15 April 2024

Prototyping of a portable sensor for VFA monitoring for domestic wastewater treatment processes

Author/Compiled by
Santiago Gómez Cuervo (AIMEN)
Miguel Placer Lorenzo, (AIMEN)

Executive Summary

What was the purpose of this prototype project?

This prototype project was about developing and field-testing a portable sensor for Volatile Fatty Acids (VFA) measurement in domestic wastewater treatment processes. As the treatment unit to be used for field-testing was not available as initially intended and no alternative application was selected, the sensor was only operated in laboratory conditions.


Project Milestones & Key-learnings

Factsheet Block Body

To summarize the following steps were taken as part of this pilot project and these were the practical learnings we made during this process:

  • Design and sensor compilation
  • Testing with pattern samples: the sensor sensitivity for measuring VFA pattern samples in laboratory conditions was very high, being able to achieve a resolution of 100 ppb for solved VFA and cover a range between 0.1 and 5 ppm for Acetic, Propionic and Butyric acid.
  • Testing with sludge samples: as a next steps, sensor testing was performed for samples from AIMEN´s lab-scale bioreactors. due to turbidity and interferences from other biological molecules with similar absorption wavelengths, transferring the performance achieved with pattern samples to real sludge samples was quite challenging. A complex manual sample preparation method was developed using filters and syringes in order to get rid of potential interferences during the measurement. It also became impossible to identify and estimate the proportion of different VFA (Acetic, Propionic or Butyric) present on the sample – which again was possible at lab scale when using pattern samples.
  • Transport to India: The sensor was unfortunately damaged during the transport to India – causing an electronic failure, so several components had to be purchased again, shipped to India, and reassembled in a second field trip to AMU plant.
  • O&M training of AMU research staff: a training was held by experts from AIMEN to AMU research staff and O&M materials were shared with the participants. The training was held in English and filmed anticipating potential staff rotations.

Field-Testing: Initially, the sensor was designed to be applied for measuring VFA in sludge of an Upflow UASB reactor. Eventually, it turned out that the unit intended to be used for this field-application was no longer operated. Up to the time this case study was compiled, no alternative field-application was selected, and no field-testing was performed.


Operational experience and performance

Factsheet Block Body

The sensor was only tested during the summer of 2022 in AIMEN laboratories using AIMEN lab bioreactors. The results are not as robust as the ones obtained with VFA laboratory pattern samples due to sludge sample turbidity and composition. Further improvement should be performed to achieve better sensitivity and get rid of the interferences in real sludge samples.

AIMEN 2023. Pathogen sensor kit

Figure 1. Pathogen sensor kit. Source: AIMEN (2023)

AIMEN 2023. Pathogen sensor field-testing at AMU

Figure 2. Field-testing campaign at AMU. Source: AIMEN (2023)


Alternative Versions to