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FP5

AGROIWATECH Résumé de rapport

Project ID: ICA2-CT-2002-10010
Financé au titre de: FP5-INCO 2
Pays: Netherlands

Report on most feasible plant layout and control strategies for wastewaters from a selected set of agro-industries in the Balkan region, based on the wastewater characteristics and anaerobic reactors

Thorough knowledge on agro-industrial wastewater characterization and anaerobic digestion process was an important base to generate treatment scenarios for several agroindustrial wastewaters.

The objective of design was to obtain the effluent quality as prescribed by the EU Directive 271 from 1991 on Urban Waste Water Treatment. The design was worked out and described in a more detailed way for brewery wastewater. The calculations were also performed for wastewater from the sugar, potato and fruit and vegetable processing factories. For all types of wastewater anaerobic digestion in a high rate UASB (Upflow Anaerobic Sludge Blanket)reactor was selected as a core technology. Further, the whole treatment scheme consisted of a pre-treatment (screening, buffer tank and plate clarifier) main treatment and post-treatment. With the main treatment in the UASB 90% of the COD is removed. When using the UASB reactor, post-treatment is needed to remove the residual solids and COD as well as nutrients.
The anaerobic reactor is more feasible than an aerobic treatment system as the required reactor volume is smaller and less excess sludge is produced.

Using an EGSB (Expanded Granular Sludge Blanket)reactor instead of an UASB reactor could also be feasible. The volume and costs for this reactor are lower than these of the UASB reactor. However more suspended solids will need to be removed in the pre-treatment as the hydraulic residence time in the EGSB reactor is much lower and less solids can be removed in the reactor. The EGSB reactor is also more complex in construction. Using an anaerobic treatment system to treat the brewery effluent is innovative for the Western Balkan. Since there is still a little experience regarding design, maintenance and operation a somewhat simpler UASB is selected in the first instance.

The wastewater entering the reactor does not need to be heated. This would cost energy and the need to install heating equipment while the profit in terms of smaller volume needed is very small as the organic load already is very low at 25oC.
The proposed treatment design can be implemented to reach the EU requirements regarding the effluent from agro-industrial industries. However more factors have to be considered like financing, available space, attitude of the factory, local regulations.
It is finally recommended to analyse the whole production process to come to the most sustainable solution. There are several points where the process water consumption can be lowered. Possibilities for water reuse should be considered. With a smaller effluent (=influent to the treatment) flow, the required reactor volume is also smaller. This would especially be interesting for breweries with a larger daily flow than the one examined in this study.

Also the possibilities of the collection of solid waste residues (e.g. for brewery yeast residues and spent grains) during the production process should be looked at. This would result in less suspended solids in the wastewater and therefore less removal needed during the pre-treatment. Some solid waste residues separately collected during the process can be reused and additional profit can be gained (e.g. yeast and spent grains can serve as cattle feed).

Contact

Jules B. VAN LIER, (Professor Dr Ir)
Tél.: +31-015-2781615
Fax: +31-015-2784918
E-mail