Scielo RSS <![CDATA[Water SA]]> vol. 41 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>WISA 2014 - Water Innovations</b>]]> <![CDATA[<b>How well do our measurements measure up? An overview of South Africa's first proficiency testing scheme for organochlorine pesticides in water</b>]]> Access to safe drinking water is a basic human right in South Africa. Therefore, the accurate measurement of water quality is critical in ensuring the safety of water prior to its intended use. Proficiency testing schemes (PTSs) are a recognised form of assessing the technical competence of laboratories performing these analyses. There are over 200 water testing laboratories in South Africa, with only 51 being accredited for testing some or all parameters (physical, chemical and microbiological content) prescribed in SANS 241. Only a limited number of laboratories test for organic contaminants, as this requires advanced, costly analytical instrumentation, such as GC-FID/ECD/MS and LC-UV/MS, as well as skilled staff. These laboratories are either looking at selected organic contaminants listed in the World Health Organisation (WHO) drinking water guidelines or performing the minimum requirements, as stipulated in SANS 241, for phenols, atrazine, trihalomethanes and total dissolved organic content. Whereas several local PTS providers are addressing the competent assessment of microbiological, physical and inorganic chemical testing of water, a clear need for a South African PTS provider for organic contaminant analysis in water was identified by NMISA (National Metrology Institute of South Africa) in 2012. The key drivers for the coordination of a local PTS stem mainly from the limited stability of analytes in the samples for analysis and the high cost and logistics of international PTS participation. During 2012 and 2013, NMISA conducted a PTS trial round, a workshop and 2 additional PTS rounds for organochlorine pesticides in water, for South African laboratories, and also several international participants from other countries in Africa. This paper will highlight some of the challenges faced by laboratories when analysing organochlorine pesticides at the ng/ℓ concentration level. Issues surrounding the comparability of measurement results, traceability, method validation and measurement uncertainty are also discussed. <![CDATA[<b>A cheap and simple passive sampler using silicone rubber for the analysis of surface water by gas chromatography-time of flight mass spectrometry</b>]]> Water pollution events may arise rapidly, requiring a methodology that is easy to implement, fast to deploy, and sufficiently sensitive to detect the trace presence of hazardous contaminants. A cheap and easy to use silicone rubber (polydimethylsiloxane (PDMS)) miniature passive sampler is described. In order to test the methodology, pollutants were concentrated, in situ, from surface water in and around Pretoria, South Africa. The versatile sampler allowed for conventional and enhanced sensitivity, solvent-free analysis by comprehensive gas chromatography - time of flight mass spectrometry (GCxGC-TOFMS) and high resolution TOFMS (GC-HRT). Contaminants detected in surface water include caffeine, personal care products, pharmaceuticals, pesticides and polycyclic aromatic hydrocarbons. <![CDATA[<b>Improved derivatization protocol for simultaneous determination of alkylphenol ethoxylates and brominated flame retardants followed by gas chromatography-mass spectrometry analyses</b>]]> An improved derivatization protocol for the simultaneous determination of alkylphenol ethoxylates and brominated flame retardants with heptafluorobutyric anhydride under triethylamine amine base was investigated. The derivatization reaction was completed in 30 min at 50°C using hexane as solvent. Under these conditions, it was observed that alkylphenol ethoxylates and tetrabromobisphenol A were derivatized successfully in the presence of hexabromocyclododecane, lower congeners of polybrominated biphenyls and polybrominated diphenyl ethers. The improved protocol was applied to recovery of analytes of interest from simulated water samples after solid phase extraction. The recoveries achieved were above 60%. The limit of detection and limit of quantification ranged from 0.01-0.20 μg/ℓ and 0.05-0.66 μg/ℓ respectively. <![CDATA[<b>Groundwater quality on dairy farms in central South Africa</b>]]> Dairy farms in central South Africa depend mostly on groundwater for domestic needs and dairy activities. Groundwater samples were collected from 37 dairy farms during 2009 and 2013. Sixteen water quality parameters were tested and compared to the standard. Four parameters in 2009 and six in 2013 exhibited 100% compliance with the standard. Nitrate, Escherichia coli and total coliforms showed relatively low compliance across farms and years. Almost all farms were non-compliant for hardness in both sampling years. T-tests revealed significant changes from 2009 to 2013 for pH (t = 2.580; p = 0.006), hardness (t = 2.197; p = 0.016) and potassium (K) (t = 1.699; p = 0.0468). For hardness, approximately 45% of the farms in 2009, and 57% in 2013, posed a health risk to sensitive consumers. More than 50% of the farms in both years demonstrated levels of nitrates that could pose a health risk, particularly for babies. High levels of coliforms and E. coli were found, indicating a health risk for clinical infections in consumers. The number of farms presenting 3 or more parameters with a health risk more than doubled from 13.5% in 2009 to 27.0% in 2013. <![CDATA[<b>The removal of N and P in aerobic and anoxic-aerobic digestion of waste activated sludge from biological nutrient removal systems</b>]]> Biological nutrient removal (BNR) activated sludge (AS) systems produce a waste activated sludge (WAS) that is rich in nitrogen (N) and phosphorus (P). When this sludge is thickened to 3-6% total suspended solids (TSS) and digested (aerobic or anaerobic), a high proportion of N and P are released to the bulk liquid resulting in high concentrations of ammonia/nitrate and orthophosphate up to several hundred mg/ℓ (without denitrification or P precipitation). This research investigates P removal by P precipitation in anoxic-aerobic digestion of P-rich BNR system WAS. The experimental setup for this work was a lab-scale membrane UCT BNR system fed real settled sewage with added acetate, orthophosphate, and cations Mg and K to increase biological excess P removal. This WAS was fed to batch aerobic digesters at various TSS concentrations, and to two 20-day retention time continuous anoxic-aerobic digesters (AnAerDig) with aeration cycles of 3-h air on and 3-h air off, one fed concentrated WAS (20 g TSS/ℓ ) and the other fed diluted WAS (3 g TSS/ℓ). Nitrogen removal has been discussed in the previous paper. This paper focuses on the P removal by P precipitation observed in the batch tests and continuous systems. The rate of polyphosphate release (bGP) during batch aerobic digestion at low TSS without P precipitation was found to be 2.5 times faster than the endogenous respiration rate (bG) of phosphorus accumulating organics (PAO), i.e. bGP= 0.1/d. This rate was then applied to the high-TSS aerobic batch tests and continuous anoxic-aerobic digesters to estimate the P precipitation at various TSS concentrations, with and without additional Mg or Ca dosing. Newberyite (MgHPO4.3H2O) and amorphous tricalcium phosphate (ACP or TCP, Ca3(PO4)2.xH2O) are found to be the most common phosphate precipitates. <![CDATA[<b>Technologies for the treatment of source-separated urine in the eThekwini Municipality</b>]]> In recent years, a large number of urine-diverting dehydration toilets (UDDTs) have been installed in eThekwini to ensure access to adequate sanitation. The initial purpose of these toilets was to facilitate faeces drying, while the urine was diverted into a soak pit. This practice can lead to environmental pollution, since urine contains high amounts of nutrients. Instead of polluting the environment, these nutrients should be recovered and used as fertiliser. In 2010 the international and trans-disciplinary research project VUNA was initiated in order to explore technologies and management methods for better urine management in eThekwini. Three treatment technologies have been chosen for the VUNA project. The first is struvite precipitation, a technology which has already been tested in multiple projects on urine treatment. Struvite precipitation is a simple and fast process for phosphorus recovery. Other nutrients, such as nitrogen and potassium, remain in the effluent and pathogens are not completely inactivated. Therefore, struvite precipitation has to be combined with other treatment processes to prevent environmental pollution and hygiene risks. The second process is a combination of nitrification and distillation. This process combination is more complex than struvite precipitation, but it recovers all nutrients in one concentrated solution, ensures safe sanitisation and produces only distilled water and a small amount of sludge as by-products. The third process is electrolysis. This process could be used for very small on-site reactors, because conversion rates are high and the operation is simple, as long as appropriate electrodes and voltages are used. However, nitrogen is removed and not recovered and chlorinated by-products are formed, which can be hazardous for human health. While urine electrolysis requires further research in the laboratory, struvite precipitation and nitrification/distillation have already been operated at pilot scale. <![CDATA[<b>Sustainable and equitable sanitation in informal settlements of Cape Town: a common vision?</b>]]> Sustainability and equity are two desirable but ambiguous concepts often used to describe goals for sanitation services internationally and in South Africa. Both concepts are mentioned repeatedly in policy documents and government reports. There is, however, a gap between policy and implementation, and part of the problem lies in the challenge of reconciling the pressure to deliver immediate results with a long-term vision to strive towards sustainable and equitable sanitation services. Perspectives, priorities, and barriers to sustainability and equity in implementation, recognised amongst water and sanitation sector stakeholders in Cape Town, were analysed and compared with policy documents and municipal records. The research methods included a review of municipal and national sanitation policy documents and reports, and unstructured interviews with municipal officials, development NGO workers, sanitation consultants and entrepreneurs working in Cape Town municipality. In this paper, challenges to integrating sustainability and equity principles into various stages of sanitation service development are highlighted, and preliminary recommendations for addressing challenges are made, with an emphasis on stakeholder participation. <![CDATA[<b>Development of emergency response plans for community water systems</b>]]> All water services systems, irrespective of size, location etc., should have emergency response plans (ERPs) to guide officials, stakeholders and consumers through emergencies, as part of managing risks in the water supply system. Emergencies in the water supply system may result from, among other causes, natural disasters, equipment failure, human error and intentional acts (e.g. vandalism). Simply put, an ERP prepares the organisation for emergencies and gives specific instructions about what to do if there is an emergency situation that may affect the water system. To assist water services institutions (WSIs), the Water Research Commission project 'Water Safety and Security: Emergency Response Plans' aimed to develop a generic ERP guide for community water systems (CWS). A CWS in this study was defined as a potable water service provided to a rural community where municipal constraints exist and there is either 'no supply' or water is provided up to a communal standpipe. Emergencies considered in this study include (i) unavailability of water or (ii) excess of water (e.g. flood) and (iii) water quality or pollution/contamination. CWS in 3 provinces in South Africa (Eastern Cape, KwaZulu-Natal and Northern Cape), were visited to (i) identify the water service delivery status, methods and possible shared threats/vulnerabilities and risks (ii) identify water services challenges experienced by these communities (iii) ascertain who owns and who is responsible for water services (e.g. whether these communities are serviced by municipalities or by local chiefs and/or trusts) and (iv) investigate whether the systems have been documented and evaluated. Following site visits, an ERP guideline document with associated templates will be developed and workshopped with the selected communities, which will include: (i) conditions identified as emergencies, (ii) communication procedures/protocol/chain of command, and (iii) procedures detailing how to attend to the specified emergencies. <![CDATA[<b>Mitigating the impact of swimming pools on domestic water demand</b>]]> South Africa is a water-scarce country where the sustainable provision of water to its citizens is one of the most significant challenges faced. A recent study in Cape Town, South Africa, investigated the impact of residential swimming pools on household water demand and found that, on average, the presence of a swimming pool increased water demand by 8.85 kℓ/ month or 37.36%. Should cities in South Africa wish to develop in a water sensitive manner - where water is treated as a scarce resource with economic value in all its competing uses - it will be vital to understand the impact of swimming pools on residential water demand. Should there be a significant increase in water demand attributable to the presence of a swimming pool on a property, it would highlight the need to consider whether it is acceptable for properties to use municipal water to fill them or top them up - especially in water-scarce/stressed areas. This paper describes a study undertaken in the Liesbeek River catchment, Cape Town, to investigate the impact that swimming pools have on domestic water demand. The results support the contention that properties with swimming pools use significantly more water than those without. This study estimated the additional demand resulting from swimming pools at between 2.2-2.4 kℓ/month or 7-8% of total water demand. The data also indicate that the presence of a swimming pool correlates with a higher indoor demand. The study shows the need to reduce the impact of swimming pools. This could include: pool covers to reduce evaporation, the recycling of backwash water, the use of rainwater to top up swimming pools, water use surcharges and, finally, appropriate regulation and enforcement to prevent the use of municipal water in swimming pools - especially during droughts. <![CDATA[<b>The potential utilisation of indigenous South African grasses for acid mine drainage remediation</b>]]> Acid mine drainage (AMD) is a significant threat to the environment in South Africa and needs to be remedied. Although active treatment methods have been and are being implemented in industry, passive treatment systems involving bioremediation have the potential to be a more cost-effective and environmentally sustainable solution. Biological treatment of AMD involves the reduction of sulphate to sulphide by sulphate-reducing bacteria in the presence of a suitable organic substrate. This study tested the potential for indigenous grasses to be used as a carbon source in the bioremediation of AMD. Bioreactor experiments were conducted over a 70-day period to investigate whether indigenous grasses can be used to effectively reduce sulphate and iron concentrations, and increase the pH of an AMD solution. The results indicated that indigenous grasses hold promise for remediating AMD, as a maximum of 99% iron removal, 80% sulphate removal, and a final pH of 8.5 was achieved from initial conditions of 2 000 mg/ℓ iron, 6 000 mg/ℓ sulphate, and a pH of 3. Optimal results occurred in the bioreactor with Hyparrhenia hirta grass amended with soil containing microbes, although all bioreactors effected some form of remediation compared to the control. <![CDATA[<b>Investigation of carbonate dissolution for the separation of magnesium hydroxide and calcium sulphate in a magnesium hydroxide-calcium sulphate mixed sludge</b>]]> South Africa is experiencing a large environmental problem due to uncontrolled discharge of acid mine water into public water courses. The need for neutralisation and desalination of acid mine drainage is a significant issue in South Africa and the sludges that result from mine wastewater treatment usually contain elevated levels of mixed contaminants derived from those originally contained in the wastewater. A more reasonable approach to ultimate sludge disposal is to view the sludge as a resource that can be recycled or reused. Carbon dioxide and a sludge mixture consisting of Mg(OH)2 and CaSO4.2H2O are by-products from acid mine drainage treatment processes. This study was carried out to explore the feasibility of separating Mg(OH)2 from CaSO4.2H2O through dissolution of Mg(OH)2 by accelerated carbonation in a pressurised, completely-mixed reactor. The effects of temperature and pressure, and of both together, on the dissolution of the sludge mixture with time were investigated. Parameters monitored included alkalinity, pH, conductivity and Ca²+, Mg²+ and SO4(2-) concentrations. OLI Analyser Studio Version 9.0 software was used for modelling predictions of chemical speciation of the mixtures. The optimum separation capacity for the Mg(OH)2-CaSO4.2H2O sludge mixture was determined to be 99.34% Mg²+ and 0.05% Ca²+ in the aqueous phase when contacted with CO2 at a temperature of 5°C and pressure of 150 kPa. The model predictions were in agreement with the experimental findings. Temperature and pressure have a significant impact on the dissolution of the mixed sludges when contacted with CO2. <![CDATA[<b>Application of the DIY carbon footprint calculator to a wastewater treatment works</b>]]> The provision of water and wastewater treatment services exerts a huge operational cost on public financial resources. A substantial portion of the operational budget is made up of carbon-intensive energy costs. Energy is consumed in this sector in pumping, aeration, motor drives, administration, transportation and in the manufacture of chemicals such as polyelectrolyte, chlorine and ozone. The high electrical power consumption exerts added pressure on the environment in terms of greenhouse gas emissions. In order to manage the energy budget and develop climate-friendly technological options, Royal HaskoningDHV (RHDHV) has developed a do-it-yourself (DIY) Excel-based carbon footprint calculator to estimate the carbon equivalent emissions for a waterworks, a wastewater treatment works or a pumping station. The DIY carbon calculator computes Scope 1, Scope 2 and Scope 3 emissions. The DIY calculator starts with establishing the baseline carbon footprint of a works and shows the relative carbon equivalent emissions for different treatment stages. The next step involves the development of strategies to reduce the carbon footprint. Inherent within a wastewater treatment works is its ability to potentially generate its own 'green' energy by using anaerobically produced methane gas as a green energy alternative. This investigation demonstrates how the baseline carbon footprint of a wastewater treatment works can be reduced by considering viable options such as biogas to power generation, process re-design and drives to improve energy efficiency. Results show that the carbon calculator was able to demonstrate the effectiveness of carbon-reducing strategies in this energy-intensive sector. This further implies that the carbon calculator can be used as an additional management and decision support tool to assist an organisation towards a low carbon footprint. <![CDATA[<b>Performance comparison of hydraulic and gravitation HybridICE filters in freeze desalination of mine waters</b>]]> HybridICE is an emerging freeze desalination technology for treating complex mine wastewaters. The technology works on the principle that growing ice crystals reject impurities during freezing. The bottleneck in the freeze desalination processes may be the separation of ice from the ice slurry generated in the freeze engine. Two types of HybridICE filter have been developed to effect ice separation from ice slurry. The two types differ in the design of the filter elements, mode of feeding the slurry into the filter, and the mechanism of separation of ice from the slurry. In both types of filter, an extruded continuous ice column is formed around the filtering element, which has some openings to allow excess concentrated process water to flow out of the filter. However, the driving force in the gravitation filter is buoyancy, while in the hydraulic filter the ice column is driven by the pressure generated from the flow of the slurry. Salt removal and ice yield from each of the filter types was evaluated when a solution of approximately 4% m/m NaCl solution, prepared by dissolving 25.1 kg of NaCl in 674 litres of water, was treated in a HybridICE freeze crystallisation pilot plant. The objective was to describe the operation of the two types of filter and compare their performance. Salt removal and ice yield were found to be higher with the gravitation filter than the hydraulic filter. <![CDATA[<b>Quantification of water usage at a South African platinum processing plant</b>]]> The mining industry utilises 3% of the total water withdrawn in South Africa and is one of the industries responsible for the deterioration of water quality in South Africa. Mine water requirements can be reduced with correct implementation and/ or improvement of current mine water management strategies. Any reduction in mine water requirements will reduce the demand on current water resources and hence the impact on water quality. The direct water footprint for 2 concentrators, a smelter and a tailings dam of a platinum processing plant were calculated using the Water Footprint Network assessment method. This includes the sum of the blue-, green- and grey-water footprints. Water footprints of chemicals used during flotation were excluded from the scope of the investigation. Water used in change houses and offices was included. The water footprint calculated from June 2012 until May 2013 was 201 m³/kg PGM (platinum group metals). The first concentrator had a water footprint of 76 m³/kg PGM, while the second had a water footprint of 110 m³/kg PGM. Overall, the total grey-water footprint made the largest contribution, accounting for 73%, the blue-water footprint was the second largest (27%), and there was no green-water footprint. <![CDATA[<b>Assessing the blue-water footprint of an opencast platinum mine in South Africa</b>]]> South Africa's extensive mineral resources have resulted in mining activities dispersed across the country, playing a critical role in its socio-economic development. In contrast to this abundance of mineral wealth, water resources are generally limited, and vulnerable to environmental impacts from the mining industry. These circumstances make tailored management of water resources in the mining sector essential. To achieve this, detailed information on water use throughout a mine operation as well as an accurate water balance account is required. Blue-water footprints have the potential to contribute to this task as they allow for quantification of direct and indirect water use across the supply chain of a process, while incorporating both spatial extension and temporal duration. As defined by the Water Footprint Network's (WFN) globally acknowledged water footprint assessment methodology, a blue-water footprint is determined by calculating the net consumptive use of water by an operation. According to the WFN, this includes water which is evaporated, incorporated into a product, or lost to outflows which do not return to the same catchment area in the same period.The applicability of this tool in the mining sector has not been fully explored. Therefore, it was decided to investigate the blue-water footprint of a South African platinum mining operation. The results showed that the largest consumption of water in the production of platinum was due to evaporation from the mineral processing plants (36.8%) and the tailings storage facilities (19.4%). To improve its water-use efficiency, measures should be taken by the operation to mitigate evaporative losses. Floating covers can assist in this effort as they reflect a proportion of the incoming solar radiation and act as a physical barrier to the passage of water vapour, both vertically and horizontally.