were (a) to test the hypothesis that E. coli survival in streambed sediment in the presence of manure material will be affected by sediment texture and organic carbon content and (b) to evaluate applicability of the exponential die-off equation to the E. coli survival data in the presence of manure material. Experiments were conducted at three temperatures (4 °C, 14 °C, and 24 °C) in flow-through chambers using sediment from three locations at the Beaverdam Creek Tributary in Beltsville, Maryland mixed with dairy manure slurry in the proportion of 1000:1. Indigenous E. coli populations in sediments ranged from ca. 10¹ to 10³ MPN g⁻¹ while approx 10³ manure-borne E. coli MPN g⁻¹ were added. E. coli survived in sediments much longer than in the overlaying water. The exponential inactivation model gave an excellent approximation of data after 6-16 days from the beginning of the experiment. Slower inactivation was observed with the increase in organic carbon content in sediments with identical granulometric composition. The increase in the content of fine particles and organic carbon in sediments led not only to the slower inactivation but also to lower sensitivity of the inactivation to temperature. Streambed sediment properties have to be documented to better evaluate the role of sediments as reservoirs of E. coli that can affect microbiological stream water quality during high flow events.     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—I. Growth potential of oxidation pond water and comparative optima for blue-green and green algal growth

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.     

Optimisation of process parameters for bioreduction of azo dyes using Bacillus firmus under batch anaerobic condition

A new dye decolourising bacterial strain was isolated from textile wastewater and identified as Bacillus firmus. The study indicated that the bacterium could efficiently decolourise different azo dyes under static culture conditions. Characterisation of the efficiency of azo dye reduction by this isolate using both spectral and HPLC analysis was found to be a function of process parameters which include dye concentration, culture broth pH, incubation temperature, aeration as well as nitrogen source. For decolourisation, the optimal pH and temperature were 7–8 and 20–35°C respectively, while remarkable dye degradation was obtained within 18 h for dye concentrations below 100 mg L^?1. With the addition of yeast extract and under optimal conditions, dye reduction was enhanced and complete colour removal was achieved within 12 h. Colour removal was shown to be due to biodegradation rather than adsorption of dyes on bacterial cells. This study confirms the ability of the new dye‐degrading strain, Bacillus firmus, to decolourise and degrade different azo dyes and highlights its high biotechnology potential for the eco‐friendly treatment of textile wastewater when optimal conditions are applied.