Primary Wastewater Treatment

Primary wastewater treatment techniques remove entrained and suspended solids from wastewater by various means.

Bar screen– Removes large objects such as wood, stones, rags, etc., prior to the grit chamber.

Grit chamber – Sedimentation tank designed to slow down the water flow in a wastewater treatment plant. Heavy solids, grit, and sand settle out in this chamber, preventing downstream damage to pumps, pipes, and other equipment.

Primary clarifier – Tank that provides long hydraulic retention time to provide a quiescent zone for solids to settle from an influent stream. Settled solids are removed from the tank and usually sent to anaerobic biological treatment processes, while clarified wastewater is directed to secondary biological treatment. Often these clarifiers incorporate surface-skimming devices to remove oils and greases and other floating material.

Centrifugation – The use of centrifugal force to promote accelerated settling of particles in a solid–liquid mixture.