Updated: July 2002

1. Introduction

The activated sludge process is widely adopted as a processing method for waste water containing a high concentration of organic matters, such as waste water from food industry or city sewage.
But, since the activated sludge process utilizes microorganism with a slow growth rate, it has such problems that it runs only in a low BOD volume load, about 0.5 kg/day, it sometimes occurs bulking to causes a failure in sedimentation, and generation of excess sludge requires the cost for its processing.
In the industrial waste water treatment, because of an increase in BOD load due to plant expansion, or a change in load due to seasonal variation of products, there are cases where it runs near the limit of specified conditions.
Furthermore, the activated sludge process makes use of biological metabolism, and it is necessary to run and control it so as to optimize the conditions for the microorganism.
On the other hand, BIOATTACK is a highly efficient and easily operable and controllable process where a high concentration of BOD load is treated with a compact unit at a low running cost with high efficiency.

2. Principle and Outline of Equipment

BIOATTACK comprises two processes, ATTACK vessel and RECEIVE vessel, so as to run a two-step activated sludge process.

In the ATTACK vessel, by the action of rapidly growing microorganism group, using AQUA-TORNADO, which is a highly efficient aeration and mixing unit, one can disintegrate about 70-80% BOD contents in the waste water in a short period of time.
Next, in the RECEIVE vessel, the Protozoa group with good sedimentation property catches and disintegrates the microorganism group and remaining BOD. Thus, sedimentation of the sludge may be good, and generation of excess sludge may be suppressed.

3. Features

(1) Stable processing of high concentration BOD
The microorganism having a high growth rate carries out efficient processing, and stable treatment is possible because it adjusts itself flexibly with the variation of water quality.
(2) Compact processing unit and low cost
The BOD digesting rate is approximately 30 times that of the standard activated sludge process, thus the volume of the processing unit may be reduced to about one third of the activated sludge process unit.
(3) Large reduction in the activated sludge generated
The rapidly growing microorganism group has also a high autolysis rate, and further the sludge generated is reduced to about one half of that in the activated sludge process due to the Protozoa preying to create a food chain.
(4) Suppression of bulking
Since almost all the organic matters in the waste water are disintegrated in the ATTACK vessel by the high-growth rate microorganism group, filamentous fungi may not grow, which are the cause for bulking.
(5) Easy expansion of the existing activated sludge process unit
By adding a compact and easy-to-install "BIOATTACK UNIT", the capacity of the existing unit may be greatly increased. "BIOATTACK UNIT" for extension comprises the following.

           BOD processing BIOATTACK
Type           capacity          vessel volume    
BA-250         250 kg/day           17 m3
BA-500         500 kg/day           33 m3
BA-750         750 kg/day           50 m3
BA-1000       1000 kg/day           66 m3
BA-1500       1500 kg/day          100 m3

4. Fields of Application

There are application cases as in the following where the introduction has brought a great merit: A new unit was constructed for processing a high BOD load in waste water: An ATTACK vessel was added to an existing activated sludge unit: Not much space was available for installation: For the purpose of reduction of the excess sludge: For the purpose of reduction in the load of operation and control necessary due to bulking.