Scielo RSS <![CDATA[Water SA]]> vol. 43 num. 4 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Distribution, exposure pathways, sources and toxicity of nonylphenol and nonylphenol ethoxylates in the environment</b>]]> Alkylphenols (APs) are ultimate breakdown products of alkylphenol polyethoxylate (APEs) that are used in cleaning and industrial processes. The most commonly used APEs in the market are the nonylphenol ethoxylates (NPEs) and octylphenol ethoxylates (OPEs). As a result of their widespread use and their lipophilic nature, these compounds are ubiquitous in the environment and are currently of concern because of their toxicity, oestrogenic properties and widespread contamination. This review summarizes the concentrations of NPE and NP in different environmental media. The sources of NPE in the environment and toxicity are reviewed. Their distribution patterns in the environment as well as exposure pathways are discussed with a view to provide better understanding of these emerging environmental contaminants. It is envisaged that this review will heighten the importance of identifying emerging issues and data gaps, and generate a future research agenda on APEs. <![CDATA[<b>Determining wetland spatial extent and seasonal variations of the inundated area using multispectral remote sensing</b>]]> Wetlands can only be well managed if their spatial location and extent are accurately documented, which presents a problem as wetland type and morphology are highly variable. Current efforts to delineate wetland extent are varied, resulting in a host of inconsistent and incomparable inventories. This study, done in the Witbank Dam Catchment in Mpumalanga Province of South Africa, explores a remote-sensing technique to delineate wetland extent and assesses the seasonal variations of the inundated area. The objective was to monitor the spatio-temporal changes of wetlands over time through remote sensing and GIS for effective wetland management. Multispectral satellite images, together with a digital elevation model (DEM), were used to delineate wetland extent. The seasonal variations of the inundated area were assessed through an analysis of monthly water indices derived from the normalised difference water index (NDWI). Landsat images and DEM were used to delineate wetland extent and MODIS images were used to assess seasonal variation of the inundated area. A time-series trend analysis on the delineated wetlands shows a declining tendency from 2000 to 2015, which could worsen in the coming few years if no remedial action is taken. Wetland area declined by 19% in the study area over the period under review. An analysis of NDWI indices on the wetland area showed that wetland inundated area is highly variable, exhibiting an increasing variability over time. An overlay of wetland area on cultivated land showed that 21% of the wetland area is subjected to cultivation which is a major contributing factor to wetland degradation. <![CDATA[<b>Supplementary household water sources to augment potable municipal supply in South Africa</b>]]> This paper addresses on-site supplementary household water sources with a focus on groundwater abstraction, rainwater harvesting and greywater reuse as available non-potable water sources to residential consumers. An end-use model is presented and used to assess the theoretical impact of household water sources on potable water demand in formal residential areas. Reliable potable municipal supply to urban consumers via the water distribution system is typically linked to relatively low uptake of household water sources. However, stringent water restrictions in some large South African cities that prohibit outdoor use, and reports of intermittent water supply, have led to increased uptake of household sources in South Africa. This paper describes the legal position regarding such sources in South Africa, and describes an end-use model to assess the theoretical impact on water demand in formal residential areas. The model provides valuable strategic direction and indicates a significant theoretical reduction in potable municipal water demand of between 55% and 69% for relatively large properties when household sources are maximally utilised (when compared to exclusive unrestricted municipal use as a baseline). This load reduction on piped reticulation systems could be an advantage in order to augment municipal supply, but water service planning and demand management are complicated by the introduction, and possible future decommissioning, of any household water source. The extent of both positive and negative impacts of household water sources requires further research. <![CDATA[<b>Hydraulic performance of sluice gate with unloaded upstream rotor</b>]]> This study presents video analysis of the hydraulic performance of a sluice gate with an unloaded upstream built-in rotor. A number of laboratory experiments were conducted using two unloaded rotor shapes. The first was the cross-shaped rotor and the second was the Savonius-like rotor. A new video analysis technique was introduced for measuring rotor angular speed and its perturbation. Swift speed cameras and Tracker software were used to measure the upstream backwater depth and to estimate the instantaneous variation of the rotor speed. The study shows that adding a rotor upstream of the gate caused the upstream water level to increase such that the averaged normalized afflux increased to 1.72 and 0.9 for the cross-shaped and the Savonius rotors, respectively. Lab experiments indicated that the water flow-structure interaction for the sluice-rotor is quite complex and nonlinear. Two main flow regimes were distinguished. The flow regimes are: the flow through a rotor with possible weir flow conditions and the orifice flow conditions. The time-averaged angular speed of the tested Savonius-like rotor ranged between 0 and 300 r/min. As the upstream backwater depth increased, the angular speed increased; however, the rate was significantly lower for the orifice flow condition compared to the flow under rotor and weir flow conditions. The video analysis also indicated that significant perturbation exists for the rotor angular speed. The normalized perturbation intensity varied from a minimum of 8% to a maximum of 60%. <![CDATA[<b>Fouling layer characterization and pore-blocking mechanisms in an UF membrane externally coupled to a UASB reactor</b>]]> A pilot-scale UASB reactor coupled with an external ultrafiltration (UF) membrane was operated under three different hydraulic retention times (HRT: 4, 8 and 12 h) for municipal wastewater treatment in order to assess the composition and distribution of the fouling layer, as well as to identify the predominant fouling mechanisms. For that purpose, membrane autopsies were carried out based on fouling layer density determination, thermogravimetric, SEM and EDX analysis. Results showed a variable density of the fouling layer (average values were 13.90 ± 0.22, 13.46 ± 1.15 and 12.78 ± 0.49 mg/cm² for HRT of 4, 8 and 12 h, respectively), indicating that this parameter had an impact on the fouling density. Organic material was predominant in the fouling layer, being around 75% of its composition for the three HRT studied. Regarding pore-blocking mechanisms, standard blocking was the predominant mechanism at the beginning of filtration, coexisting at the end of it with cake filtration. In the first filtration cycle (1 h), after standard blocking, intermediate and complete blocking developed simultaneously during a short period of time and, finally, cake filtration prevailed. However, in the last (19th) filtration cycle, standard blocking and cake filtration occurred simultaneously from the beginning, suggesting the existence of an irreversible fouling layer, in spite of chemical cleaning. <![CDATA[<b>Water and salt balances of two shallow groundwater cropping systems using subjective and objective irrigation scheduling</b>]]> Evidence suggests that, in general, subjective rather than objective irrigation scheduling decisions are adopted by farmers. Irrigators have 'calibrated' themselves with years of experience to irrigate subjectively according to perceived crop water requirements. This study aimed to determine the associated benefits of objective versus subjective scheduling of two shallow groundwater cropping systems. Weekly measurements included rainfall and irrigation amounts, soil water content, groundwater table depth, artificial drainage volumes, and electrical conductivity of irrigation water, groundwater and drainage water. Simulations of evaporation and transpiration were done with the SWAMP model. Based on soil water and salinity status, matric and osmotic stress during the four cropping seasons is considered unlikely. When rainfall-plus-irrigation was compared to evapotranspiration, objective scheduling resulted in an under-supply of 15%, and rainfall and shallow groundwater served as supplementary water sources. Subjective scheduling did not use rainfall efficiently as a source of water and resulted in an over-supply of 10%. Approximately 50% less salt was leached with objective compared to subjective irrigation scheduling. Under shallow groundwater conditions, irrigating subjectively according to crop water requirement results in excessive irrigation, salt addition and leaching compared to objective scheduling. Farmers can address some of the environmental problems associated with irrigation by adopting objective scheduling and reducing the leaching fraction (< 0.15) of shallow groundwater cropping systems. <![CDATA[<b>Use of dewatered sludge as microbial inoculum of a subsurface wastewater infiltration system: effect on start-up and pollutant removal</b>]]> Brown earth-based subsurface wastewater infiltration systems (SWISs) inoculated with/without dewatered sludge were constructed and operated under the same conditions to boost the application of SWIS in brown soil areas. Start-up period of SWIS with dewatered sludge was 28 days, 12 days shorter than that of SWIS without dewatered sludge. COD, NH3-N and TN removal efficiencies of dewatered sludge as microbial inoculum for SWIS were higher than that of SWIS without dewatered sludge under hydraulic loading rates (HLR) of 0.04, 0.07, 0.1 and 0.13 m³·m−2·d−1. Effluent concentrations of COD, NH3-N and TN in the SWIS inoculated with dewatered sludge were 44.51±4.13, 7.35 ± 0.24 and 14.03 ± 0.31 mg·L−1 under HLR of 0.13 m³·m−2·d−1, which were simultaneously lower than Chinese criteria for water discharge from municipal wastewater treatment plants. The number of bacteria, nitrifying bacteria and denitrifying bacteria in dewatered sludge as microbial inoculum for SWIS were higher than that in SWIS without dewatered sludge under the same HLR. The results will be helpful in promoting the application of dewatered sludge as microbial inoculum in brown earth-based SWISs for the purpose of shortening start-up period, effecting high levels of pollutant removal and recycling waste. <![CDATA[<b>BTEX compounds in water - future trends and directions for water treatment</b>]]> BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common water resource and potable water pollutants that are often left undetected and untreated by municipal treatment systems in spite of the negative repercussions associated with their ingestion. The US EPA has classified these pollutants as priority pollutant, yet they are persistently present in a variety of water resources. In this review paper, we highlight the sources and reported concentrations of BTEX compounds in water and explore historical remediation techniques that have been applied such as bioremediation and natural attenuation. We also highlight emerging possibilities and future directions for remediation techniques, such as nanotechnology-based materials and novel green materials (tannins) that can be applied to ensure removal of these compounds in water. <![CDATA[<b>Impact of water hardness on energy consumption of geyser heating elements</b>]]> South Africa is an electricity-stressed country with a growing energy demand. Globally, hot water appliances are major consumers of electricity. Poor water quality for domestic purposes is a concern that may affect the efficiency of hot water appliances. Therefore, the Eskom Research, Testing, and Development Business Unit embarked on a study to examine total water hardness as a chemical parameter that may impact the power consumption of electrical geyser heating elements. An accelerated scaling method was developed to lime-scale the geyser heating elements for about 2 to 3 months. In addition, the geyser heating elements were tested with and without electronic descaler technology. The results showed that the accelerated scaling method developed for shortening the scaling time of geyser heating elements was successful. Furthermore, the results proved that scale formation of 1.5kW and 3kW geyser heating elements due to high total water hardness increased the power consumption by approximately 4% to 12%. This paper also presents energy-efficient electronic descaler technology as an alternative treatment of scaling for geyser heating elements. <![CDATA[<b>TDS load contribution from acid mine drainage to Hartbeespoort Dam, South Africa</b>]]> Evidence of a mine-water impact on groundwater in the karst aquifer downstream of the actively draining West Rand Goldfield can be traced back to the early 1980s. This is attributed to the dewatering of 'fissure water' encountered during mining, and its discharge into the Bloubank Spruit catchment. Rewatering of the subsurface void following the cessation of mining in the late 1990s culminated in mine-water issuing from various point sources (shafts and boreholes) in 2002. The past 6 hydrological years have periodically produced the greatest volume and worst quality of mine-water discharge, causing widespread concern for the receiving aquatic environment. In this regard, the proximal Cradle of Humankind World Heritage Site attracts a much sharper focus than the distal, regionally important Hartbeespoort Dam. Objectivity requires that an assessment of the mine-water impact on the receiving surface water resources must recognise both the subregional and regional scales. The evaluation presented in this communication examines the temporal mine-water impact at both scales, and interprets the results in terms of the influence exerted by the natural hydrosystem in mitigating adverse impacts on the water resources environment. An analysis of the respective contributions of each of the major drainages to the quantity and quality of water impounded in Hartbeespoort Dam indicates that the median total dissolved solids (TDS) load delivered by the Bloubank Spruit system amounted to ~26 kt/a in the past 6 hydrological years. This is ~12% of the regional median total of ~224 kt/a entering the impoundment in the same period. By comparison, the preceding long-term record dating back 30 years to 1979 reflects a 66% lower median annual contribution of 8.6 kt, representing ~10% of a regional median total of ~89 kt/a. Proportionally, therefore, the recent 6-year period of high volume and poor-quality discharge from the Bloubank Spruit catchment represents only a marginally greater TDS load contribution to Hartbeespoort Dam than that which characterises the previous 30 years. <![CDATA[<b>Occurrence and survival of pathogens at different sludge depths in unlined pit latrines in Kampala slums</b>]]> Occurrence and survival of pathogens in faecal sludge was investigated in unlined pit latrines at varying depths in peri-urban areas of Kampala city, Uganda. A total of 55 unlined pit latrines, 7 private and 8 rental unlined pit latrines were sampled in the first and second phases (representing the rainy season) and 40 pits in the third phase (representing dry season), and analysed for indicator organisms and pathogens from 4 pit latrine sludge layers, at depths of 0, 0.5, 1.0 and 1.5 m, following APHA standard methods. Physico-chemical parameters of the faecal sludge were also measured. Three sampling phases were undertaken to determine the effect of seasonal variation. Results indicate that the mean temperature and pH were 25.4 ± 1.14°C and 8.0 ± 1.5, respectively; and moisture content increased with pit sludge depth, except between Depths 3 and 4. Average moisture content was 86.3 ± 3%. The measured parameters varied significantly (P &gt; 0.05) between seasons. The mean reduction in total coliforms, thermo-tolerant coliforms, E. coli, and faecal enterococci with sludge depth was significant at all depths (P < 0.05), but the least significant difference was not significant at depth levels of 1.0 m and 1.5 m. Salmonella was only detected at the top layer of faecal sludge in 60% of Phase 2 samples and in only 20% of the samples in Phase 3. About 200-4 100 eggs/g of strongyles were found in 98% of the samples and 100-1 600 eggs/g of ascarids in 55% of the samples. Temperature, pH and moisture content did not show a significant correlation with observed reductions of indicators and pathogens. With extrapolation of the generated regression models, a pit of 8 m can be recommended for reduction of bacteria. It is recommended that protective field gear be used during pit emptying and that faecal sludge treatment should be done to reduce pathogens before disposal into the environment. <![CDATA[<b>Characterization of polychlorinated biphenyls in surface sediments of the North End Lake, Port Elizabeth, South Africa</b>]]> The distribution and concentrations of 6 indicator polychlorinated biphenyl (PCB) congeners, nos. 28, 52, 101, 138, 153 and 180, were determined in surface sediments from the North End Lake in Port Elizabeth, South Africa. Forty-two surficial sediment samples were collected from different locations covering the region that receives the majority of the industrial waste, urban effluents and runoff and thus expected to be contaminated with different degrees of contamination. The analysis was achieved by gas chromatography-mass spectrometry (GC/MS) using the internal standard method. The total PCB concentrations in the samples ranged from 1.60 to 3.06 ng·g-1 dry weight (dw). The concentrations of congener profiles showed significant differences. Generally, the highest PCB concentrations were associated with high organic matter contents and small grain size. The highly chlorinated PCBs dominated with regards to the levels in sediments. PCB 138 was the major contributor to the total PCBs and was detected at 100% of sites. This study provided a snapshot of the PCB contamination status in the North End Lake sediments, and allowed for a comparison between the investigated system and other systems worldwide. <![CDATA[<b>Investigation into the kinetics of constructed wetland degradation processes as a precursor to biomimetic design</b>]]> In this study, biomimetic principles were incorporated into a kinetic study of a pilot-scale, horizontal subsurface-flow constructed wetland (6.0 m × 1.0 m × 0.5 m) in Leipzig, Germany. The bed contained glacial gravel (4-8 mm) planted with Phragmites australis. Construction was completed in October 2013 and experiments commenced in August 2015. During establishment, the system was fed with only municipal tap water (165 L·d−1). The Phragmites root system had penetrated to the bottom of the wetland within 18 months. To break into the constructed wetland 'black box', the system was divided into a three-dimensional grid of sample ports. Initially, the wetland was physicochemically characterized (prior to addition of nutrients from an external source) in order to quantify the natural, baseline state. Thereafter, an impulse-response tracer test was conducted, using a fluorometer, for continual measurement of uranine concentration. 100% tracer recovery was achieved. The RTD was multi-modal - indicating by-pass flow - and showed long tailing due to mixing, diffusive effects and dead zones. Kinetic performance was investigated via monitoring total organic carbon and total nitrogen degradation, with a continual feed of artificial domestic wastewater (110 mg·L−1 COD). 93% reduction in TOC and TN was achieved for 5 weeks (11 November - 08 December 2015), despite high inflow loading (69.9 g·m−3·d−1 TOC; 28.1 g·m−3·d−1 TN) and colder temperatures. There was a general decline in reaction rate and rate constant from late October to early December. The average rates of TOC and TN removal were 65.08 ± 2.16 g·m−3·d−1 and 26.22 ± 0.68 g·m−3·d−1, respectively (Tanks-In-Series model). These results are the first set in a series. Continual observation and repetition of these experiments into long-term operation will deepen understanding of the internal development and performance of constructed wetlands, as is in line with the biomimetic approach, and provide the basis of a framework for improved wetland design. <![CDATA[<b>Effects of prolonged elevated water salinity on submerged macrophyte and waterbird communities in Swartvlei Lake, South Africa</b>]]> Large fluxes in the physico-chemical characteristics of estuarine lakes can have profound effects on biota and processes. Where salinity in Swartvlei Lake usually ranges between 5 and 12, extended open conditions post-2007 floods, coupled with reduced freshwater inflows due to drought, resulted in salinity exceeding the upper tolerance of dominant submerged macrophytes. A resulting die-back of macrophytes equated to a 99% decline in standing crop, and was followed by a 95% decline in the biomass of waterbirds. Significant positive correlations exist between the biomass of macrophytes and both piscivorous and herbivorous waterbirds. Whereas Swartvlei Lake is expected to, in the short term, revert to its former (pre-2007 flood) state, inevitable environmental changes such as global warming and resulting changes in local climatic and marine conditions, along with increased freshwater abstraction from feeder rivers, could cause the observed large fluctuation in the abundance of aquatic biota to become more frequent. <![CDATA[<b>The use of bioassays to assess the toxicity of sediment in an acid mine drainage impacted river in Gauteng (South Africa)</b>]]> Sediment contamination may occur from various anthropogenic activities, such as mining-, agricultural- and industrial practices. Many of the contaminants arising from these activities enter the aquatic system and precipitate from the surrounding water, becoming bound to sediment particles. These bound contaminants may reach concentrations higher than in the overlying water. Although water quality may be acceptable, an aquatic system may still be at risk if the contaminated sediment were to be disturbed through flooding, bioturbation or changes in the water chemistry. These contaminants may then desorb into the water column and prove detrimental to life forms in contact and dependent on that water source. Sediment quality monitoring has been a widespread international initiative and has led to the development of sediment toxicity assessment methods. This study focused on sediment bioassays, namely, Phytotoxkit, Ostracodtoxkit F and the Diptera bioassay, in assessing sediment quality of the Tweelopiespruit-Rietspruit-Bloubankspruit river system in Gauteng, South Africa. This river is known to have been impacted by acid mine drainage (AMD) since late August, 2002. Exposure of river sediment from 7 sampling sites to these bioassays provided an eco-toxicological estimation of the acute toxicity and chronic toxicity emanating from the contaminated sediments. Physico-chemical analyses revealed higher levels of sediment contamination closer to the mine. The bioassays displayed a similar trend with greater sensitivities to sediments closer to the mine and lower sensitivities to the less contaminated sites further downstream. AMD was therefore the main driver for sediment contamination. Whilst not all contaminants were bioavailable, statistical analysis showed that there were significant correlations between the elevated contaminant concentrations closer to the mine and bioassay responses. <![CDATA[<b>Pharmaceutical and personal care products (PPCPs) as endocrine disrupting contaminants (EDCs) in South African surface waters</b>]]> Globally, water resources are under constant threat of being polluted by a diverse range of man-made chemicals, and South Africa is no exception. These contaminants can have detrimental effects on both human and wildlife health. It is increasingly evident that several chemicals may modulate endocrine system pathways in vertebrate species, and these are collectively referred to as endocrine disrupting contaminants (EDCs). Although the endocrine-disrupting effect of water pollutants has been mainly linked to agricultural pesticides and industrial effluents, other pollutants such as pharmaceuticals and personal care products (PPCPs) are largely unnoticed, but also pose a potentially significant threat. Here we present for the first time in a South African context, a summarised list of PPCPs and other EDCs detected to date within South African water systems, as well as their possible endocrine-disrupting effect in-vitro and in-vivo. This review addresses other factors which should be investigated in future studies, including endocrine disruption, PPCP metabolites, environmental toxicology, and antibiotic resistance. The challenges of removing EDCs and other pollutants at South African wastewater treatment works (WWTWs) are also highlighted. The need for focused research involving both in-vitro and in-vivo studies to detect PPCPs in water systems, and to delineate adverse outcome pathways (AOPs) of priority PPCPs to aid in environmental impact assessment (EIA), are discussed. <![CDATA[<b>Biosensors for the detection of <i>Escherichia coli</i></b>]]> The supply of safe potable water, free from pathogens and chemicals, requires routine analyses and the application of several diagnostic techniques. Apart from being expensive, many of the detection methods require trained personnel and are often time-consuming. With drastic climate changes, severe droughts, increases in population and pollution of natural water systems, the need to develop ultrasensitive, low-cost and hand-held, point-of-use detection kits to monitor water quality is critical. Although Escherichia coli is still considered the best indicator of water quality, cell numbers may be below detection limits, or the cells may be non-culturable and thus only detected by DNA amplification. A number of different biosensors have been developed to detect viable, dead or non-culturable microbial cells and chemicals in water. This review discusses the differences in these biosensors and evaluates the application of microfluidics in the design of ultra-sensitive nano-biosensors. <![CDATA[<b>Application of the water footprinting method and water accounting framework to a base metal refining process</b>]]> The key to a sustainable future lies in understanding and utilising resources more efficiently. This holds especially for industries that seek to minimise water usage through better management of resources. Most mineral processing plants have high water requirements, yet often function in an environment where water is becoming increasingly scarce. Further, an increase in population will result in an even greater demand for water, potentially beyond the limits of supply. This would lead to even greater competition for the resource. In South Africa, Gauteng and the North West Provinces are likely to be the first to experience a shortage of potable water. A base metals refinery in Rustenburg sought to understand and minimise its potable water usage, as well as report its usage using global tools and frameworks. The two tools used in this study were the Minerals Council of Australia's 'Water Accounting Framework for the Minerals Industry' (WAF) and the Water Footprinting method (WF). The potable water and stormwater systems were surveyed to assess and determine methods to improve water accountability. Using information from the survey, monthly and yearly water balances were presented in the form of a water balance sheet. Using data from the water balance, an input-output and operational model were drawn up in accordance with the WAF. The WAF models assisted in reporting data in a universally consistent manner. Blue, green and grey WFs were calculated for the refinery and recommendations were made to achieve savings in water consumption.