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A patented fixed film biological nutrient removal process has been successfully applied for organic oxidation,
nitrification and denitrification to raw wastewater treatment. The three-stage fixed film biofiltration treatment
process uses a DeepBed™ filter as the basic building block to achieve bio-oxidation and denitrification.
Microorganisms are encouraged to grow on the surface of gravel or sand media, providing the biological reaction.
The first stage is an up flow submerged denitrification filter (SDF™) for pre-denitrification in an anoxic
environmental using BOD from incoming wastewater as the carbon source for denitrifying the oxidized nitrogen (NOx-N)
in the recycle flow from the submerged aerated filter (SAF™). The second stage is the SAF™ bio-reactor, also in
an up flow mode that will oxidize the remaining BOD and NH4-N from the SDF™ effluent in an aerobic condition using
oxygen supplied by compressed air. The media utilized in both SDF™ and SAF™ bioreactors are coarse gravel such
that the excess biomass will be regularly sloughed off naturally without any intentional backwash requirements.
The final treatment stage is the Denite® sand filter as a polishing step to remove total suspended solids and
NOx-N from the final effluent. The three-stage fixed film bio-treatment process was successfully pilot tested at
Jiashan City, China. The two month pilot study has demonstrated that the fixed film biological treatment system will
be able to deliver a final effluent that can meet the most stringent effluent discharge standard in China. More
specifically, during the pilot study average BOD was reduced from 200 to 2 mg/L, NH4-N from 82 to 3 mg/L, T-N from
88 to 11 mg/L and TSS from 165 to non detect. A 20,000 m_/day wastewater treatment plant utilizing the three-stage
bio-treatment scheme is currently under construction and will be in operation in 2007.
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