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Glossary of Terms
- Acid Phase Digester - The first step of the anaerobic digestion process, which stabilizes the excess solids. In this step, the solids are heated, mixed and held for a short period (1 to 2 days) for pretreatment by hydrolysis and acidification.
- Aeration Tank - A basin or tank used to degrade organic matter. Diffused air is used to assist this treatment process.
- Biological Treatment - A process that uses living organisms to stabilize and remove organic matter.
- Dewatered Cake - The dry solids resulting from the removal of excess water in the dewatering process. The dewatered cake can be stacked and stored until it is land applied.
- Dewatering - A process that removes excess water from the stabilized solids leaving the acid-gas phase digesters. At HRSD, this is accomplished using centrifuges.
- Effluent - Treated wastewater flowing out of a treatment plant.
- Gas Phase Digester - The second step of the anaerobic digestion process, which stabilizes the excess solids. In this step, the solids leaving the acid phase digester are heated, mixed and held for a longer period (10 to 15 days). The stabilization process is completed here and all of the methane gas production is also accomplished here.
- Gravity Belt Thickener - Equipment used to remove excess water from the solids removed from the wastewater.
- Influent Piping - Pipes that carry wastewater (sewage) into the treatment plant.
- Preliminary Treatment Facility - Initial treatment step that can include screens, flow metering and grit removal equipment.
- Primary Clarifier - The initial settling basin, which separates the most readily settleable solids from the incoming wastewater.
- Screens - A screen or screens consisting of perforated plates placed in a flow to remove debris. The screenings are removed from the screen by mechanical means.
- Secondary Clarifier - The final settling basin, which allows for separation of solids from the flow stream. This equipment also allows for the return of solids to the aeration basins.
- Solids Holding Tank - Facility for temporarily storing solids removed from the wastewater.
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