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The water quality and phytoplankton community assemblage of the Khami River, a tropical river sub catchment in semi-arid southwest Zimbabwe impacted by agriculture and urban land use, were examined in March 2015. Conductivity, sulphates, total dissolved solids and salinity were higher at urban sampling points than at agricultural sampling points. In contrast, agricultural sampling points were more turbid, and had a greater content of nitrates than urban sampling points. The phytoplankton community was dominated by Cyanobacteria, mainly Microcystis aeruginosa, with densities of up to 20 times higher at urban than at agricultural sampling points. There was an increasing dominance of Cyanobacteria (M. aerugionosa and Merismopedia glauca) and Chlorophyta (Eudorina elegans, Spirogyra sp. and Pediastrum duplex) and a decreasing importance of Bacillariophyta along the agriculture-to-urban gradient. Given the increasing scarcity of water in southern Africa, not only do our findings confirm the importance of land ...

Water is a necessary medium in most coal preparation processes, but its presence in the final product has a negative impact on transporation costs, handling and specific energy value. A major contribution to the total moisture content may be attributed to the proportion of fine coal in the total product, which presents the greatest dewatering problem. This paper describes a novel process that seeks to reduce the moisture content of fine coal cakes to a level comparable to that achieved by thermal drying. In this process, superabsorbent polymers, which are granular highly crosslinked synthetic copolymers with excellent water-absorbing properties, are employed to draw water from moist fine coal. The drying or dewatering process is characterized by three main stages: (a) contacting of superabsorbents with high-moisture fine coal; (b) separation of dried fine coal from superabsorbents by screening; and (c) regeneration of used superabsorbent polymer, taking advantage of its response to changes in such conditions as pH, temperature or electric field. Depending on the polymer type, the dosage and the polymer/coal contact time, the moisture content of coal filter cake can readily be reduced from, say, 25% to 10% by mass or less. The results of laboratory and pilot scale tests conducted using pH- and temperature-sensitive superabsorbent polymers are discussed in this paper.