Wastewater Clarification
Clarification is a critical step in both municipal and industrial wastewater treatment. It is the removal of suspended solids and other insoluble contaminants through a settling or floatation process. Depending on the type of wastewater, the treatment processes may have several clarification steps: primary, secondary and tertiary. The wastewater characteristics and chemical treatment process will determine whether settling or floatation are the best technology.
Primary Wastewater Clarification
Primary Gravity Clarifier – Municipal Wastewater Treatment Plant
Primary wastewater treatment is generally the removal of suspended solids and oil & grease. Depending on the nature of the suspended solids, BOD (Biochemical Oxygen Demand) may be removed with primary clarification. Primary clarification is performed with and without the addition of chemicals to aid the process. Chemicals used are pH control chemicals, coagulants and flocculants. Gravity or Flotation Clarifiers are used for primary clarification. Gravity clarifiers are designed allow the suspended solids to settle to their bottom. They include Inclined Plate Clarifiers (IPC), Round and Rectangular clarifiers that incorporate bottom rakes to remove solids. A Dissolved Air Floatation (DAF) clarifier separates the suspended solids by floating them to the surface followed by skimming the solids off.
Primary Inclined Plate Clarifier – Industrial Wastewater Treatment Plant
Secondary Wastewater Clarification
Secondary wastewater treatment is generally the removal of suspended solids or phosphorus. It usually follows a biological treatment process that converts soluble BOD and organics into an insoluble form (called biomass). The biomass consists of living and dead microorganisms (bacteria) along with their waste material. The secondary clarification process uses Gravity or Floatation Clarification to separate the Solids. Depending upon the biological process some of or none the biomass is returned to the biological treatment process. An activated sludge biological treatment system returns some of the clarified solids (biomass) back to aeration basin. The clarified wastewater is typically discharged. Chemicals typically used include coagulants, flocculants and phosphorus precipitants.
Secondary Dissolved Air Floatation Clarification – Biological Solids Food Processor
Tertiary Wastewater Clarification
Tertiary clarification is sometimes used for final effluent polishing. Most often it is used to remove phosphorus or suspended solids as part of a biological treatment process. The tertiary clarification process uses Gravity or Floatation Clarification. Depending upon the biological process some of or none the biomass is returned to the biological treatment process. The clarified wastewater is typically discharged. Chemicals typically used include coagulants, flocculants and phosphorus precipitants.
Stainless Steel Gravity Clarifier at Stone Cutting Facility
