Oil refinery wastewater treatment in biofilm reactor
followed by sand filtration aiming water reuse
Isabelli N. Dias, Ana C. Cerqueira, Geraldo L. Sant’Anna Jr
and Marcia Dezotti
ABSTRACT
Oil refinery wastewater was sequentially treated in a moving-bed biofilm reactor (MBBR)
and a slow-rate sand filter (SF) in order to obtain an effluent with adequate characteristics
for downstream reverse osmosis (RO) operation. Experiments were conducted in bench scale
units and the results showed that the MBBR was able to remove 90% chemical oxygen
demand (COD), 75% NH
4
þ
, 95% phenols, operating with a hydraulic retention time (HRT) of 9 h.
Additional removal of COD (15–40%) and ammonia (30–60%) was achieved in the slow-rate SF
that was also effective for removing microorganisms. The silt density index (SDI) of the treated
wastewater (4.5) was below the maximum limit recommended for RO operation. The quality of
the effluent from the combined treatment system (MBBRþSF) was already adequate for cooling
tower make-up. The RO produced an effluent with quality compatible with that required for use
in boilers.
Isabelli N. Dias
Geraldo L. Sant’Anna Jr
Marcia Dezotti (corresponding author)
Chemical Engineering Program,
COPPE,
Federal University of Rio de Janeiro,
P.O. Box 68502,
CEP 21945-970,
Rio de Janeiro, RJ,
Brazil
E-mail: mdezotti@peq.coppe.ufrj.br
Ana C. Cerqueira
Petrobras, Cenpes,
Av. Horacio Macedo 950,
CEP 21941-915,
Rio de Janeiro, RJ,
Brazil
Key words | MBBR, refinery wastewater, sand filtration, water reuse
INTRODUCTION
Water scarcity is a matter of concern in many countries,
even in those that have significant water resources. Many
industries located close to urban areas face the problem of
water scarcity and have adopted practices of water economy
and water reuse.
The oil industry, by its magnitude, is looking for more sus-
tainable practices and, in particular, wastewater treatment at
very efficient levels aimed at reuse is being implemented by
several industries. However, the variety and complexity of
wastewaters generated by the oil industry is enormous.
Thus, several treatment techniques such as ozonation and
sand filtration have been investigated to produce less polluted
waters (Cha et al. ), distillation (Andrade et al. ),
Fenton and photo-fenton oxidation (Coelho et al. ), bio-
degradation in moving bed bioreactor (Schneider et al.
), biodegradation in membrane bioreactor (Viero et al.
), advanced oxidation processes and carbon biological
filtration (Souza et al. ).
Oil refineries utilize water in significant amounts,
averaging 0.25–0.35 m
3
per barrel of oil processed. Most of
these volumes are used in cooling and steam generation
units. A survey of data from Brazilian refineries was made
by Mariano () and revealed the following water uses:
steam generation (30%), cooling towers (30%), process
water (28%), potable water (5%) and other uses (7%).
Removal of organic matter and salts is an essential
requirement for water reuse in refinery boilers. Water qual-
ity requirements for cooling towers are not so strict, but
removal of organic matter, solid particles and microorgan-
isms is required.
Organic matter can be removed by several biological
processes, activated sludge being one of the most used.
Some biofilm processes are also effective in treating refinery
wastewaters, such as rotating biological contactors (RBC).
Another treatment system that has interesting features is
the moving-bed biofilm reactor (MBBR). In such a reactor,
84 © IWA Publishing 2012 Journal of Water Reuse and Desalination | 02.2 | 2012
doi: 10.2166/wrd.2012.022
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