Biosensors & Bioelectronics 14 (2000) 883–893
Immobilised activated sludge based biosensor for biochemical
oxygen demand measurement
Jing Liu, Lovisa Bjo¨rnsson, Bo Mattiasson *
Department of Biotechnology, Centre for Chemistry and Chemical Engineering, Lund Uni6ersity, P.O. Box
124
, S-
221 00
Lund, Sweden
Received 24 May 1999; received in revised form 11 October 1999; accepted 22 October 1999
Abstract
A biochemical oxygen demand (BOD) sensor, based on an immobilised mixed culture of microorganisms in combination with
a dissolved oxygen electrode, has been developed for the purpose of on-line monitoring of the biological treatment process for
waste and wastewater. The sensor was designed for easy replacement of the biomembrane, thereby making it suitable for
short-term use. The drawbacks of activated sludge based sensor, such as short sensor lifetime, were thereby circumvented. The
sensor BOD measurements were carried out in the kinetic mode using a flow injection system, resulting in 25 s for one
measurement followed by 4–8 min recovery time. Based on the results of normalised sensor responses, the OECD synthetic
wastewater was considered to be a more suitable calibration solution in comparison with the GGA solution. Good agreement was
achieved between the results of the sensor BOD measurement and those obtained from BOD
5
analysis of a wastewater sample
from a food-processing factory. Reproducibility of responses using one sensor was below 95.6% standard deviation. Reproduci-
bility of responses using different sensors was within acceptable bias limits, viz. 9 15% standard deviation. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords
:
BOD sensor; Biochemical oxygen demand; Activated sludge; Microbial consortium; Kinetic mode; Dynamic mode; Wastewater
www.elsevier.com/locate/bios
1. Introduction
Biochemical oxygen demand (BOD) is one of the
most widely used and important parameters in environ-
mental treatment processes. Conventional BOD meth-
ods include the well-known BOD
5
(APHA, 1992) and
BOD
7
(SIS, 1979) methods, which need 5 and 7 days
incubation at 20 91°C in the dark, respectively. The
BOD values indicate the amount of biochemically
degradable organic material (carbonaceous demand)
and the oxygen used to oxidise inorganic material such
as sulphides and ferrous iron. It can also be a measure
of the oxygen used to oxidise reduced forms of nitrogen
(nitrogenous demand), unless their oxidation is pre-
vented by an inhibitor (APHA, 1992). These
conventional methods are time consuming and not
suitable for in situ measurement or on-line monitoring.
Thus, it is necessary to develop a measurement method
that could circumvent the weaknesses of the conven-
tional methods given above. As an alternative, several
biosensor methods for BOD measurement have been
developed.
The first report of a BOD biosensor was published in
1977 (Karube et al., 1977). Following this report, sev-
eral kinds of microbial BOD sensor have been devel-
oped, and various modifications have been carried out
(Hikuma et al., 1979; Kulys and Kadziauskiene, 1980;
Strand and Carlson, 1984; Riedel et al., 1985, 1988,
1989; Su et al., 1986; Zhang et al., 1986; Karube et al.,
1989; Li and Chu, 1991; Tan et al., 1992, 1993; Ohki et
al., 1994; Tanaka et al., 1994; Jung et al., 1995; Sakai et
al., 1995; Sangeetha et al., 1996; Yang et al., 1996; Tan
and Qian, 1997). Most of the BOD sensors consisted of
a synthetic membrane with immobilised microorgan-
isms as the biological recognition element. The bio-oxi-
dation process was registered in most cases by means of
a dissolved oxygen electrode. A wide variety of mi-
croorganisms have been screened during the construc-
tion of BOD sensors. The microbial strains selected
were chosen for their ability to assimilate a suitable
* Corresponding author. Tel.: +46-46-222-8264; fax: +46-46-222-
9659.
E-mail address
:
bo.mattiasson@biotek.lu.se (B. Mattiasson)
0956-5663/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0956-5663(99)00064-0