J. van Heerden

Detection and risk assessment of adenoviruses in swimming pool water

Aims:  The role of swimming pool water as a source of human adenovirus (HAd) infection has previously been demonstrated. In this study, the risk of infection of HAds detected in a survey of swimming pool water from two indoor and one outdoor swimming pools over a period of 1 year was assessed.

Hepatitis A virus in surface water in South Africa: what are the risks?

Giardia spp. and Cryptosporidium spp. are recognized worldwide as highly infectious protozoan parasites that can cause severe gastrointestinal disease in humans and animals. The detection of these pathogens in activated sludge samples becomes interesting since there is an increasing trend for the use of sewage sludge (biosolids) in agriculture. A total of 22 samples were collected and evaluated by means of Centrifugal - Concentration, followed or not followed by a purification process (ether clarification and sucrose flotation). Student t tests for comparison of the two procedures indicated a higher recovery rate of Giardia cysts with Centrifugal - Concentration; with regard to Cryptosporidium oocysts, no significant differences were found between the two methods, as only two samples were positive. The Centrifugal - Concentration procedure was shown to be the simplest and cheapest to perform, as emphasized by the efficiency recovery results.

Prevalence of vaccine-derived polioviruses in stools of immunodeficient children in South Africa

Aims:  The aim of the study was to determine the prevalence of vaccine‐derived polioviruses (VDPVs) in stool specimens of immunodeficient patients such as HIV‐positive children (including those with an AIDS indicator condition, according to the Centres for Disease Control and Prevention classification) by applying various molecular techniques.

Clear air turbulence over South Africa

Clear air turbulence (CAT) at high altitude remains a hazard to aviation which can result in passenger injury and aircraft damage. Two limited surveys of CAT events over South Africa, 1993-1995 (inclusive) and 1998, are used to illustrate the most likely synoptic conditions under which CAT can be expected. A case study of CAT associated with an upper-air trough and a mountain wave is presented. The study also evaluates the effectiveness of the Ellrod Turbulence Index (ETI) derived from model data provided by the UK Met. Office. A forecast of ETI derived from the Global Spectral Model of the United States National Center for Environmental Prediction (NCEP) is also reviewed.

23 – The microbiology of phosphorus removal in activated sludge

The microbial community of the activated sludge consists of bacteria, protozoa, fungi, algae and filamentous organisms. Various methods can be used to study the microbial community in activated sludge. The bacteriological studies of the biological nutrient removal (BNR) systems emphasize the functional role of Acinetobacter in enhanced phosphorous (P) removal. Acinetobacter strains—isolated from the activated sludge—accumulate the excessive amounts of polyphosphate in pure culture, showing their importance in the enhanced biological phosphate removal (EBPR) process. There is a large discrepancy between the total direct microscopic counts and the viable plate counts for many ecosystems. Recoveries from the activated sludge systems, even with optimized media, are only between 5 and 15%. The main difference between the P-removing and the non-P-removing systems is biomass related and is not due to the microbial community structure. An increase in the biomass can lead to an increase in P-removal. Calculation of the quantity of P-removal per g of sludge suggests that there is a direct relationship between P-removal and mixed liquor suspended solids (MLSS) for a specific system.

Antibody recognition of an 18 KDa protein possibly involved in phosphate removal by activated sludge

Phosphate in wastewater effluent is implicated in eutrophication of water reserves. Enhanced biological phosphate removal by activated sludge is attributed to polyphosphate accumulating bacteria, which release phosphate during anaerobiosis and reincorporate it during aerobiosis. The aim of the study was to investigate whether the process of phosphate removal by activated sludge could be probed immunochemically. Antigen preparations from the aerobic and preceding anoxic zones of a phosphate removing system contained intact and lysed bacterial cells. Neither conventional nor subtractive immunisation strategies, the latter employing cyclophosphamide to immunofocus on unique epitopes in the zones, provided antibodies capable of distinguishing between these zones. However, a putatively protein-directed monoclonal antibody could distinguish between the aerobic zones of two activated sludge systems, differing only in phosphate removal ability: immunoblot showed five discrete bands, with molecular weights appearing to be multiples of 18 kDa, unique to the system successful at phosphate removal.