Field studies with the floating bioreactor
Type:
Presented during:
CEDA Dredging Days 2007 - The Day After we Stop Dredging, Rotterdam
Authors:
Thomas J, Beitinger E, URS Deutschland; Koch R, Technical University Brandenburg and Tessmer P, Gebrueder Kemmer, Germany
Abstract: The - Floating Bioreactor - is comparable to an airlift suspension reactor as commonly used for biological degradation processes. An integrated airlift pump was designed to loosen the sediment from the ground with minimal physical stress and to lift it above the water table. Compressed air is injected above the inlet of the riser pipe. The sediment suspension is transported by upwards streaming air bubbles. Simultaneously, an intensive venting process is started by the direct contact of sediment and injected air. Volatile compounds are stripped and treated by granulated activated coal after separating in an integrated knockout tank Basically, the removed suspension can be handled in two ways:
1) The oxygen-rich suspension can be refilled to the bottom of the water body. During and after resettling biodegradation processes are stimulated. The resettling process can be performed under controlled conditions (fixed cone shields, silt curtains) to avoid dirty clouds moving in the waters.
2) After passing through the knock-out-tank the sediment suspension is dewatered and sorted for on shore treatment, reuse or disposal.
This is a valid option for regular dredging. Dewatering and classifying can be conducted by conventional techniques.
In December 2006 a study has started funded by the German Ministry of Education and Research, BMBF. Investigations will focus on transport mechanisms during extraction, resettling and treatment with the Floating Bioreactor in a field test. The pilot unit is designed as a self-driving floating facility consisting of the airlift pump, gas-liquid-separation, vapor treatment, classifying modules, and installations for controlled re-suspension and resettling. Partner for this study are: Technical University of Brandenburg, Kemmer, and URS Germany.
Investigation was focused on following items:
- Sediment removal with minimized emission,
- Process and rate of in situ biodegradation,
- Use of modular equipment for optimized on-site sediment treatment.
Two field test sites were identified for demonstrating the range of effectiveness during full-scale operation.
Keywords: remedial works, environmental dredging, airlift, emission reduction