Some factors affecting floc formation by Zoogloea ramigera, strain I-16-M

A comparison was made between cells of Zoogloea ramigera occurring in flocs and in suspension. Suspended cells were obtained by adding cellulose to the growth medium, which prevented floc formation without damaging the cells. Differences in protein synthesis and poly-β-hydroxybutyrate production of cells in suspension and cells in flocs were only found between slowly shaken cultures. Increasing the oxygen content of such cultures did not raise the growth limitation of the cells in flocs. The oxygen uptake of the suspended cells was found to represent a zero order reaction at an oxygen concentration of the culture above 0.1 mg/l. and that of cells in flocs above 1.5 mg/l. Below 20 mg/ml glucose the glucose respiration rate of cells in flocs was lower than that of suspended cells. Above approx 20 mg/l. glucose, the glucose respiration of both types of cells was almost a zero order reaction.     

Toxicity of cadmium, cobalt, uranium and zinc to Zoogloea ramigera

The toxic effects of cadmium, cobalt, uranium and zinc to the bacterium Zoogloea ramigera have been studied. This organism, which is abundant in sewage-treatment plants, responded to media supplemented with heavy metals by showing a prolonged lag phase and by decreasing its growth rate. The length of the lag phase was proportional to the metal concentration when Z. ramigera was exposed to cadmium, cobalt and zinc. When exposed to uranium (uranyl ions) the organism altered its growth behavior by showing an extended lag phase almost independent of the metal concentration. The order of toxicity of the metals to Z. ramigera was Cd²⁺ = Zn²⁺ > Co²⁺ > UO₂²⁺.     

Some growth parameters of haliscomenobacter hydrossis (syn. streptothrix hyalina) a bacterium occurring in bulking activated sludge

A study has been made of the kinetics of two strains of the sheath-forming bacterium Halisco menobacter hydrossis (syn. Streptothrix hyalina) by growing the bacteria axenically in continuous culture, with glucose as the limiting substrate. The maximum specific growth rates were approx. 0.05 h⁻¹ for strain AN and 0.09h⁻¹ for strain AZ, corresponding to minimum doubling times of 14 and 9h, respectively. Depending on the history of the population, appreciably lower values were found in batch experiments. The maintenance coefficient was low, 20 and 21 mg glucose (g biomass)⁻¹ h⁻¹ for strain AN and strain AZ, respectively. The “true” yield coefficients were 0.59 and 0.42 g biomass (g glucose)⁻¹, for strain AN and strain AZ, respectively.     

Activity of Zoogloea ramigera growing in flocs and in suspension

A comparison was made between cells of Zoogloea ramigera occurring in flocs and in suspension. Suspended cells were obtained by adding cellulose to the growth medium, which prevented floc formation without damaging the cells. Differences in protein synthesis and poly-β-hydroxybutyrate production of cells in suspension and cells in flocs were only found between slowly shaken cultures. Increasing the oxygen content of such cultures did not raise the growth limitation of the cells in flocs. The oxygen uptake of the suspended cells was found to represent a zero order reaction at an oxygen concentration of the culture above 0.1 mg/l. and that of cells in flocs above 1.5 mg/l. Below 20 mg/ml glucose the glucose respiration rate of cells in flocs was lower than that of suspended cells. Above approx 20 mg/l. glucose, the glucose respiration of both types of cells was almost a zero order reaction.     

Injury and repair of Escherichia coli damaged by acid mine water

Pure culture suspensions of Escherichia coli B/5 were stressed by exposure to filter-sterilized acid mine water (AMW). Sublethally injured survivors were examined for their ability to repair in several resuscitation media under different conditions of pH, temperature and oxygen availability. The repair process was monitored as a function of time by periodically removing samples from the repair media and simultaneously plating on nonselective and selective media. E. coli was severely damaged by AMW; however, sublethally injured survivors repaired when placed under favorable conditions. Optimal repair occurred in trypticase soy broth supplemented with 0.3% yeast extract (TSYB) at pH 7.0 and 35°C. Resuscitation did not occur in TSYB at pH 9.0, at an incubation temperature of 20°C, or in the absence of oxygen. Lauryl tryptose broth (LTB), which is recommended for the presumptive isolation of fecal coliforms, was unable to facilitate repair of injury. The presence of the surfactant, sodium dodecyl sulfate, as well as the nutrient composition of LTB, appeared to be responsible for the inability of this medium to permit recovery of AMW-stressed E. coli.     

Environmental distribution of Zoogloea strains

Enrichment culture techniques were employed to examine the environmental distribution of fingered zoogloea (FZ)-forming bacteria. FZ were detected in surface films of cultures started with various wastewaters, polluted pond and stream waters, duck feces, garbage disposal wastes and fish aquarium waters, but were not observed in cultures started with food scraps or soils. According to most probable number estimates of FZ-forming bacteria and total populations formed in enrichment cultures. less than 0.01% of the viable bacterial population in domestic wastewater and aerobic mixed liquor suspended solids (MLSS) contained the specific zoogloea-forming bacteria. However, FZ-forming bacteria were present in 10-fold greater concentrations in MLSS than in the raw wastewater solids.An isolation procedure, employing an inoculum of concentrated and sonically treated washed FZ yielded 70 strains of zoogloea-producing bacteria, 61 of which formed typical finger-like zoogloeae in pure culture. Isolates were removed also by direct streaking of enrichment culture films. The bacteria were isolated from enrichment cultures started with raw wastewaters, polluted pond waters, greenhouse drainage, fish aquarium water and duck feces. The zoogloea-producing strains were gram negative, motile rods possessing catalase and oxidase and the ability to denitrify, hydrolyze gelatin in plates and meta cleave m-toluic acid. Certain biochemical activities were located among isolates in relation to the various habitats from which they originated. The bacteria were considered to be strains of Zoogloea ramigera.     

Benthic oxygen demand in Lake Apopka, Florida

The benthic oxygen demand of Lake Apopka, Florida was determined using laboratory core uptake and flow through system techniques. The core-uptake for 5 stations in Lake Apopka averaged 67 mg O₂ m⁻²-h and partitioning experiments indicated that the oxygen uptake was primarily biological, with bacterial respiration dominating. No significant statistical correlations were found between core oxygen uptake rates and TKN levels (r = 0.33), percent volatile solids (r = 0.49), or macroinvertebrate densities (r = 0.59). Sediment oxygen uptake rates (D_B) were logarithmically related to flow rate in the following form D_B = − A + B In flow. Flow-through system sediment oxygen uptake at each station approached similar maximum uptake rates of 130 mg O₂ m⁻²-h at high (> 200 l h⁻¹) flow rates. Lake Apopka is an extremely shallow, wind mixed system and sediment uptake rates are expected to approximate this value during periods of intense wind mixing. The relatively low sediment uptake rates obtained for Lake Apopka, a hypereutrophic lake, supports the view that during eutrophication sediment respiration is progressively replaced by respiration in the water column.     

Bacterial activity in plant (Schoenoplectus validus) biofilms of constructed wetlands

Biofilm-bacterial communities have been exploited in the treatment of wastewater in ‘fixed-film’ processes. Our understanding of biofilm dynamics requires a quantitative knowledge of bacterial growth-kinetics in these microenvironments. The aim of this paper was to apply the thymidine assay to quantify bacterial growth without disturbing the biofilm on the surfaces of emergent macrophytes (Schoenoplectus validus) of a constructed wetland. The isotope was rapidly and efficiently taken-up and incorporated into dividing biofilm-bacteria. Isotope diffusion into the biofilm did not limit the growth rate measurement. Isotope dilution was inhibited at >12 μM thymidine. Biofilm-bacterial biomass and growth rates were not correlated to the plant surface area (r² < 0.02). The measurements of in situ biofilm-bacterial growth rates both displayed, and accommodated, the inherent heterogeneity of the complex wetland ecosystem. Biofilm-bacterial respiratory activities, measured using the redox dye CTC, and growth rates were measured simultaneously. The dye did not interfere with bacterial growth. Biofilm-bacterial specific growth rates ranged from 1.4 ± 0.6 d⁻¹ to 3.3 ± 1.3 d⁻¹. In the constructed wetlands of this study biofilm-bacterial specific growth rates, compared to those of natural ecosystems, could be markedly improved through changes in wetland design that increased bacterial respiration while minimising biofilm growth.     

Growth and nutrient uptake of green alga, Scenedesmus dimorphus, under a wide range of nitrogen/phosphorus ratio—I. Experimental study

In order to elucidate the relation between algal growth and nutrients such as nitrogen and phosphorus, a chemostat culture experiment using Scenedesmus dimorphus was performed under the conditions of T-N/T-P ratio of 2–50 mg N mg⁻¹ P and dilution rate of 1–4 day⁻¹. It was ensured from the results that nitrogen and/or phosphorus is the limiting nutrient for the growth of this alga under these conditions. The optimum T-N/T-P ratio for its growth was observed to change from 20 to 5 mg N mg⁻¹ P as the dilution rate varied from 1 to 4 day⁻¹ and, in most of the range of T-N/T-P ratio and dilution rate, its growth rate was not regulated by only one of the available nitrogen and phosphorus concentrations in the medium and algal nitrogen and phosphorus contents. Based on these facts, the multiplicative effect rather than the threshold effect of these two nutrients on its growth was considered to exist. It has been suggested, however, that algal nitrogen and phosphorus contents, especially nitrogen content, are the most important factors regulating its growth. Nitrogen uptake rate of this alga increased at a given concentration of available nitrogen in the medium as T-N/T-P ratio decreased down to 2 or 5 mg N mg⁻¹ P. It is also suggested that a multiplicative effect of nitrogen and phosphorus on uptake of these nutrients by S. dimorphus may exist.     

Biocontrol of biomass bulking caused by Haliscomenobacter hydrossis using a newly isolated lytic bacteriophage

This research demonstrates the first ever application of lytic bacteriophage (virus) mediated biocontrol of biomass bulking in the activated sludge process using Haliscomenobacter hydrossis as a model filamentous bacterium. Bacteriophages are viruses that specifically infect bacteria only. The lytic phage specifically infecting H. hydrossis was isolated from the mixed liquor of a local wastewater treatment plant. The isolated bacteriophage belongs to the Myoviridae family with a contractile tail (length-126 nm; diameter-18 nm) and icosahedral head (diameter-81 nm). Titer of the isolated phage with H. hydrossis was calculated to be 5.2 ± 0.3 × 10⁵ PFU/mL and burst size was found to be 105 ± 7 PFU/infected cell. The phage was considerably stable after exposure to high temperature (42 °C) and pH between 5 and 8, emphasizing that it can withstand the seasonal/operational fluctuations under real-time applications. Phage to host (bacteria) ratio for the optimal infection was found to be 1:1000 with ∼54% host death. The isolated phage showed no cross infectivity with other bacteria most commonly found in activated sludge systems, thus validating its suitability for biocontrol of filamentous bulking caused by H. hydrossis. Following the phage application, successful reduction in sludge volume index (SVI) from 155 to 105 was achieved, indicating improved biomass settling. The application of phage did not affect nutrient removal efficiency of the biomass, suggesting no collateral damage. Similar to phage therapy in medical applications, phage-mediated biocontrol holds a great potentiality for large-scale applications as economic agent in the mitigation of several water, wastewater and environmental problems. Present study in this direction is a novel effort.     

Determination of mutagenic activity in salmonella of residual fulvic acids after ozonation

Residual organics of ozonated soil and water fulvic acids were tested for mutagenicity in the Salmonella: mammalian-microsome assay. A highly ozonated soil fulvic acid extract induced His reversion in Salmonella typhimurium strain TA100 only and did not require metabolic activation for the weak mutagenic response observed.     

Uptake of phosphorus from sediment by aquatic plants, Myriophyllum spicatum and Hydrilla verticillata

Eurasian water milfoil(Myriophyllum spicatum L.) and hydrilla (Hydrilla verticillata Royle) took up most or all of their P from the hydrosoil (sediment) when the water contained 0.015 μg P ml⁻¹Myriophyllum continued to utilize largely hydrosoil-P with 0.5 μg P ml⁻¹ in the water; however, when 2.0 μg P ml^-1 was present in the water, the uptake of hydrosoil-P decreased and the of uptake of water-P increased.Stems of Myriophyllum cut off 2 cm above the crown transferred only 4–20 μg P/plant of hydrosoil-P into the water in the first 18 h after decapitation; thereafter, no further P release occurred. A harvesting operation would thus result in the direct transfer of only a small amount of hydrosoil-P into the water; however, the organically bound-P removed in the harvested Eurasian water milfoil plants would be derived largely from the hydrosoil, not the water body. The procedure would not be effective in reducing the P content of the lake unless its P content was higher than 0.5 μg ml⁻¹.The specific activity of the P taken up by hydrilla was similar to that of the water extracted from the hydrosoil. It differed greatly from the specific activity of the P adsorbed on the sediment that was extracted from the hydrosoil by a weak NH₄F---HCI extract. This adsorbed-P fraction, believed to be important in non-aquatic soils, was not supplying the P to the solution feeding the aquatic plant roots or was not in equilibrium with the hydrosoil solution-P.     

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.     

The effects of copper on maximum respiration rate and growth rate of perch, Perca fluviatilis L.

Addition of copper to the ambient water of perch resulted in decreased daily maximum respiration rates (R_max) and growth rates. The time-course of the effect in R_max was characterized by: (1) an initial decrease over three additions; (2) a minimal “trough” lasting some 10–15 days; and (3) a phase of increasing R_max. The variation in R_max was due to copper concentration and exposure time. The decrease in growth rate was most dramatic initially and was correlated to copper concentration and perch weight. The subsequent increase in growth rate was constant and independent of copper concentration. The increase in R_max and in growth rate was interpreted as acclimatization. Up to a given sublethal copper concentration acclimatization resulted in a return to the control level of R_max but not of growth rate.     

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%.     

The unreliability of the kinetic approach to measuring bacterial mineralization activities at low in situ temperatures in an acidic aquatic environment

This paper concerns the kinetic approach to measuring glucose mineralization by planktonic bacteria in Whitson Lake, a moderately acidic lake. For all three samplings, plots of the amount of glucose mineralized vs time of incubation were linear at both high and low concentrations of added glucose. When sample water buffered around the in situ pH was used in these time studies, linear relationships were again evident, but there was a reduction in the rates of glucose mineralization activity. Nevertheless, the kinetic approach usually failed to generate the Michaelis—Menten response at the necessary level of statistical significance to justify calculations of turnover times and V_max values. And, buffering the pH around the in situ pH did not insure that the Michaelis—Menten response would be obtained.These observations are discussed in the light of our earlier observations involving an extremely acid-stressed lake.     

Continuous cultivation of Debaryomyces hansenii (LAF-3 10 U) on dodecane in synthetic desalter effluent at varying dilution rates on dodecane

Desalter effluent (DE) is typically discharged into a petroleum wastewater treatment plant, but its high salt concentration deteriorates the biological treatment. This study used various dilution rates to investigate the treatment of a synthetic DE containing dodecane under saline conditions using a halotolerant yeast, Debaryomyces hansenii, to determine the optimum substrate concentration for use in continuous stirred-tank reactors (CSTRs). A literature review indicated that this study was the first to examine the biological treatment of DE using D. hansenii in a CSTR system. At a low dodecane substrate concentration, DE did not inhibit D. hansenii growth, and the experimental data approached the Monod model, with μ_max and K_s selected as 0.08 h⁻¹ and 1575 mg L⁻¹, respectively. The optimum removal of chemical oxygen demand (95.7% and 85%) was obtained at dilution rates of 0.007 and 0.026 d⁻¹. Using D. hansenii in a CSTR system appeared to be a sustainable approach for the biological treatment of DE. Scale-up of these laboratory findings to the industrial scale is required to confirm that petroleum DE can be treated using equalization and filtration tanks as a continuous bioreactor. Adjusting the dilution rate can provide sufficient time for biodegradation and hydrocarbon removal from high salt DE by halotolerant yeasts like D. hansenii.     

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.     

Bioaccumulation potential of polycyclic aromatic hydrocarbons in Daphnia pulex

The bioaccumulation potentials by aquatic biota from aqueous solution were determined for seven polycyclic aromatic hydrocarbons (PAH). The PAH were tested usingDaphnia pulex and consisted of the following compounds: naphthalene, anthracene, phenanthrene, pyrene, 9-methylanthracene, benz(a)anthracene and perylene. Bioaccumulation kinetics were described as a first order approach to equilibrium in a two-compartment model (water and Daphnia), using a two-stage technique to estimate uptake and elimination rates, while accounting for decreasing aqueous concentrations. Estimates of equilibrium concentration factors were obtained by two methods: (1) evaluating the kinetic model as t tends to infinity and (2) direct measurement of concentration factor at t =24 h.Estimations of equilibrium concentration factors obtained by the two methods were in good agreement, and increased dramatically with increasing molecular weight within the series of compounds. The calculated n-octanol-water partition coefficient was shown to be a good predictor of bioaccumulation potential of PAH in Daphnia. PAH were concentrated from a high of about 10,000-fold for benz(a)anthracene to a low of about 100-fold for naphthalene.     

The effects of nickel and cadmium on the growth rate of Hydra littoralis and an assessment of the rate of uptake of Ni and C by the same organism

Hydra littoralis was used as a bioassay organism to determine the sublethal threshold concentrations of NiCl₂ and CdCl₂: the concentrations were found to be 75 and 20 μg 1⁻¹ respectively.The rates of uptake of ¹⁴C and ⁶³Ni were measured over periods of 24 h. It seemed that Hydra reached an equilibrium with ¹⁴C within this period, whereas the total uptake of ⁶³Ni was proportional to time.The changes in the mean specific growth rate of Hydra when related to the uptake of ⁶³Ni showed it probable that a detoxication process is taking place within the organism.