A new way of tracking how sewage sludge flows during thermal treatment could help engineers design better wastewater treatment plants and boost biogas production.

Researchers at RMIT University in Melbourne, Australia, demonstrated how the flow behavior of sludge can be used as a tool to gauge how quickly organic matter is dissolving at high temperatures. The technique could help facilitate online monitoring of process performance.

The researchers said that traditional methods of assessing the performance of thermal treatment require sampling and chemical analysis. By contrast, rheology calculations — which measure and detail how liquids flow — can be done online in real time.

The study, published in Water Research, found a correlation between how sludge dissolves and changes in its flow behavior, indicating it may be possible to monitor thermal treatment performance by tracking the flow.

Correctly estimating the rheological parameters of sludge is critical to efficient process design. The technique may enable engineers and plant operators to obtain these parameters without having to perform measurements at high temperatures themselves.

The equations in the study are based on direct measurement of sludge at conditions that mimic real-world thermal treatment processes. The new technique can measure flow behavior without destroying the samples.

The study also showed that varying the thickness of sludge has little impact on the effectiveness of thermal treatment. As a result, plant operators could increase biogas production downstream by increasing the solid content of sludge during initial treatment processes.

The research also could enable more efficient design and troubleshooting of pumps, mixers and heat exchangers in the sludge treatment process.