Plant Operations

PLANT OPERATIONS

FEBRUARY 2010

During 2009, the project team completed full evaluations of several key issues, including:

• the Plant’s ability to handle future flows and loads relative to population growth projections and water conservation strategies;
• potential regulatory requirement changes;
• current and near-future technology options for liquids and solids treatment; and
• optimization of energy production and use.

The project team narrowed the options for liquids and solids treatment by requiring each option to pass a “fatal-flaw” analysis based on anticipated future regulatory requirements and proven feasibility at other large wastewater treatment facilities.

Liquids – The project team confirmed that given the Plant’s adequate capacity, the primary and secondary steps of the current liquids treatment process are still the most cost effective and efficient treatment technologies. As a result, future investment on liquids treatment in these first two steps will focus on repair and rehabilitation of the existing infrastructure. For the tertiary and disinfection phases of liquids treatment, switching to new technologies is recommended. The type of technology and extent of related investment for these last two steps may depend on future requirements of recycled water and future regulations to limit the amount of “emerging pollutants” – chemicals that the Regional Water Quality Control Board may decide to begin monitoring and limiting.

Solids – The Plant faces a number of challenges in the area of solids treatment and disposition:

• Cost and Land Use – The least costly approach to solids drying is lagoon thickening and open-air drying, but this is also the most odorous and land-intensive approach. This process uses about 800 acres of Plant lands, which is not believed to be the land’s highest and best use. However, any new option will require significant capital investments and higher operating costs.
• Infrastructure Condition – Currently five of the sixteen digesters are out of service due to aging infrastructure. Advances and current developments in digestion technologies over the last decade present unique opportunities to further maximize energy output from the digesters.
• Landfill Closure and Regulatory Changes – Landfills nationwide are closing and wastewater facilities are faced with dwindling options for biosolids disposal or reuse. Further regulatory requirements could ban disposal or reuse at landfills in the next few decades. Newby Island Landfill currently accepts the Plant’s biosolids for reuse to cover garbage and is slated to close within the next 20 years.

Energy – All treatment options were analyzed with the goals of maximizing renewable energy production while minimizing energy use. Increases in energy production with solar and other renewable technologies combined with improved efficiency in digester gas collection and combustion will help the Plant achieve the goal of becoming energy self-sufficient by 2020. Planning for energy-related projects is already underway, including digester upgrades, a grease receiving station, optimization of the aeration process to reduce energy usage, advanced automation of the treatment processes, and installation of fuel cells and solar energy generators as renewable energy sources. Future investments in the areas of energy production and energy conservation are expected to be significant but are likely to yield higher returns on investment and may possibly offset other Plant operating expenses.

Technical Advisory Group Convened in October 2009

On October 1, 2009, the project’s Technical Advisory Group (TAG), composed of wastewater and energy experts, met for the second time to review the project team’s planning assumptions, validate the approach, and provide additional insights based on their broad national and international experience. Outcomes of the October meeting included:

• Project projections, planning parameters, strategy for managing peak flows, and depiction of future regulatory requirements are on course.
• Existing tertiary treatment filters must be replaced.
• As is the case with treatment plants nationwide, our Plant needs to consider a major investment in biosolids treatment.
• Pilot testing is essential to adapting new technologies to the specificities of our facility and stands as the best insurance against operational failure and wasted financial investment.

QUESTIONS? Contact Project Manager Kirsten Struve at kirsten.struve@sanjoseca.gov or 408-945-5180.  

 www.sanjoseca.gov/esd/plantmasterplan

PLANT MASTER PLAN GOALS

• Operational – result in a reliable, flexible Plant that can respond to changing conditions
• Environmental – improve habitat and minimize impacts to the local and global environment
• Economical – maximize economic benefits for customers through cost-effective options
• Social – maximize community benefits through improved aesthetics and recreational uses