Studium vybraných postupů čištění digestátu.

Abstract

This dissertation deals with the issue of physical-chemical treatment of agricultural digestates with a focus on the factors influencing coagulation and flocculation processes when demanding dehydration of agricultural digestate. Thesis theoretically analyzes the sludge matrix model of suspended biomass (bacterial sludge microfloc) including the character of substances dispersed in the external environment. Based on this theoretical analysis, the thesis deals with so-called soft colloidal particles - emulsoids, which are globally recognized as the main cause of the problem in permanent application of intensive separation technologies on biological anaerobic sludge. The thesis aims at specification of extracellular biopolymers and determination of surface charge sources of these substances, as well as approximation of biological cell stability against mutual collision. In addition, the digestate's buffering capacity is assessed in the work with respect to the intensity of the buffer subsystems. In the next part of the thesis there are noted patented technologies of physicochemical treatment of digestate or its liquid fraction. The efficiency of oxidation and coagulation processes to anaerobically stabilized sludge is described for comparison. The practical part is devoted to the outputs of experimental activities, which were based on the study of the theoretical background. The results of the polymeric flocculation of the digestible digestates in the context of the maximum performance of the polyacrylamide flocculants are summarized, and results in the context of the minimum necessary dosages of the polymer for successful pressure filtration depending on the particular digestate are also summarized. Further, a new treatment procedure of digestate dewatering on the filter press, which has been pilot-tested, is presented. Subsequently, the work is focused on the analysis of fermentation results of digestate with ferric sulphate, expression of the dependence of the coagulant consumption on sludge neutralizing capacity, and the dehydration of digestate with organic polymer at acidic pH and conclusion. The dehydrating action of non-typical complex cations on agricultural digestate is also described and evaluated.