Ephrata Borough Authority WRRF, located in the MidAtlantic region of the United States, has been battling chronic sludge settling issues since undergoing a BNR upgrade in 2011 to meet new permit limits. During the winter months, SVI values have reached as high as 300 mL/g. During the upgrade, the facility was converted from BOD and Ammonia removal to total nitrogen (TN) and total phosphorus (TP) removal. An additional ring was added to the existing oxidation ditch increasing detention time in order meet these new permit regulations.
In spite of the upgrades, no appreciable improvement in settling was observed. Numerous efforts were made in the last 5 years to improve settleability with minimal success. In August of 2018, the facility decided to incur the additional expense of adding polyaluminum chloride (PAC) to the system. This chemical addition was moderately successful with SVI reductions of about 50% with dosing up to 70 GPD.