Updated: July 2002

1. Purpose

As odor public nuisance becomes a serious social problem, it has become necessary to take more intensive countermeasures against odor in all fields. The methods which have been conventionally adopted include"Direct combustion method,""Chemical washing method,""Absorption method,""Water washing method,"etc. However, all these method requires consumable materials, resulting in increased operating costs for chemicals, electric power charge, etc.
The biological de-odoring method in which the odor is removed by the function of microbes is a de-odoring method using the dispensation of Nature itself. It can be said to be an economical method which requires limited operating cost and provides excellent de-odoring performance.

2. Performance and Characteristics

Linear velocity (LV): 0.1-0.3 m/s
Contact time: 7-20 s
Number of stages: 2 stages
Filling material: Porous ceramic, resin

Example of de-odoring effect (sewage sludge base odor)
Odor intensity: Approx.4

Treatment effect
Hydrogen sulfide removal ratio: 95% or over
Methylmercaptan removal ratio: 80% or over
Ammonia removal ratio: 95% or over

3. Features

1) High de-odoring performance
The biological de-odoring system provides excellent de-odoring performance against hydrogen sulfide and methylmercaptan which occupy a great part of the odor component generated in the sewage treatment plant.
2) Low-cost operating cost
Since the system will not require the use of chemicals, etc. the operating cost is extremely limited as compared with the conventional physical/chemical treatment method.
3) Easy operation
Since the operation is executable automatically and requires no sludge control, the operation can be easily executable.
4) Simplified and compact construction
It is possible to maintain the microbes at high density on the surface of the filling material. It is also possible to secure sufficient linear velocity, and thus the equipment can be designed compact as compared with the conventional method.
5) High resistibility against load fluctuation
Since the microbes are increased against the fluctuation in raw odor concentration to perform the treatment, stabilized performance can be maintained.

4. Principle of Operation

The principle of operation for filling type biological de-odoring method in which the odor gas is ventilated in the filling material adhered with microbes is considerable in the following three stages.
1) Dissolution of odor substance in water
2) Absorption of odor substance in microbes
3) Oxidation/de-composition of odor substance taken in cell

5. System Flow

The biological de-odoring system is made up of a filling layer on which the microbes are fixed, and a sprinkle unit located at the upper part of the filling layer. The de-odoring gas is ventilated in an upward stream from the lower part of the tower and is de-odored. On the other hand, the value of pH is decreased within the filling layer due to accumulation of sulfuric ion, etc., the de-odoring product, causing the microbe reaction to be interfered with. Consequently, water is sprinkled intermittently to the filling layer, to remove and clean such sulfuric acid ion accumulation. It is also possible to execute the sophisticated treatment by installing the activated carbon absorption tower, etc. as required.

6. Application Field, Object

- Sewage treatment plant
- Night soil treatment plant
- Waste incineration plant
- Other industrial waste water treatment plants
- Stock breeding (hog raising, poultry)

Biological de-odoring flowsheet