Maximum permissible technological parameters of frame-filling filters

Abstract

Relevance. Wastewater of knitting industry contains various types of dyes, synthetic surfactants, mineral salts and suspended solids in values requiring deep cleaning. It is advisable to carry out deep cleaning of these drains on non-pressure filters, which do not require large expenses and are easy to operate. We gave preference to frame-filling filters. First of all, it allows significant increase in filtration rate, and its two layers with different fractions of filter materials significantly contributes to differentiated purification of wastewater from suspended solids of various sizes. Aim. To determine the maximum permissible values of technological parameters of the frame-filling filters operation (filtration rate and duration of the filter cycle) at which high filtration effect is provided through a highly porous material-crushed expanded clay. Objects. Wastewaters of the knitting industry and the effluents of the cotton and textile industries that are similar in their composition of pollution, as well as the identical effluents of some other branches of light industry. Methods. The experimental method was used on a laboratory frame-filling filter installation. The expanded clay used was obtained by the method of swelling low-melting clays and clay rocks during their rapid firing, followed by crushing to the state of sand. In general, the proposed technological methods are justified by those comparative and generalizing methods that can improve frame-filling filter operation. Results and conclusions. Based on the results of the conducted research, the following conclusions can be drawn: Pronounced intergranular porosity (on average 1.6 times greater than that of quartz sand) allows expanded clay granules passing through a significant amount of waste water at relatively high filtration speeds (20–22 m h) and retain up to 70% of suspended solids The duration of the filter cycle when using crushed expanded clay is at least 1.5 times longer than when using quartz sand Due to the greater difference in the average coefficients of the shape of the filtering materials, more complete regeneration of filtering properties of crushed expanded clay compared to quartz sand is provided 2–3 minutes earlier, regardless of the initial concentration of suspended substances. The filtering properties of crushed expanded clay during deep wastewater treatment of the knitted production with the main concentrated pollution indicators (color intensity, BODfull, COD and surfactants) practically do not concede the quartz sand properties. Besides, crushed expanded clay is much cheaper than quartz sand; it can be used on an equal footing with quartz sand for deep cleaning of low-turbidity and slightly colored industrial wastewater.