Designing an Anoxic Tank for Livestock Wastewater Treatment

Designing an anoxic tank for treating livestock wastewater is a crucial part of wastewater treatment systems aimed at reducing nitrogen levels, especially nitrates (NO₃⁻) and nitrites (NO₂⁻), through the denitrification process. Below are the basic steps and formulas for designing an anoxic tank:

1. Determine Key Design Parameters

a. Wastewater Flow Rate (Q)

• Determine the average daily flow rate of livestock wastewater (m³/day).

b. Nitrogen Concentration (N)

• Determine the concentration of nitrogen compounds in the wastewater, usually nitrates (NO₃⁻) and nitrites (NO₂⁻), measured in mg/L.

c. C/N Ratio (Carbon/Nitrogen)

• To effectively carry out the denitrification process, an appropriate C/N (carbon/nitrogen) ratio is required. This ratio depends on the carbon source added and the nitrogen concentration.

2. Calculate Tank Volume

a. Calculate the Volume of the Anoxic Tank (V)

• The volume of the anoxic tank can be calculated using a basic formula based on the flow rate and the detention time of wastewater in the tank.

V = Q × T 

Where:

• V = tank volume (m³)
• Q = wastewater flow rate (m³/day)
• T = detention time of wastewater in the tank (hours)

Detention time (T) in an anoxic tank typically ranges from 4 to 8 hours but may vary depending on the system characteristics and nitrogen concentration.