Wastewater – Pretreatment and Primary Treatment
Wastewater treatment is the process of removing contaminants from polluted water. Polluted water can come from municipal, agricultural or industrial processes.This module describes the pretreatment and primary treatment stages of wastewater treatment, and how those stages affect one of the most common pollutants, high concentrations of organic waste.
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Learning Objectives
• Describe the purpose of wastewater treatment
• Describe the effects of high concentrations of organic contaminants in wastewater
• Describe the purpose of wastewater primary clarification
• List three mechanical processes used for pretreatment of wastewater
• Identify and describe the main components and process flows of a primary clarifier
• List the four functional zones of a primary clarifier
Specs
| Course Level | Intermediate |
| Languages | English, Portuguese, French, Polish |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
What are some common pretreatment processes applied to municipal effluent?
Common pretreatments include screening, grit settling and combination.
What is the primary physical process occuring in a primary clarifier?
A primary clarifier gives the solid particles in an effluent stream to settle out of the main stream by gravity.
What are the effects of discharging water with high levels of organic materials into a natural river or stream?
High levels of organic material in a stream will reduce the levels of oxygen in the water, leading to reduced fish populations.
What happens to the sludge collected in primary clarifiers.?
Depending on the makeup of the sludge from primary clarifiers, it can be sent to landfill, further broken down in an anaerobic digester, or dried and burned.
Where does treated water typically exit a clarifier?
Clarified water typically overflows and exits near the top of a clarifier.
Sample Video Transcript
Primary treatment clarifiers are large settling basins, which can be circular or rectangular. Circular basins are the most common. Regardless of the shape, clarifiers have four functional zones. One, the inlet zone provides a smooth transition of the incoming stream to the clarifier. The influent is slow to prevent turbulence and distributed evenly to the settling zone. In a circular clarifier, the feed enters vertically through a central feed pipe, expands out into a feed well and then flows radially into the body of the clarifier. The goal of this layout is to provide an even flow of water, which does not interfere with the settling process. Two, the settling zone is the main volume of the clarifier, where the water velocity is low and solids are given time to settle to the bottom.
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