QUESTION 2 Bar screen example

Dimension the following pre-treatment unit for a WWTP receiving a dry weather flow (dwf) of 24,000 m³/day (Assume that flow doubles during rain).

• A bar screen is used to remove the coarse waste. The rwf velocity in the screen channel (v) is 0.5 m/s and flow-through velocity of the clean screen (V) is 0.8 m/s.
  
  Calculate the required open screen area for reaching this screen velocity during treatment of the rain weather flow.
• Calculate the head loss of this clean screen using:
  
  hL =1C∗(V2−v2)(2∗g)
  
  The friction coefficient (C) for a clean screen is 0.7.
• The above screen is partly clogged. The maximum head loss that is allowed in the screen channel is 0.15 m. Take the impact of clogging on the friction factor into account with the calculation.
  
  Calculate the maximum clogging allowed before the screen needs to be cleaned.