An improved purification procedure yielded bluetongue virus free from any singlestranded ribonucleic acid (RNA) component. Double-stranded RNA obtained from purified virus or isolated from infected cells was fractionated into 5 components by means of sucrose gradient sedimentation analysis, and into 10 components by electrophoresis on polyacrylamide gels. The size of these components vary from 0.5 X 106 to 2.8 x 106 daltons, with a total molecular weight estimate of about 1.5 x 107 for the viral nucleic acid. The denaturation of the genome and separation of the resulting fragments are also discussed.A striking similarity has been found between the nucleic acid moieties of bluetongue virus (BTV) and reovirus, although the virions differ in size and morphology. Both genomes consist of double-stranded ribonucleic acid (RNA) which has been found, after isolation, to consist of a number of segments of reproducible size. In the case of reovirus, the presence of 10 doublestranded segments was demonstrated in fractionation experiments utilizing polyacrylamide gel electrophoresis (12,20), whereas electron microscopy studies using the Kleinschmidt technique indicated 9 to 11 fragments (15). In addition, a single-stranded, adenine-rich component has been found (1, 11).Previous studies on BTV-RNA indicated the presence of at least three size groups of segments, by the use of sucrose gradient sedimentation for fractionation (16).In the experiments reported here, the presence or absence of a single-stranded RNA component in BTV was investigated, and the double-stranded viral RNA was subjected to further purification and characterization. MATERIALS AND METHODSBuffers. The STE buffer consisted of 0.1 M NaCl, 0.005 M tris(hydroxymethyl)aminomethane (Tris), and 0.001 M ethylenediaminetetraacetic acid (EDTA), pH 7.4; the SSC buffer consisted of 0.15 M NaCl and 0.015 M sodium citrate, pH 7.2.Virus. BTV serotype 10 has been used throughout this work. Methods for the production of virus in BHK-21 cell cultures and for plaque titrations in Lcells have been described (4).Reovirus type 1 was obtained from N. F. Stanley, Melbourne, Australia; grown in BHK-21 cells, and purified according to the method of Bellamy et al.(1).Purification of BTV. The following modifications have been introduced into the procedure described previously (16). After extraction with Tween 80 and ether, sucrose was added to the aqueous phase containing the virus to a final concentration of about 4%, and the salt concentration was adjusted to 0.1 M. It was then layered over 2 ml of a 40% sucrose solution in STE, and the virus was pelleted through this layer for 2 hr at 102,000 X g. The pellets were dissolved in a small volume of 0.002 M Tris-hydrochloride at pH 8.0 and finally purified by centrifugation through a 10 to 30% sucrose gradient in the same buffer at 78,000 X g for 70 min. These modifications are based on the observation that purified BTV form aggregates in 0.1 M buffer, with disaggregation at a salt concentration of 0.002 M. Gradients were fractionated i...

Nutrient removal by chemical means has, over the past decade, become an expensive practice owing to the scarcity of chemicals. A new method of phosphate removal by hydroxyapatite [Ca5(PO4)3OH] crystallisation has gained increasing interest as the need for the implementation of clean technology has become more apparent as we move into the environmentally conscious nineties. This method as well as another method, viz. struvite [NH4MgPO4-6H2O] crystallisation, will be discussed using results obtained from a laboratory scale study using three types of effluent, two demonstrating hydroxyapatite crystallisation and the third, struvite crystallisation. While it has been proven that phosphate crystallisation does work as a tertiary treatment (Van Dijk and Wilms, 1991) this paper will also show that the positioning of the crystalliser can vary to suit the need of the industry for which it has been designed.

To evaluate their abilities to remove colour from textile-plant effluents, tests were run using several low cost natural adsorbent materials including vermiculite, sawdust, barbecue charcoal, maize stalks, sand, rice husks and peatmoss. With the exception of vermiculite, more than 50% of the colour was removed from the wastewater, with barbecue charcoal and rice husks showing the best adsorptive qualities (67% and 65% respectively). Under simulated industrial conditions on a laboratory scale a fixed-bed reactor was used to investigate the adsorption capacity of barbecue charcoal with respect to colour removal. An average of 28% of colour was removed at a hydraulic retention time (HRT) of 1.6 h over a period of 25 days. The effect of pH on the adsorptive capacity with respect to colour removal and represents a relatively cheap adsorbent material compared to conventionally used granular activated carbon.

SummaryPurified African horsesickness virus was shown to possess an icosahedral shape, measure approximately 55 mix in diameter and probably consist of 32 capsomeres. Electron microscopic evidence indicates a close morphological relationship between the virus and bluetongue virions. African horsesickness virus has a double-stranded RNA genome which was resolved into five components by sucrose gradient sedimentation analysis and into six segments in four size groups by means of polyacrylamide gel electrophoresis. The remarkably close relationship between African horsesickness and bluetongue viruses has led to the suggestion that these two viruses be classified in one sub-group of the newly proposed diplornavirus group.

A system of oxidation ponds in series with a biological trickling filter is described. It was known that this arrangement was incapable of reducing effectively the levels of algae present in the pond liquid even though nitrification was effected because of autotrophic conditions prevailing in the trickling filters. This very low trophic level explained the lack of adsorptive capacity present. By shortcircuiting less than 10 percent of the effluent from a fully loaded primary facultative oxidation pond to the trickling filter, the autotrophuc nature or the film in the trickling filter was sufficiently shifted towards a heterotrophic state that had sufficient adsorptive capacity to retain the majority of the algae. It is concluded that the algae, although being absorbed, stay alive on the film and do not contribute significantly to the carbonaceous load on the trickling filter. Further more the algae, although secluded from all sunlight, actually partake in the purification process, producing an effluent which, unlike a normal humus tank effluent, is surprisingly sparkling clear. This significant observation appears to be in line with laboratory findings by others who, when they artificially immobilised certain species of algae and passed water over them, concluded that the algae retained the potential to remove certain compounds from the water. Conglomerates of biologically flocculated dark-green algae are scoured off the film (or sloughed off as part of the film) and, having been photosynthetically inactive for some days, tend not to float, but settle very rapidly. A very significantly aspect of this development is the great potential it has for practical application in developing countries. The algae sloughed off the media are easily thickened and available for ultimate recovery from the water phase without the addition of chemicals.