Development of a rapid pH-based biosensor to monitor and control the hygienic quality of reclaimed domestic wastewater

The re-use of treated domestic wastewater necessitates a rigorous control a nd rapid monitoring of the hygienic quality of the reclaimed water. For thi s purpose, a new pH-based biosensor was developed. The essence of the metho dology of the sensor is the monitoring of the acidification due to bacteria l metabolism of added glucose. To improve the sensitivity, the alkalinity o f the water sample is reduced prior to monitoring the acidification. This i s done by stripping CO2 at a neutral or acidic pH value. The hygienic aspec t of the sensor lies in the applied temperature (37 degreesC) and the use o f N-2 as decarbonizing gas, thus creating conditions favorable for enteric bacteria. The developed sensor could be used onsite at an advanced stage of treatment, as an endpoint or intake quality control device. For both appli cations. a useful correlation was obtained between log total plate count an d lag time or acidification rate, respectively. Absolute detection limits l ay in the ranges of either 10(3) colony-forming units (CFU)/ml in 6 h (endp oint quality control), or less than 10(5) CFU/ml in 1 h (intake quality con trol).