Sodium Acetate in Biological Denitrification

In biological nitrogen removal, a sufficient and available carbon source is essential for denitrifying bacteria. Sodium acetate is widely used because it is:
✅ Easily absorbed and metabolized by microorganisms;
✅ Non-toxic and safer than methanol;
✅ More stable than glucose, reducing side reactions.

Mechanism of Sodium Acetate in Denitrification

During biological denitrification, nitrate (NO₃⁻-N) and nitrite (NO₂⁻-N) are reduced stepwise to nitrogen gas (N₂). Sodium acetate provides a fast, bioavailable carbon source that supports bacterial metabolism and electron transfer:

NO₃⁻ → NO₂⁻ → NO → N₂O → N₂↑

This efficient pathway ensures complete nitrogen removal while maintaining process stability.

Dosage Calculation and Control

The dosage of sodium acetate depends on total nitrogen (TN) concentration and influent C/N ratio.

● For C/N < 4, external carbon is recommended.

● Conduct jar tests to determine the optimal dosage.

● Overdosing may increase COD; underdosing leads to incomplete denitrification.

General rule:
To remove 1 mg NO₃⁻-N, approximately 2.86 mg COD is required. For sodium acetate, around 3.5 mg per mg TN is needed.

Comparison with Other Carbon Sources

Application in Various Wastewater Types

● Municipal Wastewater: Enhances denitrification under low C/N conditions.
● Food Industry Wastewater: Provides stable and continuous carbon source.
● Industrial Wastewater: Effective for chemical and pharmaceutical effluents with high nitrogen content.

FAQ

Q1: Does sodium acetate affect sludge properties?
A1: Proper dosage has no negative effect. Overdosing may cause sludge bulking.

Q2: Which is more economical — sodium acetate or methanol?
A2: Methanol is cheaper but poses safety concerns; sodium acetate is safer and more efficient.

Q3: Can sodium acetate be used with PAC or PAM?
A3: Yes, but it should be dosed separately to prevent interaction and excess COD.