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Grit transport though the grit chamber

Symptoms

  • Rapid abrasion of moving mechanical equipment downstream the grit chamber

  • High inert content in the biological aeration tank

  • Quantity of collected grit smaller than normal conditions



Main causes

  • High velocity and / or too short hydraulic retention time



Investigations and analyses

  • Measure inorganic suspended solids inflowing and out flowing the grit chamber at different wastewater flow rates

  • Measure the velocity corresponding to the different wastewater flow rates;

  • Measure the air flow rate in case of aerated grit chamber



Remedial actions

  • In the rectangular horizontal-flow grit chamber, increase the frequency of grit removal in order to increase the available water section

  • Reduce the velocity of roll or agitation

  • Increase the number of the grit chamber

  • Reduce air flow rate in case of aerated grit chamber

  • Replace the pump

  • Modify the solids removal system upstream

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