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Water demand characteristics of shared water and sanitation facilities : experiences from community ablution blocks in eThekwini Municipality, South Africa

- Crous, P., Haarhoff, J., Buckley, C.A.

  • Authors: Crous, P. , Haarhoff, J. , Buckley, C.A.
  • Date: 2012
  • Subjects: Communal sanitation , Water demand management , Sanitation services , Ablution facilities
  • Type: Article
  • Identifier: uj:5331 , ISSN 1816-7950 , http://hdl.handle.net/10210/8829
  • Description: The provision of communal water and sanitation facilities has been mandated by the South African Government as an interim measure for informal settlement upgrading. These services form the first step in the upgrading process and are essential in meeting the basic needs of the community. The eThekwini municipality is rolling out community ablution blocks to informal settlements throughout their jurisdiction. This paper investigates the water demand characteristics of these community ablution blocks, and provides a detailed methodology for collecting the data, which provides the 15-minute peak and average water demand. The results from January to November 2012 indicate that the majority of the water supply (60%) is used for laundry purposes, which includes the water used in the laundry basins and from the tap for off-site consumption, while the water demand for toilet flushing accounts for 16% of the total water supply from each facility. The peak and average water demand can be used for future hydraulic modelling of these, and other, communal ablution facilities.
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Turbidity removal at twenty-one South African water treatment plants

- Van Staden, S. J., Amod, A., Ceronio, A. D., Haarhoff, J.

  • Authors: Van Staden, S. J. , Amod, A. , Ceronio, A. D. , Haarhoff, J.
  • Date: 2002
  • Subjects: Water treatment plants , Turbidity removal
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16583 , uj:15787 , Citation: Van Staden, S.J. et al. 2002. Turbidity removal at twenty-one South African water treatment plants. 8th Biennial Conference of the Water Institute of Southern Africa, 19-23 May 2002, ICC, Durban, WISA 198, 10p.
  • Description: Abstract: The Water Research Group at the Rand Afrikaans University undertook an ambitious sampling and monitoring programme at twenty-one South African water treatment plants during 2000 and 2001. At some of these plants, there were parallel but different treatment trains due to plant extensions being made at different times. A total of 25 full or partial treatment trains could therefore be monitored. A total of 115 plant visits were made over a period of fifteen months, with samples taken throughout the plant, covering the complete treatment train from raw to final water. Amongst other parameters, the turbidity of each sample was determined on site immediately upon sampling. This paper will summarise and interpret the resulting data set of approximately 1300 turbidity values. The paper will firstly characterise the raw and final waters respectively. In other words, how does typical raw water vary, and how good is the typical final water produced? The second part will summarise the typical performance of each of the treatment processes. In other words, what reduction in turbidity is typically achieved during settling, dissolved air flotation and filtration? The paper will make a practical contribution in providing a benchmark to all operators of treatment plants by: · being able to immediately "position" themselves within a typical range of raw water values. · judging their final water quality against what is generally achieved, and · evaluating and troubleshooting their individual process units against what is generally achieved.
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How can filter cleanliness be determined?

- Haarhoff, J., Van Staden, S.J.

  • Authors: Haarhoff, J. , Van Staden, S.J.
  • Date: 2011
  • Subjects: Specific deposit , Filter media , Filter cleanliness
  • Type: Article
  • Identifier: uj:5310 , ISSN 1474-7065 , http://hdl.handle.net/10210/6800
  • Description: It is general believed that a sand filter starts its life with new, perfectly clean media, which becomes gradually clogged with each filtration cycle, eventually getting to a point where either head loss or filtrate quality starts to deteriorate. At this point the backwash cycle is initiated and, through the combined action of air and water, returns the media to its original perfectly clean state. Reality, however, dictates otherwise. Many treatment plants visited a decade or more after commissioning are found to have unacceptably dirty filter sand and backwash systems incapable of returning the filter media to a desired state of cleanliness. In some cases, these problems are common ones encountered in filtration plants but many reasons for media deterioration remain elusive, falling outside of these common problems.The South African conditions of highly eutrophic surface waters at high temperatures, however, exacerbate the problems with dirty filter media. Such conditions often lead to the formation of biofilm in the filter media, which is shown to inhibit the effective backwashing of sand and carbon filters. A systematic investigation into filter media cleanliness was therefore started in 2002, ending in 2005, at the University of Johannesburg (the then Rand Afrikaans University). This involved media from eight South African Water Treatment Plants, varying between sand and sand-anthracite combinations and raw water types from eutrophic through turbid to low-turbidity waters.Five states of cleanliness and four fractions of specific deposit were identified relating to in situ washing, column washing, cylinder inversion and acid-immersion techniques. These were measured and the results compared to acceptable limits for specific deposit, as determined in previous studies, though expressed in kg/m3. These values were used to determine the state of the filters. In order to gain greater insight into the composition of the specific deposits stripped from the media, a four-point characterisation step was introduced for the resultant suspensions based on acid-solubility and volatility.Results showed that a reasonably effective backwash removed a median specific deposit of 0.89 kg/m3. Further washing in a laboratory column removed a median specific deposit of 1.34 kg/m3. Media subjected to a standardised cylinder inversion procedure removed a median specific deposit of 2.41 kg/m3. Immersion in a strong acid removed a median specific deposit of 35.2 kg/m3.The four-point characterisation step showed that the soluble-volatile fraction was consistently small in relation to the other fractions. The organic fraction was quite high at the RG treatment plant and the soluble-non-volatile fraction was particularly high at the BK treatment plant.
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How to measure specific deposit washout and backwash efficiency of granular filters

- Van Staden, S. J., Haarhoff, J.

A standard test for filter media cleanliness

- Van Staden, S. J., Haarhoff, J.

  • Authors: Van Staden, S. J. , Haarhoff, J.
  • Date: 2004
  • Subjects: Filter deposits , Filter residue , Filter media , Floc retention
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/16413 , uj:15772 , Citation: Van Staden, S.J. & Haarhoff, J. 2004. A standard test for filter media cleanliness. Water SA, 30(1):81-88. , ISSN: 0378-4738
  • Description: Abstract: Rapid sand filters are expected to produce clean, safe water, without interruption, for many years. Unfortunately, filters very often develop some problems during this time, most of which only become apparent when the damage is already done. Routine measurement of filter media cleanliness could provide the necessary early warning, which is the reason why the American Water Works Association (AWWA) suggested a media cleanliness test for inclusion in a structured filter assessment programme at drinking water treatment plants. After performing such assessments at 3 South African water treatment plants, the authors found that the results were not consistent, the turbidity could not be measured easily and the guideline values seemed to be excessively conservative. This led to an investigation to find a method for stripping the filter deposits from the media grains with an easy, reproducible method, and for characterising the stripped deposits. After a series of tests on various filter media, using 6 stripping methods, 2 methods were identified that met the criteria in the first objective. The first, a magnetic stirrer method is a mechanical agitation method and the second, referred to as the cylinder inversion method, is a manual agitation method. Each of these methods was chosen on the basis of their operator and speed-ofagitation independence. The criteria in the second objective were met by an in-depth suspended solids (SS) analysis performed on the filter media residue, with the total mass of solids removed from the media quantitatively separated on the grounds of acid solubility and volatility at 550°C. Standard Methods (1985) 209C and 209D were applied to the sample, with and without acid addition, in order to characterise the total filter media residue using 4 groupings: Soluble, non-volatile; soluble, volatile; non-soluble, non-volatile; and non-soluble, volatile. By meeting the criteria of these 2 objectives, the previous non-specific suggestions in the literature have been improved to suggest the performing of tests in a well-specified, uniform way, the results of which can be internally compared.
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Natural organic matter in drinking water sources: its characterisation and treatability

- Haarhoff, J., Mamba, B., Krause, R. W. M., Van Staden, S., Nkambule, T., Dlamini, S., Lobanga, K. P.

The response of typical South African raw waters to enhanced coagulation

- Dlamini, S.P., Haarhoff, J., Mamba, B.B., Van Staden, S. J.

  • Authors: Dlamini, S.P. , Haarhoff, J. , Mamba, B.B. , Van Staden, S. J.
  • Date: 2011
  • Subjects: Water - Purification - Organic compounds , Organic water pollutants
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16567 , uj:15786 , Dlamini, S.P. et al. 2011. The response of typical South African raw waters to enhanced coagulation. In: Proceedings of the 4th IWA Specialty Conference on NOM: From Source to Tap and Beyond, Costa Mesa, USA. 27-29 July 2011, 11 p.
  • Description: Abstract: Drinking water treatment plants in South Africa rely almost entirely on surface water sources, which are often compromised due to high return flows and indirect reuse. The typical treatment plants focus on the removal of physical and microbial contaminants which include turbidity, colour, chemical compounds and microorganisms. A relatively new concern to this list is natural organic matter (NOM) which has become a major concern in potable water treatment due to its recent regulation. In this study, eight different raw water samples from the various water types found in the country were seasonally collected and treated for the removal UV absorbance at a wavelength of 254nm (UV254) using enhanced coagulation (EC). The efficacy of EC, which can be employed as a practical technology in the removal of both turbidity and NOM, was evaluated in remaining UV254 from these raw water sources. Jar tests were conducted, with ferric chloride used as the coagulant (due to its extensive use as a coagulant in the water treatment industry in South Africa) and specific pH values (initial water pH, 7.0, 6.0, 5.5, 5.0 and 4.5) were chosen as target values guiding the six different coagulant dosages for the jar tests. The pH of the low-alkalinity (<60mg/l CaCO3) raw waters were adjusted and raised by the addition of sodium carbonate. The response parameters of the tests were turbidity (NTU), pH and UV254. Algorithms for finding the optimum coagulant dosage for UV254 removal were developed and consistently applied to all the results. Results showed large variations in the nature of NOM across the country from SUVA values. From the UV254 values, the concentrations of NOM also varied greatly geographically than temporally. The general trend observed in the EC results suggested that the pH should always be dropped to between 4.5 and 7.0 to lower the amounts of UV254 and turbidity to reasonable levels.
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Impact of alkalinity on the removal of natural organic matter from raw waters by enhanced coagulation

- Dlamini, S.P., Van Staden, S., Haarhoff, J., Mamba, B.B.

  • Authors: Dlamini, S.P. , Van Staden, S. , Haarhoff, J. , Mamba, B.B.
  • Date: 2011
  • Subjects: Drinking water - Purification - South Africa , Water - Purification - Coagulation -South Africa , Organic water pollutants - South Africa , Ferric chloride
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16804 , uj:15810 , Dlamini, S.P. et al.(2011) Impact of alkalinity on the removal of natural organic matter (NOM) on raw waters by enhanced coagulation (EC). 12th Waternet Conference, Maputo, Mozambique, 26-28 October 2011, 13 p.
  • Description: Abstract Natural organic matter (NOM) in all soils, ground and surface waters cause negative effects in potable water quality (undesired colour, taste, odour, and bacterial re-growth in distribution systems). Numerous studies have also found that the reaction of NOM with oxidative chemicals during drinking water treatment processes can result to the formation of carcinogenic disinfection by-products (DBPs). Many countries including South Africa, have therefore established regulations to control and minimise NOM and its effects. Enhanced coagulation (EC), a multiple-objective chemical dosing strategy, offers a viable option for NOM removal, and this study explores its use for typical South African raw waters. A consistent and reproducible jar test procedure, simulating the actual coagulation and flocculation pre-treatment steps, was developed and used to investigate the treatability of NOM (measured as UV 254 nm) in all the source waters. Ferric chloride was used as the coagulant due to its extensive application in South Africa. Raw water samples representing the various water types found in the country were seasonally collected for investigation, thus corresponding to a year-long data collection period. Since the removal of NOM is linked to strict control of pH, the coagulant dosage for the jar tests aimed at specific pHs (pH 7.0, 6.0, 5.5, 5.0 and 4.5) with the use of titration curves. The response parameters for the tests were temperature, turbidity, pH and UV 254 nm. Algorithms of finding the optimum dosage for both turbidity and UV 254 nm removal were developed from jar tests and consistently applied to subsequent batch tests. The results of the study suggested that low-alkalinity waters are more amenable to coagulation than high-alkalinity waters. The results also led to the conclusion that the alkalinity and pH of a water are key factors influencing coagulation performance. The optimum pH for the waters fell within the range of 5.0 to 6.5.
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Assessments and improvement of filter media cleanliness in rapid gravity sand filters

- Haarhoff, J., Van Staden, S.J., Gendenhuys, J., Sibiya, M., Naicker, P., Adam, N.

  • Authors: Haarhoff, J. , Van Staden, S.J. , Gendenhuys, J. , Sibiya, M. , Naicker, P. , Adam, N.
  • Date: 2008
  • Subjects: Water treatment filters , Rapid sand filtration , Cleanliness
  • Language: English
  • Type: Report
  • Identifier: http://hdl.handle.net/10210/16810 , uj:15809 , Citation: Haarhoff, J. et al. 2008. Assessments and Improvement of Filter Media Cleanliness in Rapid Gravity Sand Filters. Report 1525/1/08 to the Water Research Commission, ISBN 978 1 77005 734 0.
  • Description: Introduction: Rapid sand filtration is an essential unit process in the water purification process. It captures and removes coagulated and flocculated material and other suspended matter not removed during the preceding treatment processes. The pores in the filter bed gradually become clogged and the media progressively collects deposit through the continuous use and life of the filter. During normal operations cleaning is initiated by excessive head loss, deterioration in filtrate quality or when the predetermined time for a filter run has elapsed. Air scour, to remove deposit from filter media by vigorous agitation, and wash water, to remove this deposit from the filter bed, are applied. The combined action of air and water should quickly return the media to its original perfectly clean state for the cycle to continue. However, on inspection it is often found that filter sand on purification plants is unacceptably dirty and backwash systems are clearly incapable of cleaning the media to its initial state of cleanliness. It is at times possible to relate the dirty filter media to faulty designs or poor operating procedures, but often the reasons for the media deterioration remain elusive and the media becomes dirtier the longer it is in use. As there was an almost complete lack of published or agreed upon procedures to measure the cleanliness of filter media, rudimentary methods for measuring filter media cleanliness and backwash efficiency were developed. Thereafter filter media from full-scale treatment plants was analyzed with these methods at regular intervals to establish some benchmarks for these determinants. These methods were also applied during the laboratory and pilot plant phases of the project.
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Removal of natural organic matter from different raw waters by ion exchange resins

- Lobanga, K.P., Haarhoff, J., Van Staden, S.

Natural organic matter (NOM) in South African waters : characterization, treatability and method development for effective NOM removal from water

- Nkambule, T. I., Krause, R. W. M., Mamba, B. B., Haarhoff, J., Van Staden, S. J.

Treatability of South African surface waters by activated carbon

- Lobanga, K.P, Haarhoff, J., Van Staden, S.J.

  • Authors: Lobanga, K.P , Haarhoff, J. , Van Staden, S.J.
  • Date: 2013
  • Subjects: Activated carbon , Natural organic matter , Surface water , Ultraviolet absorbance
  • Type: Article
  • Identifier: uj:4834 , ISSN 0378-4738 , http://hdl.handle.net/10210/12480
  • Description: Natural organic matter (NOM) in water resources for drinking purposes can be removed by different methods, including activated carbon adsorption. Due to the variability of NOM in natural waters, both in terms of its nature and its concentration, a study was undertaken to investigate NOM removal for a wide range of South African surface waters, sampled at different periods, by the use of granular activated carbon (GAC). NOM removal was assessed by measuring the ultraviolet (UV) absorbance at 3 wavelengths, namely, 254 nm (UV254), 272 nm (UV272) and 300 nm (UV300). A comparison of data between the three wavelengths showed that any of the three wavelengths can be used to assess NOM removal by GAC, which is well described by the Freundlich equilibrium equation. A treatment target of 40% removal of initial UV254 absorbance was considered. It was observed that, although the GAC dosage was generally a function of the initial UV254 absorbance, differences existed between waters. This suggests that GAC usage rate is not only a function of the initial UV absorbance but also of the NOM composition, indicating a need for improved NOM characterisation. Comparison between the UV absorbance and dissolved organic carbon (DOC) data suggested that for some waters UV254 absorbance can be used as a rapid substitute for DOC. Finally, the high GAC dosage rates required for the target criterion revealed that the process is inadequate for use at the initial stage of raw water treatment; GAC adsorption should be used at later stages of drinking water treatment.
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The failure probability of welded steel pipelines in dolomitic areas

- Haarhoff, J., Nel, D.T.

Comparative study for the removal of natural organic matter from different raw waters by ion exchange

- Lobanga, K.P., Haarhoff, J., Mamba, B.B., Van Staden, S.J.

Practical guidelines for enhanced coagulation using UV254

- Dlamini, S. P., Mamba, B. B., van Staden, S. J., Haarhoff, J.

  • Authors: Dlamini, S. P. , Mamba, B. B. , van Staden, S. J. , Haarhoff, J.
  • Date: 2012
  • Subjects: Natural organic matter , Enhanced coagulation
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/23316 , uj:16221 , Citation: Dlamini, S.P. et al. 2012. Practical guidelines for enhanced coagulation using UV254. 13th Biennial Conference of the Water Institute of Southern Africa, 6-9 May 2012, Cape Town, South Africa, 10 p.
  • Description: Abstract The negative effects of natural organic matter (NOM) in drinking water are well known and, where necessary, its removal is crucial. This is enforced by the increasingly stringent water regulations around the world. In South Africa, this regulation targets NOM in the form of total organic carbon (TOC), at a maximum of 10 mg/L. Enhanced coagulation (EC), a multiple objective chemical dosing strategy, offers a viable method of NOM removal, and this study explored its use for typical South African raw waters. A consistent and reproducible jar test procedure was developed and applied to 19 widely different raw water samples collected from different locations and at different times of a year long period. These samples consisted of a wide range of alkalinity, UV254 and turbidity values. Three criteria were developed and applied to determine the best EC dosage for the optimal removal of UV254 without compromising residual dissolved organic carbon (DOC) and turbidity. DOC was measured, prior to and after batch tests, to confirm removal similarities with UV254 and compliance with national standards. The resultant percentage removals of UV254 and DOC ranged between 56 to 96 % and 45 to 94 % respectively, irrespective of water source, period and coagulation dosage. The settled water residual turbidity values were less than 1.5 NTU. The costs for EC were found to be comparable to those for conventional coagulation in all cases.
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The use of filter media to determine filter cleanliness

- Van Staden, S.J., Haarhoff, J.

  • Authors: Van Staden, S.J. , Haarhoff, J.
  • Date: 2011
  • Subjects: Water treatment plants - Design and construction - Data processing , Water - Purification - Membrane filtration , Water - Purification
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/16727 , uj:15805 , ISSN: 14747065 , DOI: 10.1016/j.pce.2011.07.067 , Van Staden, S.J., & Haarhoff, J. (2011) The use of filter media to determine filter cleanlines. Journal Physics and Chemistry of the Earth 36 (14-15) 1135-1140. DOI:10.1016/j.pce.2011.07.067
  • Description: Abstract It is general believed that a sand filter starts its life with new, perfectly clean media, which becomes gradually clogged with each filtration cycle, eventually getting to a point where either head loss or filtrate quality starts to deteriorate. At this point the backwash cycle is initiated and, through the combined action of air and water, returns the media to its original perfectly clean state. Reality, however, dictates otherwise. Many treatment plants visited a decade or more after commissioning are found to have unacceptably dirty filter sand and backwash systems incapable of returning the filter media to a desired state of cleanliness. In some cases, these problems are common ones encountered in filtration plants but many reasons for media deterioration remain elusive, falling outside of these common problems. The South African conditions of highly eutrophic surface waters at high temperatures, however, exacerbate the problems with dirty filter media. Such conditions often lead to the formation of biofilm in the filter media, which is shown to inhibit the effective backwashing of sand and carbon filters. A systematic investigation into filter media cleanliness was therefore started in 2002, ending in 2005, at the University of Johannesburg (the then Rand Afrikaans University). This involved media from eight South African Water Treatment Plants, varying between sand and sand-anthracite combinations and raw water types from eutrophic through turbid to low-turbidity waters. Five states of cleanliness and four fractions of specific deposit were identified relating to in situ washing, column washing, cylinder inversion and acid-immersion techniques. These were measured and the results compared to acceptable limits for specific deposit, as determined in previous studies, though expressed in kg/m3. These values were used to determine the state of the filters. In order to gain greater insight into the composition of the specific deposits stripped from the media, a four-point characterisation step was introduced for the resultant suspensions based on acid-solubility and volatility. Results showed that a reasonably effective backwash removed a median specific deposit of 0.89 kg/m3. Further washing in a laboratory column removed a median specific deposit of 1.34 kg/m3. Media subjected to a standardised cylinder inversion procedure removed a median specific deposit of 2.41 kg/m3. Immersion in a strong acid removed a median specific deposit of 35.2 kg/m3. The four-point characterisation step showed that the soluble-volatile fraction was consistently small in relation to the other fractions. The organic fraction was quite high at the RG treatment plant and the soluble- non-volatile fraction was particularly high at the BK treatment plant
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Treatability of SA surface waters by activated carbon

- Lobanga, K. P., Haarhoff, J., van Staden, S. J.

How to measure specific deposit washout and backwash efficiency of granular filters

- Van Staden, S.J., Haarhoff, J.

  • Authors: Van Staden, S.J. , Haarhoff, J.
  • Date: 2011
  • Subjects: Water - Purification - Membrane filtration , Water treatment plants , Carbon, Activated
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/16971 , uj:15830 , Van Staden, S.J. & Haarhoff, J. (2011) How to measure the specific deposit washout and backwash efficiency of granular filters. Water Practice and Technology 6 (1) DOI:10.2166/WPT. 2011.014.
  • Description: Abstract Practical experience shows that water treatment filters develop problems over time due to the routine running of the filter, including backwashing. There are difficulties in maintaining filters in good condition, given the eutrophic state of many South African raw waters, high water temperatures and the development of difficult-to-remove biofilm as a result. Such difficulties are often related to deposits accumulated on the filter media and it is, therefore, expected that the backwash system should be good enough to ensure that the filter is kept clean in the long run. This paper deals with a fairly simple operational option to significantly improve backwash efficiency at treatment plants where air and water are used consecutively. The paper describes methods used and typical results obtained in the testing of the quantitative benefits of multiple wash cycles. Multiple washing shows great promise for improving backwash efficiency, with an average of an additional 40% to 50% of the solids that would have been washed out with a single wash, removed by a second wash. Furthermore, third and even fourth washes continue to remove additional dirt from the filter. Multiple washing, therefore, may be a useful tool for the effective rehabilitation of a filter, as well as for routine operation procedures.
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Bulk water distribution power supply failures

- Nel, D.T., Haarhoff, J.

  • Authors: Nel, D.T. , Haarhoff, J.
  • Date: 2011-04
  • Subjects: Bulk water supply , Power supply , Power supply failures , Power supply reliability , Pump systems reliability
  • Type: Article
  • Identifier: uj:5312 , ISSN 1021-2019 , http://hdl.handle.net/10210/7735
  • Description: This paper considers the probability of power supply failures at bulk water distribution pump stations. Electrical power supply is important within the bulk water distribution environment, particularly when pumping is required. Reliability of power supply is commonly expressed by means of indices, such as amongst others, the SAIDI and SAIFI indices as defined by the Institute of Electrical and Electronics Engineering (IEEE). These indices are used to calculate the probability of failure associated with power supply. Data was obtained from a number of sources and used to benchmark the reliability of South African power supply against that of other countries. The reliability of power supply from seven South African Water Board (Rand Water) pump stations is also analysed. Limited data seems to be available that allows one to quantify the reliability of pump systems, taking into account the reliability of the various system components.
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Optimized coagulation for the removal of natural organic matter (NOM) from low alkalinity : hardness South African raw waters

- Dlamini, S.P., Van Staden, S., Haarhoff, J., Mamba, B.B.

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