INVESTIGATION OF HIGH FECAL COLIFORMS IN THE FINAL EFFLUENT

Detroit Wastewater Treatment Plant experienced occasional high sporadic fecal coliform test results in the final effluent in 2001. Although these did not result in any violations, an investigation was initiated to determine the cause of the high results. The investigations indicate that at current operation guidelines, TRC in the final effluent was not a 100% effective indicator for disinfection. The accuracy of chlorine demand, original fecal coliform levels, organic Nitrogen content in wastewater played important roles in affecting disinfection efficiency. To avoid increasing current chlorine dosage, adding rapid monitoring of levels of original fecal coliform, organic Nitrogen could be beneficial to adjusting chlorine dosage. At current lower TRC level, ORP indicator did not correlate well with final MPN compared with TRC.