Updated: July 2002

1. Outline

With the high rate and high accuracy, SS in wastewater (raw water) are removed through high rate upward flow filter using the ball-shaped filtering media of fiber. Such a filtering medium called "Bio-Ball"means a bundle of fine chemical fiber which is specifically shrunk-wound and firmly bound at the center to make into a ball shape. The description of high rate upward flow filter "IZUMI"operation is shown by Figure 1. Raw water in the upward flow is passed through the filtering layer held between the fixed upper supporting plate and the lower supporting plate having its elevating device. During the continuation of filtering, when the pressure loss increases, raw water automatically moves into the backwashing process. In this process, first the lower supporting plate is lowered to secure the backwashing space assuring fluidity of the filtering media. Next, from below, cleaning air and the backwashing water (raw water) are supplied at the same time and then the filtering media is washed.

2. Characteristics

1) Very high filtering rate: 35m/h.
2) Low pressure loss: Max. 1mH2O (usually scores cm)
3) Large voids of filtering layer: More than 90%
4) Less back washing water: 2-3% volume of filtered water
5) High SS removal rate: More than 75-90%
6) Filtering media Bio-Ball:
(1) Specification: dia. 33mm, wt. 3.2g, spec., gravity 1.7, bulk spec. gravity 0.1, fiber dia. 80µm
(2) Adequate stability with self-compressibility
(3) Light weight, so conveyance and handling are easy.
(4) Easy to wash, so optimum for continuous treatment of SS

3. Application

Advanced waste treatment facility
1) For sewage, community plant, and industrial drainage
2) For pollutants of lakes, ponds, rivers and waterways

Figure1 Description of IZUMI operation (Upward flow)