How does Activated Sludge work? Referring to the above illustration: PLANT INFLUENT is the raw wastewater that arrives at the facility. This is normally about 80% domestic sewage and 20% industrial wastewater. During wet weather, groundwater infiltration can triple the facilitys normal flow of 6 million gallons per day (MGD). After screening to remove large particles, the flow is directed to one or both of the two 487,000 gallon Primary Clarifiers. Flow in these large tanks is slow enough to allow settleable matter to sink to the bottom as Primary Sludge, where it is removed to the sludge disposal system. Flow leaving the Primary Clarifiers (Primary Effluent) still has significant impurities in the form of dissolved and colloidal organic matter. Primary Effluent is combined with Return Activated Sludge and sent to the eight, 390,000 gallon Aeration Basins. Return Activated Sludge is a thin sludge containing agglomerated particles of organic solids (called floc) and live microbes. In the Aeration Basins the microbes use the dissolved and colloidal organic matter for growth and reproduction, essentially converting unsettleable matter into settleable matter. Effluent from the Aeration Basins goes to one or both of the 800,000 gallon Secondary Clarifiers. Activated Sludge settles very quickly, ordinarily settling to ½ of its initial volume within 5 minutes. This settled sludge forms the Return Activated Sludge, which is pumped back to be combined with the Primary Effluent. Excess accumulated sludge is sent to the Primary Clarifiers to be settled and removed with the Primary Sludge. Flow leaving the Secondary Clarifiers is essentially the Facility Effluent. During warm weather (May 15 to October 15) the Effluent flow is treated with chlorine for disinfection and sulfur dioxide for de-chlorination before discharge to the Tioughnioga River.
For a more complete description of the entire treatment process, click here.