Semi-volatile organic compounds in the Campaspe River system (Victoria, Australia)

The levels of semi-volatile organic compounds (SVOCs) in the Campaspe River system, North Central Victoria, Australia, were monitored from January to September 1995, and the environmental trends and sources of these compounds were determined. The land use within particular catchments dictated the complexity of the SVOCs in run-off water. Run-off from native forest contained the greatest number of SVOCs. Soil and ground litter were shown to contain the greatest complexity of SVOCs, mostly terpenes. However, only a small proportion were leached by run-off with the remainder being tightly bound to the soil or volatilizing to the atmosphere. Under the prevailing drought of early 1995, the rivers contained no detectable SVOCs until the first catchment run-off after significant rainfall in May. The maximum complexity and concentration of the SVOCs coincided with extensive run-off after heavy rainfall in June, effecting a surge of SVOCs with the flood peak. Fatty acids, their amides and hydrocarbons made up the majority of the compounds identified and were in the 1-39 micrograms/l concentration range. The levels then diminished as the catchment was flushed by continual run-off. These results support Lake's 1967 hypothesis that natural floodwaters contain a signature of SVOCs entering from the catchment. The downstream passage of these compounds was obstructed by a man-made storage, Lake Eppalock, with only low concentrations of SVOCs (1-3 micrograms/l) in the outflow, displaying no correlation to run-off.     

Amphibians as a model to study endocrine disruptors: I. Environmental pollution and estrogen receptor binding

Many chemicals released into the environment without toxicological risks have the capacities to disrupt the function of endocrine systems. These endocrine disruptors disturb normal endocrine mechanisms and have been observed in nearly all classes of vertebrates. The aim of this research is to develop a comprehensive model to study endocrine disruption using the amphibian Xenopus laevis. The assessment of estrogenic potencies of endocrine disruptors includes several levels of investigation: (I) binding to liver estrogen receptor, (II) estrogenic activity in vitro by inducing vitellogenin synthesis in primary cultured hepatocytes, and (III) in vivo effects on sexual development caused by exposure of larvae. The present paper is focused on the first part by establishing a radioreceptorassay for [3H]17 beta-estradiol ([3H]E2) binding using liver cytosol fraction. In order to get optimum binding conditions we performed kinetic, saturation, and competitive displacement experiments. Association of [3H]E2 to estrogen receptor revealed that maximum specific binding is achieved between 18 and 48 h of incubation. Scatchard analyses of saturation experiments resulted in a homogenous saturable population of estrogen receptors having no significant differences of binding parameters between both sexes. The values of Kd (dissociation constant) in males and females were 22.4 +/- 6.0 and 15.0 +/- 2.8 nM (mean +/- S.E.M.; n = 5), respectively, while corresponding Bmax (maximum binding capacity) revealed 89 +/- 46 and 136 +/- 46 fmol [3H]E2/mg protein. The specificity of estrogen receptors as shown by competitive displacement experiments demonstrated receptors being highly specific just for estrogens, but not for other endogenous steroids having the following ranking of binding affinities: E2 > estrone > dehydroepiandrosterone > aldosterone > or = testosterone > or = corticosterone > or = progesterone. The affinity ranking of environmental chemicals compared to E2 was: E2 > tetrachlorbiphenyl > diethylphthalate > 2,2-bis-(4-hydroxyphenyl)-propan (bisphenol A) > or = 4-nonylphenol > or = 3-t-butyl-4-hydroxyanisole > or = 4-octylphenol > dichlor-diphenyl-trichlor-ethan (4,4'-DDT). Analyses of five sewage effluents for displacement of [3H]E2 binding resulted in three samples displacing more than 50% of specific binding at their original concentration. Taken together the established radioreceptorassay for [3H]E2 binding in Xenopus laevis liver cytosol is useful to screen estrogen receptor binding of pure compounds or complex mixtures of them, which is the prerequisite for causing either estrogenic or antiestrogenic effects.     

THE EFFECTS OF IMPROVING SEWAGE SLUDGE DIGESTION

A model was developed and tested to investigate the effects of various parameters on the processing costs of anaerobic digestion. The model was based on empirical data collected from full-scale plants which varied in size from 35,000 to 900,000 population equivalents. (Equivalent to loading rates of 0.5 to 2.7 kg VS/m³/d.) In spite of different operating regimes and conditions of the plants analysed, various relationships were discovered between: sludge quality and volatile solids destruction; sludge quality and biogas yield; and, effluent volatile solids and dewatering. Where correlations existed, these were used to make predictions on operating costs of the digestion and dewatering plant based on sensitivity analysis. The results of the model were used to make recommendations on how to optimise the operation of an anaerobic digestion plant.     

Design Water Levels in Tidal River Systems under the Influence of Typhoons

Water levels in tidal rivers are subject to the influence of both fluvial and tidal factors. The interaction between these factors is rendered more complex in regions affected by typhoons, which typically result in the combined occurrence of heavy rainfall and high sea levels.
Previous studies have outlined an analytical approach for calculating design water levels based on dividing the fluvial and tidal series into a typhoon and a non-typhoon component. This paper illustrates the steps involved in the analytical approach and describes its application to drainage basins in Hong Kong.
The approach provides a practical means for calculating design water levels, and is recommended for final design purposes. The results of using the full analysis may be approximated by using a sub-set of analytical results, and should prove satisfactory for the purposes of outline design.     

Oxygen consumption and activity of the white sucker (Catostomus commersoni), in lethal and nonlethal levels of the organochlorine insecticide, methoxychlor

The survival, oxygen consumption and spontaneous activity of suckers were determined at 15°C in water containing different concentrations of methoxychlor in ethanol, ethanol, and no added substances. A dynamic bioassay was used to estimate the 96 h LC50, which was found to be 0·0345 ppm. Routine oxygen consumption was determined in a continuous-flow respirometer, and the activity was recorded in separate experiments by measuring the water disturbance using silver wire electrodes.After 24 h fish exposed to untreated, ethanol-treated and 0.01 ppm methoxychlor-treated water had oxygen uptake rates which were relatively constant and near standard levels. At 0.10 ppm methoxychlor (lethal to all fish within 85 h), oxygen consumption rates were 2–3.5 × as high as those of control fish. Activity also greatly increased. The fish lost their balance along with the coordination between opercular and locomotor movements. Suckers that died in 0.04 ppm methoxychlor showed oxygen uptake rates and poisoning symptoms similar to 0.10 ppm treated fish, while those that survived this treatment had rates similar to control fish. The increase in ventilation which accompanies this hyperactivity may result in increased uptake of insecticide and thereby explain the irreversible nature of the response.     

Rapid enumeration of water bacteria

The research reported in this paper is devoted towards the development of a rapid bacteriological test for water. The proposed technique consists in measuring “Cold T.C.A. insoluble portion” of metabolized phosphorus in multiplying bacterial cells with recourse to radioactive phosphorus-32 as a tracer and enumerates bacteria in 1 h incubation time. A linear correlation (coefficient of correlation = +0·989) has been shown to exist between this portion of phosphorus and cell population for bacterial species of public-health significance, thereby providing a point d'appui for this approach of enumerating water bacteria.The data reported in the paper reveal a promise for the differential enumeration of Grams positive and negative cells by incorporating suitable chemical inhibitors in appropriate concentrations in the test portions for rapid test.The technique has been exhibited to be applicable to field samples drawn from surface and underground sources of water. Its reproducibility and economics are comparable with “Standard Method” procedures.     

Dynamic analysis and optimal feedback control synthesis applied to biological waste treatment

The dynamics and optimal feedback control of biological waste treatment processes are examined. Modern feedback control theory is applied and results are obtained for both proportional and proportional plus integral control. A dynamic mathematical model of the system is developed by employing a Monod kinetic model, which is modified to account for endogenous metabolism, and a complete mixing flow model in the growth chamber. The feedback control is implemented via the flow rate so as to maintain desired effluent concentrations. External disturbances which cause changes in substrate concentration and/or cell concentration are considered and optimal control effort is applied. Results are also presented for impulse and step changes in the influent substrate concentration. It is found that by changing the values of the weighting factors in the objective function, it is possible to obtain good control of either the effluent substrate concentration or cell concentration.