integration of photo fenton and activated sludge processes to

FERNANDO C. N. Sassano, 1; José Ermírio E. F. Moraes, 2,3; Cláudio A. O.
Nascimento, 1,3
Departamento de Engenharia Química, Escola Politécnica, Universidade de São
Paulo, CEP: 05508-900, São Paulo, Brasil.
Escola Paulista de Engenharia Química, Universidade Federal de São Paulo, CEP:
09972-270, Diadema, Brasil.
Centro de Capacitação e Pesquisa em Meio Ambiente (CEPEMA-USP), Universidade
de São Paulo, CEP: 11525-970, Cubatão, Brasil.
Due to the toxic nature of some phenolic compounds the Environmental Protection
Agency (EPA-USA) has set a water purification standard of less than 1 part per billion
(ppb) of phenol in surface waters (Melo et al., 2005). They are often found in industrial
effluents such as from pulp and paper, timber, plastics and synthetic polymer,
pharmaceutical, pesticide, oil and petrochemical industries. Conventional oxidative
methods for the wastewater treatment utilize the combination of biological, physical and
chemical treatments. Biotreatment processes tend to be very large due to the slow rate
of the biological reactions; physical methods generally transfer waste components from
one phase to another; chemical treatment, such as chlorination, can result in the
formation of chlorinated phenols and their byproducts which are as toxic and nonbiodegradable as the original medium (Kusic and Koprivanac, 2006). Advanced
Oxidation Processes (AOP´s) have been used as one of the most effective processes to
remove organic pollutants from aqueous solutions containing soluble organic
compounds that are either toxic or non-biodegradable. AOP´s involve the generation of
the hydroxyl radical (•OH), which has a very high oxidation potential and is able to
oxidize almost all organic pollutants (Esplugas et al., 2002; Kusic and Koprivanac,
2006). Although these processes have shown high efficiency for water and wastewater
treatment, they have high costs related to investment (complex installations) and
operation (high consumption of energy and/or reagents) (Esplugas et al., 2002). A
promising alternative to complete oxidation of biorecalcitrant wastewater is the use of
an AOP as pre-treatment to convert the highly toxic organic compounds to readily
biodegradable intermediates (Devlin and Harris, 1984), followed by biological
oxidation of these intermediates to biomass and water (Hsu et al, 2004; De Morais and
Zamora, 2005; Al Momani, 2006). Fenton’s reaction may be recommended as a pretreatment process to enhance later microbial transformation, lowering the operational
costs, by increasing its biodegradability, generally through the cleavage of large organic
compounds into smaller ones (Walling , 1975; Chamarro et al., 2001; Zazo et al, 2005).
This work aims to treat a phenol solution via Fenton reaction to enhance medium
biodegradability and using it as an effluent in a continuous activated sludge (biological)
process. In the condition used in this work, the wastewater could be pos-treated by
conventional biological processes, resulting in a reduction in the operational costs and
time reaction from both advanced oxidation and biological processes.