Industrial: Massachusetts, USA


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Project Name:
Central Waste Treatment Facility

Massachusetts, USA

Type of Plant:

Technology Used:
Biowater Aeration - Organic Removal

Operational Since:


The Challenge

The facility’s original aeration system wastes energy due to inefficient oxygen transfer. Surface wave action and the inability to maintain a positive residual dissolved oxygen concentration are evident.


The Design

The biofilm reactor that houses the original coarse bubble aeration grid measures 18,800 gallons (71 cubic meters) and tank dimensions of 12 feet width, 25 feet length, and 10 foot side walls with an operating liquid level of 8.375 feet.  Biowater’s medium bubble aeration grid is housed in a 12 ft diameter by 14 ft wall.

Parameter    Limit/target
Design Flow 17.42 gpm (25,000 gpd or 95 m3/day)
Influent BOD5 7,000 mg/L (1,464 lb BOD/d load)
Effluent BOD5 <= 2,373 mg/L
Design Temp. 30˚C
Design SALR @ 30˚C 36.6 g BOD5/m2-day (est. 61 g COD/m2-day)
Design Removal Rate @ 30˚C 24.2 g BOD5/m2-day (est. 40.3 g COD/m2-day)


The original aeration grid provides 3.32 lbs O2 per hour with 60 connected horsepower and the Biowater aeration grid provides 2.55 lbs O2 per hour with 21 connected horsepower. Therefore, the Biowater system transfers oxygen 2.19 times more efficiently. The apparent alpha factor of the wastewater is 0.4 and the in-field oxygen transfer efficiency of each grid is 0.6 percent/foot of submergence for the coarse bubble aeration grid and 1.18 percent/foot of submergence for the medium bubble aeration grid, respectively. Standard oxygen transfer formulas were used in evaluating performance: