Class frequency distribution for a surface raw water quality index in the Vaal Basin

A harmonised in-stream water quality guideline was constructed to develop a water quality index for the Upper and Middle Vaal Water Management Areas, in the Vaal basin of South Africa. The study area consisted of 12 water quality monitoring points; V1, S1, B1, S4, K9, T1, R2, L1, V7, V9, V12, and V17. These points are part of a Water Board’s extensive catchment monitoring network but were re-labelled for this paper. The harmonised guideline was made up of 5 classes for NH4+, Cl-, EC, DO, pH, F-, NO3-, PO43- and SO42- against in-stream water quality objectives for ideal catchment background limits. Ideal catchment background values for Vaal Dam sub-catchment represented Class 1 (best quality water), while those for Vaal Barrage, Blesbok/Suikerbosrand Rivers and Klip River represented Classes 2, 3 and 4, respectively. Values above those of Klip River ideal catchment background represented Class 5. For each monitoring point, secondary raw data for the 9 parameters were cubic-interpolated to 2 526 days from 1 January 2003 to 30 November 2009 (7 years). The IF-THEN-ELSE function then sub-classified the data from 1 to 5 while the daily index was calculated as a median of that day’s sub-classes. Histograms were constructed in order to distribute the indices among the 5 classes of the harmonised guideline. Points V1 and S1 were ranked as best quality water (Class 1), with percentage class frequencies of 91% and 60%, respectively. L1 ranked Class 3 (34%) while V7 (54%), V9 (53%), V12 (66%) and V17 (46%) ranked poorly as Class 4. B1 (76%), S4 (53%), K9 (41%), T1 (53%) and R2 (61%) ranked as worst quality (Class 5). The harmonised in-stream water quality guideline resulted in class frequency distributions. The surface raw water quality index system managed to compare quality variation among the 12 points which were located in different sub-catchments of the study area. These results provided a basis to trade pollution among upstream-downstream users, over a timeframe of 7 years. Models could consequently be developed to reflect, for example, quality-sensitive differential tariffs, among other index uses. The indices could also be incorporated into potable water treatment cost models in order for the costs to reflect raw water quality variability.Keywords: class frequency distribution; cubic interpolation; harmonised in-stream water quality guideline; ideal catchment background; Vaal basin; water quality inde

Water management tools as a means of averting a possible water scarcity in South Africa by the year 2025

South Africa, currently categorised as water stressed country is forecasted to experience physical water scarcity by the year 2025 with an annual freshwater availability of less that 1 000 m3 per capita. With the trends in population growth and its attributes and continuous pollution of the available water sources, there is bound to be increased pressure on the available water probably resulting in increased conflict over its allocation and a further stress on this resource leading to scarcity. Most countries in the world including South Africa have developed most of their water resources with very little scope for further expansion. This study attempted to establish possible solutions to this scenario. Possible solutions would be as follows. First is the demand management of the water through developing and or improving existing systems that improve water use efficiency in the various demand sectors thereby increasing access to more users and uses for a given volume of water. Second is identifying and developing alternative supply systems suitable for the various demand sectors in order to augment the conventional supply volumes. Third is the application of feasible, special management techniques to improve water quality to appropriate standards for particular uses in areas where natural poor quality water occurs. Fourth is the reallocation of some water from low benefit uses to higher benefit uses. Fifth is the possibility of water transfer from surplus areas to deficit area. A water management tool/model suitable for the various sectors of demand and suitable areas of application in each sector is envisaged as the output of this study. If found to be practicable, and eventually utilised, this model will have the potential to increase the water availability for the various sectors and avert possible conflicts in water allocation. The impact of this economically, socially and environmentally in South Africa and possible application in other water stressed countries with similar conditions will be significant. Water SA Vol. 30 (5) 2005: pp.120-12

Fluoride removal performance of phosphoric acid treated lime: Breakthrough analysis and point-of-use system performance

Fluoride in drinking water above permissible levels is responsible for dental and skeletal fluorosis. In this study, removal of fluoride ions from water using phosphoric acid treated lime was investigated in continuous and point-of-use system operations. In the continuous column operations, fluoride removal performance was investigated as a function of the fluoride concentration, flow rate and amount of adsorbent mass. Early saturation and lower fluoride removal were observed at higher flow rate and initial concentration, and at lower mass. Two domestic defluoridation point-of-use systems operated intermittently to process 20 ..day.1 of water were used. High fluoride uptake capacity (FUC) from groundwater was observed depicting the suitability of the new media in defluoridation. However, further research is required to optimise the point-ofuse systems performances

Performance of multistage filtration using different filter media against conventional water treatment systems

This study was aimed at introducing multistage filtration (MSF) (a combination of slow-sand filtration (SSF) and pretreatment system - horizontal flow roughing filter (HRF)) as an alternative water treatment technology to the conventional one. A pilot- plant study was undertaken to achieve this goal. Evaluating the MSF performance vs. the existing conventional system in removing selected physical and chemical drinking water quality parameters together with the biological water quality improvement by the MSF without chemical use was done. Evaluation of the effectiveness of the MSF system utilizing locally available material, i.e. gravel, improved agricultural waste (charcoal maize cobs) and broken burnt bricks as pretreatment filter material was also done The benchmark was the Kenya Bureau of Standards (KEBS) values for the selected parameters. Results showed that with proper design specifications, MSF systems perform better than conventional systems under similar conditions of raw water quality and environmental conditions. The tested locally available materials can also be effectively used as pretreatment media with each allowing a filter run greater than 82 d and therefore could serve as alternatives where natural gravel is not readily available. With special reference to the bacteriological quality improvement, the MSF greatly improved the bacteriological quality of the water recording removal efficiencies of over 99% and 98% respectively for E. coli and total coliforms. Despite the observed performance, MSF should be complemented with chlorination as a final buffer against water-borne diseases. However, in this case, the dosing will be greatly reduced when compared to the conventional system. WaterSA Vol.30 (3) 2004: 361-36

The Cyclical Development of Trypanosoma vivax in the Tsetse Fly Involves an Asymmetric Division

International audienceTrypanosoma vivax is the most prevalent trypanosome species in African cattle. It is thought to be transmitted by tsetse flies after cyclical development restricted to the vector mouthparts. Here, we investigated the kinetics of T. vivax development in Glossina morsitans morsitans by serial dissections over 1 week to reveal differentiation and proliferation stages. After 3 days, stable numbers of attached epimastigotes were seen proliferating by symmetric division in the cibarium and proboscis, consistent with colonization and maintenance of a parasite population for the remaining lifespan of the tsetse fly. Strikingly, some asymmetrically dividing cells were also observed in proportions compatible with a continuous production of pre-metacyclic trypomastigotes. The involvement of this asymmetric division in T. vivax metacyclogenesis is discussed and compared to other trypanosomatids

Verification of Wegelin\'s design criteria for horizontal flow roughing filters (HRFs) with alternative filter material

Wegelin\'s design criteria founded on the “1/3 – 2/3” filter theory are still to date the most comprehensive models applied in design of roughing filters. This study aimed at verifying these criteria based on gravel as a filter medium and two other possible alternative filter media, namely broken burnt bricks and charcoal maize cobs. Gravel was used as a control medium since it is one of the most commonly used roughing filter media and also because it was used in developing these criteria. The per cent reduction in raw water suspended solids (SS) concentration was compared against the expected model prediction. SS was used as a parameter of choice since the “1/3 – 2/3” filter theory is based on SS reduction. A pilot plant study was undertaken to meet this objective. The pilot plant was monitored for a continuous 85 days from commissioning till the end of the project. Results showed that in general, filters filled with charcoal maize cobs and broken burnt bricks were off model prediction by 13% compared to gravel\'s 15%. The performances also varied in both low- and high-peak periods. It is concluded that the Wegelin\'s design criteria should be used as a guideline step followed by actual field and laboratory tests to establish the actual filter design parameters in line with the filter media in use and the quality of the raw water to be treated. Water SA Vol 32(1)pp:105-10

An efficient optimisation method in groundwater resource management

Uncertainty in input parameters to groundwater flow problems has been recognised as an impediment to designing efficient groundwater management strategies. The most popular approach to tackling this problem has been through the Monte Carlo approach. However, this approach is generally too expensive in terms of computer time because of the number of scenarios required to ensure reliable statistics. Furthermore, solutions obtained through this approach are not necessarily robust. In this paper, it is shown how groundwater management problems, where input parameters are uncertain can be reformulated as second-order cone optimisation (SOCO) problems, which are efficiently solved by recently developed interior-point methods. Results for a real-world case application of a groundwater aquifer found in Kenya are presented. Water SA Vol.29(4): 359-36