When the state’s Central Valley Regional Water Quality Control Board handed down stricter wastewater discharge standards in 2001, it sent cities across California scrambling to meet them.
Among other compounds, the state legislated more stringent requirements for biological oxygen demand — a measure of the amount of nutrients in the water — ammonia, total suspended solids, turbidity, coliform, aluminum, iron, filtration and selenium.
“For example, our BOD limit today is 30 mg/L, and in 2017 it will be 10 mg/L,” explained Michael Lindquist, the city’s civil engineer and wastewater treatment plant upgrade project manager.
However, the most important aspect is that the city is required to provide tertiary treatment (filtration) by 2017.
For Davis, the effluent standards resulted in the city’s wastewater treatment plant rehabilitation project, set to cost around $95 million.
The cost of the project, which has been divided into two phases, will be spread out to the Davis ratepayers over the next five years through the sanitation sewer rate increases the City Council approved in 2011.
If the maximum rates are needed to fund the improvements, residents could see their bills jump from an average of about $40 per month to about $48 by 2015, according to Lindquist.
“(But) because fees are partially based on winter water use, each customer will be effected differently,” he said.
The project will mostly rework the way wastewater is treated in Davis. It should be completed by 2017 when the city’s deadline for meeting the state’s effluent standards comes up.
Construction could begin as early as this month.