Water Research 36 (2002) 2695–2702
Effect of acidity consumption/production on the pH of
aeration tankduring the biodegradation of acetic acid/
*, Hyung-Soo Kim
, Yun-Chul Chung
Water Environment Research Center, Korea Institute of Science and Technology, Seoul 136-791, South Korea
Civil & Environment Department, SungKyunKwan University, Suwon 440-746, South Korea
Received 25 June 2001; received in revised form 26 October 2001; accepted 15 November 2001
In order to elucidate the biologically driven pH ﬂuctuation phenomena in industrial wastewater treatment, the
contrary effects of acetic acid (AA) and epichlorohydrin (ECH) on the pH of aeration tankwere investigated. Two
simple equations were derived to estimate optimum neutralization pHs for the biological AA/ECH wastewater
treatment, and the calculated optimum neutralization pHs were compared with experimental results. The pH in
aeration tankwas expected to ﬂuctuate sharply with the smallest deviation of neutralization pH from the optimum
value. However experimental results showed that real pH ﬂuctuation is smaller than the theoretical one. It was
considered that carbonate buffer in aqueous system relieves the pH ﬂuctuation. The deviation between experimental
and theoretical optimum neutralization pH could be mainly caused by volatility of AA and ECH. The deviation was
larger with ECH wastewater of which volatility is larger than AA. Finally, this theory was successfully applied to the
real petrochemical wastewater treatment. The pH of aeration tankwas properly maintained when acidiﬁed wastewater
(pH 3.4) was supplied. r 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Petrochemical wastewater; Wastewater treatment; pH regulation; Acidity
Activated sludge process has been widely used for the
treatment of domestic and industrial wastewater.
Though some general operational parameters have been
thoroughly investigated, it is still not fully understood.
The main obstacles of the biological wastewater treat-
ment are connected with a settlability of the biological
sludge in a secondary clariﬁer. Therefore the operational
parameters concerning the settlability, i.e. hydraulic
retention time (HRT) of wastewater, mixed liquor
suspended solid (MLSS), dissolved oxygen (DO), pH,
sludge return rate from secondary clariﬁer etc., have to
be occasionally checked in biological wastewater treat-
The relative difﬁculties in treating wastewater depend
on the characteristics and origin of the wastewater. For
example, most of domestic wastewaters containing
enough and various inorganic nutrients are easy to be
treated only if proper HRT and DO are maintained. In
many cases of industrial wastewaters, however, biologi-
cal wastewater treatments have been frequently faced
with various difﬁculties because of the unpredictable and
diverse properties of industrial wastewaters. In fact,
industrial wastewaters usually are lackof some inor-
ganic nutritional components and/or contain recalci-
trant organics. Therefore, not only nutrient addition but
also primary chemical treatments for the removal of the
recalcitrant materials are often needed.
In industrial wastewater treatment, one of the most
frequently faced problems is related with pH regulation.
*Corresponding author. Global Research Center, Nalco
Chemical Company, Naperville, IL 60563-1198, USA. Fax:
E-mail address: firstname.lastname@example.org (S.-H. Yoon).
0043-1354/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0043-1354(01)00501-2