How does secondary water treatment work?

Secondary Treatment The secondary stage of treatment removes about 85 percent of the organic matter in sewage by making use of the bacteria in it. The principal secondary treatment techniques used in secondary treatment are the trickling filter and the activated sludge process.

What does a secondary clarifier remove?

The Secondary Clarifiers are identical to the Primary Clarifiers; materials in the wastewater sink and float and rotating arms remove this material from the water. After treatment in the Secondary Clarifiers, the wastewater is now ready to be released to the Napa River, or further treated to produce recycled water.

What is secondary clarification in wastewater treatment?

Secondary clarification follows the biological treatment process with the main goal of returning activated sludge. During the secondary clarification process the biomass from microorganisms settles to the bottom in the form of activated sludge.

Why is a secondary clarifier needed after an aeration tank?

The sludge settling to the bottom of the secondary clarifiers contains the microorganisms from the aeration tanks. These microorganisms are needed to clean the wastewater. By recycling the ones that have been removed from the clarifiers, the concentration of microorganisms can be maintained.

How do clarifiers work?

The clarifier works by permitting the heavier and larger particles to settle to the bottom of the clarifier. The particles then form a bottom layer of sludge requiring regular removal and disposal. Clarified water then proceeds through several more steps before being sent for storage and use.

What is removed during secondary treatment?

Secondary treatment removes the soluble organic matter that escapes primary treatment. It also removes more of the suspended solids. Removal is usually accomplished by biological processes in which microbes consume the organic impurities as food, converting them into carbon dioxide, water, and energy…

What happens in secondary treatment plant?

During secondary treatment, biological processes are used to remove dissolved and suspended organic matter measured as biochemical oxygen demand (BOD). These processes are performed by microorganisms in a managed aerobic or anaerobic process depending on the treatment technology.

Why does sludge float in secondary clarifier?

Denitrification – small nitrogen gas bubbles float the sludge in the clarifier creating floating sludge chunks with small bubbles entrapped. Fats, Oils & Grease – simply put, FOG floats on water. When entrapped in floc, excessive grease or oil can cause floating biomass.

Why is secondary clarifier important?

The function of the secondary clarifier is to separate the activated sludge solids from the mixed liquor. These solids represent the colloidal and dissolved solids that were originally present in the wastewater. In the aeration unit they were incorporated into the activated sludge floc, which are settleable solids.

How do I lower the sludge in my aeration tank?

Floating-sludge clumping due to septicity may be remedied by maintaining dissolved oxygen at a minimum level of 1.0 Mg/L, along with making sure adequate mixing is occurring in the aeration tank.

What do clarifiers do in water treatment?

Clarifiers are settling tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. A clarifier is generally used to remove solid particulates or suspended solids from liquid for clarification and (or) thickening.