12 results on '"du Preez, H."'
Search Results
2. Significance of bacteria associated with invertebrates in drinking water distribution networks.
- Author
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Wolmarans, E., Du Preez, H. H., De Wet, C. M. E., and Venter, S. N.
- Subjects
- *
INVERTEBRATES as carriers of disease , *WATER utilities , *CONTAMINATION of drinking water , *PATHOGENIC microorganisms , *WATER quality management , *PUBLIC health - Abstract
The implication of invertebrates found in drinking water distribution networks to public health is of concern to water utilities. Previous studies have shown that the bacteria associated with the invertebrates could be potentially pathogenic to humans. This study investigated the level and identity of bacteria commonly associated with invertebrates collected from the drinking water treatment systems as well as from the main pipelines leaving the treatment works. On all sampling occasions bacteria were isolated from the invertebrate samples collected. The highest bacterial counts were observed for the samples taken before filtration as was expected. There were, however, indications that optimal removal of invertebrates from water did not always occur. During the investigation, 116 colonies were sampled for further identification. The isolates represent several bacterial genera and species that are pathogenic or opportunistic pathogens of humans. Diarrhoea, meningitis, septicaemia and skin infections are among the diseases associated with these organisms. The estimated number of bacteria that could be associated with a single invertebrate (as based on average invertebrate numbers) could range from 10 to 4000 bacteria per organism. It can, therefore, be concluded that bacteria associated with invertebrates might under the worst case scenario pose a potential health risk to water users. In the light of the above findings it is clear that invertebrates in drinking water should be controlled at levels as low as technically and economically feasible. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
3. Monitoring of water transfer from Katse Dam into the Upper Vaal river system: water utility's perspective.
- Author
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Lepono, T., Du Preez, H. H., and Thokoa, M.
- Subjects
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WATER quality management , *WATER transfer , *WATER supply , *BIOLOGICAL monitoring , *COMPOSITION of water , *WATER utilities , *DRINKING water ,KATSE Dam (Lesotho) - Abstract
Water quality is of prime importance to Rand Water's core business of ensuring a reliable supply of good quality drinking water to more than 10 million people. Rand Water has, therefore, implemented a water quality monitoring programme of the source water as well as the drinking water produced. The establishment of the Lesotho Highlands Water Transfer scheme necessitated the expansion of the monitoring programme. In 1996, Rand Water and Lesotho Highlands Development Authority (LHDA) signed an agreement to jointly develop an extensive water quality monitoring programme for the Lesotho Highlands Water Project (LHWP). Prior to this agreement, monitoring was mainly undertaken by consultants on behalf of LHDA in the main feeder rivers within the Katse Dam catchment (donor system). On the recipient system (Ash/Liebenbergsvlei), extensive physical and chemical monitoring was undertaken by Rand Water and Department of Water Affairs and Forestry (DWAF). Biological monitoring was however only carried out superficially prior to the release of water. Information gained from carrying out biological and chemical assessments clearly indicates that the water from LHWP has negatively impacted on the biological communities in the recipient system. The importance of detailed before and after biological and physiochemical monitoring of both donor and recipient systems is emphasized. [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
4. Ruminal and postruminal digestion of dietary protein and...
- Author
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Meissner, H. H. and du Preez, H. P. F.
- Subjects
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ENERGY dissipation , *PROTEINS - Abstract
Studies the effect of protein concentration and degradation and energy content of the diet in two Latin Square trials with ruminal and duodenally fistulated steers. How the study was conducted; Results of the study.
- Published
- 1996
5. CAPTAIN STROVER'S REWARD.
- Author
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du Preez, H. M.
- Subjects
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SHIP captains , *ARMORED vessels , *WAR memorials , *SHIPS , *AWARDS - Abstract
The article discusses on the reward trophy presented by East India Co. to Captain John Strover of East Indiaman Essex vessel for his activities in False Bay, California in 1796. This trophy has an extraordinary two handled urn-shaped cup and cover with classic Adam style. It has exquisite refined craftsmanship from the top decoration to the circular, beaded foot. This craft was made by Thomas Chawner a famous silversmith. The cup and its cover has commemorative dedications which include the arms of the East India Co. and the following legend and was perfectly preserved by the Strover family.
- Published
- 2006
6. Application of a basic monitoring strategy for Cryptosporidium and Giardia in drinking water.
- Author
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Sigudu, M. V., du Preez, H. H., and Retief, F.
- Subjects
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DRINKING water , *WATER quality management , *CRYPTOSPORIDIUM , *GIARDIA , *WATER supply - Abstract
Despite the health risks associated with exposure to Cryptosporidium and Giardia, there is no uniform approach to monitoring these protozoan parasites across the world. In the present study, a strategy for monitoring Cryptosporidium and Giardia in drinking water was developed in an effort to ensure that the risk of exposure to these organisms and the risks of non-compliance to guidelines are reduced. The methodology developed will be applicable to all water supply systems irrespective of size and complexity of the purification works. It is based on monitoring procedures proposed by the US Environmental Protection Agency, the Drinking Water Inspectorate, Australia and New Zealand, as well as the risk-based procedure followed by Northern Ireland. The monitoring strategy developed represents a preventative approach for proactively monitoring Cryptosporidium and Giardia species in drinking water. The strategy consists of 10 steps: (i) assessment of the monitoring requirements, (ii) description and characterisation of the source water types, (iii) abstraction of source water, (iv) assessment of the water purification plant, (v) water quality monitoring, (vi) cryptosporidiosis and giardiasis outbreak, (vii) risk assessment, (viii) sample collection and laboratory processing, (ix) data evaluation, interpretation and storage, (x) process evaluation and review. Proper implementation of this protocol can contribute to the protection of drinking water consumers by identifying high-risk source water, identifying areas of improvement within the water treatment system, and also preventing further faecal pollution in the catchments. The protocol can also be integrated into the Water Safety Plans to optimise compliance. Furthermore, this methodology has a potential to contribute to Blue Drop certification as it should form part of the incident management protocols which are a requirement of Water Safety Plan implementation. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
7. Total photosynthetic pigments in addition to turbidity during the selection of coagulant treatments: a drinking water treatment perspective.
- Author
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Ewerts, H., Swanepoel, A., du Preez, H. H., and der Walt, N. Van
- Subjects
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PHOTOSYNTHESIS , *TURBIDITY , *PHYTOPLANKTON , *CHLOROPHYLL , *COAGULANTS - Abstract
Total photosynthetic pigments (TPP) or chlorophyll-a analysis can be useful in selecting coagulant treatments that will improve phytoplankton removal and reduce treatment costs. The objectives of this study were to compare the efficacy of phytoplankton and turbidity removal when using TPP and turbidity as indicator parameters of appropriate coagulant treatments as well as to evaluate the cost impacts thereof. During seven different sampling occasions, source water samples with substantially different TPP and turbidity contents were collected from two South African freshwater sources (Benoni Lake and Vaal Dam) to conduct jar stirring tests. After sedimentation, TPP and turbidity analyses were performed to assess the efficacy of coagulant treatments (Ca(OH)2-SiO2, Ca(OH)2-organic polymer and organic polymer). Results showed that TPP analysis is indeed a useful indicator parameter to consider purifying source water enriched with phytoplankton. Ca(OH)2-organic polymer treatment was more costly than Ca(OH)2-SiO2 and organic polymer, but the only coagulant treatment that met the removal criteria after sedimentation. Benoni Lake source water (TPP: 34.29 µg/l; 4.29 NTU) was more costly to treat than Vaal Dam source water (TPP: 2.29 µg/l; 80.29 NTU). Findings made from this study confirm that high phytoplankton concentrations in source water due for treatment will increase the treatment costs. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
8. Implementing a protocol for selection and prioritisation of organic contaminants in the drinking water value chain: Case study of Rand Water, South Africa.
- Author
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Ncube, E. J., Voyi, K., and du Preez, H.
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ORGANIC water pollutants , *DRINKING water - Abstract
Approaches that prioritise chemicals according to their importance as environmental contaminants have been developed by government agencies and private industries. However, it has been noticed that few approaches, such as one published by the United States Environmental Protection Agency (USEPA), address the needs of the drinking water industry. There is also no generic approach to the selection, prioritisation and monitoring of organic contaminants in the drinking water value chain. To safeguard drinking water industry customers, it was necessary to develop a generic protocol to assist with the identification of a list of organic contaminants for monitoring in the drinking water value chain. Once the protocol was developed, it was validated in a prototype drinking water value chain. This paper describes the implementation of such a generic protocol. The exercise comprised of testing each step of the protocol, from selection of the 'pool of organic contaminants' (Step I) to recommending the final priority list of organic contaminants (Step VII). Successful implementation of the protocol took place in the Rand Water (South Africa) drinking water value chain (from catchment to tap). Expert judgment was emphasized during the implementation as each step was validated and the opinion of key stakeholders used to shape the process. The tailor-made prioritisation criteria, reflecting the drinking water industry perspective, proved to be successful in selecting and prioritising organic contaminants for monitoring in the drinking water value chain. The organic contaminants were successfully prioritised in 3 classes: short-term priority for analysis, medium-term priority for analysis and long-term priority for analysis. This is a very important guide to assist water utilities in optimising their resources while not compromising the role of public health protection. Finally, a priority list of organic contaminants was identified for use by Rand Water and other water utilities. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
9. Seasonal study on Bothriocephalus as indicator of metal pollution in yellowfish, South Africa.
- Author
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Retief, N.-R., Avenant-Oldewage, A., and du Preez, H. H.
- Subjects
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WATER pollution , *METALS & the environment , *WATER levels , *BOTHRIOCEPHALUS , *LARGEMOUTH bass , *FISH kills ,ENVIRONMENTAL aspects - Abstract
Eighty largemouth yellowfish, Labeobarhus kimherleyensis, were collected between April 2005 and February 2006 with gill nets close to the island (26° 52, 249‱ S, 28° 10, 249‱ E) in the Vaal Dam. The fish were killed, weighed and their length determined. Muscle, liver and spinal cord tissues were collected from each fish and the intestines removed and opened to expose Bothriocephalus acheilognathi. The tapeworms were collected in glass bottles and frozen. Water and sediment, as well as liver, muscle and tapeworm samples were digested and thereafter metal concentrations of 23 elements (lithium, beryllium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, tellurium, barium, mercury, thallium, lead and uranium) were determined with an ICP-MS. Bioconcentration of metals (selenium, mercury, and lead during autumn; copper, zinc, selenium, cadmium, antimony, thallium and mercury during winter; lithium, zinc, selenium, cadmium and antimony during spring; and zinc during summer) occurred in tapeworms. The highest mean value was recorded in sediment, followed by water, tapeworms and host tissue. A seasonal trend showed that a higher concentration of the metals had accumulated in tapeworms during winter when water levels were at their lowest. [ABSTRACT FROM AUTHOR]
- Published
- 2009
10. Exposure of rural households to toxic cyanobacteria in container-stored water.
- Author
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Fosso-Kankeu, E., Jagal, P., and du Preez, H.
- Subjects
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CYANOBACTERIA , *PROKARYOTES , *CYANOBACTERIAL blooms , *AQUATIC microbiology , *MICROBIOLOGY , *BACTERIAL pollution of water , *MARINE microbiology - Abstract
Cyanobacteria are potent producers of cyanotoxins that may present a health risk to people. This is especially important in rural areas where people use untreated surface water, containing cyanobacteria, for household purposes including cooking and drinking. Water is collected from these sources mainly in plastic containers, transported home and stored during use. This study investigated the occurrence of cyanobacteria and their associated toxins in these containers as well as in the associated surface water sources. The results suggest that cyanobacteria are transferred from the water sources to the containers and then survive and possibly grow in biofilm forming inside the vessels. Their associated cyanotoxins were not found in any health-significant quantities in containers. However, the occurrence of cyanobacteria in the water used by the households collected in containers clearly indicates that it can be an important route of exposure especially if toxic cyanobacteria are present in the source water. In several cases a risk of cyano-intoxication might exist unless the households undertake preventative measures. [ABSTRACT FROM AUTHOR]
- Published
- 2008
11. The use of cestode parasites from the largemouth yellowfish, Labeobarbus kimberleyensis (Gilchrist and Thompson, 1913) in the Vaal Dam, South Africa as indicators of heavy metal bioaccumulation
- Author
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Retief, N.-R., Avenant-Oldewage, A., and du Preez, H.
- Subjects
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TAPEWORM infections , *PARASITES , *FISHES , *BIOACCUMULATION - Abstract
Abstract: Twenty Largemouth yellowfish Labeobarbus kimberleyensis (Gilchrist and Thompson, 1913) were collected in the Vaal Dam in the vicinity of RAU Island (Groot Eiland). Muscle-, spinal cord- and liver tissue were removed from each fish and the intestine opened to obtain Bothriocephalus acheilognathi. The tissues were then digested in a microwave digester and the metal concentrations were determined in each tissue with an ICP-MS. The results indicate that the worms have potential use as bioindicators, because in 8 elements (lithium, beryllium, manganese, selenium, mercury, thallium, lead and uranium) out of the 23 elements measured the cestodes have accumulated the highest metal concentrations, and in 7 elements (chromium, iron, zinc, molybdenum, cadmium, tin and barium) out of 23 elements the cestodes had the second highest metal accumulation recorded. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
12. Effect of polyphenol content on the hydrolysis and fermentation of grain sorghum starch
- Author
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De Jong, Fiona M., Lategan, P. M., and Du Preez, H. C.
- Subjects
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FERMENTATION - Published
- 1987
- Full Text
- View/download PDF
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