Wastewater Department

The BVCSD WWTP is a Tertiary Treatment Grade 3 Wastewater Treatment Plant with a designed average daily flow (ADF) of .25 MGD (million gallons a day).  Tertiary wastewater treatment is an advanced level of treatment that goes beyond the primary and secondary treatment processes commonly employed in standard wastewater treatment plants.   Currently, the BVCSD’s annual ADF is approximately .093 MGD.  

The BVCSD WWTP has three certified wastewater operators on staff to maintain compliance with regulations and operations dictated by the State and Regional Water Quality Control Board.  The BVCSD WWTP currently serves 485 active sewer lateral connections.  Additionally, the BVCSD Wastewater Department maintains seven miles of collection system piping and one sewer lift station.  The collections system allows the raw sewage to reach the WWTP for treatment. While primary and secondary treatments are effective at removing solid particles and a significant portion of organic matter, tertiary treatment focuses on further reducing the remaining pollutants to produce high-quality effluent that can be safely discharged into the environment or reused for various purposes.

The Treatment Process

Step 1 - The Headworks

The headworks is the first process of the BVCSD WWTP.  It utilizes a manually cleaned/raked bar screen to remove debris in the sewage such as, roots, rags, cans, and other large objects that might be in the incoming sewage (influent).  The bar screen is cleaned daily.  Debris that is removed at the headworks is allowed to dry and then disposed of properly.

This step helps protect equipment downstream from damage and prevents clogging in subsequent treatment stages. This is why we run the "Trash It, Don't Flush It" educational campaign each year.

Step 2 - Biological Treatment

From the headworks, the wastewater enters the biological treatment stage. The oxidation ditch or aeration tank is a secondary biological process that creates a stable environment for microorganisms or “bugs” to live and begin stabilizing organic matter, converting it into a form that is easier to remove from the wastewater.   The "bugs" are aerobic bacteria that need oxygen available in the water to function properly.  The water inside of the oxidation ditch at this point is referred to as “mixed liquor” or “activated sludge”.  A rotating brush partially submerged in the oxidation ditch aerates the mixed liquor providing the oxygen needed for the bugs to live and work.

Step 3 - Secondary Clarifier

The next step in the BVCSD WWTP treatment process is the Secondary Clarifier (Clarifier).  The clarifier acts as a settling tank for the mixed liquor/activated sludge.  When the mixed liquor enters the clarifier, the solid particles begin to separate from the water and settle to the bottom of the tank.  The water flows over a weir into a trough and on to the next stage in the system.  Bugs remain in the settled solids in the bottom of the clarifier.  At this point the bugs are pumped or “returned” from the bottom of the clarifier back to the aeration tank to continue breaking down organic matter and a small portion is pumped or “wasted” to sludge drying beds for disposal.  The volume of bugs returned or wasted is determined by internal lab testing and calculations conducted by the Wastewater Operators.

Step 4 - Balancing Tank

The balancing tank acts as an effluent (treated wastewater) holding tank for the tertiary stages that follow.  The balancing tank is level controlled by float switches.  When the water level in the balancing tank reaches the upper float switch it energizes pumps to deliver the effluent to the next process in the system.  When the pumps lower the water level down to the lower switch, the next process shuts off.  This cycle repeats itself daily.  A small dose of sodium hypochlorite (liquid chlorine) is also injected into the effluent in the balancing tank to begin disinfecting the treated wastewater.

Tertiary Treatment

Step 5 - Flocculation Tank

From the balancing tank, the treated effluent is pumped to the flocculation tank. Here it is injected with Aluminum-sulfate (alum).  The alum acts similarly to glue. The alum and gentle mixing in the tank allow the smaller particles that remain in the effluent to combine and stick to each other creating larger particles. This allows the next stage of treatment to capture and remove the particles more effectively.  The amount of alum utilized during this step again is determined from internal testing and calculations performed by the Wastewater Operators.

Step 6 - Filtration

The BVCSD WWTP has two sand filters for removing particles from the effluent leaving the flocculation tank.  The effluent enters the underside of the filter, flows upward through the sand filter media, and discharges into a collection channel. The channel directs the flow to the next stage of treatment.  A sampling tube also allows a small portion of effluent to a testing meter to make sure the effluent meets required clarity standards of the operational permit.  To prevent the filter from “plugging up”, air is injected into the media. The air allows the sand to be fluffed and cleaned while operating, preventing the particles from plugging the inlet side of the filter, avoiding back-ups in the system.As it percolates through the sand, several physical and biological mechanisms contribute to the removal of impurities:

• Straining: The sand particles act as a physical barrier, straining out larger suspended solids and particles from the water. These particles get trapped in the void spaces between the sand grains
• Adsorption: Some fine particles and organic matter may adhere to the surface of the sand grains due to electrostatic forces or Van der Waals interactions. This adsorption process helps in the removal of certain contaminants.
• Biological Activity: Within the sand filter bed, a microbial community develops on the sand surface and within the sand pores. These microorganisms contribute to the degradation of organic matter, breaking down complex compounds into simpler forms.

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Step 7 - Disinfection‍

To eliminate pathogens and harmful microorganisms, the treated wastewater is disinfected using techniques like chlorination. This step ensures the production of safe and environmentally-friendly effluent. Upon entering the chlorine contact chamber from the sand filter, sodium hypochlorite is again be injected into the effluent.  By design, the Cl2 Contact Chamber, through a series of channels, allows the effluent to have adequate contact time with the sodium hypochlorite for disinfection.  Additional sampling and testing is conducted from this site to ensure permit compliance with the State and Regional Water Quality Control Boards.  The effluent from the CL2 Contact Chamber flow to the next step in the BVCSD process, the effluent holding pond.

Step 8 -De-chlorination & Effluent Discharge or Reuse

De-chlorination can be achieved by allowing the treated wastewater to undergo natural de-chlorination through exposure to sunlight and air. At this point, no further treatment is needed for the effluent to be utilized as a beneficial re-use to the environment.  In the warmer months of the year the treated effluent is directed and re-used to irrigate turf (grass) the Bear Valley Golf Course.  When the grass on the golf course cannot meet the demand of the water due to colder and wetter months, the effluent is discharged down Sycamore Canyon.

Benefits of recycled water:

There are several benefits to recycled water.  Specific benefits to the Bear Valley community are fuller lake levels.  When the treated effluent is utilized as irrigation from the BVCSD WWTP it allows less water to be drawn from the lakes to full-fill the irrigation needs of the golf course.  Another benefit relating to recycled water use and lake levels is that it helps preserve ground water levels.  In the drier seasons when rain and snow run-off cannot fill the lakes of Bear Valley, water is pumped out of the ground from non-potable wells to help fill the lakes.

Sludge Treatment:

Throughout the treatment process, sludge is continuously generated and collected. This sludge undergoes further treatment, such as anaerobic digestion, dewatering, and  drying to reduce its volume and stabilize it for proper disposal.

Biosolids are collected and hauled off site by a 3rd party. These biosolids can be further processed and utilized in various beneficial ways, providing an environmentally sustainable approach to waste management. It's worth noting that the use of dried biosolids is subject to regulations and guidelines to ensure proper handling, application, and adherence to environmental and public health standards.

Uses for Biosolids

1. Agricultural Fertilizer: Dried biosolids can be used as a nutrient-rich organic fertilizer in agriculture. They contain valuable nutrients like nitrogen, phosphorus, and potassium, as well as micronutrients and organic matter. Applying dried biosolids to agricultural land helps replenish soil nutrients, improve soil structure, and enhance crop productivity. The biosolids are typically spread or incorporated into the soil, following established guidelines and regulations to ensure proper application rates and minimize any potential risks.
2. Land Reclamation and Landscaping: Dried biosolids can be utilized for land reclamation projects, such as restoring degraded soils or reclaiming mine sites. They can improve the soil quality, enhance vegetation growth, and stabilize the land. Dried biosolids are also used in landscaping applications, such as turfgrass and ornamental plant production, to enrich soil fertility and support healthy plant growth.
3. Composting and Soil Amendments: Dried biosolids can be composted or used as a component in composting processes. When combined with other organic materials, such as yard waste or food scraps, the biosolids contribute valuable nutrients and organic matter to the compost. The resulting compost can be used as a soil amendment, providing improved soil structure, increased water-holding capacity, and nutrient enrichment for gardening, horticulture, or landscaping purposes.
4. Energy Generation: Dried biosolids have the potential to be utilized as a renewable energy source. They can be used as a feedstock in anaerobic digestion facilities to produce biogas, a mixture of methane and carbon dioxide. Biogas can be used for energy generation through combustion in engines or turbines, providing heat and electricity. The byproduct of anaerobic digestion, known as digestate, can also be further processed and used as a nutrient-rich fertilizer.
5. Construction Materials: In some cases, dried biosolids can be used in the production of construction materials. They can be mixed with cement or clay to create bricks, tiles, or building blocks. The incorporation of dried biosolids into these materials can improve their strength, thermal insulation properties, and reduce their environmental impact.
6. Research and Development: Dried biosolids are often utilized for research and development purposes to explore innovative ways of extracting valuable resources or to investigate their potential in new applications. Researchers and scientists are continuously studying ways to maximize the beneficial use of biosolids while minimizing any potential environmental or health risks.

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