City of Merced, CA

Description
The Wastewater Treatment Plant provides treatment of all wastewater collected through the sanitary sewer system.

Mission
Protect public health, the environment, and the waters of the State of California by providing appropriate treatment processes to all wastewater collected within our service area while monitoring and ensuring water discharged meets or exceeds State and Federal requirements.

Goals
* Operate and maintain the City of Merced’s Wastewater Treatment Plant in a reliable, safe, productive, and cost-efficient manner.

* Maintain compliance with State Water Resources Control Board, National Pollutant Discharge Elimination System (NPDES), and Clean Water Act permit requirements.

* Promote safety in the workplace through increased employee involvement, as well as taking full advantage of the industry’s educational and technical programs, which are in compliance with Cal- OSHA and Fed- OSHA regulations.

City of Merced Initiates Design of New Wastewater Treatment Facilities

The City of Merced has initiated a significant upgrade and expansion design project to the City’s wastewater treatment plant (WWTP). The WWTP, originally built in 1977, currently serves the City's population of over 76,000. The project is required to comply with new state and federal water quality mandates as well as expansion of treatment capacity for the City and the new UC Merced Campus. “We are very committed to improving water quality and educating the Merced community on water reuse," says John Raggio, City of Merced Director of Public Works.

As a first step, the City has contracted with ECO:LOGIC Engineering and Erler & Kalinowski, Inc. for the facility design and permitting. The City has also selected Environmental Science Association to complete the required environmental documentation. Design activities and environmental studies will be completed in 2006.

The existing WWTP can process up to 10 million gallons of wastewater per day. This project will increase the capacity to treat and dispose up to 16 million gallons per day. It will include among other things:

* Site access improvements and security

* New laboratory and administration building

* New preliminary treatment (screens, grit removal and pumping)

* Expansion of primary and secondary treatment processes

* Denitrification Basins

* Tertiary facilities (chemical addition, filtration)

* Ultra violet light disinfection

* Effluent re-aeration

* New outfall pipe to Hartley Slough

* Expanded sludge digestion facilities

* Mechanical dewatering

* Sludge digestion and drying

With the new upgrade, wastewater generated within the City, is conveyed to the City’s WWTP. The wastewater is screened, rocks and sand removed; and water is then pumped to the primary clarifiers that allow any particles in the water to settle. The water flows to aeration basins where bacteria consume organic material and secondary clarifiers are then used to settle out the bacteria. Secondary effluent is chemically conditioned, filtered, and disinfected with ultraviolet light. The treated water is then aerated prior to discharge into Hartley Slough. After final treatment, the water will also be suitable for unrestricted reuse for agriculture purposes. The waste solids, or sludge, is digested and dried so the material can be applied as soil conditioner.

Recently, the City pilot tested two potential filtration technologies that could be incorporated into the WWTP. Based on the study, the City will be able to assess required chemical coagulants, filter media, and filter size. There are several options being considered with costs ranging from $130 million to $185 million and would represent the single largest public works project the City has undertaken. The City will be developing a detailed project financing plan and will be providing regular updates to the community through flyers, public meetings, and newspaper articles.

As stated by the City Engineer, David Tucker, “A significant portion of California’s population growth is expected to find its way into the San Joaquin Valley and Merced, and like many other Valley Communities, we must be prepared to respond to the challenges and changes that population growth pressures will bring to this area, especially water quantity and water quality.”