The study of the column flotation capacities for stimulation of potash ore flotation

Potassium ore contains readily sludgable water-insoluble silicate–carbonate impurities which actively adsorb cation collectors (primary alkylamines) used in sylvine flotation. This fact determines inclusion of multistage de-sludging flowsheets, with rougher and cleaning flotation of sludge in the processing technology. A prerequisite for flotation de-sludging of ore is pre-flocculation of sludge. Flotation of sludge in mechanical flotation machines is carried out with intensive mechanical stirring of the suspension, which impairs the selective separation of sludge into the flotation froth and leads to the partial destruction of sludge floccules, which causes an increased consumption of the flocculant. In column machines, flotation is carried out in a laminar-upward flow of finely dispersed air bubbles ejected into the suspension in the lower part of the column, and is characterized by the minimal hydromechanical effect on the mineral particle–air bubble attachment. An important feature of flotation in column machines is the adjustability of the foam layer height in a wide range of values (up to 0.5 m and more) and its washability, which makes it possible to increase the recovery selectivity of the floated material into the foam product. The design of column machines for enrichment of potash ores, which are water-soluble and floatable in rich salt solutions, should ensure elimination of crystallization of the aeration system for supplying air to the column machine. The tests of column flotation of sludge produced from potash ores of the Upper Kama deposit with different contents of water-insoluble impurities were carried out on the experimental installation of ERIEZ Flotation Division. The results of the comparison of flotation efficiency and selectivity in mechanical and column flotation machines are presented. The possibility of de-sludge flotation of potash ores with different contents of water-insoluble impurities (1.5–4%) with the significant improvement of flotation selectivity at the lower consumption of reagents is shown. The use of column flotation creates conditions for simplifying the instrumental and technological flowsheet of flotation.

Removal of organic matter from surface water during coagulation with sludge flotation and rapid filtration – a full-scale technological investigation

Coagulation with sludge flotation and rapid filtration was selected as a surface water treatment technology to be optimised with a full-scale investigation, which was carried out in Poland between August and October 2013. The river water treated was characterized by low alkalinity, high-temperature variability and a high organic matter content. In the course of technological studies, the processes of coagulation with sludge flotation and rapid filtration were analysed. The studies were performed in the most adverse conditions for the applied technology i.e. during the period of algal bloom and subsequent decomposition of dead plankton. Throughout the study, the river water contained mainly dissolved organic matter, with occasional increases in the concentration of the undissolved fraction during algal bloom. The undissolved total organic carbon (TOC) fraction was effectively removed through coagulation while small doses of ClO2 added prior to coagulation enhanced the process. The process of coagulation using high-coagulant doses at pH = 6.5 did not provide a reduction in the TOC value below the level of 4 mg C/L required for treated water. The effect was achieved by adding powdered activated carbon (PAC) before the filters. The coagulation products were characterised by low-hydraulic resistance which should be taken into account at the stage of water delivery to the filters, after flotation.

Characteristics of granular sludge in a single upflow sludge blanket reactor treating high levels of nitrate and simple organic compounds

Simultaneous denitrification and methanogenesis were accomplished in a single upflow sludge blanket (USB) reactor. More than 99% and 95% of nitrate and chemical oxygen demand (COD) removal rates were obtained at a loading of 600 mg NO3-N/L·d and 3,300 mg COD/L·d, respectively. The specific denitrification rate (SDR) increased as COD/NO3-N ratios decreased. Maximum SDR with acetate could reach 1.05 g NO3-N/gVSS·d. Significant sludge flotation was observed at the top of the reactor due to the change of microbial composition and the formation of hollow granules. Granules became fluffy and buoyant due to the growth of denitrifiers. Microscopic examination showed that granules exhibited layered structure and they were mainly composed of Methanosarcina sp., Pseudomonas sp., and rod-shaped bacteria.