Symptoms

• % removal lower than the normal

• Presence of suspended solids in the effluent

Main causes

• High overflow rate

• Presence of short-circuit in the clarifier

Investigations and analyses

• Measure TSS content in the clarifier inflow and outflow

• Measure HRT, overflow rate and compare with the design ones

• Check the possibility of dead zone presence and eventually evaluate with tracer test

Remedial actions

• If the trouble is caused by the high overflow rate, evaluate the possibility of realize another clarifier or equalization tank

• If the trouble is caused by short-circuit, modify the flow characteristics installing screens and enhancing the inlet and outlet distribution systems