Updated: July 2002

1. Purpose

This system is a two-stage denitrification system consisting of a packed-bed reactor for aerobic nitrification and another packed-bed reactor for anoxic denitrification. Raw wastewater containing organic, ammonia, nitrate and nitrite nitrogen is passed through these two reactors in series, each charged with ceramic packing media.

2. Principle

As shown in the flow diagram, the N Contact system has a reaeration tank downstream of the above-mentioned nitrification and denitrification reactors. The function of each reactor tank is as shown in the flow diagram. When raw wastewater contains carbon source, there is no need to use methanol and the denitrification reactor is placed ahead of the nitrification reactor.

3. Characteristics

The attached-growth reactors of N Contact can retain larger amounts of microorganisms than suspended-growth reactors. Therefore, N Contact can take larger BOD loadings, and does not require any subsequent sludge separation and settling tank, which makes the N Contact system very compact. What is more, N Contact shows better protection against fluctuations in raw water quality.

4. Application

The N Contact system has been installed for the denitrification of power station composite and desulfurization wastewater, food processing wastewater and so forth.

[Examples of N Contact Performance]

                             Feed wastewater total N
Power station wastewater             300 mg/l
Food processing wastewater            50 mg/l
                              Treated water total N
Power station wastewater            < 10 mg/l
Food processing wastewater          < 10 mg/l

5. Flow Diagram