INHIBITORY EFFECT OF HYDROXYLAMINE ON NITRITE OXIDIZERS

The inhibition of nitrite oxidizers by hydroxylamine was examined in batch experiments. Selective inhibition of nitrite oxidizers is important as it could be used to reduce the cost of biological nitrogen removal because the formation of nitrate is bypassed. The inhibition of nitrite oxidizers was examined at pH 7.6-8.4, nitrite concentrations of 100-1000 mg/L as N and 100- 150 mg/L of VSS. Hydroxylamine dosages of 7.0 and 8.9 mg/L resulted in complete inhibition of nitrite oxidation at pH 8.4 and 7.6, respectively. These hydroxylamine dosages also resulted in measured concentrations of 0.35 and 5.5 mg/L in solution. An inhibition model was developed as a function of free-hydroxylamine concentration and pH. The model fit the data well (R2 = 0.84-0.97). The relationship between hydroxylamine dosage/residual and other system parameters will be important to determine for application to waste water systems. The model provides a useful tool for further investigating selective nitrite oxidizer inhibition in waste water systems. Hydroxylamine can be used to complete inhibit the activity of nitrite oxidizers.