REASONING OF THE EFFICIENCY OF CONSISTENT FILTRATION ON RAPID FILTERS

Abstract

Consistent filtration of water through rapid filters with different filter loadings is a promising way to reduce operating costs at water treatment plants. Operating costs are related with the need to regenerate the granular loading, i.e. restore its retention capacity. Regeneration is carried out by washing with clean water, which removes retained sediment from the loading pores. Washing takes place with a fairly high intensity, which is the reason for significant volumes of washing water. The amount of washing water can be reduced increasing the period between washings. The frequency of washing is also influenced by the turbidity of the initial water. When increase of rapid filters efficiency is reasoning, it is necessary to take into account oscillations in initial turbidity. Purpose is reasoning of the practicability of using a consistent scheme and research of its effectiveness under conditions of change in the content of suspended solid in the initial water. Theoretical studies were carried out on the basis of the known dependencies of the theory of filtering by D.M. Mintz. These dependencies establish a relationship between the time of the protective action and the time when the head loss reaches the limit values with the filtering parameters: filtration rate, equivalent diameter of the granular loading, thickness of the loading layer, quality of the water entering the treatment. The algorithm and principle of comparison of consistent and traditional schemes are described. Graphical dependences of the influence on the efficiency of consistent filtration of pretreatment degree and turbidity of the initial water were obtained. As an efficiency criterion, the ratio for the compared schemes of the longest periods of filter operation between washings is taken. The effectiveness of increasing filtration rate when the initial water quality is worsening is shown. The conducted studies showed the advantages of consistent using of rapid filters: an increase in the period between washings, more stable operation when the turbidity of the initial water changes. Keywords: consistent filtration, protective action, head losses, filtering granular loading, turbidity.