Black River Wastewater Treatment Plant Aeration System Replacement

The City of Dunn turned to DMP to replace the Black River Wastewater Treatment Plant (WWTP) Aeration System when replacement of the 1980’s equipment was necessary to avoid major disruption of the City’s wastewater treatment process and potential NPDES permit violations. 

The Black River WWTP was constructed in the early 1980’s and last updated in 2011.  The WWTP biological process is a conventional single stage activated sludge basin with approximately 15 hours detention time at 3.75 mgd design capacity. The existing coarse bubble aeration system was installed in the early 1980’s and has reached the end of its useful life. There are numerous air leaks in the underground and in-basin piping is failing with increasing frequency. Review of the WWTP operating records show that dissolved oxygen (DO) levels are often less than 0.5 mg/L even with a relatively weak influent BOD loading.  

DMP first prepared a Technical Memorandum comparing different aeration equipment. The City ultimately selected new Hybrid Positive Displacement Blowers and Fine Bubble Membrane Diffusers.  DMP prepared an application to NCDEQ, Division of Water Infrastructure (DWI) and the City was awarded a zero-interest state loan.