Measures to make Horikawa River
LimpidImplementation by Nagoya City

Sep. 27th 2014
Nagoya City
Greenification & PublicWorks Bureau
River Dep. River Plannning Div.

1 Reservation of Water Source◆ Use of Shallow Ground Water
Upstream area of Horikawa River

Upstream of Seko Brdg. 0.01m3/s
Upstream of Tsujie Brdg. 0.01m3/s
Sanage Brdg.

Upstream of Kizune Bridg. 0.01m3/s
Upstream of Sanage Brdg. 0.01m3/s

Shimizu wakuwaku-sui 0.0005m3/s

Nagoya Castle2

■Reservation of Water Source Use of Shallow Ground Water
Upstream area of Horikawa River

Upstream of
Sanage Brdg. 0.01m3/s
Sanage Brdg.

Nagoya Castle3

■Reservation of Additional Water Source（FY2014）
 Upstream of Shiga Bridge
0.01 m3/s of water will be added （March 2015）

Sanage Brdg.

Upstream ofShiga Brdg.
Nagoya Castle

4

■Improvement of Water Quality◆Removal of Sludge

FY 1994～2013
146,000 m3 of sludge had been removed5

■ Reservation of Water Source◆Use of Reclaimed WastewaterMoriyama Water
Treatment CenterMax. 4,000m3/day of wastewater reclaimed atMoriyama Water Treatment Center has been
conducted into Horikawa River （since Aug. 2011）

Flat membrane unit inthe aerobic tank(400 sheets×12 units)

Shonai
Irrigation
ChannelUpper membrane case(cartridge storing 200 sheets )Lower membrane case(cartridge storing 200 sheets )HorikawaRiver※Reclaimed wastewater is conducted during
irrigation season(Apr.-Oct.)

Flat membrane unit6

■ Removal and Inflow reduction of Pollutants◆Garbage Catcher（below Johoku Bridge）

FY 2013 collection result

0.8t7

■ Removal and Inflow reduction of Pollutants◆ Advanced water treatment in Meijo Water Treatment Center
Filtering equipment (disc filters) removes
fine particles remaining in treated water.

Averagebeforeintroduction（2007～2009）

Average（2011～2013）

BOD

5.5

4.3

SS

3.3

1.08

■ Removal and Inflow reduction of Pollutants◆ Control of combined sewer overflow
Rain-water reservoirs (RWR) for pollution control are constructed
for storing rainwater temporarily and decreasing pollution load.

Ozone RWR

Completed in 2006
（12,000ｍ3）

Horikawa-Ugan RWR

Completed in 2010
（13,000ｍ3）

Horikawa-Sagan RWR

Under construction（14,000ｍ3）

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Appearance of Sludge
Sludge appears from river bed on ebb tide.

Toxic and stinking H2S gasses
pass out from exposed sludge.

Outline of Clarification Experiments
・We implemented several clarification experiments

focused on sludge appeared on ebb tide.

１１

Outline of Clarification Experiments
 Location of Experiments・about 300m long
・3m width from each edge

Gojo Brdg.
Appearance of sludge

Naka Brdg.

▽low water level

１２

Outline of Clarification Experiments
 Experiment① cover with sand bed
Cover the sludge with 30cm-thick sand bed
Appearance of sludge▽low water level【Expected effects】
・inhibit elution of nutrient salt ⇒ prevent deterioration of water quality
・inhibit generation of H2S ⇒ remove a bad odor・as H2S is inhibited, ecosystem is getting restored and water quality
will be more improved.

１３

Outline of Clarification Experiments
 Experiment ② cover with clarification materials
Cover the sludge with 30cm-thick clarification materials**made from solid clinker ash(by-product of coal thermal power station)Work as H2S absorber for its porousness

Appearance of sludge▽low water level【Expected effects】
・perform like sand bed
・with feature of clarification material, might be able to leads better result
than sand bed cover

１４Outline of Clarification Experiments
 Experiment ③ cover with sand bed （after removing sludge）
remove 30cm-thick sludge, and cover with same-thick sand bed

Appearance of sludge▽low water level④ cover with clarification materials（after removing sludge）
remove 30cm-thick sludge, and cover with same-thick materials

Appearance of sludge▽low water level

We focused on difference between the case of coveringand the case of covering after removing sludge.

１５Outline of Clarification Experiments■Experiment⑤ settle infiltrator
settle corn-shaped infiltrators made with solid clinker ash
every 1m through sludge bed

Appearance of sludge▽low water level

About 40cm
【mechanism of infiltrator】
・stream was generated inside the facilities by ebb and flow
・supply bottom layer with oxygen ⇒ improve the bottom layer around facilities【Expected effects】
・improve sludge layer by supplying it with oxygen
・the ecosystem getting restored and the water quality
will be improved more

１６

Outline of Clarification Experiments
 Images after the experiments
Experiment image

Present condition

 Plan of monitoring survey
We verify effect of experiments for several years.
Survey items…bottom layer, odor, benthic organism
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