Measures to makeHorikawa River Limpid
Implementation by Nagoya City

Feb.15 2015
Nagoya City Greenification & PublicWorks Bureau
River Dep. River Plannning Div.
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■Reservation of Water Source◆Use of Shallow Ground Water
Upstream area of Horikawa River

Upstream of Seko Brdg. 0.01m3/s
SanageSanageBridgeBridge

Upstream of Tsujie Brdg. 0.01m3/s
Upstream of Kizune Bridg. 0.01m3/s
Upstream of Sanage Brdg. 0.01m3/s
Shimizu wakuwaku-sui 0.0005m3/s

Meijo ParkNAGOYA castle
NAGOYAcastle
KoshioBridgeNaya Bridge

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

SanageBridge

Upstream ofShiga Bridge
Meijo ParkNAGOYA castle
Koshio Bridge
Naya Bridge

3■Improvement of Water Quality◆Removal of Sludge

JR,Meitetsu
Bridge
OtoBridge
FY2014
Removalpoint

FY 1994～2013
146,000 m3 of sludge had been
removedSumiyoshiBridge
4■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.
Average beforeintroduction（2007～2009）

BOD

5.5SS3.3

Average after
introduction（2011～2013）

4.3
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■Removal and Inflow reduction of Pollutants◆Control of combined sewer overflow（set up garbage removal devices for drainage system)

Beforegarbage removal device(for drainage system)
overflow

To watertreatment center

After

Rainwater overflow withgarbage

overflow
Rainwater overflow without
garbage

To watertreatment center

Garbage removed by device flow towater treatment center with wastewater6

■Removal and Inflow reduction of Pollutants◆Garbage Catcher（below Johoku Bridge）since FY 2006
Set up the inflow gate and Garbage collection basket converted the weir of sewage④ Collect Pick up thecollected garbage
regularly for the disposal

weirGarbage
collection basket

Garbage collection basket

Drain the rainwater
In case of heavy rain
Suspended garbage

Drain the rainwater
In case of heavy rain

Upstream

Downstream① Catch floating garbage by thefence by using tidal river flow
toward up and downstream③ Collect the garbage inthe basket

Sewage(combined sewer)

Situation of the facility

Inflow gate

Inflow gate

Catching fence

SanageBridgeTo WaterTreatmentcenterHorikawaRiver② Collect floating carbage whenthe gate gets open automatically
based on the water level

Cross section (Image)

JohokuBridge
Meijo ParkNAGOYA castle
Koshio Bridge

collection result in FY2011

2.3t

collection result in FY2012

1.1tcollection result in FY2013

0.8t

Naya Bridge

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■ Reservation of Water Source◆Use of Reclaimed WastewaterMoriyama water
treatment center

Reclaimed wastewater from Moriyama Water
Treatment Centerflat membrane unit
in aerobic reactor
tank(400 sheets×12 units)

Shonai
Irrigation
channelUpper case

Horikawa River

Lower case
Each cartridge stores 200 sheets
Flat membrane unit

※ Reclaimed wastewater is conducted during
irrigation season (Apr. to Oct)8

Appearance of Sludge
Sludge appears from riverbed on the ebb tide.
Toxic and stinking Ｈ2Ｓ gas
pass out from exposed sludge.

Outline of Clarification Experiments
・We, City of Nagoya implemented several
clarification experiments that focused on sledge
appeared on ebb tide.

：現在の断面10

Outline of Clarification Experiments■ Location

・300m long
・3m wide on each side

Exposed sludge
Gojo Bridge▽ low water level

Naka Bridge

・5 kinds of trial patternin this section11

Outline of Clarification Experiments■ Experiment ① cover with sand bed
cover the sludge with 30cm thick sand bed

Gojo Bridge

Exposed sludge▽ low water level【expected effects】
・inhibit elution of nutrient salt ⇒ prevent deterioration
・inhibit generation of H2S ⇒ remove bad odor

Naka Bridge

・As H2S is inhibited, ecosystem is getting restored
and water quality will be improved more.

12Outline of Clarification Experiments■ Experiment ② cover with clarification materials
cover the sludge with 30cm thick clarification materials
made from ash (by-product of coal thermal power station)

Gojo Bridge

and absorbing for its porousness
Exposed sludge▽ low water level【expected effects】
・works like ① sand bed (see P12)

Naka bridge・might get better result than sand bed does
due to features of clarification materials

13Outline of Clarification Experiments■ Experiment ③ cover with sand bed

after removing sludge

Exposed sludge

remove 30cm thick sludge andcover with 30cm thick sand bed

Gojo Bridge▽low water level▽朔望平均干潮位④ cover with clarification materials
remove 30cm thick sludge
Exposedsludge
露出ヘドロand cover with 30cm thickclarification materials▽ low water level▽朔望平均干潮位

Naka bridge
In order to see the difference between ①, ②, ③ and ④

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Outline of Clarification Experiments■ Experiment ⑤ settle infiltrators
settle corn-shaped infiltrators made with solid clinker ash
every 1m through sludge
露出ヘドロ
Exposedsludge

Gojo Bridge
40cm▽▽朔望平均干潮位
low water level【mechanism of infiltrator】
・make stream inside the facilities by ebb and flow
・supply oxygen into the bottom⇒ improve the bottom layer

Naka bridge【expected effects】
・improve sludge layer by supplying oxygen
・restored ecosystem made water quality better

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Making the experiment sitefrom Jan.16 to Jan.23

Construction machines set on a float
made the experiment site.
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Making the experiment site
（upstream of Naka Bridge）

Before works

After works
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Survey of the experiment■ verification of the effects
We, Government of Nagoya City verify the effects ofexperiments for several years
survey items…bottom layer, odor, benthic aoganism■ sensory survey
We hope Horikawa Sen-nin Chosatai makessensory surveys.
Example…impression of water clearness, odor, living things
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