BIOLOGICAL DENITRIFICATION

PROCESS

PROBLEM

While nitrate is essential for all living systems, at concentrations above 10 mg/L it can pose a serious human and livestock health hazards, especially to infants.  Nitrate concentrations in surface and ground waters have markedly increased worldwide over the last decade. This accumulation of nitrate in the environment results mainly from non-point source runoff from the over-application of nitrogenous fertilizers, from poorly treated human and animal sewage and many industrial processes including paper and munitions manufacturing. Over two million people, mostly in rural communities, have been exposed to higher than acceptable nitrate levels.  Compounding this problem, nitrite is generally difficult to remove using conventional lime, softening and filtration water treatment technologies.

SOLUTION

Biological denitrification process provides an economical method to treat nitrate contamination at the source.  The process removes nitrate to low levels (<5.0 mg/L), using short treatment times (~5 hrs), at low treatment costs (<$0.10/1,000 gallons).  The process can be used in situ and in combination with other metal and inorganic removal processes to minimize treatment system costs.

BIOLOGICAL DENITRIFICATION  PROCESS BENEFITS

• Uses naturally-occurring bacteria reduce nitrate to N₂ at near neutral solution pHs

• Nitrate can be removed simultaneously with metal contaminants

• Uses economical low-maintenance bioreactor systems and short retention times

• Uses balanced (C:N:P:S:vitamins:trace elements) economical nutrients (<$0.10/1,000 gal)

• Field proven with both mining and agricultural wastewaters

• Requires minimal or no solution pretreatment

VALIDATION

·      Full-scale biological denitrification process implementations have been achieved at nutrient costs below $0.10/1,000 gallons in pilot- and full-scale pump and treat and in situ applications

·       The modular biological denitrification process has been successfully applied in stand-alone and complete water treatment system configurations to also remove selenium, cyanide, uranium and other metals

·       Process nitrate-N concentrations up to >1250 mg/L have been treated to discharge criteria using 18 hr retention times

·       Full-scale treatments for mixed contaminant wastewaters have been implemented at flows rates up to 450 gpm

TECHNOLOGY COMPARISON

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