• 
• Japanese
• 
• IETC's Focal Area
• Waste Management
• Publications & Tools
• Meetings & Workshops
• Global Partnership on Waste Management
• Water and Sanitation
• Publications & Tools
• Meetings & Workshops
• Resources
• Publications & Tools
• About IETC
• Background and History
• Director
• Activity Reports
• Supporting Foundations
• Contact Us

3.2 Denitrification of Wastewater

Technical Description

This technology is based upon biological denitrification and thermal decomposition of the ammonium carbonate. The phases and operations of the process are neutralization of nitrate and ammonia enriched waters (waters containing NH4NO3 and NH3) with carbon dioxide (CO2), followed by biological denitrification in an anaerobic activated sludge media. During this process, pH corrections are made with the CO2, and the biomass is stirred at the same time. The organic carbon source for bacterial growth is contained within the wastewater. Subsequently, the effluent is subjected to temperatures of 90oC to 95oC, at which temperatures thermal decomposition of ammonium carbonate occurs. Gases containing ammonia (NH3), CO2, nitrogen (N2), and water vapour, may be recycled into fertilizer production where they can be converted from the calcium nitrate, Ca(NO3)2, phase into ammonium nitrate, NH4NO3.

Extent of Use

This technology is used in Romania.

Operations and Maintence

Operation of this technology requires provision of biological denitrification in a treatment system with two compartments, having an internal connection which allows the biomass to be stirred by the hydrostatic pressure differentials created by the CO2 used for pH corrections during the denitrification process, which is injected under pressure. The second element of the process is a column for ammonium carbonate, (NH4)2CO3, decomposition, and NH3 and CO2 stripping. The activated sludge portion of the treatment process, if lacking adequate organic carbon for bacterial growth, may require addition of methanol as a carbon source. The system requires specialist operating personnel.

Level of Involvement

This technology is implemented at the municipal and industrial levels.

Costs

The estimated cost of a purification plant treating wastewater at a rate of 200 m3/h is approximately $6.1 million. Approximately $5 million of this cost is incurred in plant construction.

Effectiveness of the Technology

This technology is best suited for treating wastewater flows of 200 m3/h, having a contaminant composition 5 000 mg/l NO3- and 2 500 mg/l NH4+. For wastewaters meeting these characteristics, the technology is highly efficient, and produces a treated effluent with a contaminant concentration of less than 50 mg/l NO3-. In comparison with the classic nitrification-denitrification and ammonia stripping-denitrification processes, this technology allows the elimination of the nitrification phase and the corresponding reductions in the consumption of energy, oxygen, and sodium bicarbonate (Na2CO3); the elimination of the use of sodium hydroxide (NaOH) as a free NH3 source in the stripping process; the elimination of the use of sulphuric acid, H2SO4, as a neutralizer in the denitrification process and avoids pollution of the water with sodium, Na+, and sulphate, SO42-, ions as a consequence; and the reduction of energy consumption for mechanical stirring of the biomass in the bioreactor by using CO2 pressure.

Suitability

This technology is suitable for use in industries treating wastewater contaminated with nitrogen fertilizers.

Advantages

This technology may be extended to provide for reuse of the product water and byproducts. It may also be modified to achieve heavy metal removal.

Disadvantages

No disadvantages have been identified.

Cultural Acceptability

The technology is culturally acceptable as an improved wastewater treatment technique.

Further Development of the Technology

The technology is fully developed.

Information Sources

ICPEAR (Institutul de Cercetari pentru Epurarea Apelor Reziduale - Research Institute for Waste Waters Treatment), Sos. Pandrui nr 90-92, sector 5 Bucuresti, Bucharest COD 76231, Romania, Tel./fax: ( 40-1) 410 67 16.

Table of Contents

• Brochure
• 
• 



• International Year of Forests
• 
• 



• World Environment Day
• 
• 



• UNEP Campaign
• 
•