Target Water Quality Range Research Articles

Investigating a surface water quality monitoring approach for QwaQwa, South Africa, by combining biological in vitro tests and chemical analyses

IntroductionWater quality assessment is a fundamental requirement for comprehensive water management. Access to water is not exclusively a quantitative issue, as human activities often lead to negative impacts on water quality due to pollution. This results in a need for the systematic monitoring of water bodies to surveil ongoing pollution dynamics and, if needed, facilitate the implementation of suitable solutions for water quality management.MethodsTo that effect, in March 2022 and July 2023, we conducted two sampling campaigns in four headwater streams in QwaQwa, South Africa, to assess the water quality under high (summer) and low (winter) flow conditions. The overarching aim was to support local decision-makers with relevant information on water quality in a semirural and less studied area. Beside the hydrological characterization of the catchment, which drains the mountainous areas around Phuthaditjhaba (the main town of the region), physicochemical and biological monitoring were conducted, including in vitro tests detecting endocrine disruption, dioxin-like impacts, and genotoxic potentials in the water.ResultsThe elemental analysis showed that at several sampling sites, Al, Cu, Mn, Fe, and Zn were above the Target-Water-Quality-Range (TWQR) for aquatic ecosystems and Fe, Al, and Mn were additionally above the TWQR for domestic use. Interestingly, the organic micropollutants (OMPs) revealed a region with a high incidence of HIV infections, given the occurrence of the drugs efavirenz, its transformation product 8-OH-efavirenz and nevirapine, among other micropollutants. Possibly, the signals from the in vitro tests for endocrine disruption are also induced by the detected micropollutants. Our results ultimately show that even though anthropogenic impacts increase from upstream to downstream, none of the sampling sites are without concern. This indicates the urgent need for measures to increase the water quality of these headwater streams in this region.

Assessing the adverse effects of a mixture of AMD and sewage effluent on a sub-tropical dam situated in a nature conservation area using a modified pollution index

Currently water resources in nature conservation areas are under severe pressure due to external drivers of anthropogenic pollution. There is a lack of monitoring tools to determine water quality status of dams situated in nature reserves receiving a mixture of pollutants over space and time. The present study was conducted over a 12-month period with the aim of applying a modified pollution index (PILD) to determine the water quality and phytoplankton status of the Loskop Dam situated in the Loskop nature reserve, South Africa. From the data generated in the current study, it was evident that the PILD effectively determined nutrient enrichment and heavy metal pollution in the dam. Furthermore, the study showed that the most pollution tolerant phytoplankton species was the diatom Melosira varians followed by the dinoflagellate Ceratuim hirundinella and the cyanobacteria Microcystis aeruginosa. Chemical variables during the sampling period that exceeded the limits of the South African, Canadian, Australia and New Zealand guideline levels were Zn, TP, Cl, Fe, Mn and NH4. The occurrence of concentrations of Cl above the target water quality range for aquatic ecosystems (5 µgl−1) over the entire sampling period, may have been related to point source sewage pollution in the upper catchment. The PILD showed poor water quality conditions during the months of September and October during the dam’s destratification (lake overturn). By modifying an existing index to incorporate physico-chemical variables that are strongly related to a mixture of pollutants, it should have application on global scale applied to different waterbodies with differ phytoplankton indicator species across different geographical regions. Furthermore, it could also in the future serve as a decision support tool for conservation managers to determine the pollution status of a dam situated in nature conservation areas receiving a mixture of pollutants.Graphic abstract

Treatment of acid mine drainage with coal fly ash in a jet loop reactor pilot plant

A 1500 L batch jet loop reactor pilot plant was designed, constructed, and evaluated for performance in the treatment of acid mine drainage (AMD) using coal fly ash with a view to optimize its operation and generate performance data. Results showed that concentration of major contaminants (sulfate, Al, Fe, Ca, Mg), and minor contaminants in the treated AMD can be significantly lowered (between one and four orders of magnitude) compared to the raw AMD. It was shown that the one-step treatment process recovered at least 66.6% (728.56 kg) of treated water depending on the degree of dewatering required for slurry pumping. The energy consumption of 2.655 kW used for pumping indicated that an oversized centrifugal pump (15 kW capacity) was used for the neutralization cycle, as only a small fraction of the pump capacity was utilized. The treated water met the target water quality range (TWQR) limit for agricultural irrigation in South Africa. The analysis of the solid residue shows its suitability for backfilling of mine voids or for making geopolymer such that AMD treatment with fly ash results in a zero discharge process. The treatment process offers a cradle-to-cradle solution to acid mine drainage and coal fly ash.

Assessment of surface water quality status of the Aby Lagoon System in the Western Region of Ghana

The pollution status of the Tendo Lagoon, the upstream section of the Aby Lagoon System, was investigated. The water temperature, pH, turbidity, dissolved oxygen (DO), electrical conductivity (EC), nitrates (NO3-), and phosphate (PO43-) levels were evaluated using samples taken during the wet and dry seasons to assess the variabilities in water quality in the area. The water quality data was subjected to paired t-test, One-way ANOVA, Factor Analysis, Cluster analysis (CA) as well as a Water Quality Index (WQI) evaluation using the Canadian Council of Ministers of the Environment (CCME) model. The paired sample t-test confirmed that the surface water quality varies significantly between the wet and dry season samples (p < 0.05) except for phosphate loads which may be contributed largely by year-round municipal waste discharges. The results of the ANOVA showed that the variation of the water quality parameters among sampling stations was not statistically significant except for turbidity which was relatively higher in the upstream sections where the Tano River enters the lagoon. The results of FA indicated that three significant factors–relating to the degradation of organic materials, suspended solids (turbidity) and nutrients- accounted for 73.65% of spatio-temporal variations in the water quality. The CA showed that the eight sampling stations can be grouped into four distinct clusters based on their water quality. The source of pollution in the demarcated sections of the Aby Lagoon was concluded to be largely due to the result of localized anthropogenic inputs of domestic waste and sediments carried from the upstream in the Tano River. An evaluation of the CCME WQI for the sampling stations revealed that all the sampling stations showed marginal water quality relative to the target water quality range recommended by the Water Resources Commission (WRC) of Ghana for domestic use and protection of aquatic life. Monitoring programs were recommended with effective management measures instituted and implemented for the sustainability of the lagoon and the Tano River Basin.

An Appraisal of Groundwater Contamination : A Case Study of Shallow Wells In Agbowo Community, Southwestern Nigeria

Abundant as it may seem in Nigeria, access to clean and potable water is a great challenge. Hence the reason for determination of the physico-chemical properties of the groundwater in Agbowo community in Ibadan, Oyo state Southwestern Nigeria for domestic uses. Water samples collected from thirty-four (34) shallow wells with varying depths were subjected to chemical analysis. The water quality parameters were analyzed in accordance to standard methods. The groundwater analysis reviewed includes pH, electrical conductivity, total dissolved solids (TDS), others include Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt; Na&lt;sup&gt;+&lt;/sup&gt;, Fe&lt;sup&gt;2+&lt;/sup&gt;, NO&lt;sub&gt;3&lt;/sub&gt;, Cl&lt;sup&gt;-&lt;/sup&gt; SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; and HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;- &lt;/sup&gt;The results indicated that the parameters analyzed have some falling within the limits and some above the maximum permissible limits in accordance to Nigeria Industrial Standard (NIS) and World Health Organization (WHO) guidelines for drinking water. In general, the data revealed that maxima and minima concentrations of the priority physico-chemical water quality parameters examined in the thirty-four (34) water points were mostly within the Target Water Quality Range (TWQR) for domestic use with little exceptions at some points. However, high nitrate concentrations and Total Dissolved Solids (TDS) above the permissible limits in some of the well water sampled are causes for serious concern. Poor construction, lack of maintenance, proximity to sewage tank and stream, as well as indiscriminate dumping of refuse are suggested as the major causes of this development. The overall implication of this observation call for sustenance and improved water resource management strategy for the area in order to prevent the deterioration of the water sources quality, which may pose associated health risks and environmental hazards.

A comparison of water quality and macroinvertebrate community structure in endorheic depression wetlands and a salt pan in the Gauteng province, South Africa.

Depression wetlands (colloquially referred to in South Africa (SA) as pans) are found worldwide and primarily occur in arid regions including North and South America, southern and central Africa and southern and western Australia. Surface water resources in SA, and specifically in Gauteng, are under pressure from urbanisation, poor agricultural practices and untreated mining and industrial effluent. Research of these wetlands will benefit the development of health assessment tools for these unique aquatic resources. The aim of this project was to determine the water quality and macroinvertebrate community structure for each perennial pan during consecutive dry and wet seasons and to establish a possible comparison between these pans that can be used as a baseline for future research on pans. The sampled pans in Gauteng presented higher TDS, Cl and Mg results compared to other South African studies, and similar SO4 results to pans in the Mpumalanga province. Ammonia, Al and Zn results of all pans through all sampling events exceed the Target Water Quality Range (TWQR) for aquatic ecosystems of the Water Quality Guidelines (WQG) from the Department of Water and Sanitation (DWS). The water quality from selected systems is suitable for livestock watering based on the DWS TWQR. Macroinvertebrate species of all sampled pans were mostly low water quality tolerant species with a predator dominant community structure. Seasonal variation of species was evident. Macroinvertebrate families found in the wet season include Hydrophilidae, Aeshnidae, Pleiidae, Ephemeroptera, Belostomatidae and Notonectidae. Families found in the dry season include Planaridae, Dysticidae, Hirudinidae and Daphnidae. Graphical representation of ordination analyses with Canoco version 5 (Ter Braak and Šmilauer 2012) indicated that TDS, temperature, pH, sulphates and hardness are strong drivers of the existing macroinvertebrate community in most of the pans.

Survival and development of embryos of &lt;i&gt;Gallus gallus domesticus&lt;/i&gt; treated with inorganic bromide

The range of bromide (Br-) in groundwater sources surveyed in South Africa is 0 - 18.4 mg/L. The research aimed to establish chicken embryo sensitivity to a range of Br- treatments (mg/L) injected into fertilised Ross-308 eggs in three phases: (1) five eggs injected with 10 mg Br-/L; (2) 45 eggs divided into groups and injected with 0, 1 and 5 mg Br-/L; (3) 148 eggs divided into groups injected with 0, 0.01, 0.05, 0.5, and 1 mg Br-/L. Incubation was at standard conditions. Breakout analysis was done at various stages of incubation. The mass of the embryo and of the heart, liver and brain was measured at Day 20. Statistical analysis used Statistical Analyses System® software FREQ procedure to determine the chi-square goodness-of-fit test for percentages of live or dead embryos within and between treatments. The GLM procedure was applied to test for differences in relative organ mass (g) between treatments using F-test. The results showed: (1) 10 mg Br-/L is toxic; (2) Br- is lethal to embryos at concentrations &gt;1 mg/L and toxic at 1 mg/L; and (3) embryo survival was significantly negatively correlated (R2 = -0.92) with increasing Br- concentrations. Concentrations &gt;0.5 mg Br-/L showed greater risk on differential development. Concentrations &gt;0.01 mg Br-/L showed potentially severe effects on developing embryos. The heart showed the greatest relative growth response followed by the brain. The no observed adverse effect level target water quality range (NOAEL-TWQR) in developing chicken embryos was 0 - 0.01 mg/L.Keywords: Bromine, embryo model, halogens, maximum residue level, toxicity, water quality

Cradle to cradle solution to problematic waste materials from mine and coal power station: Acid mine drainage, coal fly ash and carbon dioxide

During mining, minerals such as FeS2 are exposed to O2, H2O, and microorganisms resulting in the oxidation and generation of acidic water. The acidic water causes chemical weathering of the adjacent rocks and leaching of potentially toxic metals and the resultant water is often termed acid mine drainage (AMD). Coal power stations produce an alkaline aluminosilicate waste material called fly ash (CFA). Modern waste resource management emphasises finding useful applications of waste generated from processes to achieve a green economy. CFA was, with additional lime and Al(OH)3 used to treat AMD at a 80L pilot scale. Most of the physical and chemical parameters of the treated water were within South African target water quality range (TWQR) for irrigation. Carbonation of the water after treatment with CFA, lime and Al(OH)3 produced water that was within the TWQR for irrigation with respect to all parameters and resulted in the sequestration of 15–123L of CO2 per 80 L of AMD treated at standard ambient temperature and pressure. CO2 reacted with Ca ions in the water and solid residues to form CaCO3. Carbonation improves the ease of disposal of CFA, the AMD quality as well as reducing the amount of CO2 emissions by coal power plants through mineral carbonation. The solid residues from the overall process are suitable for the back filling of mine voids thereby preventing AMD generation by excluding air and water. This is an innovative cradle to cradle solution for the disposal of waste materials from coal mines and power stations.

Water quality and antifungal susceptibility of opportunistic yeast pathogens from rivers.

Yeasts from water sources have been associated with diseases ranging from superficial mucosal infections to life threatening diseases. The aim of this study was to determine the water quality as well as diversity and antifungal susceptibility of yeasts from two rivers. Yeast levels and physico-chemical parameter data were analyzed by principal component analysis to determine correlations between physico-chemical data and yeast levels. Yeast morphotypes were identified by biochemical tests and 26S rRNA gene sequencing. Disk diffusion antifungal susceptibility tests were conducted. Physico-chemical parameters of the water were within target water quality range (TWQR) for livestock farming. For irrigational use, total dissolved solids and nitrates were not within the TWQR. Yeast levels ranged between 27 ± 10 and 2,573 ± 306 cfu/L. Only non-pigmented, ascomycetous yeasts were isolated. Saccharomyces cerevisiae and Candida glabrata were most frequently isolated. Several other opportunistic pathogens were also isolated. A large number of isolates were resistant to azoles, especially fluconazole, but also to other antifungal classes. Candida species were resistant to almost all the antifungal classes. These water sources are used for recreation and religious as well as for watering livestock and irrigation. Of particular concern is the direct contact of individuals with opportunistic yeast, especially the immune-compromised. Resistance of these yeast species to antifungal agents is a further health concern.

Assessment of Heavy Metals and Radionuclide Concentrations in Mafikeng Waste Water Treatment Plant

A study was carried out to assess the heavy metal and radionuclide concentrations of water from the waste water treatment plant in Mafikeng Local Municipality. Ten water samples were collected from various stages of water treatment (n = 2 per stage) which included sewage delivered to the plant, the two treatment stages, the effluent and the community water. Samples were analyzed for heavy metal content using Inductive Coupled Plasma Mass Spectrometer. Gross α/β activity concentrations in water samples were evaluated by Liquid Scintillation Counting whereas the concentration of individual radionuclides was measured by gamma spectroscopy. The results showed marked reduction in the levels of heavy metal concentration from 3 μg/L (As) - 670 μg/L (Na) in sewage into the plant to 2 μg/L (As) - 170 μg/L (Fe) in the effluent. The gross α activity in all the water samples (7.7 - 8.02 Bq/L) exceeded the 0.1 Bq/L limit set by World Health Organization (WHO). Gamma spectroscopy revealed very high concentrations of 235U and 226Ra in water samples, with the lowest concentrations (9.35 and 5.44 Bq/L, respectively) in the in-coming sewage and highest concentrations (73.8 and 47 Bq/L, respectively) in the community water. All the values were considerably higher than the limits of South Africa Target Water Quality Range and WHO. However, the estimated total doses of the two radionuclides for the analyzed water samples (10.62 - 45.40 μSv·yr-1) were all well below the reference level of the committed effective dose of 100 μSv·yr-1 recommended by WHO.

Analysis of physico-chemical and bacteriological quality of drinking water in Mafikeng, South Africa.

Mafikeng, the capital of the North West Province, receives water from two sources, namely the Molopo eye and the Modimola dam. Once treated, the potable water is mixed and supplied to the city via distribution systems. This study was designed to assess the quality of drinking water in Mafikeng and also to determine whether the water from the two sources has an impact on the mixed water quality. Physico-chemical parameters and bacteriological quality (faecal coliforms (FCs), total coliforms (TCs), heterotrophic bacteria and Peudomonas spp.) was monitored at three drinking water sites weekly for 4 months. The results revealed that the physico-chemical quality of the water was generally acceptable. The pH ranged from 5.7 ± 0.18 to 8.6 ± 0.14, the temperature ranged from 18.3 ± 0.69 to 25.1 ± 0.69 °C and the total dissolved solids (TDS) ranged from 159.9 ± 22.44 to 364.4 ± 12.44 mg/l. These values are within the target water quality range for drinking water as prescribed by WHO, Department of Water Affairs and SANS 241. What is of concern was the microbial quality of the water. FCs, TCs, heterotrophic bacteria and Pseudomonas spp. were present in some of the treated water samples. The most significant finding of this study is that all drinking water samples were positive for Pseudomonas spp. (>100/100 ml).

Analysis of grey-water used for irrigating vegetables and possible effects on soils in the vicinity of Umtata Dam, Eastern Cape

In the search for alternative and reliable water sources to irrigate vegetables for backyard gardens, an experimental field was set up in the vicinity of the Umtata Dam, north-west of the town of Umtata, to test grey-water quality and its effects on soil nutrient content following 4 successive growing seasons. Samples of grey-water that were generated from informal housing adjacent to the Umtata Dam were collected from kitchen and bath tubs/washing basins. These samples were analysed before being used for irrigating vegetable crops. The results showed that grey-water quality was efit for purposef for irrigating edible vegetable plants. Although the average Na+ (16 mg/.) and Cl- (15 mg/.) ions were significantly higher (p = 0.05) for grey-water than other treatments, both were below the limit of 100 mg/. set in the South African Water Quality Guidelines. The concentrations of nutrients and heavy metals found in the grey-water samples were significantly lower compared to the World Health Organization guidelines for the safe use of grey-water and within the target water quality range (TWQR) prescribed by South African guidelines for irrigation water. However, the study strongly recommends that grey-water be diluted in order to lower the salt content and to improve the irrigation water quality. Results from an analysis of soil samples showed no significant differences in pH as a result of applying grey-water throughout the soil profile of up to 90 cm depth. Na content of the soil irrigated with grey-water was not significantly different than that of plots where diluted grey-water and potable water were used. Therefore, the grey-water used in this study does not appear to cause an accumulation of salts and heavy metals in soil, in the short term. Keywords : grey-water, vegetables, soil, heavy metals, pH

Fate of the naturally occurring radioactive materials during treatment of acid mine drainage with coal fly ash and aluminium hydroxide

Mining of coal is very extensive and coal is mainly used to produce electricity. Coal power stations generate huge amounts of coal fly ash of which a small amount is used in the construction industry. Mining exposes pyrite containing rocks to H2O and O2. This results in the oxidation of FeS2 to form H2SO4. The acidic water, often termed acid mine drainage (AMD), causes dissolution of potentially toxic elements such as, Fe, Al, Mn and naturally occurring radioactive materials such as U and Th from the associated bedrock. This results in an outflow of AMD with high concentrations of sulphate ions, Fe, Al, Mn and naturally occurring radioactive materials. Treatment of AMD with coal fly ash has shown that good quality water can be produced which is suitable for irrigation purposes. Most of the potentially toxic elements (Fe, Al, Mn, etc) and substantial amounts of sulphate ions are removed during treatment with coal fly ash. This research endeavours to establish the fate of the radioactive materials in mine water with coal fly ash containing radioactive materials. It was established that coal fly ash treatment method was capable of removing radioactive materials from mine water to within the target water quality range for drinking water standards. The alpha and beta radioactivity of the mine water was reduced by 88% and 75% respectively. The reduced radioactivity in the mine water was due to greater than 90% removal of U and Th radioactive materials from the mine water after treatment with coal fly ash as ThO2 and UO2. No radioisotopes were found to leach from the coal fly ash into the mine water.

Ecological status of Hout River Dam, Limpopo province, South Africa, using fish condition and health assessment index protocols: a preliminary investigation

The ecological status of Hout River Dam was evaluated in 2011 by assessing fish health, based on condition factor (K), health assessment index (HAI) and inverted parasite index (IPI), which provided a simple and rapid means of establishing the health of fish. Surveys were conducted during summer, winter and spring 2011. To verify results, water quality was analysed during each survey. Clarias gariepinus, Oreochromis mossambicus and Cyprinus carpio were collected using conventional angling gear and gillnets. Mean K values of 0.6, 2.0 and 1.4, and HAI scores of 38, 41 and 35, were recorded for each species, respectively. The metrics that correlated best with fish health scores were haematocrit values and ecto- and endoparasite indices. Differences in K, HAI, and HAI using IPI determinations, were insignificant (p > 0.05) between species, while water contaminants, with the exception of ammonium (NH4), nitrate (NO3) and aluminium (Al) concentrations in summer, fell within the levels stipulated by the South African target water quality range guidelines for aquatic ecosystems. It was thus inferred that the dam was in a good ecological state.

Chemical characteristics and limnology of Loskop Dam on the Olifants River (South Africa), in light of recent fish and crocodile mortalities

A declining crocodile population and fish mortalities attributed to pansteatitis, along with increasing blooms of Microcystis aeruginosa and Ceratium hirundinella, have led to serious concerns about water quality in Loskop Dam, on the Olifants River, South Africa. Major impacts include acid mine drainage and eutrophication associated with sewage effluent. However, the specific causes of pansteatitis remain elusive. In 2011 the water chemistry and limnology of Loskop Dam were studied to determine factors that may be influencing aquatic ecosystem health. Long-term monitoring data collected by the Department of Water Affairs were analysed for trends using a seasonal Mann-Kendall trend test, and were used to determine the trophic state of Loskop Dam using the Carlson index. Multiple sites were sampled which showed the reservoir was heterogeneous with regard to nutrient concentrations, algal biomass and dissolved metals. Specifically, the transitional zone was characterised by frequent algal blooms, resulting in fluctuating dissolved oxygen (range = 2.1–14.5 mg/ℓ) and pH (range = 7.35–10.59) levels. Using total phosphorus, Secchi depth, and chlorophyll-a concentrations, the trophic state of Loskop Dam was classified as meso- to eutrophic. Significant positive trends were observed in total (Tau = 0.422) and dissolved inorganic (Tau = 0.193) phosphorus.The reservoir showed a monomictic pattern of summer stratification (October to April) and holomictic winter circulation (June to July), with an increase in the depth and extent of anoxia in the hypolimnion when compared to previous research. Simultaneous elevated concentrations of manganese (&gt;370 μg/ℓ) and iron in near-bottom water samples coincided with hypolimnetic anoxia. Aluminium concentrations exceeded the target water quality range (&gt;10 μg/ℓ) during summer (December) in both surface and near-bottom water samples. We conclude that fish in Loskop Dam are periodically exposed to several physiological stressors including elevated ammonia, aluminium, iron and manganese and possibly hydrogen sulphide, as well as low dissolved oxygen. While these factors have never individually been linked to pansteatitis, their combined impacts have not been studied. To ensure the sustainability of Loskop Dam, catchment management plans must focus on reducing phosphorus inputs, and continue seeking treatment solutions for mine-water associated with abandoned and working coal mines.Keywords: Loskop Dam, limnology, pansteatitis, eutrophication, Olifants River

Heavy metal concentrations in the water of the Nyl River system, South Africa

The Nyl River floodplain, a Ramsar site that provides habitat for a number of endangered species, is one of the jewels in the arid Limpopo province and thus its conservation and protection are vitally important. Very little work has been done on assessing its water quality and no data have been published on the metal concentrations found in this valuable system. The aim of this project was thus to provide baseline data for metal concentrations in the Nyl River floodplain system and to determine whether there were any point sources of pollution or if its metal levels were natural. Eighteen localities along the course of the Nyl River were selected as sampling sites. Water samples were collected quarterly, between August 2001 and July 2002, and analysed using ICP-MS to determine metal content. Zinc, copper, iron, selenium, cadmium, lead, aluminium, arsenic, chromium and manganese concentrations were determined. Although metal concentrations in the water were greater than target water quality range (TWQR) values for aquatic ecosystems, they remained relatively constant throughout the system and posed little or no potential threat to the system. The results suggest that the metal content originates from natural sources.

Diversity and characteristics of yeasts from water sources in the North West Province, South Africa

Yeasts form an important part of ecosystems. Yeast biodiversity in the North West Province, South Africa, remains largely unexplored. The purpose of this study was to determine the diversity and characteristics of yeasts from water sources in the North West Province. Yeasts were isolated from four rivers and an inland lake. Various parameters were measured to determine the physico-chemical quality of the water. Isolation was done on yeast-malt-extract (YM) agar and identified using biological methods. Physico-chemical parameters were within a target water quality range for various water uses. Yeasts were detected at 22 of the 23 sampling sites. Levels ranged from 3 to 8,680 cfu/L and were broadly divided into pigmented and non-pigmented yeasts. Pigmented yeasts could potentially be an indication of pollution, while non-pigmented yeasts could potentially be pathogenic species. Levels of yeasts could be statistically associated with some physico-chemical parameters. A large percentage of isolated yeasts could grow at temperatures ranging from 4 to 40 °C. Candida spp., Cryptococcus spp., Rhodotorula spp. and Zygosaccharomyces spp. were identified. Our results provide preliminary information on the distribution and diversity of yeasts in water sources in the North West Province.

A study on the health of the Olifants River as reflected by the aquatic macro-invertebrate biodiversity and selected abiotic factors.

Aquatic macro-invetrebrates and selected abiotic factors were used to evaluate the river health. Preliminary results indicate that the ecological categories of the study sites vary from natural to critically modified and that the Target Water Quality Range is hardly ever met.

Leaching characteristics of selected South African fly ashes: Effect of pH on the release of major and trace species

Fly ash samples from two South African coal-fired power stations were subjected to different leaching tests under alkaline and acidic conditions in an attempt to assess the effect of pH on the leachability of species from the fly ashes and also assess the potential impact of the fly ashes disposal on groundwater and the receiving environment. To achieve this, German Standard leaching (DIN-S4) and Acid Neutralization Capacity (ANC) tests were employed. Mineralogical characterization of the fresh fly ashes revealed mullite and quartz as the major mineral phases with minor peaks of CaO and calcite. Chemical characterization by X-ray fluorescence (XRF) spectrometry revealed that the two fly ashes are similar, and consist of SiO2, Al2O3, Fe2O3 and CaO as the main components with Cr, Co, Ni, Cu, Zn, V and Pb as minor components. Ca, Mg, Na, K and SO4 were significantly leached into solution under the two leaching conditions with the total amounts in ANC leachates higher than that of DIN-S4. This indicates that a large fraction of the soluble salts in unweathered fly ash are easily leached. These species represents the fraction that can be flushed off initially from the surface of ash particles on contacting the ash with water. Al and Si were only observed in the leachates of the ANC test. Results obtained from the total acid-digestion and DIN-S4 leaching test indicated some toxic elements in the fly ashes are not easily solubilized. The amounts of toxic trace elements such as As, Se, Cd, Cr and Pb leached out of the fly ashes when in contact with de-mineralized water (DIN-S4 test) were low and below the Target Water Quality Range (TWQR) of South Africa. This is explained by their low concentrations in the fly ashes and their solubility dependence on the pH of the leaching solution. However the amounts of some minor elements such as B, Mn, Fe, As and Se leached out at lower pH ranging between 10 to 4 (ANC test) were slightly higher than the TWQR, an indication that the pH of the leaching solution plays a significant role on the leaching of species in fly ash. The high concentrations of the toxic elements released from the fly ashes at lower pH gives an indication that the disposal of the fly ash could have adverse effects on the receiving environment if the pH of the solution contacting the ashes is not properly monitored. The study indicated that on contact with water in a disposal scenario fly ash will release high amounts of soluble species.

The microbiological quality of groundwater-derived drinking water after long storage in household containers in a rural community of South Africa

To investigate the effect of long storage and household containers on the microbiological quality of water in a rural community, borehole water from the reservoir and seven standpipes was used. Borehole water was stored for a period of 72 h in household containers (polyethylene-PE and galvanised steel-GS), which are commonly used by the rural community of Mgquba village. Heterotrophic plate count (HPC) and faecal coliform bacteria were used as the main parameters. Standard spread plate procedure and membrane filtration method were used to enumerate HPC and faecal coliform bacteria respectively. The results of this study revealed three factors that affected the microbiological quality of drinking groundwater used by the rural community of Mgquba village: the intake water, the duration of storage and the household container. The initial levels of faecal coliform (range of faecal coliforms: 0.1–2 cfu · 100 ml −1 in the reservoir water, 0–57 cfu · 100 ml −1 in the standpipe water) and HPC bacteria (average counts: 5 log cfu · ml −1 in the reservoir water, 7 log cfu · ml −1 in the standpipe water) in both reservoir and standpipe waters far exceeded the limit allowed by the South African Water Quality Guidelines for Domestic Use (no risk target water quality range: 0 count · 100 ml −1 for faecal coliforms, 0–100 counts · ml −1 for HPC bacteria). The persistence of faecal coliforms in polyethylene-stored water was observed after 72 h of storage while their complete elimination in the galvanized steel-stored water occurred after 48 h of storage. Escherichia coli was the most dominant faecal coliform found in the initial and stored waters. Although the yield of HPC bacteria increased in water samples during storage in both polyethylene and galvanised steel containers, the microbiological quality of drinking groundwater deteriorated consistently with the length of the storage. Water stored for 72 h displayed a higher yield of HPC (average counts: 7 log–8 log cfu · ml −1 in PE-stored water, 6 log–8 log cfu · ml −1 in GS-stored water) than the water stored for 48 h or 24 h (average counts: 5 log–8 log cfu · ml −1 in PE-stored water, 5 log–7 log cfu · ml −1 in GS-stored water). Statistical analysis indicated a significantly higher number of HPC bacteria in the water stored in polyethylene than in the water stored in galvanised steel ( P =0.02). Significant differences in HPC bacteria were also noted within household container-stored water from standpipes ( P =0.0001 for PE, P =0.0002 for GS).