Joint International Conference on Long-term Experiments ...

The managerial plan of breweries consist in introducing some measures and methods
meant to assure a minimum consumption and a maximum recirculation, achieved
through integrated systems such as: wastewater treatment by recovering and reusing
both the water and the sub-products resulted after the treatment process.
The main wastewater treatment methods from breweries are based on: mechanical
purification, chemical treatment and biological purification assuring in this way the
removal of CBO5 to maximum 30%, 75% and respectively 95%.
Mechanical treatment is based on physical proprieties aiming at the separation of
suspensions and other materials; it uses decanters.
Chemical purification aims at separating or transforming the settling substances or
in suspension by using chemical reactives, assuring in this way the neutralization, the
separation of colloidal and dissolved substances, etc.
Biological purification is based on the use of dissolved and undissolved organic
substances by the micro organisms for multiplication and conservation. According to
the presence or lack of oxygen, the transformation of organic substances by bacteria can
be achieved in aerobe and/or anaerobe processes.
The residues discharged from breweries represent around 39 kg/hl of produced
beer and are mainly made up of 55% carbon hydrates, 27,8% proteins, 6,7% cellulose
and 6,4% grease. The evacuated wastewater charge is reduced to 70-90% as a result of
fermentation process, the resulted fermented sludge is a very good fertilizer.
Among biological treatment systems one can distinguish between anaerobic and
aerobic processes. Anaerobic treatment is characterized by biological conversion of
organic compounds (COD) into biogas(CH4 70-85% and CO2 15-30% with traces of
hydrogen sulphide). During aerobic treatment oxygen is supplied to oxidize the COD
into CO2 and H2O. Both biological processes produce new biological biomass.
The overall basic reactions are:
Anaerobic: COD → CH4 + CO2 + anaerobic biomass
Aerobic: COD + O2 → CO2 + H2O + aerobic biomass
Table 1 presents a general comparison between anaerobic and conventional aerobic
biological treatment systems.(Driessen W. et al., 2003)
Table 1: Anaerobic treatment as compared to aerobic treatment
AEROBIC SYSTEMS ANAEROBIC
SYSTEMS
COD removal 90 - 98% 70 – 85%
Nutrients (N/P) removal high low
Biosolides production high low
Space requirement high low
Energy consumption high low
Energy production no yes
Anaerobic pre-treatment followed by aerobic post – treatment will result in a positive
energy balance, reduced sludge production and space saving.
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