Performance of biofilter for the removal of hydrogen sulphide odour

Laboratory scale experiments were performed to evaluate the feasibility of biofilters for the removal of H[2]S from wastewater treatment plant waste air. The effects of changes in air flow rate and contaminant concentration on biofilter performance treating H[2]S odours were also assessed. Compost was used as media in biofilter. The study was carried out in six different phases, by increasing H[2]S concentrations gradually. In the first phase only humidified air was supplied to acclimatize and develop the biofilm, within the biofilter conditions. In the second phase, inlet H[2]S concentration was kept up to 10 ppm with the humidified air, H-[2]S removal efficiency was very high around 98%. It was concluded that the biofilter, used in the study, was more efficient [>95% removal efficiency] for low contaminant concentrations [up to 30 ppm]. However, as the concentration of H[2]S was increased to 50 ppm the removal efficiency decreased to 85%. The study results showed that biofilter could withstand longer starvation period and required less time to recover to its full efficiency. The effect of operating parameter such as moisture content was also assessed. The study revealed that the compost biofilter may be successfully adopted for various industrial operations where a reduction in emissions of H[2]S is required

Value of D-dimers assay in diagnosis of pulmonnary Embolism

To determine the value of D-Dimers assay in the diagnosis of Pulmonary Embolism [PE] at Armed Forces Institute of Pathology, Rawalpindi, Pakistan from January to November 2000. Forty three consecutive patients clinically suspected of suffering from pulmonary embolism and referred to Armed Forces Institute of Pathology for Ventilation-Perfusion scan of lungs were inducted in the study. A detailed history was taken and clinical examination was performed. All patients were then subjected to Perfusion and/or Ventilation scan, which was taken as the standard for the diagnosis of PE. Blood samples were collected from all patients in trisodium citrate. Platelet poor plasma obtained from the samples was tested for D-Dimers semi-quantitatively using latex agglutination method. Out of 43 patients 14[32.6%] had completely normal ventilation-perfusion scan hence the diagnosis of PE was excluded. In 6 [13.9%] patients the results were considered indeterminate. Abnormalities suggestive of pulmonary embolism were detected in 23 [53.5%] patients. D-Dimers were less than the cut off value of 500 ng/ml in 19 [44.2%] patients, whereas in 24 [55.8%] the levels were more than 500 ng/ml. When compared with the results of ventilation-perfusion scan the sensitivity of D-Dimers was 91.3% and specificity was 100%. Positive predictive value of the test was 100% whereas negative predictive value was 87.5%. D-Dimers assay combined with high clinical evidence is a cost effective, readily available test which can safely exclude the diagnosis of pulmonary embolism in majority of the cases