The primary DAF is designed to remove gross inorganic, colloidal content as well as some hydrocarbons (identified in the analysis as Oil & Grease) which may be inhibitory to the sensitive anaerobic process. pH adjustment utilizing acid/alkali is also completed at this step in preparation for digestion.
It is chosen instead of conventional clarification because it is more efficient at removing complex hydrocarbons which are more difficult to break down in the following treatment steps.
DAF works by generating dissolving large quantities of air under pressure and releasing them into the feed stream of the DAF unit to form micro-bubbles. These micro-bubbles carry a net charge and attach to the waste material in the effluent, causing them to float.The solid particles which have been floated to the surface of the DAF tank are removed by a set of scraper blades which push sludge into a collection hopper for further processing.