Symptoms

• High TSS content in the secondary clarifier effluent

• Floating sludge presence in the secondary clarifier

Main causes

• Denitrification process in the secondary clarifier

Investigations and analyses

• Assess the nitrification process measuring ammonia, nitrite and nitrate concentration in the effluent of the aeration tank

• Evaluate the HRT in the aeration tank

• Evaluate the sludge retention time in the clarifier

Remedial actions

• Reduce SRT

• Reduce sludge retention time in the clarifier