TDSS Thermal Disintegration of Sewage Sludge

Project start :01.12.2000Duration :12 months

The goal of the disintegration step, is to release the cell components to stabilize and mineralise the sludge and to reduce foam production. The turnover in the anaerobic digester is increasing. The gas yield increase and the quantity of dewatered sludge will be reduced.

A regenerative heat exchanger interposed between the treated and untreated sludge ensures a more economic efficiency.

 

Objectives:

- Assessment of thermal disintegration technologies and process comparison

- Process development for optimised sludge treatment and reduction of sludge production

- Investigation for the disintegration of floating sludge to destroy filamentous organisms and

  reduce foam production

- Thermal disintegration in technical scale on wwtp Wansdorf (funded by the BMBF)

- Operation of a mobile pilot plant for thermal/chemical treatment on wwtp Waßmannsdorf

 

The results of the investigations are presented at first for the thermal disintegration of sewage sludge and after that for experiments on the thermal and chemical/thermal disintegration of floating sludge on the wwtp Waßmannsdorf:

 

Figure 1: Floating sludge before thermal treatment
Figure 2: Floating sludge after thermal treatment (128 °C, 70 min)

Thermal Disintegration of Sewage Sludge

Goals and advantages of the process Results from the investigations
1. Increase of the gas About 100% in respect to the excess sludge
2. Reduction of the amount of sludge About 20 - 30 % in respect to excess sludge
3. Relief of the digestion sector and thereby improving the stability of the process (eventually saving space required for digestion by reducing the volume) yes
4. Reduction of foam produced during digestion yes
5. Improvement of de-watering characteristics after sludge digestion yes
6. Possibility of reducing the need for flocculating yes

The microscopic pictures of the original floating sludge (figure 1) and the disintegrated sludge (figure 2) mainly differed regarding the form and density of the flocs, but there was only a slight difference in the quantity of the visible filamentous bacteria.

The floating sludge showed mainly loose, dismembered flocs, which were all held together by filaments of Microthrix. In the disintegrated sludge larger and more compact flocs were observed, and filaments were attached around the floc edges. But, on the other hand, a destruction of the structure of the sludge, i.e. a considerable reduction of the exposed surface of the sludge flocs was achieved and probably no floating of the disintegrated sludge may be expected in this condition after refeeding.
 

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Contact:

Dr. Bernd Heinzmann (Berliner Wasserbetriebe)
bernd.heinzmann(at)bwb.de