COSTA, A. G.; http://lattes.cnpq.br/5470691976610432; COSTA, Adriana Guimarães.
Résumé:
The working principle of aerobic treatment systems consists of maintaining a
bacterial population in the system and supply sufficient oxygen for the bacterial mass to
metabolise the organic matter that is present in the influent. In most aerobic systems
oxygen is transferred from the atmosphere by mechanical aerators which normally are
driven by electrical motors. The availability of oxygen is necessary in order to maintain
the bacterial mass alive and with a high metabolic capacity however in practice there
may be interruptions of the aeration due to power failures or to planned interruptions
during hours of high tariff of electrical power. On the other hand it may be possible that
there is no organic load during certain periods (for example during weekends in the case
of industrial effluents, so that in principle it would be convenient to reduce oxygen
consumption. For these reasons there is an interest to evaluate the influence of
interruptions of the aeration on the survival of activated sludge and on its activity just
after such an interruption. In this thesis a study was carried out to evaluate the feasibility
of the sludge from a Bardenpho system after periods without aeration. For this the
oxygen uptake rate (OUR) of a sludge batch was determined during the phase of
endogenous respiration before and after applying different periods without aeration.
Also the influence of the duration of the aeration interruption on the activity of the
heterotrophic bacteria (those that metabolise the organic matter) and the autotrophic
bacteria (the nitrifiers of ammonium). For this purpose, OUR was determined after
adding excess sodium acetate (for the heterotrophs) and ammonium chloride (for the
autotrophs). The experimental results indicate that interruption periods of up to one
week have little effect on the survival and the activity of activated sludge. For periods of
two to three weeks there was a gradual decrease of the active sludge mass as well as of the sludge activity of the surviving organisms. It was also established that both the
heterotrophic and the autotrophic bacteria preserve their metabolic capacity for a period
of up to one month. It is concluded that the bacterial mass that develops in the activated
sludge system is capable of withstanding long periods without aeration.
