Raw Wastewater Filtration to Increase Organic Removal Efficiency and Achieve Significant Electrical Savings

Raw Wastewater Filtration Could Result In Significant Electricity Savings

Kennedy/Jenks Consultants


Irvine, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

Project results have shown that primary filtration consistently removed 75-85 percent of suspended solids and 40-63 percent of organics from screened raw wastewater. Based on the 18-month demonstration at Linda County, full-scale primary filtration is a feasible replacement of primary clarification. Primary filtration is expected to have estimated annual energy savings ranging from $22,000 to $35,000 per million gallons per (mgd) day of facility average capacity. The project has also shown wastewater capital costs can be reduced in the range of $640,000 to $1.1 million per mgd of facility average capacity. The capital cost savings come from the 60-70 percent reduction in primary treatment footprint and increased secondary treatment capacity.[br /]
[br /]
Project team will continue to market this technology to interested water utilities.

The Issue

The secondary biological wastewater treatment process is usually the most energy intensive process of a wastewater treatment plant (WWTP). The most common secondary biological treatment method is called the "activated sludge process", and is accomplished by aerating wastewater. On average the activated sludge process accounts for 40 to 60 percent of total WWTP electricity consumption. The electricity used for aeration is proportional to the organic load entering the aerated activated sludge process. Achieving a higher degree of removal of the organic load before the aerated activated sludge process provides a breakthrough opportunity to reduce electricity consumption.

Project Innovation

This project is extending the application of Cloth Depth Filters (CDF) to raw wastewater filtration at three wastewater treatment plants in California. The CDF concept replaces the current technology of primary clarification by offering the following advantages: (1) substantially higher removal of organic load resulting in significantly lower aeration electrical power demand, and (2) smaller footprint requirements both for primary and secondary treatment steps. CDF employs established principles of gravitational forces which results in minimal operational and maintenance complexities. The unique attribute which offers promise for CDF technology in raw wastewater is the vertical placement of the filter medium and flow direction of this filtration process. Unlike prevailing filtration systems, the vertical orientation of the filter medium permits heavy solids to settle within the tank.

Project Benefits

This project uses cloth depth filtration (CDF) for raw wastewater filtration to reduce the organic load on the secondary wastewater treatment step, which is the most energy intensive step in the treatment process. This breakthrough treatment using CDF has never been tested nor implemented at wastewater treatment plants. [br /]
[br /]
Project results from the 18-month pilot demonstration at Linda County showed that a full-scale primary filtration using CDF technology is a feasible replacement of primary clarification process in the treatment of wasterwater in California.

Lower Costs


The project could reduce the cost of wastewater plant operations within California by reducing wastewater treatment plant electricity consumption (CPUC Metrics 1f and 1h). Assuming 10 percent market implementation by the wastewater treatment sector, this could result in annual savings of 34 million kWh and $3.6 million in reduced operating costs.

Contact the Team