Flocculation and filtration of sludge

Meijerink, M.P. (2013) Flocculation and filtration of sludge. Bachelor's Thesis, Chemistry.

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Abstract

This report is written in order to get insight in the processes present at the wastewater treatment plants in Garmerwolde and Heerenveen. A literature study is done to make an operational comparison between the two plants. The comparison consists of a description of the hardware present including how is it used and controlled. The comparison is mainly focused on flocculation and filtration. Both processes are used to dewater sludge, which is a side product from the purification of sewage water. The main difference in flocculation between the two plants is the concentration of the added polyelectrolyte (PE) and the mixing of this PE with the sludge stream. Garmerwolde uses a 1 wt% PE solution and a dynamic mixing system. On the other hand Heerenveen uses a 0.15 wt% PE solution and a static mixing system. It is expected that the way of mixing has much influence on the properties of the flakes and therefore the dewatering ability during filtration. In both plants filtration is done by chamber filter presses. The presses are operated in the same way; however Garmerwolde (25.87% DSC) achieves a higher dry solid content of the sludge cake than Heerenveen (23.69% DSC). This is the result of a higher dry solid content of the sludge stream into the presses due to digestion. However, also the efficiency of the chamber filter press is higher in Garmerwolde. In addition, experiments are conducted with a flocculation set-up. This is done to see if the process conditions for flocculation are the optimal conditions. The result for Garmerwolde (145 gram FeCl3/kg D.S.; 12.5 gram PE/kg D.S.) was quite different than the current coagulant and flocculent dosage (65 gram FeCl3/kg D.S.; 7.5 gram PE/kg D.S.), but for Heerenveen the results (75 gram FeCl3/kg D.S.; 7 gram PE/kg D.S.) were almost similar (55 gram FeCl3/kg D.S.; 7 gram PE/kg D.S.). However, the flocculation set-up is a quantitative method and is primarily used to determine the range where coagulation and flocculation occurs.

Item Type:	Thesis (Bachelor's Thesis)
Degree programme:	Chemistry
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	15 Feb 2018 07:53
Last Modified:	15 Feb 2018 07:53
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/11078

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