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Biomedical subjects

J N Lester

Publications and source records attributed to J N Lester.

At least 55 records · Page 3Linked to original sources
PubMed1991

The impact of heavy metals on lowland rivers and the implications for man and the environment.

Increased public awareness of river water quality problems has led to concern over the continued discharge of low-level contaminants in sewage treatment work (STW) final effluents. This paper discusses the source and nature of heavy metals during sewage treatment processes and examines their behaviour and fate in the aquatic environment. The influences of physico-chemical parameters and chemical speciation on metal mobility during sewage treatment and in receiving waters have been assessed. The importance of metal speciation with regard to aquatic toxicology is discussed and the effectiveness of current legislation in controlling the release of heavy metals to lowland river systems has been reviewed.

Animals↗
PubMed1990

Heavy metal binding by the polymeric organic fractions of sewage sludges.

Organic complexes in sewage sludge play an important role in the speciation and transformation of metals into potentially more toxic and bioavailable forms. Two organic fractions, bacterial extracellular polymer and fulvic acid, were extracted from mixed liquor and digested sewage sludge by methods established as the most appropriate. The homogeneity of the extracts was verified using gel permeation chromatography. Conditional stability constants and complexation capacities of the organic fractions from the sludges with copper, cadmium, nickel and zinc have been determined using equilibrium dialysis titration. Organic fractions extracted from digested sludge demonstrated a greater capacity to complex metals over mixed liquor extracts. Copper formed stronger complexes than nickel with the mixed liquor biomass and cadmium exhibited the greatest affinity for digested sludge organic matter.

Journal Article↗
PubMed1988

The removal of phosphorus during wastewater treatment: a review.

Phosphorus removal from wastewater can be achieved either through chemical removal, advanced biological treatment or a combination of both. The chemical removal of phosphorus involves the addition of calcium, iron and aluminium salts to achieve phosphorus precipitation by various mechanisms which are discussed. In addition, the effects of operating conditions, especially wastewater characteristics; sludge production in terms of quality and quantity; optimisation of chemical use and re-use; points of chemical addition combined with biological treatment; alternative chemical/physical treatments and examples of full-scale applications are also reviewed. Biological phosphorus removal is dependent upon the uptake of phosphorus in excess of normal bacterial metabolic requirements and is proposed as an alternative to chemical treatment. Early developments and the postulated removal mechanisms are reviewed; these include either natural chemical precipitation, enhanced biological removal, or a combination of both. The nature of excess biological phosphorus removal in activated sludge wastewater treatment plants is evaluated, considering various operating parameters, bacteriology and process designs.

Journal Article↗
PubMed1988

The use of model compounds to elucidate metal forms in sewage sludge.

Model phases of metal precipitates and organically bound metal were used to corroborate the nature of metal species found in sewage sludge by a sequential chemical extraction scheme. Model phase extractions supported the identification of the major species of Cd and Ni as carbonate (EDTA-extractable), Zn as organically-bound (Na(4)P(2)O(7)-extractable) and Pb as organically-bound or carbonate, although considerable overlap of fractions was apparent. Identification of the major species of Cu as sulphide (HNO(3)-extractable) could not be confirmed. The selectivity and efficiency of certain reagents was found to differ when used in sequence with other reagents, as opposed to being applied individually to model metal phases. Sample preparation was found to influence metal fractionation profiles in a model organic phase.

Journal Article↗
PubMed1986

Biotechnology for phosphorus removal during wastewater treatment.

Advanced biological wastewater treatment for the removal of phosphorus in excess of the normal metabolic requirements of activated sludge type processes has been developed as an alternative to chemical addition. Current laboratory and pilot plant investigations have confirmed that a preliminary anaerobic zone and plug-flow type configuration are necessary for good enhanced biological phosphorus removal. Nitrate in the anaerobic stage inhibits the process whereas acetate enhances phosphorus uptake. The bacteria probably responsible are of the Acinetobacter genus and the presence of stored polyphosphate within these bacteria has been demonstrated. It has also been shown that pure cultures of Acinetobacter do not necessarily take up soluble substrate as phosphate is released during the anaerobic phase, in contrast to the current proposed mechanism, and that in certain cases natural chemical precipitation could make a significant contribution towards overall phosphorus removal. Several studies of pilot and full-scale plants have been reported.

Journal Article↗
PubMed1986

Effect of salinity gradients and heterotrophic microbial activity on biodegradation of nitrilotriacetic acid in laboratory simulations of the estuarine environment.

The biodegradation of nitrilotriacetic acid (NTA), a synthetic replacement detergent builder, in the estuarine environment was examined by using a laboratory estuarine simulation. Two interdependent microcosms were used; each of five vessels was equilibrated with a saline gradient between 1.30 and 17.17%, with the final vessel subsequently being increased to a maximum salinity of 31.6%. Each microcosm was seeded simultaneously with heterotrophic bacteria from both fresh and saline sources. Viable counts demonstrated the ability of each microcosm to sustain a mixed heterotrophic bacterial community throughout the range of salinities for 183 days after a stabilization period. Isolation studies demonstrated that both systems contained four bacterial species, representatives of the genera Vibrio and Flavobacterium and members of the coryneform group and the family Enterobacteriaceae. Total bacterial numbers and species diversity decreased with increased salinity. NTA was administered at low and high concentrations, one concentration to each microcosm, initially with the least amount of saline. Removal of both concentrations of NTA occurred and was attributed to biodegradation after a period of bacterial acclimatization. Subsequent dosing of NTA to vessels of higher salinity demonstrated that biodegradation was incomplete at observed mean salinities of greater than 9.18% at low influent NTA concentrations and greater than 5.08% at high influent NTA concentrations. Therefore, acclimatization was dose dependent. It was concluded that NTA acclimatization at the higher salinities ceased because of salinity stress-induced failure of NTA catabolism and not the disappearance of a particular bacterial species.

Acetates↗
PubMed1984

Behaviour of persistent organochlorine micropollutants during primary sedimentation of waste water.

The removal of polychlorinated biphenyls and the organochlorine insecticides gamma-HCH, aldrin, dieldrin and endrin during primary sedimentation of raw sewage has been studied using a pilot plant facility. A matrix of sixteen experiments was performed, where the pilot plant was operated at four different hydraulic loadings with four different influent suspended solids loadings. Significant removals of micropollutants into the primary sludge were observed, although no particular relationship with the removal of suspended solids was evident. It is concluded that a proportion of the organic microcontaminants present in raw sewage were associated with non-settleable solids and were also in the dissolved form. The significance of the behaviour of organochlorine micropollutants in waste water treatment processes and the hydrological cycle are discussed in the context of water re-use operations.

Insecticides↗
PubMed1984

Significance and behaviour of heavy metals in wastewater treatment processes. IV. Water quality standards and criteria.

Literature on the health aspects of the presence of heavy metals in water and wastewaters is reviewed and quality standards, criteria and legislation promulgated by the World Health Organisation, European Economic Community, U.S. Environmental Protection Agency and Government of the U.S.S.R. are assessed and compared. It is evident from the literature that standards applied differ according to the projected water use and that although standards for potable water are generally based on human health criteria, other factors including available technology and economics may be limiting. Emphasis has been placed on the protection of raw water quality as a result of the limited ability of potable water treatment processes to remove certain heavy metals. It is apparent that limitations on heavy metals in discharges from the chlor-alkali and cadmium salts and pigments industries are more stringent in the United States than in the European Economic Community. It is concluded that the finite availability of unpolluted freshwater will result in greater water re-use and that appropriate standards are required to protect potable supply, raw water and agricultural land from contamination by heavy metals.

Europe↗
PubMed1983

Organic contaminants in the aquatic environment. III. Public health aspects, quality standards and legislation.

Literature on the health aspects and possible risks of the presence of organic micropollutants in water and waste waters is reviewed and the quality standards and legislation pertaining to certain organic compounds which have been promulgated by some countries and international organisations are assessed and compared. It is evident from the literature that different standards may be applied to waters which are designated for particular uses and that quality standards for protection of the aquatic environment (aquatic organisms) are generally more stringent than those applied to drinking water. Quality standards developed by different countries and organisations display a broad similarity in most cases, but differ where various approaches have been employed in determining the toxicity of and hazards presented by individual compounds. It is concluded that such legislation will become more comprehensive in the future, with the inclusion of more substances and recommendations for treatment procedures.

Carcinogens, Environmental↗
PubMed1983

Organic contaminants in the aquatic environment. IV. Analytical techniques.

The analytical techniques available for the determination of organic pollutants in raw, potable and waste waters are reviewed. General measures of organic pollution are considered, together with a range of chromatographic and instrumental methods for the analysis of specific groups of pollutants. Gas liquid chromatography and high performance liquid chromatography are the most widely used techniques for the measurement of specific compounds while mass spectrometry and combined gas liquid chromatography/mass spectrometry are the most definitive methods of analysis. Consideration of the range of sample extraction procedures which are available indicates that solvent extraction procedures are the most suitable for non-volatile organic substances, and gas purging or stripping techniques are favoured for the isolation of volatile compounds. Sample purification or clean-up procedures, including column and thin layer chromatography, are of particular importance when waste water samples are to be analysed, owing to the relatively high concentrations of extraneous materials which have to be removed prior to analysis. The merits and limitations of currently available analytical procedures are discussed.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed1982

The roles of staging laparotomy, chemotherapy, and radiotherapy in the management of localized diffuse large cell lymphoma: a study of 75 patients.

A retrospective study of 75 laparotomy-studied Stage I and II patients with diffuse large cell (histiocytic) lymphoma was conducted to determine the relative contributions of laparotomy, radiotherapy, and combination chemotherapy to their management. The treatment programs were radiotherapy alone, radiotherapy followed by adjuvant chemotherapy, and alternating chemotherapy-radiotherapy. Treatment selection was based on disease presentation, with limited therapy used for favorable patterns and intensive therapy used in prognostically unfavorable settings. Disease-free survival was best in those treated with initial chemotherapy, even though these patients comprised the least favorable prognostic group. A select subset of patients, those with extranodal head and neck disease, obtained good results with radiotherapy alone, but for other presentations this was not a successful approach. Differences in results for the three treatment programs are discussed in relation to future treatment decisions.

Abdominal Neoplasms↗
PubMed1980

The value of sewage sludge to agriculture and effects of the agricultural use of sludges contaminated with toxic elements: a review.

The effects of organic matter, nitrogen, phosphorus and toxic elements in sewage sludges applied to agricultural land are reviewed. Organic matter may improve the structure and water holding capacity of poor soils and the nitrogen and phosphorus in sludge have fertiliser value. However, and important consideration in applying sludge to land is the limitation of addition of toxic elements and any beneficial effects are secondary to this. Crops can accumulate toxic elements from sludge-amended soils and where heavily contaminated sludges and excessive rates of application are used plants may accumulate concentrations which are phytotoxic. The extent of accumulation varies considerably with plant species and cultivar; cereals and legumes accumulating lower concentrations than leafy plants such as lettuce and spinach. Although guidelines limit the addition of toxic elements in sludges and soils, thus reducing the quantities of these elements accumulated by plants, total concentrations of toxic elements in soil provide no indication of their availability to plants. The procedures applied to the determination of the forms of elements in sludges and soils and attempts to relate forms extractable in a variety of reagents to their availability to plants have been discussed. The factors which influence the forms of nutrient and toxic elements, their long term availability and hence their accumulation by crops are also reviewed.

Agriculture↗
PubMed1980

Interactions of heavy metals with bacteria.

The toxicity of heavy metals to bacteria, with particular reference to metal forms and species, has been reviewed. Factors which influence metal forms and thus their potential toxicity, such as pH, chelation and competitive interactions have been discussed. The mechanisms whereby bacteria may influence the forms of heavy metals to which they are exposed have been discussed with reference to the importance of the role of bacteria in immobilisation and environmental cycling of metals. Bacterial resistance to metal toxicity is an environmentally important phenomenon. It may occur from non-specific mechanisms, such as impermeability of the cell, or it may be due to specific resistance transfer factors. The coincidence and co-selection of resistance factors for antibiotics and heavy metals in bacterial populations and the clinical implications of this have been described.

Anti-Bacterial Agents↗
PubMed1980

Comparison of bacterial extracellular polymer extraction methods.

Five different bacterial extracellular polymer extraction methods and a combination of two of these methods were compared on cultures of activated sludge, synthetic activated sludge, and Klebsiella aerogenes. High-speed centrifugation was the most effective extraction method for the K. aerogenes culture, based on the comparatively small amount of cell disruption and the relatively high extracellular polymer yield. Steaming treatment was the most effective extraction method for the activated sludges, since it released a significant quantity of extracellular polymers from the flocs and caused less cellular disruption than ethylenediaminetetraacetic acid and sodium hydroxide treatments. Sodium hydroxide treatment caused extensive disruption in all cultures. Ultrasonication released low concentrations of extracellular polymers from all cultures. However, it caused no significant cell disruption and therefore may be useful as a preliminary treatment in conjunction with another extraction method.

Journal Article↗
PubMedDate not supplied

Potential ecological and human health risks associated with the presence of pharmaceutically active compounds in the aquatic environment.

Recently, considerable interest has developed regarding the presence of pharmaceuticals in the environment, but as yet the potential ecological effects associated with the presence of these compounds have been largely ignored. In this review, laboratory-based acute and chronic toxicity data, as well as studies concerned with the effects of pharmaceuticals on a variety of different organisms, are examined, along with the reported environmental concentrations of pharmaceuticals in aquatic systems. The possible sources and pathways of these compounds to the environment and the effects of a variety of medicines on a range of organisms are also highlighted, and recommendations are made for further research.

Animals↗