Technology Details
At present there are over 30 full-scale BNR WWTPs using BIOGRADEX technology with flows from under 500 m3/d up to 35,000 m3/d in service. Feasibility designs for 300,000 m3/d applications indicate BIOGRADEX technology to be very cost effective at this size as well. Designs completed for plants of 50,000 - 60,000 m3/d flow per train indicate this technology will also be effective for very large BNR WWTPs.

The most sophisticated leading-edge suspended growth activated sludge BNR Processes used with BIOGRADEX technology can also benefit from substantially reduced land requirements, and lower construction and operating cost with this new technology.

For conventional BNR WWTPs, denitrification typically occurs also in the secondary clarifiers settled sludge. Water in the sludge is also normally Nitrogen Saturated. This situation produces micro nitrogen bubbles that are released and trapped in the settled sludge floc structure. As more nitrogen is produced, more and more micro bubbles are enmeshed and that causes the sludge to be bulky, stop settling / thickening and produce scum on clarifiers.

In contrast for BIOGRADEX technology WWTPs, MLSS degassing reduces 100 % saturation of dissolved nitrogen conditions down to the range of 50-75% saturation as the MLSS enters secondary clarification. The sludge can then operate in stable, nitrogen non-saturated conditions, is not bulky and can continue to settle and thicken in the clarifiers even during continuing denitrification conditions. Nitrogen released during denitrification is thus dissolved in water rather than otherwise becoming micro nitrogen bubbles enmeshed in sludge floc which contributes to high SVI conditions. The resulting thick, low SVI settled sludge even with high levels of filamentous organisms in the MLSS, can then be recycled to Biotreatment Cells with low RAS flow and high % solids concentration. Very high RAS concentrations then allow ground-breaking high MLSS concentrations to be achieved which proportionally reduces the size of the WWTP Biotreatment tanks.

The BIOGRADEX technology MLSS vacuum degassing process also breaks up the activated sludge floc as dissolved gas micro bubbles are removed. The floc is then reformed by BIOGRADEX technology to produce floc that settles better than before degassing. The degassed sludge in the clarifier does not become bulky after settling. Also the resulting elimination of scum on secondary clarifiers helps prevent nocardia infestation which is one of the major operating risks for BNR type WWTPs.

Treatment process and operation enhancements by BIOGRADEX technology vacuum degassing of mixed liquor has been proven to achieve full-scale, ground-breaking WWTP enhancements that are unparalleled for BNR activated sludge wastewater treatment technology. A new BNR treatment benchmark has now been established by BIOGRADEX technology for cost effective, compact wastewater Biological Nutrient Removal, as well as a new standard of WWTP operational efficiencies, stability and flexibility.