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  • Patrick Kiely

SENTRY validated for biogas monitoring

The SENTRY system was installed July 2017 at CNETE (Centre National en Electrochimie et en Technologies Environnementales) or National Center in Electrochemistry and Environmental Technologies testing facility in Quebec, Canada.


SENTRY sensor system installed

A system was installed in two duplicate Anaerobic Digesters processing waste activated sludge. A pre-treatment step was added to one of the reactors, and the differences between the systems were analyzed using a SENTRY system installed in each. The sensor is demonstrated to be a key tool in understanding the conditions in test and control AD systems.


For continuing anaerobic digestion activities the sensor could be applied to

(1) Characterizing the impact of pre-treatment on influent wastewater streams,

(2) Providing correlations to real-time biogas production and

(3) Optimizing feed cycle times to ensure removal of bio-available carbon.


SENTRY data recorded for paralell AD systems

The major conclusions from the report are outlined as follows:


(1) Characterizing impact of pre-treatment:

· The pre-treatment accounted a 22.9% increase in biogas production between the test and control system. Further analysis of fractionation of the remaining organic material could be beneficial for understanding the full effect of the pretreatment.

· The pre-treated wastewater showed more consistent activity throughout the week, suggesting the pretreatment was having a good effect of maximizing the biological activity in the reactor. This also suggested that a potentially longer HRT could produce even higher biogas production and removal rates.


(2) Biogas production:

· Biogas production (and therefore reactor activity) trended well with SENTRY output. This shows great promise as a way to fill in the gaps of data that exist in daily sampling.

· This biogas trend was especially helpful for understanding reactor A (no pretreatment) as the batch mode beginning and end was clearly noticed (typically between noon and 7pm). IWT believes additional loading to this reactor could be achieved during times of low MET.

· The pretreatment step has clearly increased the potential for biogas production of the microbes based on the current HRTs of the reactor.




(3) Process feeding monitoring:

· The SENTRY sensors were able to pick up distinct batch run cycles for each system. 3 times higher average biological activity (MET) and longer cycles were noted in the reactor receiving the pre-treated influent (reactor B), suggesting a more biologically active feed material.

· The sensor displayed the weekly patterns of the feed cycle and response to the feed cycle in real time with sensors placed inside the reactors. Feed dates/times can be observed, as well as when reactions inside the system had slowed down.

· SENTRY data provides operator the option to optimize feeding cycles more closely to MET output. Waiting for BES data to return to baseline would be a suitable strategy for optimized cycle times.



CONCLUSION:

The sensor is demonstrated to be a key tool in understanding the conditions in test and control AD systems. For continuing anaerobic digestion activities the sensor could be applied to

(1) Characterizing the impact of pre-treatment on influent wastewater streams,

(2) Providing correlations to real-time biogas production and

(3) Optimizing feed cycle times to ensure removal of bio-available carbon.


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