Improving local air quality is a priority 365 days per year. Since its successful inception in 1995 the Odor Control Program (OCP) has a number of operational procedures which are repeated each year but also focuses on special odor sources that need improvement. During 1998 two projects will receive special attention, the Mill Street biofilter, and the four remaining surface aerators in the aeration tanks.

Mill Street Biofilter

The biofilter was developed in the early 1980's and began operation in 1988. At that time the facility was designed with state of the art technology to treat a large portion, but not all of, the odorous sewer gases at the Mill and Locus Street intersection. Odorous air not drawn into the facility can be released into the local community through openings in catch basins and manhole covers.

The facility was upgraded after comparing current biofilter design and operation against those utilized in the early 1980's. The biofilter media was removed and replaced using a new blend of materials. The air distribution system was removed, upgraded, and replaced. Finally a larger motor was installed on the blower to increase the volume of air passing through the facility for treatment.

These changes should improve air quality in the local community around the Mill and Locus Street intersection. 

Replacement of Surface Aerators

The aeration tanks began operation in 1977 with 28, 100-horsepower surface aerators to supply oxygen for biological treatment of the wastewater. Recently a $10 million project replaced all but four of the aerators with a new, cost effective, fine bubble aeration system involving about 40,000 air diffusers situated on the bottom of the aeration tanks. The first aerator was left in each aeration tank to allow a long-term, beneficial mode of process operation to continue. As local air quality standards continue to increase, the excessive turbulence, and resulting odors, from those units needs to be reevaluated.

This summer each of the four remaining surface aerators will be replaced with four submersible pumps which will produce very little turbulence. The upgrade will cost about $250,000 and should be completed by the Fall. Benefits from the upgrade include: energy cost savings, improved process operation, improved mixing, and a reduction in surface turbulence which will reduce the release of odors.