Aromatic Plants, K.V. Peter (Eds.) 2007, New India Publishing Agency, Pitam Pura, New Delhi, 110 088, ISBN: 81-89422-45-6, Price; $95.50, 290 pages including 42 colour photographs, Web: www.bookfactoryindia.com, E-mail: [email protected]

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Measurement and expression of granular filter cleanliness

Abstract The problem of dirty filter media at water treatment plants, despite having good backwash systems, is a serious challenge that requires constant monitoring and maintenance. To aid the systematic analysis of filter media and the troubleshooting of problem filters, this paper firstly proposes a standard procedure for quantification of the specific deposit on filter media, including tentative guidelines for the interpretation of the results. Secondly, a standard procedure is proposed for the characterisation of the specific deposit, based on its volatility and its acid solubility. These fractions are helpful to trace the origin of excessively dirty filter media. Thirdly, the utility of the proposed procedures is demonstrated by the results of a South African treatment plant survey. This confirms some earlier observations that there often is a real problem with recalcitrant specific deposits that cannot be readily removed by backwashing, a fraction that correlates with the organic fraction in the specific deposit

An improved filter media test for troubleshooting and rehabilitation of problem filters

Abstract: A standard “floc retention test” was made available by the American Water Works Association1 to provide a routine measure of filter media cleanliness. This would allow early detection of the potential for serious problems. The test is performed by preparing a 50g media sample and shaking it vigorously in 100ml of water. The resultant suspension is then decanted and, after five repetitions, the turbidity of the combined suspension is measured, doubled and reported as NTU (nephelometric turbidity units)/100g of sand. The turbidity, according to AWWA guidelines, ranges from < 60 (clean filters) to 300 NTU/100g (filters with a possible mudball problem)2. At many South African plants, filters appear to be inadequately cleaned by routine backwash procedures. The hypothesis is that the root of this phenomenon lies in the high degree of biological activity within filter beds. This presumably results in a sticky biofilm on the media grains, which is difficult to remove. The floc retention test proved to be an indispensable tool for a systematic survey of water filtration plants currently being carried out to test this hypothesis. To improve reproducibility and insight into the reasons for media fouling, the floc retention test was refined in a number of ways, which is the main focus of this presentation

Measuring the cleanliness of filter media

Abstract: Filter media starts its working life as almost pure silica, freshly crushed, sieved, washed and dried. Upon examination a few years later, we find discoloured, often sticky material hardly recognisable as the original. As long as the media retains its granular character and the filter beds stay smooth and level, this is no cause for great concern. However, when the media forms clumps, when cracks become apparent in the bed or the filtrate quality deteriorates for no apparent reason, the media demands closer attention. Such media investigations have been carried out for more than a decade at the Water Research Group of the University of Johannesburg. Drawing on this reservoir of experience and case studies, this paper reviews the different approaches to measuring and expressing the degree of cleanliness of in situ filter media. A conceptual model of the different types of specific deposit on the media is developed first, classifying the specific deposit into those fractions that are washed out by the treatment plant backwash system, the fraction hat can be additionally washed out by a laboratory column, the fraction that needs mechanical agitation to be stripped off the media, and the fraction that can only be chemically stripped. Typical values for the four fractions, as measured during a comprehensive survey of South African water treatment plants, are presented, together with suggested remedial measures for each of the media fractions

Effective filter backwashing with multiple washes of air and water

Abstract: In general, filters develop problems over time due to the routine running of the filter, including backwashing. The difficulties in maintaining filters in good condition, given the eutrophic state of many of our raw waters, the high water temperature and resulting development of difficult-to-remove biofilm, are well known to South African water treatment plant operators. These difficulties are usually related to the deposits accumulated by the filter. The backwashing system, therefore, has to be really good to ensure filter cleanliness 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. If air scour continues for more than about a minute, the media compacts, air channels form and the abrasion amongst media grains largely ceases. By interspersing shorter cycles of air and water, rather than using one single cycle, the media is repeatedly fluidised, giving each new burst of air renewed opportunity to effectively abrade the media grains. This concept is not new – at some South African treatment plants the “double” or even “triple” wash had been used for 15 years with reputed success. However, from 2003 to 2005, the Water Research Group at the University of Johannesburg (UJWRG) has systematically investigated this concept at five water treatment plants and in the laboratory, through the testing of both media and backwash water samples, to determine the quantitative benefits of multiple wash cycles. The paper describes the methods used and the typical results obtained. Multiple washing does indeed show great promise for improving backwash efficiency. On the average, a second wash removes about an additional 40% to 50% of the solids that would have been washed out with a single wash. Furthermore, a third and even fourth wash still continues to remove additional dirt from the filter. Multiple washing, therefore, may be used as a useful tool for effective rehabilitation as well as for routine operation

An ecological study of the plant communities of Marakele National Park

Please read the abstract in the section 06back of this documentDissertation (MSc)--University of Pretoria, 2009.Centre for Wildlife Managementunrestricte

Effect of scale of operation on heap leaching performance

The extent to which differences in bulk density and in irrigation geometry contribute towards the differences observed in leaching performance between laboratory-scale columns versus commercial-scale heaps was investigated. Furthermore, the contributions of segregation and stratification, which are absent from columns but unavoidable in heaps, were also investigated. Four case studies provided data whereby the column and heap leaching of the respective sample materials could be directly compared. The first involved gold-bearing ore, the second gold-bearing sand, a third was conducted on oxide-copper ore and the fourth case study was performed on sulphidic copper ore. The first case study was published by others, while the other three were conducted by the author himself. Furthermore, custom-designed boxes were constructed whereby the segregation and stratification of ore could be simulated. Tests were performed to observe the leaching performance of segregated and stratified ore samples, compared to unsegregated and unstratified ore samples. The leaching characteristics of each case was quantified in terms of the parameters of a mathematical model, based on dual-porosity hydrology and diffusion with chemical reaction, which provided optimised fits to the experimental data. Furthermore, fundamental relations were derived for the impact that changes in bulk density and changes in drip-irrigation spacing are theoretically expected to have on the same model parameters. These relations were tested against the actual trends observed in the model parameters that best fitted the data of the four case studies and of the segregation/stratification experiments. It was found that the diffusional distance, which places a mass-transfer limitation on the over-all rate of leaching, can be governed by either the ore bulk density, or by the irrigation dripper spacing. The relations derived under this study can be used to estimate the maximum dripper spacing that can be permitted to prevent dripper spacing from becoming the rate-limiting parameter. Estimates of the impact of dripper spacing on the ultimate extent of extraction are also provided. However, neither segregation nor stratification exhibited significant or reproducible effects on leaching kinetics. These findings can place the drafting of heap leaching design parameters on a more fundamental footing

Development of an accountability framework in the public procurement system : case of the emerging market

The government of South Africa uses citizens’ tax money to procure products to meet citizens’ needs (Fourie, 2009) in areas such as education, health, road safety, and transportation. Having public service officials who are accountable will improve public administration and ensure a comprehensive standard of living for its citizens (Auditor-General of South Africa [AGSA], 2017). Whenever a public institution lacks accountability, it will have an adverse effect on a country’s budget and contribute to poverty, unemployment, and criminal activity. This research aimed to develop a framework to ensure accountability throughout public procurement. A comparison was conducted through a multiple case study, of five departments in Limpopo on the challenges as identified by the Auditor-General. The study provides an understanding of the public procurement dynamics through its collaborative and hybrid nature. It addresses various aspects that enforce an accountability framework, such as internal control, procurement systems, risk management, records management, value for money, and consequence management. Furthermore, adjustments to the South African e-governance procurement system in alignment with best practices found in other countries will save money and time, and procurement officers will be more productive.https://virtusinterpress.org/-Corporate-Governance-and-Organizational-Behavior-Review-am2023School of Public Management and Administration (SPMA