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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 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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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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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.

Greywater: What can we do?

- Van Staden, S. J.

How can filter cleanliness be determined?

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

  • Authors: Van Staden, S. J. , Haarhoff, J.
  • Date: 2010
  • Subjects: Water - Purification , Water treatment plants
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16461 , uj:15775 , Van Staden, S.J. & Haarhoff, J. 2010. How can filter cleanliness be determined? In: Proceedings of the 11th WaterNet/WARFSA/GWP-SA Symposium, 27-29 October 2010, Victoria Falls, Zimbabwe:676-690
  • 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 exacerbate the problems with dirty filter media as such conditions lead to the formation of biofilm in the filter media, shown to inhibit the effective backwashing of sand and carbon filters A systematic investigation into filter media cleanliness was therefore started in 2002 at the University of Johannesburg (the then Rand Afrikaans University), involving 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 characterization 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 South African surface waters by enhanced coagulation

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

  • Authors: Lobanga, K. P. , Haarhoff, J. , Van Staden, S. J.
  • Date: 2014
  • Subjects: Water , Water treatment , Surface waters - South Africa , Water - Coagulation
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/23782 , uj:16223 , Lobanga, K.P., Haarhoff, J. & Van Staden, S.J. 2014. Treatability of SA surface waters by enhanced coagulation. Water SA, 40(3):529-534.
  • Description: Abstract: The majority of South African inland surface water sources are compromised due to a long-standing national policy of mandatory return flows. With renewed emphasis on the removal of organic carbon in the latest SANS 241 water quality standard, many South African water treatment managers may need to consider adoption of enhanced coagulation (EC) in the near future to achieve both turbidity and NOM removal. From the study of 4 South African inland waters, this paper demonstrates that UV254 absorbance provides a more accessible, reliable and rapid way of monitoring NOM at treatment plant level. This report also provides a detailed procedure for determining the dosages for EC in terms of UV254 absorbance at jar test level. Using ferric chloride as coagulant, a correlation was established to estimate the coagulant dosage for any desired level of UV254 absorbance removal. This correlation enables a preliminary assessment of EC as a means of planned NOM removal. Should EC promise to be a candidate process for NOM removal, it should be verified at jar test level using the proposed procedure.
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A practical course on filter assessment for water treatment plant operators

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

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