De-colourization of textile effluent using immobilized Geotrichum candidum: an insight into mycoremediation.

Textile effluent is generally complicated to manage because of its extremely noxious and recalcitrant coloured compositions. Mycoremediation is an extensively used strategy for the competent degradation of hazardous pollutants present in textile effluent. Fungus could be immobilized in synthetic or natural matrices. The current study shows the decolourization of the textile effluent by 85·5 and 98·5% within 6 h using suspended and immobilized fungus, Geotrichum candidum with optimized parameters like inoculum size (5%), pH (4·5), and temperature (30°C). To maintain a high biomass of fungal population and enhance the retention of fungal strain in the contaminated sites, the fungi need to be immobilized. Hence, the fungus was immobilized naturally onto the selected inert support that is, coconut fibres by the means of adsorption, where they grew as active films on the fibres after being grown in the culture broth. The optimized process parameters of inoculum size, fibre quantity and agitation speed for immobilized G. candidum were 5%, 2·2 g l-1 of effluent and 100 rev min-1 respectively. High level of laccase (22 and 25 U l-1 in suspended and immobilized fungal cells treatment respectively) was observed during the process of decolourization and it was found that decolourization was directly proportional to the laccase activity. The UV-vis, FTIR, 1 H NMR and GC-MS analyses of treated textile industrial wastewater revealed the degradation of toxic pollutants in the textile effluent and formation of lower molecular weight intermediates. The study revealed a higher efficacy of immobilized G. candidum in comparison to suspended fungal culture, employing ligninolytic enzyme laccase, which catalyzes the degradation/transformation of aromatic dyes in the textile effluent thus decolourizing it.

Elucidation of fungal dye-decolourizing peroxidase (DyP) and ligninolytic enzyme activities in decolourization and mineralization of azo dyes.

AIM: The aim of the study is to investigate the efficiency of Geotrichum candidum in the decolourization and mineralization of synthetic azo dyes. METHODS AND RESULTS: It includes screening of enzymes from G. candidum and its optimization, followed by decolourization and mineralization studies. Decolourization was observed to be maximum in methyl orange (94·6%) followed by Congo red (85%), trypan blue (70·4%) and Eriochrome Black T (55·6%) in 48 h, suggesting the plausible degradation of the azo dyes by G. candidum. The enzyme activity study showed that DyP-type peroxidase has highest activity of 900 mU ml-1 compared to that of laccase (405 mU ml-1 ) and lignin peroxidase (LiP) (324 mU ml-1 ) at optimized pH (6) and temperature (35°C). Moreover, the rate of decolourization was found to be directly proportional to the production of laccase and LiP, unlike DyP-type peroxidase. Furthermore, mineralization study demonstrated reduction in aromatic amines, showing 20% mineralization of methyl orange. CONCLUSION: Geotrichum candidum with its enzyme system is able to efficiently decolourize and mineralize the experimental azo dyes. SIGNIFICANCE AND IMPACT OF THE STUDY: The efficient decolourization and mineralization of azo dyes makes G. candidum a promising alternative in the treatment of textile effluent contaminated with azo dyes.

Hygiene aspects of occupational exposure to waste anaesthetic gases in Ontario hospitals.

Exposure of workers to waste anaesthetic gases in the operating and recovery rooms of hospitals is an ongoing concern because a number of epidemiological and mortality studies have reported significant adverse effects. To evaluate the health risks if any, and to assist in the development of guidelines or regulations for the hospital sector in Ontario, the Health and Safety Support Services Branch of the Ontario Ministry of Labour conducted this extensive study. The results of the hygiene study show that exposure to waste anaesthetic occurs because of leaks in the anesthetic equipment. The three major sources of leaks (i.e. exhalation valves, masks and high-pressure fittings) produced concentrations above the limit of detection of nitrous oxide (1000 ppm of N2O) in a significant number of samples. Of the samples taken at leak sources those taken at the exhalation valve had the highest percentage of samples above 1000 ppm, which suggested that scavenging systems were not receiving proper service and maintenance. Only 23% of the operating rooms surveyed met the Ontario Ministry of Health Criterion of 24 air changes per hour. Dilution ventilation was less effective than scavenging in keeping down concentrations of air contaminants. The sampling data show that the anaesthetists have the highest time-weighted average exposure (median value range 56-79 ppm) of the major group of occupations surveyed and that the general surgeons' TWA is much lower (28 ppm). It was concluded that the dilution ventilation rate of 24 air changes per hour should be maintained in all operating rooms and that there should be no recirculation of exhaust air when operations are in progress. To keep down concentrations of anaesthetic gases scavenging systems should be provided in all operating rooms. In each hospital maintenance should be the responsibility of a qualified staff member who has been adequately trained in the repair and maintenance of anaesthetic delivery systems. Finally, a qualified staff member should be responsible for conducting periodic personal monitoring in operating rooms (ORs) and recovery rooms (RRs) and the sampling strategy should include individuals and the exhaust grilles.

A review of health risks in acrylonitrile industry.

The Occupational Health Branch of the Ontario Ministry of Labour began a study in 1978 for the evaluation of health risks associated with acrylonitrile (AN) exposure. Detailed hygiene and medical investigations were conducted in fourteen plants for evaluating AN exposure in various industrial processes. For companies were also studied in relation to mixed chemical exposure representing acrylic fibres, nitrile rubber, ABS-resin, and acrylic emulsions production. The possible interaction between AN and other coexisting chemical exposures was reviewed since dimethyl formamide, styrene, and butadiene have similar pharmacokinetics and possible synergistic effects. Exposure in acrylic fibre production may be synergistic and carcinogenic. Results of air monitoring indicated exposure levels to AN below 2 ppm (TWA) in most cases. Exposure to other co-existing chemicals was evaluated. Results of medical tests indicated no significant abnormalities in chest x-rays or liver function tests in currently exposed workers.

Employee education, management support can halt respirator abuse.

Workers need to know why they wear respirators. And their use of protective equipment must always be supervised and governed by written procedures.

Silica flour exposures in Ontario.

A total of 16 cases of silicosis are reported in Ontario plants where there was exposure to silica flour. Dust counts expressed as mppcf are shown for four of these plants taken over a period of 37 years. A relationship has been obtained experimentally to permit conversion of the counts to respirable mass concentrations. Based on the information obtained, a TLV of 0.05 mg/m3 for silica flour is proposed.

A statistical analysis of asbestos fiber counting in the laboratory and industrial environment.

The reproducibility of standard fiber counts in the laboratory and four industrial plants is discussed in detail. Under field conditions the standard deviation of the results varied between 0.4-1.2 f/ml. Under ideal laboratory conditions the standard deviations of the counts were approximately 0.2 f/ml. It is concluded that the standard method is sufficiently precise for industrial measurements.