Current Circumstances

At the Waterworks Bureau’s purification plants, tiny suspended solid in raw water is sunk to the bottom of the sedimentation basin. This sedimentation sludge is then condensed, drained, and dehydrated into cakes. It must be handled as industrial waste.

In Osaka City, as we attempt to establish a recycling-based society, we are moving ahead with initiatives to reduce waste and to re-use materials, and from this standpoint we are working to make effective use of dehydrated cakes in the purification process.

The volume of dehydrated cakes coming out of the Waterworks Bureau’s three purification plants stands at approximately 20,000 tons/ year, and we are working to make effective uses of these materials for making cement, garden soil, and so on. The rate of re-use of the materials stood at approximately 57% for FY2005, and our goal is to bring this figure to 100%.

At the Osaka City Waterworks Bureau, we are always searching for parties that can make effective use of the dehydrated cakes as part of our initiatives to re-use the materials.

Mechanical dehydrated cake

Sun dried cake

Current Use of Dehydrated Cake Generated in the Water Purification Process Unit: tons (FY2005)

(1) Dehydrated Cake Data

Kunijima Purification Plant

• Amount Generated: approx. 50 tons/ day
• Method: Mechanical dehydration
• Water Content: approx. 60％
• Address: 1-3-14 Kunijima, Higashiyodogawa-ku, Osaka

Niwakubo Purification Plant

• Amount Generated: approx. 30 tons/ day
• Method: Mechanical dehydration
• Water Content: approx. 60％
• Address: 11-31 Yodoe-cho, Moriguchi

Toyono Purification Plan

• Amount of Stock: approx. 800 tons
• Method: Sun drying
• Water Content: approx. 50-60％ or less
• Address: 1-1 Uzumasatakatsuka-cho, Neyagawa

Use of Dehydrated Cake for Gardens

The “River Soil” and “Soil of Yodo” products are examples of effective use of dehydrated cake for gardens.

(1) River Soil

To make River Soil, the dehydrated cakes are crushed and granulated. This product is appropriate for gardening uses including flower beds.

(2) Soil of Yodo

This consists of River Soil mixed with various ingredients designed to improve soil quality, including bark, perlite, coco peat, vermiculite, etc.

It is appropriate for use in potting, planter, etc. As part of initiatives to educate community residents in recycling, one-liter bags of “Soil of Yodo” are distributed for free at the Water Festival, local festivals, etc.

1) Rich in organic matter, it is highly fertile.
2) It is highly water-retentive and water/air permeable.
3) As the raw material for light soil, it can also be used for cultivation on artificial grounds. Due to the fact that it contains improved soil materials, Soid of Yodo features an excellent balance of water retention and water/air permeability.

River Soi

Soil of Yodo