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Wastewater Treatment

Wastewater from more than 10,000 homes and businesses reaches the plant through 100 miles of underground pipeline. Where the water cannot flow by gravity, it is pumped by four strategically placed pump stations. An average of 2 million gallons per day reach the treatment plant.
Use the guide below to go through the processes:

plant diagram
  1. Headworks: The wastewater passes through a conveyor belt screen that removes plant influent and large debris.
  2. Clarifiers: The clarifiers slow the flow of water, allowing heavy particles to settle to the bottom of the tank. The solids or sludge are pumped to the sludge thickener and the digester (8) for further treatment.
  3. Biofilter: The biofilter continually distributes water over rocks that provide a home for microorganisms. The microorganisms break down dissolved organic material into simpler inorganic chemicals. The biofilter conditions mimic the environment of rocky streams and ocean coasts.
  4. Biotower: Bacteria living in the biotower convert ammonia in the water to a form of non-toxic nitrogen.
  5. Sandfilter: The sandfilters remove any remaining particles that might interfere with the next step: the ultraviolet (UV) disinfection.
  6. UV Disinfection: High intensity Ultra Violet light is used to inactivate any remaining bacteria to prevent spread of harmful diseases before final discharge into the marsh.
  7. Outlet to Marsh: The water discharges to the marsh, providing wildlife habitat. Since wastewater provides organic and inorganic nutrients, it contributes to the basic food chain of the marsh.
  8. Sludge Digestion: Sludge removed from the clarifiers is pumped into digesters where bacteria break down solids and produce methane gas. The methane gas is recovered to heat the digester.
  9. Sludge Processing: Solids from the digesters, which are now called biosolids, are dried in a centrifuge before being used as alternative daily cover at a landfill.


Sand Filter and Ultraviolet Disinfection

The Mt. View Sanitary District operates a Dynasand® filter system. The system removes solids from the secondary effluent achieving a clarity that allows downstream disinfection with ultraviolet light. The Dynasand® filter is a continuous-backwash, upflow, deep-bed, granular-media filter system. The filter media is continuously cleaned by recycling the sand internally through an airlift pipe and sand washing. The cleansed sand is redistributed on top of the sand bed, allowing for continuous, uninterrupted flow of filtrate and reject (backwash) water.

The Mt. View Sanitary District utilizes the Trojan UV 3000™disinfection system. The first POTW (Public Owned Treatment Works) operated in Northern California to use ultraviolet light for disinfection on a full scale operation, MVSD has been able to totally eliminate the use of gaseous chlorine, sulphur dioxide and ammonia, all Acutely Hazardous Materials (AHMs), which can be toxic to both humans and wildlife. The Trojan system uses the same UV found in sunlight, but in a concentrated dose, to destroy harmful microorganisms present in the wastewater. The elimination of AHM’s from the plant premises has increased staff and public safety while decreasing District liability.

What is ultraviolet light?
UV light is defined as electromagnetic radiation having a wavelength less than that of visible light (400 nm) and greater than that of X-Rays (100 nm). The unit of wavelength is a nanometer (nm), equal to 10-9 meters. The optimum UV wavelength for germicidal effect is 253.7nm, which is found only in small amounts in the solar radiation because energy at these wavelengths is absorbed by the atmosphere.

The source of UV energy that MVSD utilizes is low pressure mercury arc lamps. The radiation is generated by striking an electric arc through mercury vapor. Discharge of the energy generated by excitation of the mercury results in the emission of UV light.

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