Updated: July 2002

1. Preface

With the increase of wastewater treatment processes, the environment around its treatment plant has become a greater concern more than ever. Among the problems, deodorization process for the treatment of odors generated in the treatment process are essential and unavoidable.
We have early noticed the activities of microbes such as sulfur bacterium during decomposition of odor substances, and studied media for immobilizing the odor substance decomposing bacterium in high densities. The biological deodorization process using special media, which is developed in this manner, is more economically efficient and maintainable than conventional methods and expected to be a new system which is easy on the environment and one which has no fear of secondary pollution.

2. Mechanism

The principle is such that odor substances are dissolved in water and oxidatively decomposed by an aerobic microbe such as sulfur bacterium, before being removed. The following three steps are passed through in the filled layer to carry out deodorization.

3. Flow Diagram

The process is constituted of by only the main bodies of a biological deodorization tower, circulation pumps and a fan. Odor substances are introduced into the biological deodorization tower and decomposed by a microbe while passing through the special media packed portion in which the microbe is immobilized in a high concentration, before being removed. When more advanced treatment is required, activated carbon would be added after this system. Water is supplied by a water sprinkler from the top of the tower for maintaining the activities of the microbe and for washing away sulfate ions, etc., formed by biological reactions.
The feature of this process is to carry out efficient treatment by actively controlling the habitat segregation of the microbe suitable for the removal of each odor substance. For this purpose, two deodorizing tower are used, and the air flow velocity, the amount of water circulated and the pH are adjusted to control the optimum environment for the microbe. As a result of this control, it has become possible to efficiently treat methyl mercaptan, dimethyl sulfide and dimethyl disulfide, and the like, which have been said to be hardly removed by biological reactions.

4. Diagram

5. Advantage

1) The maintenance costs are lower than 10%: When aimed at the odors of a sludge treating process, the maintenance costs for combined treatment of this process and the process using activated carbon alone is not higher than 10% that of the process using only activated carbon.
2) Simple operation: As only treated water is used, the operator can be freed from periodical chemical supply and related maintenance.
3) Compact equipment: The equipment can be operated at as high a speed as an LV value of 0.2 m/s and an SV value of 300 to 500h^-1 (for the odors of a sludge treatment process), and therefore can be placed in a small space.
4) Stable deodorizing performance with high efficiency is assured for a long period of time: The pressure loss of the equipment is very low and shows no deterioration of the media nor change in the performance due to pressure condensing during long-term operation.

6. Example (for the odors of sludge treatment process)

(Note) Operation condition: LV value 0.20m/s,
Total SV value 300h^-1.