Feb 26, 2016

Feb 26, 2016

Feb 26, 2016

# Types of Grit Chambers in Waste Water Treatment

/ On: Apr 28, 2017 /

The objectives of Grit Chambers are:

1. Protect moving mechanical equipment from abrasion and abnormal wear
2. Reduce formation of heavy deposits in pipelines, channels and conduits
3. Reduce the frequency of digester cleaning caused by excessive accumulation of grit

## Types of Grit Chamber

### 1. Horizontal flow (Rectangular or square) (configuration type)

#### Designing a Rectangular horizontal flow type grit chamber:

• Cross-sectional area, Ax = (Qdesign / Vh) for each unit (Vh ≈ 1 ft/sec), depth ≈ 3-5 ft
• Assuming (tD = 1-2 minutes), determine the length L = Vh * tD (Add 10% additional)
• Check the SLR (1200-1700 m3/m2-day) and Vs (≥ 0.01 m/sec). Grit produced is about 1.5 ft3/ML of wastewater flow. Add to depth {1ft FB + grit}

### 2. Aerated Grit Chamber

#### Basic Info

• Air is introduced along one side of a rectangular tank to create a spiral flow pattern perpendicular to the flow through the tank.
• If the velocity is too great, grit will be carried out of the chamber; if it is too small, organic material will be removed with the grit.

• Normally designed to remove 0.21-mm-diameter or larger, with 2-5-minute detention periods at the peak hourly rate of flow

• Air diffusers are located about 0.45 to 0.6m above the normal plane of the bottom.

#### Designing an Aerated grit chamber:

• Assume a “tD” (3-4 min), determine the volume of the basin.
• Assume a depth (D = 08-15 ft), determine the surface area of the basin. And check the SLR (1200-1700 m3/m2-day)
• The amount of grit produced is about 1.5 ft3/ML of wastewater flow. Add suitable depth from grit and free board.
• Calculate the amount of air required (0.2-0.5 m3/min/m length of the tank)