Efficacy of conventional drinking water treatment processes in removing problem-causing phytoplankton and associated organic compounds

Seven phytoplankton groups were recorded in the source water supplied to South Africa’s largest conventional drinking water treatment plant (DWTP). Two phytoplankton genera, Anabaena and Ceratium were identified as the problem-causing phytoplankton due to their ability to interfere with the water treatment process and negatively impact on water quality. The objectives of this study were to identify problem-causing phytoplankton genera and investigate the efficacy of unit processes in removing phytoplankton genera and associated organic compounds. Phytoplankton and organic compound data were obtained from four different sampling localities throughout the treatment plant and statistically analysed to evaluate the removal efficiencies of unit processes. The highest percentage removal for the Cyanophyceae average seasonal concentration (> 1 000 cells/mℓ) was recorded at 98%, while the highest percentage removal for the Dinophyceae average seasonal concentration (± 9 cells/mℓ) was recorded at 100%. Microcystis and Anabaena were removed by the processes of coagulation, flocculation and sedimentation (> 95%), while Ceratium cells were removed by sand filtration (> 80%). Ineffective removal of Ceratium by coagulation, flocculation and sedimentation (and subsequent penetration to the sand filtration step) will negatively impact on filter run times when these phytoplankton genera are present in high concentrations in the source water. Total photosynthetic pigments (TPP) were removed effectively by all the different water treatment processes. Not enough statistical evidence could be displayed to suggest effective removal of geosmin in this conventional water treatment plant. With good removal of intact cyanobacteria cells during coagulation, flocculation and sedimentation, geosmin concentrations in the final water could be kept to accepted organoleptic levels of 5–10 ng/ℓ in the final water. Optimising conventional drinking water treatment processes can effectively remove problem-causing phytoplankton as well as their associated organic compounds and thereby reduce the potential risk to drinking water consumers.Keywords: coagulation, sand filtration, drinking water, Ceratium, Anabaena, Microcystis, geosmi

The occurrence and removal of algae (including cyanobacteria) and their related organic compounds from source water in Vaalkop Dam with conventional and advanced drinking water treatment processes

Cyanobacterial bloom formation in freshwaters, such as rivers, lakes and dams, is known to occur throughout the world. The Vaalkop Dam, which serves as source to the Vaalkop drinking water treatment works (DWTW), is no exception. Blooms of cyanobacteria occur annually in Vaalkop Dam as well as in dams from which Vaalkop is replenished during low-rainfall periods. These blooms during the summer months are associated with the production of cyanotoxins and taste and odour compounds such as geosmin and MIB. The Vaalkop DWTW uses a combination of conventional and advanced water treatment processes to deal with the cyanobacteria and their related organic compounds in the source water. The overall objectives of this study were to: (i) investigate the occurrence of algae (including cyanobacteria) and cyanotoxins in the Vaalkop Dam; (ii) establish which environmental variables are responsible for the development and onset of algae, and (iii) determine whether the Vaalkop DWTW is able to eliminate the influence that algae (including cyanobacteria) may have on the drinking water. Multivariate statistical analyses revealed seasonal variation in algal assemblages in the raw water. The risk of cyanobacteria bloom formation proved to be especially high during the summer months as the nutrients needed for cyanobacterial growth are available and the temperature range is optimal, causing the production of geosmin, MIB and microcystin. The presence of Ceratium hirundinella (O.F. Müller) Dujardin, in the source water appears to exacerbate the negative effect that cyanobacteria have on the drinking water treatment process. When Ceratium hirundinella is present, floc formation is inhibited, causing more of the problematic algae to penetrate into the drinking water. Even though advanced treatment options such as ozone and granular activated carbon filters are used at Vaalkop DWTW, the effects of the organic compounds produced by cyanobacteria are not entirely eliminated during the treatment process.Keywords: potable water treatment, geosmin, MIB (2-methylisoborneol), microcystin, granular activated carbon (GAC), ozon

Application of a basic monitoring strategy for Cryptosporidium and Giardia in drinking water

Despite the health risks associated with exposure to Cryptosporidium and Giardia, there is no uniform approach to monitoring these protozoan parasites across the world. In the present study, a strategy for monitoring Cryptosporidium and Giardia in drinking water was developed in an effort to ensure that the risk of exposure to these organisms and the risks of non-compliance to guidelines are reduced. The methodology developed will be applicable to all water supply systems irrespective of size and complexity of the purification works. It is based on monitoring procedures proposed by the US Environmental Protection Agency, the Drinking Water Inspectorate, Australia and New Zealand, as well as the risk-based procedure followed by Northern Ireland. The monitoring strategy developed represents a preventative approach for proactively monitoring Cryptosporidium and Giardia species in drinking water. The strategy consists of 10 steps: (i) assessment of the monitoring requirements, (ii) description and characterisation of the source water types, (iii) abstraction of source water, (iv) assessment of the water purification plant, (v) water quality monitoring, (vi) cryptosporidiosis and giardiasis outbreak, (vii) risk assessment, (viii) sample collection and laboratory processing, (ix) data evaluation, interpretation and storage, (x) process evaluation and review. Proper implementation of this protocol can contribute to the protection of drinking water consumers by identifying high-risk source water, identifying areas of improvement within the water treatment system, and also preventing further faecal pollution in the catchments. The protocol can also be integrated into the Water Safety Plans to optimise compliance. Furthermore, this methodology has a potential to contribute to Blue Drop certification as it should form part of the incident management protocols which are a requirement of Water Safety Plan implementation.Keywords: Cryptosporidium, Giardia, monitoring, risk score, drinking wate

Parsimonious Higher-Order Hidden Markov Models for Improved Array-CGH Analysis with Applications to Arabidopsis thaliana

Array-based comparative genomic hybridization (Array-CGH) is an important technology in molecular biology for the detection of DNA copy number polymorphisms between closely related genomes. Hidden Markov Models (HMMs) are popular tools for the analysis of Array-CGH data, but current methods are only based on first-order HMMs having constrained abilities to model spatial dependencies between measurements of closely adjacent chromosomal regions. Here, we develop parsimonious higher-order HMMs enabling the interpolation between a mixture model ignoring spatial dependencies and a higher-order HMM exhaustively modeling spatial dependencies. We apply parsimonious higher-order HMMs to the analysis of Array-CGH data of the accessions C24 and Col-0 of the model plant Arabidopsis thaliana. We compare these models against first-order HMMs and other existing methods using a reference of known deletions and sequence deviations. We find that parsimonious higher-order HMMs clearly improve the identification of these polymorphisms. Moreover, we perform a functional analysis of identified polymorphisms revealing novel details of genomic differences between C24 and Col-0. Additional model evaluations are done on widely considered Array-CGH data of human cell lines indicating that parsimonious HMMs are also well-suited for the analysis of non-plant specific data. All these results indicate that parsimonious higher-order HMMs are useful for Array-CGH analyses. An implementation of parsimonious higher-order HMMs is available as part of the open source Java library Jstacs (www.jstacs.de/index.php/PHHMM)

Ruminal and postruminal digestion of dietary protein and starch in steers: 1. Effect of protein concentration, degradation of protein and energy content of the diet.

No Abstract

Rate and extent of ruminal degradation of crude protein from selected feedstuffs used in cattle feedlots as measured by the in sacco technique

No Abstract

The effect of copper and zinc at neutral and acidic pH on the general haematology and osmoregulation of Oreochromis mossambicus

The objective of this study was to determine the effect of sublethal copper and zinc concentrations at a neutral and an acidic pH, on selected haematological parameters as well as on the total osmolality and electrolyte concentrations of Oreochromis mossambicus. In general, at neutral pH copper and zinc caused blood acidosis, increases in circulating white blood cell numbers, causing stimulation of the immune system, and a rapid release of red blood cells from haemopoietic tissue, as reflected in the decreases in mean corpuscular volume. Increases in red blood cells are attributed to an increase in the oxygen-carrying haemoglobin as an adaptation to altered respiratory homeostasis caused by copper and zinc. These increases are therefore a secondary reaction to the metals and not the result of direct stimulation of the haemopoietic tissue. In contrast, at an acidic pH copper and zinc concentrations usually caused blood alkalosis and decreases in white blood cell numbers, due to the bioconcentration of metals which blocks and suppresses the leucopoietic tissue. Decreases were also recorded in red blood cell counts, haemoglobin, haematocrit and mean corpuscular volume, which can be ascribed to anaemic and hypoxic conditions, gill damage and impaired osmoregulation. Key words: copper; zinc; neutral pH; acidic pH; haematology; osmoregulation; Oreochromis mossambicus; Olifants River; South Africa (Afr J Aqua Sci: 2002 27(1): 61-84

Uptake and distribution of a copper, iron and zinc mixture in gill, liver and plasma of a freshwater teleost, Tilapia sparrmanii

Since polluted environments contain mixtures of different contaminants, the aim of this study was to investigate the time-integrated uptake of individual metals by a freshwater teleost, Tilapia sparrmanii following exposure to a metal mixture containing Cu, Fe and Zn. The metal concentrations used during the bioassays were chosen to represent ecologically relevant concentrations as found in the Olifants River, Kruger National Park, South Africa. The concentrations used in the bioassay were 0.16 mg·ℓ-1, 4.3 mg·ℓ-1 and 1.003 mg·ℓ-1 for Cu, Fe and Zn respectively. Gill, plasma and liver were sampled at 0, 2, 4, 6, 12, 24, 24, 48, 72, 96 h and four weeks. Gill tissue is the initial site of accumulation of water-borne metals. Although the fish were exposed to a metal mixture, the interactions between metals and the external gill surface, as well as the subsequent uptake rate, were associated with the particular chemical properties of individual metals. The tendency of the individual metals in the metal mixture to bind to the external gill surface via ionic bonds, and to gill cytosolic compounds via covalent bonds, was Cu > Fe > Zn. The ensuing uptake rates into the extracellular compartment (blood) and intracellular compartment (liver tissue) were Zn > Fe > Cu. The toxic effects of Cu and Fe were, therefore, primarily exerted on the gill surface and in the gill cytosol, whereas the toxic action of Zn was primarily limited to the internal organs. WaterSA Vol.27(1) 2001: 99-10

The effect of copper and zinc at neutral and acidic pH on the blood coagulation of Oreochromis mossambicus

The effect of copper and zinc on fish blood coagulation under alkaline and acidic conditions and the possible occurrence of disseminated intravascular clotting under these conditions have been poorly studied to date. It was found that the blood coagulation system of adult O. mossambicus exposed to copper and zinc at neutral and acid pH levels was altered. Deviations from normal coagulation times are either inherent or are due to factors such as liver damage, vascular abnormalities, and mineral and vitamin deficiencies. Exposure to copper and zinc at neutral pH caused prolonged blood coagulation, whilst at acidic pH exposure to these metals caused accelerated coagulation. Haemostatic conditions induced by these metals were fibrinolysis, haemophilia, thrombocytosis (hypercoagulability) and thrombocytopaenia. Keywords: copper; zinc; neutral pH; acidic pH; blood coagulation; Oreochromis mossambicus; Olifants River; South Africa (Afr J Aqua Sci: 2002 27(1): 47-60

Metal concentrations in Clarias gariepinus and Labeo umbratus from the Olifants and Klein Olifants River, Mpumalanga, South Africa: zinc, copper, manganese, lead, chromium, nickel, aluminium and iron

The upper catchment of the Olifants River, from its origin near Bethal to its confluence with the Wilge River, north of Witbank, and its tributaries are being subjected to increasing afforestation, mining, power generation, irrigation, domestic and industrial activities. These activities have a profound effect on the water quality. The major point sources of pollution in the study area include mines, industries and very importantly, combined sewage purification works that are located alongside the river. In addition to oxidizable material, these sources contain detergents, nutrients and metals. It was therefore necessary to determine the extent to which these activities affect the water quality of the system. The bioaccumulation of zinc (Zn), copper(Cu), manganese (Mn), lead (Pb), chromium (Cr), nickel (Ni), aluminium (Al) and iron (Fe) in the skin, muscle, liver and gill tissues of Clarias gariepinus and Labeo umbratus from the Upper Olifants River and Klein Olifants River was investigated over the period February 1994 to May 1995. The highest concentrations of these metals were found in the gill and liver tissues of both species, with lower concentrations in the skin and muscle tissues. Bioaccumulation patterns were found to vary according to the species of the fish, mainly according to their different feeding habits and the routes of metal uptake. It also varied as a function of the different localities. Accumulation was size specific, with higher concentrations of metals found in smaller fish. WaterSA Vol.28(4) 2002: 433-44