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At least 847 records · Page 47Linked to original sources
PubMed2001

The mechanism and design of sequencing batch reactor systems for nutrient removal--the state of the art.

The Sequencing Batch Reactor (SBR) process for carbon and nutrient removal is subject to extensive research, and it is finding a wider application in full-scale installations. Despite the growing popularity, however, a widely accepted approach to process analysis and modeling, a unified design basis, and even a common terminology are still lacking; this situation is now regarded as the major obstacle hindering broader practical application of the SBR. In this paper a rational dimensioning approach is proposed for nutrient removal SBRs based on scientific information on process stoichiometry and modelling, also emphasizing practical constraints in design and operation.

Biodegradation, Environmental↗
PubMedDate not supplied

[Occupational exposure to formaldehyde at a service of pathologic anatomy].

OBJECTIVE: Aim of the present study is to evaluate the air pollution produced by formaldehyde in pathological anatomy. METHODS: This study was made with instrumental approach based on environmental evaluation of 10% formaldehyde used in pathological anatomy, by an infrared gas analyser (Brüel & Kjaer), and clinical approach of pathological anatomy personnel. RESULTS: The final result is not very comforting because we found values of formaldehyde during specific activities which exeeded the current limits proposed by industrial hygienist, infact we found in a different settings 1.81 ppm, 3.78 ppm, 8.3.05 ppm. The personnel exposed reported subjective symptoms as reactive airway symptoms, headache, skin problems. CONCLUSIONS: To reduce air pollution we have indicated technical precautions as forced ventilation which is a major engineering control for reducing risk from chemical agents, use of personal protective equipment (PPE) as last resort for protection, behavioral rules and health surveillance.

Air Pollutants, Occupational↗
PubMedDate not supplied

[Organohalogen contamination of a dialysis-water treatment plant].

On March 2001 the regular quality control test of the water used for dialysis in an urban centre using a reverse osmosis system revealed a high level of organo-halogenated contamination. The compounds implicated were: trichloroethylene (trielene) [M.Wt. 131 D], tetrachloroethylene, trichloromethane (chloroform) [M.Wt. 121 D], chlorodibromomethane. The dialysis unit was closed. Water samples were analysed in duplicate. The table shows the values (in ppm or microgram/l) obtained for chloroform at the given times: March 8th, altered sample; March 12th, confirmation sample; March 16th, after osmosis membranes change; March 22nd, after carbon filtration replacement; March 26th, after softener resins substitution. The AAMI doesn't recommend any value for organo-halogenated compounds in dialysis water. In the past, the European Pharmacopoeia and the Italian Health Ministry released some reference values for tap water, values which were extended to water used for dialysis. The values are 1 ppm as reference value, 30 ppm as maximum accepted value for the sum of all organo-halogenated compounds, and 10 ppm as the recommended value. In conclusion, the problem was solved by progressive replacement of the components of the water treatment system, even though the real cause remained undetermined. No clinical symptom was recorded and no level of chloroform or trielene was detected in patients' sera despite the low molecular weight and low protein binding of the compounds. A strict control of the water quality and a more comprehensive and updated reference guide are needed for better and safer dialysis delivery.

Charcoal↗
PubMed2004

Struvite scale formation and control.

Struvite scale formation is a major operational issue at both conventional and biological nutrient removal wastewater treatment plants. Factors affecting the formation of struvite scales were investigated including supersaturation, pH and pipe material and roughness. A range of control methods have been investigated including low fouling materials, pH control, inhibitor and chemical dosing. Control methods exist to reduce scale formation although each has its advantages and disadvantages.

Chemical Precipitation↗
PubMed2004

Optimal reconstruction of historical water supply to a distribution system: A. Methodology.

The New Jersey Department of Health and Senior Services (NJDHSS), with support from the Agency for Toxic Substances and Disease Registry (ATSDR) conducted an epidemiological study of childhood leukaemia and nervous system cancers that occurred in the period 1979 through 1996 in Dover Township, Ocean County, New Jersey. The epidemiological study explored a wide variety of possible risk factors, including environmental exposures. ATSDR and NJDHSS determined that completed human exposure pathways to groundwater contaminants occurred in the past through private and community water supplies (i.e. the water distribution system serving the area). To investigate this exposure, a model of the water distribution system was developed and calibrated through an extensive field investigation. The components of this water distribution system, such as number of pipes, number of tanks, and number of supply wells in the network, changed significantly over a 35-year period (1962--1996), the time frame established for the epidemiological study. Data on the historical management of this system was limited. Thus, it was necessary to investigate alternative ways to reconstruct the operation of the system and test the sensitivity of the system to various alternative operations. Manual reconstruction of the historical water supply to the system in order to provide this sensitivity analysis was time-consuming and labour intensive, given the complexity of the system and the time constraints imposed on the study. To address these issues, the problem was formulated as an optimization problem, where it was assumed that the water distribution system was operated in an optimum manner at all times to satisfy the constraints in the system. The solution to the optimization problem provided the historical water supply strategy in a consistent manner for each month of the study period. The non-uniqueness of the selected historical water supply strategy was addressed by the formulation of a second model, which was based on the first solution. Numerous other sensitivity analyses were also conducted using these two models. Both models are solved using a two-stage progressive optimality algorithm along with genetic algorithms (GAs) and the EPANET2 water distribution network solver. This process reduced the required solution time and generated a historically consistent water supply strategy for the water distribution system.

Algorithms↗
PubMed2005

Chemical genetic approaches to kinase drug discovery.

Chemical genetics is an important approach in biological research that utilizes small molecules to study protein function. In the context of kinase drug discovery, chemical genetics has broad applications in identifying and validating targets, demonstrating the druggability of a target and providing potential kinase inhibitor leads for further optimization. The successful application of this approach demands that the small-molecule kinase inhibitors used achieve a desired potency and selectivity. However, given the high number (> 518) and homology of kinases in the human genome, identifying potent and selective kinase inhibitors presents a major challenge. This article reviews recent advances in small-molecule kinase inhibitor design, with an emphasis on selectivity, and also discusses recent progress in the development of analog-sensitive kinase allele (ASKA)-based chemical genetics technology, which creates genetically engineered versions of protein kinases that are fully functional and can be selectively inhibited by a unique reference orthogonal inhibitor. Examples of how ASKA technology can be applied to kinase drug discovery is discussed.

Animals↗
PubMed1992

[Structure and family of proteins, a puzzle].

It now seems quite clear that the number of modes of three-dimensional arrangement of peptide chains of globular proteins is much smaller than the great sequential variability would suggest. Structural families and super families are formed with members which show little if any sequential identity (in the statistical sense) with older members of these families. In addition, it is evident that many proteins are formed like puzzles, by the juxtaposition of domains and sub-domains. Each brick usually has a well-defined intrinsic biological function. The components of these macro molecular puzzles have very different sizes, from a few amino acids to complete protein globules of several hundreds of amino acids, via intermediary local secondary ans super-secondary structures. This building system, the result of a long evolution after duplication or replication of genes, offers banks (sequences and three-dimensional structures) while limiting the complexity of the protein world.

Genetic Engineering↗
PubMed1987

[Comparative evaluation of mathematical models of the process for the biological treatment of the wastes from antibiotic manufacture].

The main kinetic relationships of the process of biological oxidation of antibiotic production sewage were studied in laboratory models of mixer aerotanks. A relationship between the specific rates of BOD (biological oxygen demand) decreasing and BOD concentration in aerotanks was developed on the basis of the results relating to treatment of 8 types of the sewage within the ranges of the pure water BOD equal to 18-220 mg/l and the loads of 0.18-3.85 g BOD/g X day. To describe this relationship the following models were tested for their adequacy: Michaelis-Menten and Mozer models, a general model and a model of the first order reaction equation. The Mozer model with the relative root-mean-square deviation of 18.3 per cent proved to be the best in description of wide ranges of pure water BOD changing. The first order model with deviation of 12 per cent was the best in describing the process with low loads.

Anti-Bacterial Agents↗
PubMed1993

[Lead in drinking water--determination of a new limit value and the problem of lead pipes].

The problem of lead in drinking water with regard to sensitive groups of the general population (e.g. unborn, babies that are not breast-fed, infants and children) is discussed. In respect of children in nurseries, the question regarding the relation of blood-lead levels to neurobehavioural deficits due to lead as well as a theoretical "tolerable" daily intake of lead is discussed. A provisional daily intake of approx. 1.2-1.3 micrograms Pb/kg body weight for children and pregnant women is proposed. For non-pregnant adults a double to three times higher intake may be tolerated (base: high blood pressure). These doses are well three times below the still recognised Provisional Tolerable Weekly Intake of led (PTWI-values, WHO), when related to daily intake. Considering the water consumption as well as the proportionate share of other exposure routes which result in the total lead exposure of risk groups, a toxicologically tolerable level of 10 micrograms Pb/l in drinking water is suggested. A reduction of the actual limiting value in drinking water (40 micrograms Pb/l) is advised. A special problem arises from lead tubes within the water distribution system. Water in stagnation as well as in use in these tubes may have enhanced lead concentrations. Therefore, it is recommended to exchange lead tubes preferentially in areas of sensitive use (e.g. as in the kitchen).

Adult↗