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  • Patrick Kiely

SENTRY validated for real-time BOD measurement

Updated: Aug 22, 2018

The most recent SENTRY commercial system was installed at an Atlantic Canada wastewater treatment plant. Sensors were installed in the influent and effluent of the plant. The sensor was demonstrated to be a functional tool for the on-site operator in understanding key process factors such as:

(1) real-time organic loading to the plant,

(2) real-time effluent water quality monitoring and

(3) quantification of impact on on-site cleaning events on process performance.


Atlantic Canada WWTP

BOD correlations were performed on the influent and effluent samples. Initial plotting of this data shows that the sensors microbial electron transfer (MET) value at these time points predicts the BOD with an R2 of 0.98. Using these values as an estimate for the influent and effluent concentration, the average influent concentration was 230.3 mg/L +/- 24.7 mg/L and the average effluent concentration was 11.3 mg/L +/- 6.9 mg/L.




SENTRY used to pick up impact of regular cleaning events!

A pump station cleaning event discharged a lot of organic material into the wastewater treatment system. The influent SENTRY system was able to identify this event with an increase in signal that day of 11% above a typical Wednesday measurement. The effluent SENTRY system picked up a clarifier cleaning event, showing a clear spike in output of 3-5 times increase from normal MET for one hour that morning, followed by just over 4 hours of 2 times increase before returning to normal.




SENTRY used to pick up daily / weekly performance patterns at the plant!!

An analysis of the daily cycle was performed. The period between 4 - 8AM was the lowest concentration, with an increase from 8AM till 3PM, with a general plateau from 3PM till ~12AM. These shifts represented approximately a 25% change throughout the day. An analysis on the weekly trends was performed, using average MET per day. The sensor showed that the metabolic activity of the wastewater was lowest on Mondays (at -5%) and had highest activity on Wednesdays and Fridays (at +2%), and a clear weekly pattern was observed. Using this daily and weekly data, the operator can gain additional understanding of the changing demands on the system.


SENTRY dashboard providing real-time BOD measurements

How can SENTRY help operators of WWTP facilities??

This allows the operator to understand logical times and days for maintenance down times (during low flow/low stress times such as Monday early morning), and when to maximize performance from the plants (aeration/sludge return: midweek and the afternoon). Additionally, this info can be used to understand the stress on the system and potentially how close the system is to coming out of compliance.


SENTRY sensor installed in a wastewater stream.

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(+1) 902-894-1366

Email: pkiely@islandwatertech.com

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