Biochemical mediator demand--a novel rapid alternative for measuring biochemical oxygen demand.
The biochemical oxygen demand (BOD) test (BOD5) is a crucial environmental index for monitoring organic pollutants in waste water but is limited by the 5-day requirement for completing the test. We have optimised a rapid microbial technique for measuring the BOD of a standard BOD5 substrate (150 mg glucose/l, 150 mg glutamic acid/l) by quantifying an equivalent biochemical mediator demand in the absence of oxygen. Elevated concentrations of Escherichia coli were incubated with an excess of redox mediator, potassium hexacyanoferrate(III), and a known substrate for 1 h at 37 degrees C without oxygen. The addition of substrate increased the respiratory activity of the microorganisms and the accumulation of reduced mediator; the mediator was subsequently re-oxidised at a working electrode generating a current quantifiable by a coulometric transducer. Catabolic conversion efficiencies exceeding 75% were observed for the oxidation of the standard substrate. The inclusion of a mediator allowed a higher co-substrate concentration compared to oxygen and substantially reduced the incubation time from 5 days to 1 h. The technique replicates the traditional BOD5 method, except that a mediator is substituted for oxygen, and we aim to apply the principle to measure the BOD of real waste streams in future work.
Pasco
N
N
Lincoln Technology, Lincoln Ventures Ltd, Lincoln University, Canterbury, New Zealand. pascon@lincoln.ac.nz
Baronian
K
K
Jeffries
C
C
Hay
J
J
D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005292:Ferricyanides / Q000378:metabolism*; D008828:Microbiological Techniques; D009930:Organic Chemicals / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
D005292:Ferricyanides; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; C028033:potassium ferricyanide