Novel Hydrodynamic Separation Technology for Wastewater Treatment

Novel Wastewater Filtration without the Use of Physical Barrier Filters.

Palo Alto Research Center, Incorporated


Palo Alto, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

Due to unforeseen limitations in the pilot system, only two stages of second generation stacks (36 and 1.25 liter per minute, respectively) could be rigorously tested at the Sunnyvale wastewater treatment plant for a total of 16 hours of operation. Based on the pilot testing results, an ideal HDS system saves about 40 kWh/mgd and about $1,650/mgd/year in energy costs when compared to a conventional activated sludge plant. If an HDS system had performance similar to what was achieved during the pilot study, it would use about 220 kWh/mgd and cost about $9,335/mgd/year more to operate than a conventional activated sludge plant

The Issue

Wastewater treatment plants (WWTPs) include primary treatment consisting of clarifiers to remove settleable solids prior to biological treatment (secondary treatment). Biodegradable solids not removed in primary treatment result in greater oxygen demand in the downstream biological processes (causing increased electricity demand). Improved primary treatment performance can yield energy benefits both from the increased mass of solids sent directly to anaerobic digestion for methane (energy) production and from reduced electrical demand for biological treatment (aeration energy demand).

Project Innovation

PARC manufactured Hydrodynamic Separation (HDS) channels that separated and concentrated organic solids from primary effluent at a wastewater treatment plant. Rigorous testing occurred at the Sunnyvale Wastewater Treatment Plant for a total of 16 hours. The best performance of 70% and 63% harvest efficiencies (HE – is the mass capture rate in the concentrate stream) for the first and second stage, respectively, was documented at the beginning of testing. HE performance deteriorated during testing due to channel fouling. Cleaning the first stage channels using backflow and high pressure (20 pounds per square inch) returned HE to pre-pilot performance.

Project Benefits

The PARC project team has made significant strides in development of this promising "filter-less" filter technology, particularly in the areas of channel design (geometry and flow splits), fabrication of individual channel, and in the assembly of stacks for scalability. The results from this project will help PARC and other institutions (public or private) to further the research in the area of wastewater filtration without the need of physical barrier filters.

Lower Costs


Increased onsite biogas production results in increased electricity generation at wastewater plants in California.

Match Partners


Palo Alto Research Center, Inc.


Contact the Team