الفهرس 
PRIMARY SLUDGE
APPLICABILITYOnly 14 pages are availabe for public view
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Abstract
Gravity thickeners are most commonly used in wastewater treatment plants in Egypt. Gravity thickeners are designed so as sedimentation happens due to physical reactions only, but what actually happens is that due to other
incomprehensible reactions the sedimentation efficiency is affected. These incomprehensible reactions are the subject of this thesis. This research contains:
Firstly, Data collecting for available information on the parameters affecting the gravity thickener and the troubles affecting the performance of the gravity thickeners. In addition to visiting some wastewater treatment plants in Egypt for
investigations and data collections. Secondary, the experimental works have two stages batch-scale lab experiments to determine the best mixture ratio
between primary & secondary sludge for thickener and also to determine the retention time to give maximum thickening efficiency, field-scale pilot unit experiments to determine the simulation model for the thickener behavior.
Finally, discussing both experimental works results and producing the simulation model and its verification. It was concluded from this research as the
following:
1. Based on the bench-scale lab experiments the best mixed ratio between primary sludge (PS) and waste activated sludge (WAS) with the gravity
thickener is found (40 % PS+ 60 % WAS).
2. from the bench-scale lab experiments, the big effect of biological action was presentable after 16 hrs.
3. The study proved that hydrolysis phase by anaerobic action can be
happened from start settling by gravity thickener depends on the sludge characteristics and sludge age.
4. Based on field pilot experiments, the maximum efficiency of gravity
thickener for primary sludge is highest than efficiency of mixed sludge (40%PS + 60% WAS) and then efficiency of waste activated sludge with retention time 16 hr.
5. The study model produced a simulation model for the gravity thickener. It was found that the gravity thickener works by three equations depending
on retention times and sludge types, thickening efficiency .