Decontamination of water by combined solar advanced oxidation processes and biotreatment - Solar Energy Sciences and Engineering Applications - page 384

Figure 12.3.1 Evolution of TOC, COD and AOS during the solar photo-Fenton treatment of an
industrial wastewater.
almost until the end of the experiment (circled in blue). This means that from this
point on, the chemical nature (oxidation state) of the mixture is not going to change
significantly, because oxidation is causing mineralization. Parallel behavior of the COD
and TOC also makes this very clear. Before this point (treatment time less than 200
minutes), the AOS rose sharply (sharp drop in COD along with slow fall in TOC).
It can therefore be assumed that the biodegradability of the effluent should change
from 0 to 200 minutes, but not after, and therefore, any bioassay for determining
biodegradability enhancement should be applied while AOS is still changing and only
until it stabilizes but not afterwards. As bioassays are usually difficult, expensive and
slow, reliable and rapid chemical analyses, such as COD and TOC are useful aids in
deciding the best time for their application.
12.3.2 Activated sludge respirometry
Respirometry assays measure the Oxygen Uptake Rate (OUR) in live biomass and
are an indicator of the microbiological activity present in it. The oxygen demand
determined in respirometric assays has recently been found to be an excellent con-
trol parameter, as it represents a direct measure of the proper activity and viability of
microorganisms in aerobic activated sludge. Furthermore, as this test directly assesses
the primary function of an activated sludge process, it can be used for efficient mea-
surement of any acute toxicity in industrial wastewater that could affect the activated
sludge in a Municipal Wastewater Treatment Plant (MWWTP) (Gutiérrez et al., 2002).
Aerobic biomass activity at different stages of AOP treatment of industrial wastewater