Page 172 - Materials Chemistry, Second Edition

Fungal Treatment of Pharmaceuticals in Effluents 153

transformations (due to partial degradation) or metabolites has been reported after
wastewater treatment practices. Little is known about the occurrence, fate, or activ-
ity of transformed compounds and metabolites in the environment. However, these
transformed compounds, which are generally considered to be less toxic, might be
even more toxic (in the case of pro-drugs or transformations after oxidation processes)
than the parent compound. However, in some cases, structural transformations or
metabolites are not even analyzed or reported (Kümmerer, 2009) as the transformed
compounds. The new molecule might not be recognized by the employed analyti-
cal method and simply reported as removed. Therefore, special care must be taken
when these compounds are present. Coupling toxicity tests with the analytical test is
therefore necessary when analyzing the effectiveness of treatment practices, includ-
ing fungal treatment.
To date, most of the practices for the removal of PhACs via fungal treatment have
been carried out in in vitro sterilized conditions employing synthetic liquid media
and controlled conditions of pH and temperature. The results of these studies might
be irrelevant for real wastewater practices, in which a community of microorganisms
is growing and possibly interfering with the fungal treatment. In addition, the pH and
temperature that are optimal for the fungi may change the structure of the parent
compound and make these applications impractical. Spiked concentrations of the
compounds (milligrams per liter) have been used, which might not reflect the condi-
tions in real WWTP influent. Therefore, the degradation yields that are reported in
those studies might not be achieved for real WWTP effluents, in which the concen-
tration of the substance is in the range of nanograms per liter.
The other concern regarding the successful implementation of fungal treat-
ment relates to scale-up considerations and reactor design factors. Various reac-
tor configurations have been suggested for the use of WRF for reliable, efficient,
and rapid removal of PhACs from the wastewater effluent. The choice of the
reactor configuration and design parameters depends on several factors affecting
the performance and activity of the employed organism. A detailed study of the
process is required for determination of parameters such as the optimal tempera-
ture, operational pH, dissolved oxygen concentration of the effluent and fixed
nitrogen concentration, reaction kinetics, effect of physical phenomena, reaction
rate and yield, and materials of construction. The control over the process and
the process economic factors are also substantial factors, which are important
for the purpose of scaling up. Combinations and interactions of these factors
make the scale-up study more complex. In addition, on the one hand, the flow
of the municipal WWTPs’ influent is huge, and on the other hand, the fungal
treatment of the effluents would be a slow process, requiring a high hydraulic
retention time in the fungal bioreactor. In addition, the oxygen supply or aeration
that is required in the reactors imposes extra costs on the process. Therefore,
the implementation of fungal treatment for the removal of pharmaceuticals from
municipal wastewater at the current WWTPs might not be practical. However,
for the effluent of pharmaceutical manufacturers or hospitals, or industrial sew-
age, the use of fungal treatment could be practical, as the concentration of the
PhACs in the influent is high, and the volume is comparably lower than the influ-
ent of the WWTPs.