SUBAIR Process

SUBAIR BNR/CBR Process

Biological Nutrient Removal / Continuous Batch Reactor

PROCESS DESCRIPTION

With PLC-based controls, two bioreactor tanks are operated in parallel under staggered batch operating conditions. Wastewater feed is continuous to one tank or the other during the entire batch cycle. Mixed liquor is continuously drained, by gravity, from one of the tanks to a rotary filter thickener. MLSS is maintained at 1%-2% concentration. Mixed liquor is thickened to 4-6% solids and most of it returned to the SBR tanks. Filtrate (effluent) drains to a microscreen for tertiary solids removal to meet more stringent criteria. Waste sludge, at 4-6% solids, is sent to disposal or further processing. Aeration and mixing is provided in both tanks by PEI’s SUBAIR submerged aerators/mixers.

PROCESS EQUIPMENT

1. SUBAIR Submerged Aerator/ Mixer

   • The SUBAIR is a submerged, motor driven pump, which recirculates mixed liquor, combined with air, drawn from the surface or a booster blower. The aerator discharges, at the tank bottom, through a static vane arrangement throughout the 360º arc around the mixer. Air is discharged as fine bubbles and dispersed in the high velocity discharged liquor, where it rises to the surface, transfers oxygen and induces greater mixing due to its density difference with the surround water. During the mixing-only phase (anoxic, anaerobic periods), the pump continues to provide mixing without aerating. This is achieved by simply closing a valve or turning off the booster blower.

2. TRIAD Rotating Drum Thickener

   • From the SUBAIR BNR/CBR tank(s), mixed-liquor, of 1%-2% concentration, is received by gravity, thickened to 4-6% solids and then discharged from the rotating filter thickener to the RAS/WAS return pump. The RAS and WAS is pumped back to the reactor tank(s) or to waste using a PEI progressive cavity pump.

3. ROTOFILTER Microscreen

   • The PEI ROTOFILTER Microscreen provides a positive means to remove residual TSS from the final effluent to tertiary discharge levels (<10 mg/l). This durable screening unit, using 20- 40 micron screen openings, eliminates any concern for hard to settle solids. Automated, simple operation and minimum maintenance are inherent features in this equipment.

4. Optional TRIAD Belt Filter Press

   • Thickened WAS is received and dewatered from 4-6% to 15-18% solids for final disposal. Standard features of the TRIAD Belt Filter Press include 304 SS construction, equalization tank with mixer, automated belt tracking, manual or automated belt tensioning, belt wash assembly, doctor blade and drive motors/reducers. Local control panel is typically included.