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 Meeting Stringent Phosphorus Limits Within Extremely Tight Footprint Constraints

 Challenge

​​​The Billerica, Mass., wastewater treatment facility needed to meet a new total phosphorus (TP) permit limit of 0.2 mg/L while fitting tertiary clarifiers within the walls of existing concrete tanks.

 Solution

​​One of the features that made the CoMag® system particularly attractive to Billerica was its small footprint. To reduce upgrade costs, Billerica needed to fit tertiary clarifiers within the walls of two existing concrete tanks. Reusing the existing tanks eliminated demolition and excavation costs. The CoMag System was ideal for this configuration because it requires signfiicantly smaller clarifiers than conventional systems to treat equivalent flow rates.  Only two 23-ft. (7-m.) circular clarifiers were needed, which easily fit in the existing concrete tanks.

 

The CoMag® system requires a smaller footprint than conventional systems to treat equivalent flow rates.  Only two 23-ft. tertiary clarifiers were needed, which fit within the walls of two existing concrete tanks, shown here.  Reusing the existing tanks eliminated demolition and excavation costs.

 Results

Initial Pilot Testing​​

In the summer of 2007, a pilot of the CoMag​® system proved its ability to meet the new TP limit with alum, polyaluminum chloride (PACL), ferric chloride or sodium aluminate coagulants.  Additionally, the pilot proved that the CoMag system could meet future permit limits as low as 0.05 g/L without polishing filters by simply increasing the coagulant dose.  


 
Full-Scale Installation Results

Since it was first installed at Billerica in 2010, the CoMag®​ system has proven to be a reliable and versatile tertiary treatment process with the capability to achieve any effluent TP target down to less than 0.05 mg/L, while also achieving significant reductions in total suspended solids (38 percent), BOD (59 percent) and other contaminants.


 
To download the full case study PDF, click here​.