Environmental Engineering Reference
In-Depth Information
Figure 12.4.2 Biodegradability of several samples from intermediate stages of the photo-Fenton
treatment of biorecalcitrant wastewater containing 550mg/L of TOC. Samples at
TOC > 250mg/L are not shown as biodegradability belowTOC = 254mg/L.
a period of adaptation, higher organic loads could be fed to the bioreactor. This is dis-
cussed later, under full-sized plant results. From these results, it can be concluded that
the best treatment option for this wastewater, containing around 550 mg/L of TOC
was solar photo-Fenton until around 60% mineralisation followed by biotreatment.
The full-sized solar photo-Fenton reactor consists of a 3000-L buffer or recir-
culation tank and 100 m 2 solar collector field made up of three rows of compound
parabolic collectors (CPCs) specially developed for photo-Fenton applications. The
total system volume is 4000 L (1260 L of illuminated volume). The aerobic biolog-
ical treatment part of the plant consists of three modules: a 5000 L neutralization
tank, a 2000 L conditioner tank, and a 1000 L fixed-bed biofilm reactor colonized
by activated sludge from the wastewater treatment plant installed at the pharmaceuti-
cal company itself. This biological system was operated directly in continuous mode.
It was operated in batch mode only during the start-up phase (inoculation, bacteria
fixation, and growing, etc.) and for the first experiments, such as the one shown in
Figure 12.4.3. A detailed description can be found elsewhere (Oller et al., 2007). From
the point of view of operation, the industrial saline wastewater partially oxidized by
photo-Fenton is discharged into the neutralization tank where water is roughly neu-
tralized with concentrated NaOH and iron is settled and removed when necessary.
Then the photo pre-treated effluent is transferred to the conditioner tank, where the
pH is automatically adjusted to between 6.8 and 7.5. Then the effluent is pumped to
the bioreactor.
According to previous laboratory and pilot plant-scale biological tests performed
(Figure 12.4.2), biodegradability enhancement of industrial wastewater by photo-
Fenton is accomplished when TOC is reduced to approximately 40%. At that moment
partially treated wastewater is transferred to the aerobic biological reactor. No min-
eral medium is usually added to the photo-Fenton pretreated effluent as the seawater
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