Last but Not Least: The Tertiary Stage for Wastewater Treatment

Amanda Jones August 21 , 2019

 

Without following the wastewater treatment process and the three stages of treatment that provide decontamination, company's wouldn't be able to have reusable water that is necessary for survival. 

If you need a quick refresher about the secondary stage before moving on to the third and final stage of wastewater treatment, check out our blog - The Secondary Stage & How Vital It Is for the Wastewater Treatment Process.

The last and final stage in the process being referred to in this post is the tertiary stage. During this step, most, if not all contaminants will be removed from the wastewater. Keep reading to figure out how!

ultraPULSE Ultrafilltration System

Figure 1: A bioprocessH2O ultraPULSE Ultrafiltration Airlift System

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The Tertiary Stage:

Although this is the last step in the wastewater treatment process, it is certainly not the stage to be overlooked. In fact, it helps to provide the wastewater with the deepest level of treatment to remove any contaminants remaining from the biological treatment stage, while also providing disinfection to get rid of any dangerous pathogens. Tertiary filtration is almost always required before wastewater can be reused or discharged directly to a body of surface water (river, stream, etc.).

The tertiary stage involves a few additional steps that each have the goal of further reducing any of the organics, turbidity, nitrogen, phosphorus, metals, and/or pathogens that are still located in the wastewater.

A typical form of tertiary treatment involves removing the remaining suspended solids left behind by the secondary treatment stage.

Methods to remove solids:

  • Membranes
    • Microfiltration (0.1 to 5 micron; a typical human hair is about 50 microns)
    • Reverse osmosis (0.1 nanometers, a strand of human DNA is about 2.5 nanometers in diameter).
  • Disc filters
  • Sand filters

Another goal of tertiary filtration is to disinfect the wastewater in order to kill any pathogens. There are a few methods for achieving the required level of disinfection, but the simplest method involves exposing the treated wastewater to high levels of UV radiation. Other methods involve diffusing fine bubbles of ozone in the wastewater or dosing with chemicals such as chlorine to prevent pathogens from being discharged.

With all of the impurities discarded, the water is able to be reused or released back into the environment.

bioTRIPURE

Figure 2: The bioTRIPUREā„¢ UF Water Reuse System Produces High-Quality Effluent

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Institutional Industry Case Study:

For this Massachusetts High School, the problem involved the existing RBC system which was not capable of consistently meeting the discharge permit regulations. By creating an on-site treatment system that focused on making the water safe enough to be reused, the high school was able to have all Total Suspended Solids (TSS) removed and reduce the turbidity levels, while meeting permit regulations for direct discharge!

Click the photo below to read more about how the bioprocessH2O team was able to reduce the TSS & Turbidity levels to meet the high school's discharge permits by implementing a bioTRIPUREā„¢ Ultrafiltration (UF) System.

2013-09-09 09.06.04-037461-edited.jpgFigure 3: TSS & Turbidity Levels Were Reduced to Meet High School's Discharge Permits

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