Symptoms
Quantity of grit removed higher than the normal
Dark colour of the grit removed
Mixture more doughy than the normal
Foul smell from the collected grit
Main causes
Low velocity and / or too high hydraulic retention time
Investigations and analyses
Analyse, daily, the volatile content in the collected grit
Measure the velocity corresponding to the different wastewater flow rate
Measure the air flow rate in case of aerated grit chamber
Remedial actions
If possible, reduce the number of the grit chambers working in parallel
In case of rectangular horizontal-flow grit chambers, reduce the water section or modify (reduce) the water level in the chamber by regulating the weir
In case of aerated grit chamber increase the air flow rate
Increase the velocity of roll or agitation