ETP Interview Questions
Q: Why is DAP used in the aeration tank for dosing?
DAP is dosed in the aeration tank to supply Nitrogen and Phosphorus, ensuring balanced nutrient availability for microorganisms, which improves biodegradation efficiency and overall plant performance.
1. DAP stands for Diammonium Phosphate.
It is a source of Nitrogen (N) and Phosphorus (P) — essential nutrients for microbial growth.
2. Purpose in Aeration Tank:
In the biological treatment process, microorganisms degrade organic matter (BOD/COD).
For effective microbial activity, a proper nutrient balance (C:N:P ratio) is required — typically 100:5:1.
Industrial wastewater often lacks Nitrogen and Phosphorus, so DAP is dosed to maintain this balance.
3. Function of DAP:
Provides Nitrogen (NH₄⁺) → supports cell growth and enzyme formation.
Provides Phosphorus (PO₄³⁻) → essential for energy transfer (ATP) and cell structure.
Enhances biomass growth, BOD removal efficiency, and stabilizes treatment performance.
4. Result/Benefit:
Ensures healthy microbial population, stable dissolved oxygen levels, and consistent effluent quality.