Browsing by Author "Willis, James P"

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    Assessment of the suitability of composted sewage sludge as an adsorbent for the treatment of heavy-metal contaminated wastewater, with special reference to cadmium
    (1995) Schwegler, Frank Rudolf; Fey, Martin V; Willis, James P
    A large proportion of sewage sludge in South Africa contains heavy metal concentrations which are deemed to be above threshold limits for its use as a fertiliser. Furthermore, sewage sludge has a high affinity for heavy metals. Until the sources of heavy metal contamination of municipal sewage sludge are considerably reduced the contaminated sewage sludge must either be disposed of or used for some other purpose. The use of contaminated sewage sludge as an adsorbent for treating heavy metal-contaminated wastewaters may provide an alternative and practical use for this material. The objective of this study was to assess the potential of composted sewage sludge (which is more stable and has a higher permeability than ordinary sewage sludge), produced from municipal sewage sludge in Milnerton, as an adsorbent for the extraction of heavy metals from contaminated wastewaters. The study was conducted with specific reference to cadmium since it is one of the most toxic of the heavy metals and occurs in many types of wastewaters.
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    Chemical characterisation of landfill leachate and its potential mobility through the Cape Flats sand
    (1996) Harraway, Trevor John; Fey, Martin V; Willis, James P
    Researchers have expressed concern about pollution of groundwater at Coastal Park, a large, general waste landfill situated on the False Bay coastline above the Cape Flats Aquifer. The landfill was constructed without a liner, but with an average 2m separation of calcareous sand providing a "buffer" zone between the waste pile and the water table. Water balance studies and application of a model, FLOW, have predicted that leachate will be generated seasonally. This study was initiated as a result of uncertainties about hydrological and geochemical aspects, such as the hydraulic conductivity of the soil in the buffer zone and the degree of leachate attenuation occurring in this zone. The Coastal Park soil was classified as an aeolian, calcareous, medium quartzitic sand with negligible organic carbon content. Extreme clay-depletion would render the soil almost incapable of leachate attenuation, although calcite and aragonite, found by X-ray diffractometry, would impart a significant pH buffering capacity to the soil. The solid phase of a locally-derived landfill leachate (sampled from Vissershok landfill, about 35 km NW of Cape Town) was found to contain amorphous sulfides of iron and heavy metals, and green rusts which are mixtures of Fe²⁺ - Fe³⁺ hydroxides, in addition to organic matter. The solid phase was isolated by centrifugation, freeze-dried, and analyzed by XRF and XRD. Distribution coefficients of heavy metals in the leachate (at pH 7.7) demonstrated the high affinity of heavy metals, such as Cu, Zn, Cr, Ni and Pb, for the solid phase. The leachate solid phase consists of amorphous solids, with high Ca and Cl concentrations in the liquid phase leading to halite and calcite formation upon evaporation of the liquid phase. According to locally specified requirements by Department of Water Affairs and Forestry, a landfill liner material must have a hydraulic conductivity (K) not higher than 1 x 10⁻⁷cm.s⁻¹. Air dried samples of Coastal Park soil were treated with various amendments to test their efficacy as landfill liners. An 8 % kaolinite plus 4 % gypsum treatment was the most effective, maintaining a minimum K of 10⁻⁴⁵ cm.s⁻¹, which, however, is still higher than the local requirement. Amendment with 8 % Na-bentonite initially achieved a minimum K of 10⁻⁷·⁸ cm.s⁻¹, but the high electrical conductivity (EC) of the leachate (26.8mS.cm⁻¹) caused shrinking and severe side-wall seepage, which rapidly enhanced hydraulic conductivity, reaching a maximum K of about 10⁻⁴·⁷ cm.s⁻¹. Both treatments of the sand do show promise as possible liners, although the use of higher percentage concentrations of clay should be investigated further. LEACHW (the water regime submodel of LEACHM) was used to predict leachate discharge from the Coastal Park landfill, assuming a hypothetical capping system of 1 or 2 m soil depth with 0, 50, 70, or 90 % vegetation cover (Acacia cyclops), and based on the assumption that drainage from this layer into the waste pile contributes directly to leachate generation. The model predicted that under average rainfall conditions the landfill, with a 2 m soil depth and 0 % vegetation cover, would not generate leachate. However, under the wettest conditions not even a 90% vegetation cover and 2 m soil cover would be sufficient to prevent the landfill from generating leachate, suggesting that, under such conditions, a more effective leachate management strategy, such as leachate collection sumps, should be implemented. This exercise demonstrated the use of LEACHM as an alternative means of predicting leachate discharge from landfill sites.
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    A geochemical investigation of the aquatic sediments, groundwater and surface water of the Verlorenvlei coastal lake, with special reference to nitrate transformations
    (1995) Harck, Terry Richard; Willis, James P; Fey, Martin V
    The incorporation of nitrogen in living cells gives rise to cycling between atmospheric, inorganic and organic forms of nitrogen. Nitrogen cycling is largely controlled by microbial respiration and metabolism. In aquatic systems, N-cycling occurs dominantly in sediments. Removal of nitrogen from aquatic sediments occurs through the successive Ntransformation processes of mineralisation (organic N -> NH4+), nitrification (NH4+ -> NO3-) and denitrification (NO3- -> N2). Denitrification, mineralisation and also immobilisation of inorganic N (NO3-, NH4+ ) to organic N occur under reducing conditions. Build-up of the nitrate (NO3- ) concentration in groundwater is a widely-recognised phenomenon. Groundwater nitrate may contribute significantly to the N input to aquatic bodies that receive groundwater flow. The Verlorenvlei coastal lake on the arid south-west coast of South Africa is an important ecological habitat and also a valuable agricultural water resource. Analyses conducted in this study indicate that the groundwater, which flows towards the lake, has a significantly higher NO3- concentration than the lake water. The difference in NO3- concentration is due to: 1. Dilution of groundwater by a larger quantity of low-nitrate water in the lake, and/or, 2. Removal of nitrate from groundwater through microbial processes in the lake sediments. Insufficient information is available concerning the magnitude of groundwater flow into the lake to investigate the importance of option 1. Experiments were conducted on two lake sediments (high organic content and low organic content) to determine the relevance of option 2. Sediment subsamples were incubated under reducing conditions and amended with 25mg/l and 100mg/l NaNO3-N solutions with and without the addition of 40mg/l glucose and with and without irradiation. After 10 days incubation, a period chosen to simulate the residence time of groundwater in the sediments, the added NO3- had all been removed through denitrification or immobilised as organic N. The exact removal pathway could not be determined. The high organic content sediment was found to remove nitrate more efficiently. It was concluded that the decrease in nitrate concentration as high-nitrate groundwater flows into the Verlorenvlei lake can probably be ascribed to denitrification or immobilisation processes under reducing conditions in the sediment lining of the lake.
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    A geochemical investigation of the water and sediments of Barber's Pan, North West Province
    (1996) Knesl, Oliver; Willis, James P; Fey, Martin V
    Pans comprise a large proportion of southern African wetlands and yet remain poorly classified. Very little data is available on the aqueous chemistry of southern African saline systems, and with the exception of a few publications dealing, in part, with the soil and associated materials of pan floors and margins, soil and sediment information on pans is similarly limited. Barber's Pan is a shallow, alkaline lake situated in the North West Province of South Africa. It is a unique system in several respects, but is considered most valuable from the aspect of bird conservation, since it is perennial in an area characterized by shallow, seasonally filled pans. Its perennial state is the consequence of anthropogenic intervention in the early part of this century which resulted in the diversion of the Harts River back along its fossil course. The biogeographical importance of Barber's Pan is emphasised by its designation as the only RAMSAR site in the North West Province. The overall objective of this study was to provide a geochemical characterization of Barber's Pan. This was approached by reviewing pertinent literature on the origin and geochemical characteristics of pans and saline lakes through an investigation of the water and sediments of Barber's Pan. The study focused on four aspects of the pan geochemistry, namely: the levels of certain nutrients and potential pollutants in the pan; gaining an understanding of the dynamics of phosphorus, as well as other nutrients, in the pan; geochemically characterizing the sediments; and investigating the impact of evaporative concentration of the pan water on the overall geochemistry of the system. Comparative investigations were carried out on the sediments of the Harts River diversion and Leeupan, a neighbouring, actively deflational, ephemeral pan.
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    The geochemistry and sedimentology of quaternary shelf sediments of the Tugela River, Natal, South Africa
    (1984) Felhaber, Taryl Ann; Willis, James P
    This thesis is comprised of geochemical, mineralogical and sedimentological studies of 101 sediment samples recovered from the continental shelf off the Tugela River Mouth, Natal, South Africa, and nine samples taken from the Lower Tugela River. The purpose of the research was to examine the geochemical nature of the sediments in relation to their particle size distributions and the hydrological conditions present in the area in order to elucidate the relationship between an inner shelf mud belt and an outer shelf mud belt located in the area. The river samples were analysed to help in understanding the changes undergone by the continental shelf sediments during their residence on the shelf. All samples were analysed for 10 major and 23 trace elements by X-ray fluorescence spectrometry, particle size distribution, carbonate and organic matter content. X-ray diffractograms were run on all samples to obtain qualitative mineralogy. Multivariate statistical tests were used to aid the interpretation of the data, and to statistically distinguish between the two mud belts. A detailed sedimentological model of the hydraulic populations of sediment in the area has been formulated. The information from this model, taken in conjunction with the mineralogy, provided a framework within which the geochemical data could be interpreted. A geochemical model of sedimentation was developed, based upon the information from the results of the statistical tests and the known geochemical associations of elements in sediments. A geochemical distinction was found between the inner and outer shelf mud belts. An age of 40 650 yr BP was previously reported for a sample on the mid-shelf in the study area, supporting the reconstruction of a paleoenvironment · showing the outer shelf mud belt to be the paleodepocentre for the Tugela River with the inner shelf mud belt representing the present-day depocentre of the Tugela River.
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    The geohydrology of the Swartkops River Basin : Uitenhage Region, Eastern Cape
    (1996) Maclear, Limont Gordon Alexander; Willis, James P; Fey, Martin V
    A hydrocensus of all groundwater users in the Swartkops River Basin was conducted in 1992 and 1993 to assess the occurrence and quality of groundwater in the Basin, as well as the characteristics of the various aquifers in the Basin. The extent of pollution of the groundwater reserves was noted. This specialist study was carried out to assist the Department of Water Affairs and Forestry in formulating a water quality management plan for the river basin, and was prompted by concern regarding the deteriorating water quality of the region. It was determined that the only aquifer in the river basin which was severely polluted in places was the Swartkops River Alluvial Aquifer. Following recommendations arising from the initial survey, a groundwater monitoring network of shallow boreholes was installed in the alluvial aquifer in 1994 and groundwater sampling runs commenced in 1995. Groundwater occurs in the region in a shallow alluvial aquifer and a deeper fractured secondary aquifer. These aquifers are separated from one another by an impermeable, confining layer of Cretaceous sediments in the central and eastern parts of the study area, causing artesian conditions in places. The groundwater of the aquifers in the study area has a sodium-chloride character of low salinity in the western high-lying portion of the study area, with mineralisation increasing eastward, as aquifer lithology and distance from recharge sources change. The hydrochemical character of the groundwater is a function of the proximity of the basin to the sea, as well as connate conditions existing in the sediments of marine origin. It is shown that pollution of both the surface and shallow sub-surface water bodies is occurring, mainly in the industrial and residential areas of Uitenhage and Despatch. These polluted zones are not extensive when compared with the whole catchment area but have a definite effect on local conditions. Estimations of pollution load volumes are made based on hydraulic parameters derived from aquifer tests. This study represents an overview of the geohydrology of the Swartkops River Basin, thereby providing a reference tool for water-resource management purposes in the region. It includes a unique study on the geohydrology of the Swartkops River Alluvial Aquifer and the extent of pollution of this aquifer, as well as a detailed account and discussion on the historical and present factors affecting variations in groundwater flow and artesian conditions in the area. A summary of suggested aquifer management practices is given to ensure the long-term sustainability of the groundwater resources of the river basin.
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    Gradient ion chromatographic determination of rare earth elements in coal and fly ash
    (1992) Ridley, Mark K; Watkins, Ron; Willis, James P
    Rare Earth Element (REE) determination in samples of coal and fly ash was undertaken by gradient high performance ion chromatography (HPIC). Ion chromatographic analysis requires that samples be in solution and that the matrix transition metals be removed. Coal samples, weighing 0.20g, were successfully dissolved in sealed pressure vessels in a microwave oven. Standard ashing procedures, followed by acid dissolution, were carried out to allow comparison with the microwave digestion technique. A lithium metaborate/tetraborate fusion and acid dissolution technique was used for the dissolution of fly ash. For the technique of REE determination the sample matrix was removed by off-line cation exchange. In an initial stage of the HPIC analysis the transition metals were removed by anion exchange using pyridine-2,6 dicarboxylic acid. The REE were then analysed using gradient elution of oxalic and diglycolic acid. Typically a 100μ1 volume of sample solution was employed for REE determination, but in the case of low ash (low REE) coal samples, prepared by microwave digestion, on-line concentration of 3-5 ml of sample, was necessary. The separated REE were reacted with 4-(2-pyridylazo)-resorcinol (PAR) and detected photometrically using a visible light detector at a wavelength of 520nm. Reproducibility for each REE was typically better than 5%CoV. Results from the analysis of coal and fly ash international standard reference materials were in acceptable agreement with values from alternative analytical procedures. Smooth, coherent trends obtained when the data were plotted on chondrite and "shale composite" normalised diagrams provided some support for the accuracy of the technique. The application of HPIC to the determination of REE in coals was demonstrated by the analysis of a new international reference coal sample, USGS CLB-1. Differences in REE concentrations between coal samples prepared by microwave digestion and ashing were observed. The HPIC analytical technique was also applied to the determination of REE in fly ash. The REE concentrations of fly ash from sequential electrostatic precipitators, from Lethabo and Kendal power stations, were determined to elucidate the behaviour of REE after the combustion of coal. REE concentrations increased through the sequential precipitators.
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    A low dilution fusion technique for the determination of major, minor and trace elements in Lamproite and Kimberlite samples by X-ray fluorescence spectrometry
    (1986) Eastell, Julie; Willis, James P
    A low dilution fusion technique using a 2:1 flux:sample ratio has been developed for the accurate determination of major, minor and trace elements by x-ray fluorescence spectrometry (XRFS). This method has been used to analyze geological samples of widely varying and unusual composition such as lamproites and kimberlites. The results are shown to be of comparable if not better accuracy than other methods of sample preparation for XRFS. Analytical conditions, including corrections for spectral line interferences are reported for all the elements determined. For major element analysis three methods of calculating appropriate alpha coefficients were investigated, namely (1) multiple regression analysis, (2) Norrish and Hutton method and (3) a computer program, NBSGSC, involving fundamental parameters and the COLA equation. Methods (1) and (2) gave poor results for rock types of widely varying composition. The third method requires that the variation of alpha coefficients with varying weight fraction of the analyte element be taken into account when calculating alpha coefficients if accurate values for major and minor elements are to be obtained on low dilution fusion discs. For trace element analysis the average relative error was less than 5% and there was a decrease in sensitivity by about a factor of 2 compared with XRFS determinations on powder pellets. The elimination of particle size effects in the homogeneous glass fusion discs is a major advantage over the use of powder pellets, especially for the determination of elements such as Ba, Cr and the REEs. A loss on fusion technique has been employed to ensure complete loss of volatiles from the rock samples. Data presented highlight the problems encountered in the determination of the volatile content in geological samples. The oxidation and retention of sulphur in the discs was also investigated.
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    Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent
    (1995) Mills, Anthony; Fey, Martin V; Willis, James P
    The Manganese Metal Company (MMC) situated in Nelspruit, Eastern Transvaal, South Africa produces a manganiferous saline effluent from a manganese ore leaching process. The high NH₄ content of the waste has been identified as a possible nitrogen fertilizer source. Irrigation of the MMC waste over nearby kikuyu ( Pennisetum clandestinum) pastures could thus potentially solve a waste disposal problem as well as provide fertilization of the pastures, although the high manganese content of the waste poses a risk of manganese toxicity or pollution. The kikuyu pastures are presently used as a land disposal system for a saline waste from a pulp bleaching process. Due to process changes, the dominant salt type in the waste is anticipated to change from KaCl to Na₂SO₄. Pot experiments with kikuyu were undertaken to investigate NaCl versus Na₂SO₄ salinity effects, Mn toxicity threshold levels and MMC waste versus a standard nitrogen fertilizer (NH₄NO₃) yield response. The results demonstrated that kikuyu grass is both salinity and Mn tolerant. Kikuyu salinity tolerance, using electrical conductivity as a salinity index, was significantly greater in NaCl than Na₂SO₄ salinity. This difference was attributed to the formation of SO₄ neutral ion pairs in Na₂SO₄ treatments which decreased cation uptake, increased osmotic stress relative to electrical conductivity and led to a possible SO₄-induced Ca deficiency. Cl adsorption in manganous sulphate and Na₂SO₄ treated soils was speculatively attributed to the formation of an undocumented ettringite-like mineral. Kikuyu exhibited both a fertilization effect and a Mn toxicity effect with manganous sulphate applications. An increase in yield occurred between Mn applications of 800 and 1600 mg/kg soil. This effect was attributed to increased nutrient availability as a result of nitrogen mineralisation and soil desorption processes. Mn applications of 3200 and 8000 mg/kg resulted in severe Mn toxicity symptoms and reductions in yield. Fertilization of kikuyu with NH₄NO₃ and MMC waste produced similar yield responses. Manganese toxicity did not manifest itself in MMC waste treated kikuyu, even at nitrogen loadings of 800 kgN/ha. Manganese attenuation in the soil by MnCO₃ precipitation, oxidation of Mn²⁺ and Mn adsorption are expected to prevent excess Mn²⁺ accumulation which would pose a Mn toxicity and water pollution risk. The disposal of untreated MMC waste as a nitrogen fertilizer substitute for kikuyu pastures is thus in principle a feasible operation in terms of maintaining pasture sustainability and preventing pollution of water resources.
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    Some aspects of the geochemistry of gallium in silicate rocks and stony meteorites
    (1979) Willis, James P
    The objects of the work presented here were: to develop an accurate method for the determination of gallium on a routine basis in rocks and meteorites at concentrations down to or less than 1 ppm Ga with a precision (c.o.v.) at the 10 ppm level and above of 1-2% (1s); to apply this technique to the determination of Ga in rocks and meteorites; by critically examining the high quality data thus obtained, to compare the distribution of gallium in various meteorite types, as well as in igneous, sedimentary and metamorphic rocks, seeking to define, where possible, the fine structure of its distribution and its relationship with aluminium during geological processes; and to evaluate the possibility of using variations in the gallium contents and Ga/Al ratios of rocks both to assist in the interpretation of the geochemical history of differentiated suites and to define regional differences, as has been done with other trace elements. Bibliography: pages 219-247.