Aqua Assist improves settling, increases clarification capacity at 58-MGD WWTP


  • Settling Volume (SSV) showed a 37% reduction over the 4-week demonstration
  • Sludge Volume Index (SVI) improved from 140 to about 80 ml/g – a 42.8% decrease.
  • Clarification capacity increased by about 960 gals/, or enhanced capacity for the clarifier to handle 4-5X of average flow during high flow events.

The 58-MGD WWTP operates a highpurity oxygen-activated sludge wastewater treatment process. It runs two
parallel aeration batteries with three passes each. The North Aeration Battery had historically better settling behavior than the South Aeration Battery.

Dryletʼs innovative biocatalyst draws from material science and microbiology. Its Aqua Assist product is comprised of
carefully selected beneficial microbes embedded inside non-toxic particles made of an engineered porous media
substrate. The particles are approximately 200-600 µm in size. They protect the microbes, allowing them to
thrive and replicate fast so they can be effectively integrated into microbial ecosystems.

The demonstration was intended to determine whether Aqua Assist could be a viable, non-chemical option for enhancing settling and improving clarifier capacity during high flow periods. The acclimation period was about two weeks; the effects of the Drylet product lasted for about two weeks after dosing was stopped.

It was jointly decided by Drylet and the WWTPʼs operational team to dose Aqua Assist during 24 days to the South Aeration Battery, which had worse settling. The acclimation period was about two weeks and the effects of the Drylet product lasted for over two weeks after dosing was stopped.

The SVI trends were higher in the South Aeration Battery (green line in Figure 1) prior to the start of the dosing. Within two weeks, the SVI trends between the North and South Aeration Batteries had converged. From then onward, the South Aeration Battery showed much improved settling behavior. The improved settling in the South Aeration Battery continued to be observed almost two weeks after dosing stopped.

Settling Trends

Changes in settling volume and SVI in the North and South Trains

After two weeks, the SVI differential between the North and South train was closed from about 23% to about 8% (see
Figure 2 at left). By the end of week 3, the SVI in the South train had reached 16% less than the value in the North Train. Similarly, settling volume went from being 30% higher in the South vs. North train to being 23% lower over the duration of the test.