Updated: July 2002

1. Outline

In the activated sludge processing, generally with a higher MLSS content, more BOD or COD can be treated. Therefore the more rational and economical process is to first separate the wastewater into high density, difficult-to-decompose wastewater and dilute, easy-to-decompose wastewater. KURABO has developed over 20 years the industrial wastewater treatment system after a great success with dyeing plant's wastewater treatment system KRACLEAN of its own. The high density wastewater is treated in its condition of maximum loading and maximum MLSS to obtain a maximum treatment efficiency over 90%. Then the treated high density wastewater is added to the low density wastewater, and treated at low loading to obtain values within regulation.
1) Double Step Aeration Method
However, where the discharge regulation value is relatively high, low volume and low density wastewater can be treated by one step aeration process which simplifies the equipment and operation.
2) High Density MLSS Single Step Aeration Method
Single Step Aeration Method suits for where relatively mild COD regulation value (50-100mg/l) is permissible and Double Step Aeration Method suits for where the regulation value is severe like under 50 ppm. KRACLEAN fits for treatment of wastewater containing difficult-to-decompose COD component and the sedimentation tank is specially constructed that a high density sludge is returned form high density MLSS aeration tank.
This is the basic principle of KRACLEAN
Also not only in domestic but in the Republic of Korea, Taiwan and the other countries of the overseas, the superiority of this technique accepts and it has many actual results.

2. Merit

1) High efficiency of COD removal rate: 85-95%
(According to an ordinary method: 50-70%)
2) Compact equipment's according to high efficiency of treatment.
3) Rational design is available thanks to highly efficient treatment of difficult-to-decompose Cod component.
4) Simple and easy operation.
5) Cheap running cost.

3. Performance

Performance example is given in the Table below.

Performance Examples (At "A"company, PVA wastewater, 10,000m³/d, COD-500mg/l, PVA-250mg/l)

(*)Step 1: Conc. water 3,000m³/d
Step 2: Conc. water 3,000m³/d-dil water 7,000m³/d

4. Flow Sheet

An example of KRACLEAN flow at a large scale dyeing plant is illustrated in the figure below.

KRACLEAN PROCESS FLOWSHEET

5. Application

KRACLEAN fits well for reduction of COD and BOD in organic wastewater and is applied such fields as mentioned below.
- Dyeing wastewater, Desizing wastewater, Scouring wastewater
- Adhesive wastewater
- Film manufacturing wastewater
- Polyvinylalcohol wastewater
- Pulp and paper manufacturing wastewater
- Paper coating wastewater
- Organic industrial waste (Petroleum, Paint, Resin, etc.)
- Food processing wastewater

6. Photo

An installation example is seen in the Photo below.