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SZAKMAI - TUDOMÁNYOS ROVAT
• Another important removal mechanism for addition to cometabolism, bacterial plas-
micropollutants is adsorption. Approximately mid uptake and the adaptive process of the
33 % of micropollutants can be removed by degradation population also play a major
adsorption. Organic micropollutants have role in the biodegradation of drugs.
a high sorption tendency to raw sludge. Due • Sufficiently high sludge residence time (SRT)
to their hydrophobic nature, micropollutants is essential (10-15 days) for the degradation
are bound from the aqueous phase to the lipid of micropollutants, and high SRT allows the
fraction forming the lipophilic cell membrane proliferation of slow-growing bacteria (with
of the biomass. The other process is adsorp- long generation times) and the development
tion, where the micropollutants adsorb on the of a more diverse biocoenosis capable of
surface of solids (sludge). Adsorption involves degrading micropollutants. The biocoenosis
electrostatic interactions between positively in a nitrifying system can be expected to
charged groups (e.g. amino groups) and the have a SRT longer than 10 days, which is
negatively charged cell membrane surface. beneficial for degradation.
• Post-treatment UV oxidation (22 % remo- • The hydraulic residence time (HRT) deter-
val) and other oxidation processes (ozone mines the average residence time of soluble
post-oxidation) lead to chemical transfor- substances in the system. For example, the
mation. Ozone oxidation can remove 70- anaerobic degradation of the plasticizer
90 % of the micro-pollutant content of the di-(2-ethylhexyl) phthalate (DEHP) increa-
treated effluent after biological treatment. sed from 14% to 23% when the HRT was
• Conventional anaerobic sludge treatment increased from 5 to 14 hours in the reac-
is an option for the removal of adsorptively tor. In addition, it was observed that during
bound micropollutants in sewage sludge the rainy season, when the dilution of the
(raw and excess sludge). This treatment effluent causes HRT to decrease and the
method is not considered effective. The removal efficiency of micropollutants to
removal efficiency is highly variable, varying decrease significantly.
between 50 and 80 %. • Temperature plays an important role in
biodegradation: in countries where the avera-
Summary of factors affecting the biological ge temperature is 15-20 ºC, the degradation
removal of micropollutants: of micropollutants is more efficient than
in cold countries where temperatures are
• In principle, biodegradation of pollutants mostly below 10 ºC. Operational experience
is achieved by metabolism, where the pol- has shown that the removal of pharmaceuti-
lutant is used by bacteria as a primary source cals such as ibuprofen, benzafibrate, diclofe-
of carbon or nutrients and/or energy. The nac, naproxen and ketoprofen is increased in
other pathway is cometabolism, where the the summer compared to the winter period
micropollutant is transformed by the orga- (7 ºC) when temperatures reach 17 ºC.
nisms (bacteria) that perform the biological • An increase in biomass concentration from
metabolism, through the action of extracel- 3 gTSS-L to 5 gTSS-L significantly increased
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lular enzymes they produce, but the cells the removal of colloidal suspended solids
do not use the transformed products. In and moderately degradable compounds
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