How Shepherd Works

Based on BACTEST’s patented CYTOMAIA technology platform, Shepherd comprises a combination of a robust test chamber, sensors and a data logger as well as algorithms and curve stabilizing software which monitors the chamber, processes the information, and converts it into a visual output.

The test chamber is a sealed unit of 2 litre working volume which resides in a buoyancy collar and floats in the activated sludge lane. The sample is drawn directly from the activated sludge lane, analysed and returned on a programmable cycle of approximately one hour. The test chamber houses an air recirculation and exchange system that converts the biomass’ respiratory gas exchange, and hence its activity, into a headspace pressure variable. The absence of pumping for sample loading and unloading prevents fouling of the system. Barrier-protected sensors monitor sensitive pressure changes within the test chamber headspace and data loggers convert them into a near real time BOD5 proxy suitable for managing and optimizing plant processes.

The Shepherd Process


Top and bottom valves open allowing the sample to enter the test vessel to a pre-determined volume as the sample reaches the same height as the outside sludge.

STEP 2. Monitoring:

  • Top and bottom valves close making the vessel completely air tight.
  • The circulation pump drives head space air through a fine bubble aerator for mixing and rapid gas exchange.
  • Oxygen used by respiring microbes reduces the pressure in the vessel which is measured by barrier protected sensors.
  • Data is transferred to software that converts the pressure change into information and  operational advice communicated through the local control panel display, cloud based dashboard, and E mail.  

STEP 3. Sample expulsion:

  • Top and bottom valves open and air is forced into the vessel under pressure to drive out the sample and clean components.
  • Pressurised air flow stops and sample enters again in Step 1. 


STEP 4. Data processing:

On completion of its test cycle, the captured data is analysed to generate a BOD5 proxy and a recommended airflow which is then displayed directly on the control panel.
This process information is then sent to the cloud-based dashboard which in turn generates an email that is sent to all subscribers.