Abstract

The influence of a solid phase concentration in the model sludges of wet gas purification, as well as the flocculant consumption, on a change in the solid phase sedimentation rate and the strength of floccules has been examined. This is important because fluctuations in the solid phase concentration in waste water represent an uncontrolled process that significantly affects the kinetics of the solid phase sedimentation and leads to an increase in the flocculant consumption. We have proposed a procedure for determining the sedimentation rate of the flocculated sludge and the strength of floccules following the hydromechanical influence, which takes into consideration the solid phase concentration and the flocculant consumption. The study was carried out on model waste water, synthesized by mixing the dust from dry gas purification at actual production site with water. It has been determined that the solid phase concentration affects the rate of floccule deposition. It has been established that the optimum conditions for aggregate formation within a given model system are observed at the solid phase concentration in the interval 8–12 g/l. Increasing the solid phase concentration above 16 g/l decreases the floccule sedimentation rate disproportionately to the flocculant concentration. It is possible to reduce flocculant consumption and to optimize its dosage by carrying out a cleaning process taking into consideration the specified patterns. It was established that the hydromechanical influence on aggregates exerts the destructive effect, whose degree depends on the solid phase concentration. In particular, increasing the rate of fluid motion leads to greater damage to floccules than increasing the time for a less intense exposure. The way to minimize the destructive effect on floccules could be lowering the suspension transportation speed resulting from a decrease in the installation performance or through the increased cross-section of the channel (a pipeline). An increase in the solid phase concentration of the model system above 16 g/l is accompanied by a significant reduction in the strength of floccules. Therefore, when designing wastewater treatment plants that utilize flocculants, it is necessary to provide optimum conditions for aggregation and to minimize the hydromechanical effects on floccules by lowering the velocity of fluid motion

Highlights

  • Industrial activities related to processing natural raw materials at steel making enterprises are accompanied by the formation of significant quantities of anthropogenic waste, including sludge waste water, which is discharged into external sludge collectors

  • Our study has found that the rate of floccule deposition depends on the solid phase concentration (Fig. 1)

  • This leads to the conclusion that the optimization of flocculant consumption at wastewater treatment implies the search for conditions for the best aggregation

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Summary

Introduction

Industrial activities related to processing natural raw materials at steel making enterprises are accompanied by the formation of significant quantities of anthropogenic waste, including sludge waste water, which is discharged into external sludge collectors. Ecology into external sludge collectors is the low efficiency of water circulation treatment plants. One of their most problematic areas is the insufficient cleaning of sludges from suspended substances, which leads to significant contamination of the clarified water and the need for additional dilution of sludge (recharge) with clean tap water. This relates to that the flocculation of sludge at the inlet to a thickener does not occur with proper efficiency, despite the supply of a flocculant solution. The complexity and lack of detailed studies of the processes of flocculation, formation, as well as the destruction of formed aggregates in the transportation of fine-dispersed sludge, render relevance to the experimental and theoretical research into these processes

Literature review and problem statement
The aim and objectives of the study
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