Use of microbial electrodes for observation of microbiological nitrogen elimination process.

Microbial electrodes for the determination of ammonia and the estimation of biochemical oxygen demand (BOD) were applied to the nitrogen elimination process. The dimensions of the nitrification and the denitrification vessels were 170 and 70 L, respectively. The wastewater used for the experiment was obtained from a fermentation factory and adjusted to 470-530 mg/L of total Kjeldahl nitrogen and 1700-3000 mg/L of BOD. The ammonia electrode was assembled with a membrane containing nitrifying bacteria and an oxygen probe. The BOD electrode was similarly constructed, except it used a membrane containing the yeast, Trichosporon cutaneum. A flow system was employed for the automatic measurement of samples every 30 min. The nitrification and denitrification rates of the activated sludge were measured to investigate the optimum conditions and evaluate the capacity of the plant. The various data obtained by the microbial electrodes allowed us to inspect the situation of the plant and estimate control parameters such as nitrogen and BOD loadings. The average removals of ammonia nitrogen and total Kjeldahl nitrogen were 96% and 89%, respectively, during the experiment for period of 2 weeks.

Microbial sensors for volatile compounds.

A microbial sensor consisting of immobilized microorganisms, a gas permeable membrane, and an oxygen electrode was prepared for the continuous determination of methyl alcohol. Immobilized methyl alcohol utilizing bacteria was employed for the sensor. The response time of the sensor was within 10 min by the steady-state method. A linear relationship was observed between the current decrease and the concentration of methyl alcohol below 22.5 mg l-1. The selectivity of the microbial sensor for methyl alcohol was satisfactory. Microbial sensors using Trichosporon brassicae for ethyl alcohol and acetic acid are also described. A microbial sensor consisting of immobilized nitrifying bacteria (isolated from activated sludges), a gas-permeable Teflon membrane and an oxygen electrode was prepared for the amperometric determination of ammonia. When the sensor was inserted in a solution containing ammonia, the current decreased to a steady-state with a response time of 4 min. The relationship between the current decrease and the ammonia concentration was linear up to 42 mg l-1. The minimum concentration for the determination was 3.5 mg l-1. The current decrease was reproducible within 4 per cent of relative error. The current output of the sensor was almost constant for over 10 days and 200 assays.