negligible when the compound is dep

negligible when the compound is deprotonated. Similar results
have been measured for IBP, although the maximum removal observed
for this compound was somewhat lower than for NPX (Table
2). These results agree quite satisfactorily with those reported
by Carballa et al. (2005).
The anti-epileptic drug CBZ and the tranquiliser DZP were generally
not eliminated from the liquid phase, with the exception of
S2 in November for which a depletion of 21% and 35%, respectively,
were measured, which was indeed somewhat lower than the effi-
ciencies reported by Carballa et al. (2005). In the case of CBZ,
whose pKa is 7, removal could depend on pH which determines
the protonation degree of its amide group. In fact, removal was
only observed in the sample with the lowest pH, which contains
the highest portion of protonated specie which can establish covalent
interaction with the negatively charged surface of solids
(adsorption).
The fate of fragrances and DCF was analysed on the basis of total
concentrations of the compounds (Eq. (2)) and compared with the
minimum removal efficiency expected according to separation of
TSS and sorption coefficients of these compounds (Eq. (3)). The corresponding
results are shown in Fig. 5. As occurred in the coagulation
assays, removal of fragrances and DCF was significantly higher
than expected on the basis of TSS separation, even in the absence of
external flotation additives. Removal of DCF was only observed
when wastewater collected in November was subject to flotation,
at efficiencies in the range of 13–51%, very close to the removal
of 20–45% previously reported by Carballa et al. (2005) for this type
of treatment. Surprisingly, the highest efficiency of flotation was
achieved with the sample of S2 collected in November (Fig. 5b)
which does not correspond to the sample with the highest amount
of fat as occurred during coagulation, but with the most acidic one.
Removal efficiency seemed to be dependant on the state of the
acid-base equilibrium of this acidic compound.
As expected beforehand, highest efficiencies with flotation were
measured for the most lipophilic compounds, namely fragrances.
Removals of 65–85%, 57–92% and 48–86% were obtained for HHCB,
AHTN and ADBI, respectively (Table 2), being these upper limits
slightly lower than those achieved by coagulation. Generally, the
use of coagulants improved the process, offering the aluminium
based reagent better results than the ferric one. As occurred in
coagulation experiments, the degree of musk separation correlated
with the fat content of the wastewater used, which confirms that
the process is mainly driven by absorption, as had been already
postulated by Carballa et al. (2005).
3.3. Continuous experiments
The hospital effluent was first continuously treated in the coagulation-flocculation
pilot plant at three different conditions: (i)
without external additions (blank); (ii) using 25 mg L1 of
Al2(SO4)3 as coagulant; and (iii) in the presence of 25 mg L1 of
FeCl3. The selection of these operational conditions was based on
the results obtained during batch experiments, which indicated
that working at the higher coagulant dose of 50 mg L1 did not lead
R