8 Reactors for Water Treatment

Reactor

the place where a physical process, chemical reaction, or biological reaction is carried out

Types of reactors

• Tanks

• Vessels

• Lagoons

• Mixing chambers

• Pipes

Batch Reactor

• Reactants added at the beginning of the incubation time

• Stirring or mixing (maybe)

• Concentration of reactants changes over time

• Example: BOD test; biological wastewater treatment

Completely Mixed Stirred Tank Reactor

• Liquid or slurry continuously pumped through

• Concentrations are uniform throughout the reactor

• Example: Chemical flocculation of water; biological treatment of wastewater

Plug Flow Reactor

• Liquid or slurry continuously pumped through

• Flow moves through as a discrete “plug” with no/little longitudinal mixing

• Concentrations vary along the length of the reactor

• Example: Chlorine contact chambers; biological treatment of wastewater

Hydraulic Retention Time (detention time) equation

HRT = V / Q

Types of basins

• Rectangular sedimentation tanks

• Circular sedimentation basins

• Flocculator clarifier

Horizontal flow-through velocity Equation

V = Q / A (cross-sect)

Weir Loading Equation

Weir loading = Q / weir length (perimeter of circle or length of effluent channel)

Overflow rate equation

Vo = Q / A (surface)

Velocity of water through the screens (water treatment)

< 3 fps

Velocity of wastewater through screens

< 2.5 fps