Relationship between flocculation of activated sludge and composition of extracellular polymeric substances

Activated sludge floes are a flocculated mass of microorganisms, extracellular polymeric substances (EPS) and adsorbed organic and inorganic material. The structure of the floes is very heterogeneous and floes with very different properties and morphologies may occur, depending on the conditions in the activated sludge treatment plant and wastewater composition. Present thinking suggests that cations, such as calcium, create cationic bridges with EPS excreted by the bacteria and thereby hold the various floe constituents together. However, due to the complex and heterogeneous nature of activated sludge, the mechanisms have neither been thoroughly investigated nor successfully quantified. A better understanding and description of the biological flocculation process is necessary in order to establish more efficient operational strategies. The main aim of this study was to get a comprehensive and unique insight into the floe properties of activated sludge and to assess the relative impact of chemical and physical parameters. A variety of sludges from full scale treatment plants with different settling properties were characterised. The interrelationships between floe parameters such as composition of EPS, surface properties and floe structure, and their effect on the flocculation and separation properties were assessed. The results indicate that the EPS, both in terms of quantity and quality, are very important for the floe properties of the activated sludge. However, presence of filaments may alter the physical properties of the floes considerably. The EPS showed positive correlations to sludge volume index (SVI) if only sludges with low or moderate numbers of filaments were included. The surface properties were more affected by the composition of the EPS than by the number of filaments. The EPS showed positive correlation to negative surface charge and a negative correlation to relative hydrophobicity and flocculation ability. The negative correlation between flocculation ability and amount of EPS was surprising. The shear sensitivity, measured as degree of erosion of floes when subjected to shear, was more affected by floe size and number of filaments than amount of EPS.

Herbs or natural substances as complementary therapies for chronic kidney disease: ideas for future studies

Chronic kidney disease (CKD) is an increasingly common condition with limited treatment options that is placing a major financial and emotional burden on the community. The use of complementary and alternative medicines (CAMS) has increased many-fold over the past decade. Although several compelling studies show renal toxicities and an adverse outcome from use of some CAMS, there is also emerging evidence in the literature that some may be renoprotective. Many nephrologists are unaware of these potential therapeutic benefits in treating CKD, or they are reluctant to consider them in research trials for fear of adverse effects (including nephrotoxicity) or deleterious interaction with co-prescribed, conventional medicines. The increased use of self-prescribed CAMS by their patients suggests that practitioners and researchers should keep abreast of the current information on these agents. A primary goal of this article was to review the available scientific evidence for the use of herbs or natural substances as a complementary treatment for patients with CKD. A further goal was to report the literature on herbs that have been reported to cause kidney failure.

Number and type of substances in alcohol and drug-related completed suicides in an Australian sample

Background: The association between substance use and suicide is well-established, but evidence is scant regarding the relationship between the number, type, and level of substances and other risk factors in completed suicide across the lifespan. Aims: To examine the relationship between social/demographic characteristics and the number, type, and level of drugs present in an unrestricted age sample of completed suicides in Australia. Method: An analysis was undertaken of 893 substance-related suicides using data from the Government Statistician's Office for the years 1989-1992. Results: The number and type of substances present in suicide victims was related to the individual's gender, age, marital status, employment status, and method of suicide. Blood alcohol level was significantly different between the methods of suicide, but was unrelated to demographic characteristics of the individual. The level of antidepressants and minor tranquilizers in the individuals was also unrelated to demographic characteristics. Conclusion: Examination of the type and number of substances present in completed suicides is an important component in creating profiles of potential suicide victims.

Spatial, temporal, and human dimensions of air pollution in Brisbane

Arriving in Brisbane some six years ago, I could not help being impressed by what may be prosaically described as its atmospheric amenity resources. Perhaps this in part was due to my recent experiences in major urban centres in North America, but since that time, that sparkling quality and the blue skies seem to have progressively diminished. Unfortunately, there is also objective evidence available to suggest that this apparent deterioration is not merely the result of habituation of the senses. Air pollution data for the city show trends of increasing concentrations of those very substances that have destroyed the attractiveness of major population centres elsewhere, with climates initially as salubrious. Indeed, present figures indicate that photochemical smog in unacceptably high concentrations is rapidly becoming endemic also over Brisbane. These regrettable developments should come as no surprise. The society at large has not been inclined to respond purposefully to warnings of impending environmental problems, despite the experiences and publicity from overseas and even from other cities within Australia. Nor, up to the present, have certain politicians and government officials displayed stances beyond those necessary for the maintenance of a decorum of concern. At this stage, there still exists the possibility for meaningful government action without the embarrassment of losing political favour with the electorate. To the contrary, there is every chance that such action may be turned to advantage with increased public enlightenment. It would be more than a pity to miss perhaps the final remaining opportunity: Queensland is one of the few remaining places in the world with sufficient resources to permit both rational development and high environmental quality. The choice appears to be one of making a relatively minor investment now for a large financial and social gain the near future, or, permitting Brisbane to degenerate gradually into just another stagnated Los Angeles or Sydney. The present monograph attempts to introduce the problem by reviewing the available research on air quality in the Brisbane area. It also tries to elucidate some seemingly obvious, but so far unapplied management approaches. By necessity, such a broad treatment needs to make inroads into extensive ranges of subject areas, including political and legal practices to public perceptions, scientific measurement and statistical analysis to dynamics of air flow. Clearly, it does not pretend to be definitive in any of these fields, but it does try to emphasize those adjustable facets of the human use system of natural resources, too often neglected in favour of air pollution control technology. The crossing of disciplinary boundaries, however, needs no apology: air quality problems are ubiquitous, touching upon space, time and human interaction.

School Science Lessons

This website is linked to UNESCO.org and is free to download for educational purposes. It contains a database of school science experiments and investigations in physics, chemistry, biology, astronomy, geology, weather studies, agriculture projects for primary and secondary schools; and sexuality education and drugs education. It is based on a revision, updating and expansion of the "New UNESCO source book for science teaching", 1979 edition, UNESCO, Paris. It contains experiments from the "low cost" science teaching movement, simplified versions of classical experiments, experiments using locally available substances and kitchen chemicals, and environmental science. Some experiments anticipate experiments usually done in senior high school or college classes. The experiments should be "student-friendly" and "teacher-friendly" because there is no overwhelming technology. Enough theoretical background is included to remind teachers of the theoretical context of the experiment. Every experiment is based on materials listed in a modern commercial catalogue of chemicals and equipment for use by educational institutions. The procedures and safety standards are consistent with instructions issued by Education Queensland (Ministry of Education), State of Queensland, Australia.

The effect of protein binding on the hepatic first pass of O-acyl salicylate derivatives in the rat

In this work the in-situ perfused rat liver has been used to examine the effect of changing the protein content of the perfusate on the hepatic extraction of O-acyl esters of salicylic acid. The hepatic availability (F) of these solutes was studied at a flow-rate of 30 mt min(-1) with perfusate albumin concentrations of 0, 2, and 4% w/v. The hepatic availability of the esters was shown to decrease with increasing carbon-chain length in the O-acyl group; for all the esters the hepatic availability increased with increasing albumin concentration in the perfusate. The dispersion-model-derived efficiency number (R-N) Of the esters was shown to increase with increasing lipophilicity and decrease with increasing albumin concentration in the perfusate. The unbound fraction (f(u),) of the esters decreased with lipophilicity. R-N/f(u), for acetylsalicylic acid remained relatively constant as the albumin concentration was increased. However, R-N/f(u), for n-pentanoyl- and n-hexanoylsalicylic acids increased significantly as albumin concentration increased from 0% to 4%. Thus, for the more lipophilic solutes (n-pentanoyl- and n-hexanoylsalicylic acids) the presence of albumin apparently facilitates the uptake of unbound solute relative to acetylsalicylic acid.

Anthocyanin synthesis, growth and nutrient uptake in suspension cultures of strawberry cells

Strawberry (Fragaria ananassa cv. Shikinari) cell suspension cultures carried out in shake flasks for 18 d were closely examined for cell growth, anthocyanin synthesis and the development of pigmented cells in relation to the uptake of carbohydrate, extracellular PO4, NO3, NH4, and calcium. Cell viability, extracellular anthocyanin content, pH and electrical conductivity of the broth were also monitored. The specific growth rate of strawberry cells at exponential phase was 0.27 and 0.28 d(-1) based on fresh and dry weight, respectively. Anthocyanin synthesis was observed to increase continuously to a maximum value of 0.86 mg/g fresh cell weight (FCW) at day 6, and was partially growth-associated. Anthocyanin synthesis was linearly related to the increase in pigmented cell ratio, which increased with time and reached a maximum value of ca. 70% at day 6 due to reduction in cell viability and depletion of substrate. Total carbohydrate uptake was closely associated with increase in cell growth, and glucose was utilized in preference to fructose. Nitrate and ammonia were consumed until 9 d of culture, but phosphate was completely absorbed within 4 d. Calcium was assimilated throughout the growth cycle. After 9 d, cell lysis was observed which resulted in the leakage of intracellular substances and a concomitant pH rise. Anthocyanin was never detected in the broth although the broth became darkly pigmented during the lysis period. This suggests that anthocyanin was synthesized only by viable pigmented cells, and degraded rapidly upon cell death and lysis. Based on the results of kinetic analysis, a model was developed by incorporating governing equations for the ratio of pigmented cells into a Bailey and Nicholson's model. This was verified by comparison with the experimental data. The results suggest Bat the model satisfactorily describes the strawberry cell culture process, and may thus be used for process optimization.

Volatile solvent use among western Australian adolescents

Semistructured interviews were conducted with 40 adolescents who reported inhaling volatile solvents. Their average age was 14.2 years, and they used a range of substances. All were aware of the short-term health risks involved in volatile solvent use, and most reported experiencing ill effects, such as headaches and vomiting. Users were found to be organized into groups and peer networks, which often were involved in theft, prostitution, and other risk-taking behaviors. More chronic users had higher status within the group. Suggestions pertaining to intervention were obtained, and these are discussed in light of the findings.

Characteristics of DSM-IV and ICD-10 cannabis dependence among Australian adults: results from the National Survey of Mental Health and Wellbeing

A representative sample (n = 10 641) of Australian adults completed a structured diagnostic interview assessing the prevalence of mental and substance use disorders in the last year. The prevalence of DSM-IV (1.5%) and ICD-10 (1.7%) cannabis dependence was similar. DSM-IV and ICD-10 dependence criteria comprised unidimensional syndromes. The most common symptoms among dependent and non-dependent users were difficulties with controlling use and withdrawal, although there were marked differences in symptom prevalence. Dependent users reported a median of four symptoms. There was good to excellent diagnostic concordance (kappas = 0.7-0.9) between systems for dependence but not for abuse/harmful use (Y = 0.4). These findings provide some support for the validity of cannabis dependence. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Gender-related symptoms and correlates of alcohol dependence among men and women with a lifetime diagnosis of alcohol use disorders

This study explored gender-related symptoms and correlates of alcohol dependence in a cross-sectional study of 150 men and 150 women with a lifetime diagnosis of alcohol use disorders (AUD). Participants were recruited in equal numbers from treatment settings, correctional centres and the general community. Standardized measures were used to determine participants' use of substances, history of psychiatric disorders and psychosocial stress, their sensation seeking and family history of substance use and mental health disorders. Multivariate analyses were used to detect patterns of variables associated with gender and the lifetime severity of AUD. Men had a longer history of severe AUD than women. Women had similar levels of alcohol dependence and medical and psychological sequelae as men, despite 6 fewer years of AUD. More women than men had a history of severe psychosocial stress, severe dependence on other substances and antecedent mental health problems, especially mood and anxiety disorders. There were differences in family history of alcohol-related problems approximating same-gender aggregation. The severity of a lifetime AUD was predicted by its earlier age at onset and the occurrence of other disorders, especially anxiety, among both men and women. The limitations in the generalizability of these findings due to sample idiosyncrasies are discussed.