Innovation Zone: BACTEST Shepherd

This month, we look at a monitoring system that can reveal the aeration demands of the activated sludge process on an hour-by-hour basis

The Shepherd system floating in an aeration lane

What is it?

Developed by Cambridge-based BACTEST, Shepherd is a monitoring and management system which can help wastewater utilities and trade effluent sites optimise the level of aeration necessary within the activated sludge (AS) treatment process. Sitting within the biological floc which is central to AS treatment, it calculates the Biological Oxygen Demand (BOD) of the floc on an hourly basis. The figure allows plant operators to increase or reduce the airflow appropriately, making the best use of energy.

What’s innovative about it?

The test typically used to measure the health of the floc in activated sludge is called BOD5, because it takes five days to produce results. The figure produced in Shepherd’s hourly testing (known as a BOD5 proxy) is much more helpful operationally because it enables management of the process in close to real time. Shepherd is also able to raise alerts for unusual activity which allows a faster response to toxic events or serious plant failure.

Who is using it at the moment?

Launched commercially a year ago, Shepherd’s first operational trial was with Anglian Water, where it achieved excellent results; Thames Water is also among its early users.

How does it work?

Shepherd uses the same microbial respirometry technology platform as a previous BACTEST product, Speedy Breedy, which was launched in 2013. Shepherd comprises a proprietary sensor that floats in the AS lane coupled with a three tier software system. Its sealed test chamber has a 2-litre capacity and houses an air recirculation and exchange system that converts the biomass’ respiratory gas exchange, and hence its activity, into a headspace pressure variable. The sample is drawn directly from the activated sludge lane, analysed and returned on a programmable cycle of approximately one hour. The software includes a cloud-based dashboard that provides an audit trail and plant management information, a traffic light display alongside the AS lane for in-situ operator updates and an email notification system for remote monitoring of unmanned AS sites.

What benefits does it bring?

Currently, the lack of an up-to-the minute method of calculating BOD means that utilities usually err on the side of caution by over-aerating. The optimisation enabled by the hourly test allows energy saving which BACTEST says can repay the cost of the kit within 12 months. Because the activated sludge process accounts for 60% of energy used in wastewater treatment overall, the long-term energy and cost savings could be considerable.

What associated technologies are available?

BACTEST’s first product, Speedy Breedy, is a portable unit providing rapid detection of microbial contamination in clean water, swabs and other liquids. Its quick testing for the presence of bacteria such as E.coli can allow for a speedier response to contamination incidents.