Parameters of wastewater flocculation with subsequent filtration on press filters

The higher is the sludge moisture content, the higher are the costs for further sludge processing. Thus, agglomerated sludge is dehydrated in order to reduce the cost of its subsequent drying and transportation. The purpose of this research was to study the parameters of wastewater flocculation with cationic flocculants, followed by filtering the sludge on press filters. To improve the sludge dehydration, the following chemical reagents were used: cationic polyelectrolytes “Zetag-7664”, “Zetag7689” and “Zetag-7692”. Settling velocity of solid particles, flocculating ability and flocculating effect have been determined. The moisture content of the sludge after filtration on press filters has been measured. It has been established that the highest settling rate (7 mm/s), the highest flocculating activity and flocculating effect (0.66 and 26.2, respectively) belong to the medium cationic flocculant “Zetag-7689”. The lowest residual moisture content after filtration on press filters was shown by the medium cationic flocculant “Zetag7689” (36 %). The high cationic flocculant “Zetag-7664” and the low cationic one “Zetag-7692” had residual moisture content after flocculation and press filtration of 39 and 37%, respectively. The residual moisture content of the sludge filtered on the filter press meets the technological requirements. The release of water from this structure during filtration can be explained by the phenomenon of capillarity. A liquid meniscus is formed between the particles. In the meniscus on the opposite side of the liquid, the capillary potentials are directed in opposite directions, but their absolute values are not equal. As a result, liquid moves through the capillary until the potentials are equal. To achieve reasonable dehydration of the sludge, it is necessary to carry out test flocculation as it allows studying the processes of polyelectrolyte adsorption on the sludge, the rheological properties of wastewater suspensions and flocculant solutions. It is obligatory to select and control filter press parameters.

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