Monitoring of microbial phosphorus release in batch experiments using electric conductivity

The ionic conductivity of an enhanced biological phosphorus removing (EBPR) sludge shows a clear behavior during the non-aerated phase. It decreases during denitrification and increases under anaerobic conditions proportionally to the phosphate concentration. The absolute value of this increase related to the release of phosphorus was determined between 1.66 × 10−4 to 1.99 × 10−4 S m2 g−1P (at 293 K and an ionic strength of about 650 × 10−4 S m−1). Theoretical calculations are in good agreement with these results. Potassium, magnesium, calcium and phosphate show a positive, whereas acetate and pH show a negative correlation to the ionic conductivity. This method is an easy and inexpensive in-line method providing more information about phosphorus release. Under some circumstances (low salinity, sequencing batch reactor) it may be used to estimate the anaerobic increase of phosphorus concentration.