Measures to makeHorikawa River Limpid
Implementation by Nagoya City
Sep.5th 2015
Nagoya City Greenification & Public Works Bureau
River Dep. River Plannning Div.
1

Outline of Clarification Experiments
by Covering SandSludge appearing from riverbed on the ebb tide.

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

3

Outline of Clarification Experiments■Location

・about 300m long
(600m on both sides)
・3m wide on each side

Exposed sludge
Gojo Bridge▽low water level

Naka Bridge

・5 kinds of trial patternin this section
4Outline of Clarification Experiments■Experiment① covering sandcover the sludge with 30cm thick sand bed

Gojo Bridge
Exposedsludge
露出ヘドロ▽low water level▽朔望平均干潮位

Naka Bridge

5

Outline of Clarification Experiments■Experiment② cover with clarification materials
Gojo Bridge

cover the sludge with 30cm thick clarificationmaterials made from ash (by-product of coal
thermal power station) and absorbing for its
porousness

Exposedsludge
露出ヘドロNaka Bridge▽low water level▽朔望平均干潮位

6

Outline of Clarification Experiments■Experiment ③ covering sand after removing sludge
remove 30cm thick sludge and cover with 30cm thicksand bed

露出ヘドロ
Exposedsludge

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

Exposedsludge
露出ヘドロNaka Bridge▽low water level▽朔望平均干潮位7

Outline of Clarification Experiments■Experiment⑤ settle infiltrators
Gojo Bridge

settle corn-shaped infiltrators made with solid clinker
ash every 1m through sludge

Exposedsludge
露出ヘドロ

about 40cm

▽low water level▽朔望平均干潮位【mechanism of infiltrator】

Naka Bridge・make stream inside the facilities by ebb and flow
・supply oxygen into the bottom⇒ improve the bottom layer8Construction of the experiment sitefrom Jan.16 to Jan.23

Machines set on a float
constructed the experiment site.

9The situation of Clarification
Experiments in Gojo Bridge area.

the view of Gojo Bridge from riverside.
10

Ｍｏｎｉｔｏｒｉｎｇ Ｓｕｒｖｅｙ
１．Smell survey point
above covering sand, etc.
（above bottom sedimentat permeating facility）
２．Bottom sediment survey pointbelow covering sand, etc.
（around purifying material
at permeating facility）
３．Benthos survey point
surface of covering sand,etc.
11Monitoring Survey Result （bottom sediment and smell）
・pre-survey (before construction)
Aug. 25,26 2014
・post-survey (after construction)
Jul. 31 2015

Survey was conductedduring low tide in spring tidesmell③covering sand（after removal ofsludge）④purifying material⑤permeating facility【coal ash】（after【coal ash】
removal of sludge）①covering sanddate

beforeafter

beforeafter

beforeafter

beforeafterbefore

aftertemp.(℃)

28.4

34.7

30.2

33.2

28.2

34.4

30.2

34.3

30.2

33.4

water temp.(℃)

25.7

26.8

25.7

26.8

26.0

26.6

26.3

26.8

25.7

26.8

mud temp.(℃)

26.3

24.6

26.3

27.0

26.0

26.4

25.8

24.3

26.5

25.4

color

black-grayblack

black-gray

black

black

black

black-grayblack

black-gray

black

clay

silt mixed
with sandsilt mixed
with clay

silt mixed
with sandclay

silt mixed
with sandsilt mixed
with clay

silt mixed
with clay

clay

smell

silt mixed
with sandand stone
weak H2S

weak H2S

H2S

weak oilstrong H2S

weak oil

H2S

weak H2S

H2S

weak oil

pH

7.9

6.6

7.8

6.7

7.8

6.4

7.5

6.5

7.6

6.5

COD（mg/g-dry）

27

24

28

22

45

1630

26

27

22

T-N（mg/g-dry）

1.6

1.8

2.7

1.6

4.2

2.1

2.7

2.5

2.3

1.6

T-P（mg/g-dry）

1.9

1.9

2.1

1.1

4.1

1.3

3.2

1.7

1.6

1.4

T-C(%)

2.4

3.0

6.8

3.4

9.5

3.1

5.1

5.2

6.2

3.9

free sulfar（mg/g-dry）

0.36

0.25

0.71

0.44

1.10.34

0.24

0.90

1.1

0.35

sulfar（mg/g-dry）

8.9

14

4.8

12

9.2

3.7

8.5

11

9.7

6.5

ORP(mV)-200-87-240

12-21040-290-46-240

3

ignition loss（%）

6.0

6.3

13.5

6.7

13.5

7.4

9.4

12.2

14.2

8.3

loose on drying（%）

32.4

42.1

51.1

32.7

46.9

40.0

43.7

47.3

48.8

38.6

H2 S(mg/kg-dry)

<0.1

<0.1

230

<0.1

370

<0.1

0.1

<0.1

32

<0.1

H2 S（ppm）<0.0005

0.00060.00130.00340.00180.010<0.0005

0.14<0.0005

0.0025soil

bottomsediment②purifying material【coal ash】

point12

Monitoring Survey Result （bottom sediment）
・pre-survey (before construction)
Aug. 25,26 2014
・post-survey (after construction)
Jul. 31 2015

COD
[mg/g-dry]
50

before
実施前

[mV]

after
実施後

100
50

40

ORP（Oxidation-Reduction Potential）①covering sandenough dissolved oxygen030②purifying material【coal ash】

-50

poor oxygen

20-100

10-150③covering sand（after removal ofsludge）(Naya bridge)

-200

0
①

②

③④

⑤④purifying material【coal ash】（afterremoval of sludge）（Ｎａｙａ Bｒｉｄｇｅ）①covering sand ②purifying material③covering sand ④purifying material（③,④：after removal of sludge）⑤permeating facility

-250
-300
-350
beforeafter⑤permeatingfacility【coal ash】

improved
not improved

COD improved in all sections
13

Monitoring Survey Result （bottom sediment）
・pre-survey (before construction)
Aug. 25,26 2014
・post-survey (after construction)
Jul. 31 2015

T-N (total nitrogen)[mg/g-dry]
54
3

実施前
before2after
実施後

organic matter andnutritious salt decreased.

10
①

②

③④⑤improved
not improved（Ｎａｙａ Bｒｉｄｇｅ）①covering sand ②purifying material③covering sand ④purifying material （③,④：after removal of sludge）⑤permeating facility[mg/g-dry]T-P (total phosphorus)

T-C (total carbon)

[％]

5

10.0

48.0

3

実施前
before6.0

実施前
before2after
実施後

4.0

after
実施後

1

2.0

0

0.0
①

②

③④⑤（Ｎａｙａ Bｒｉｄｇｅ）①covering sand ②purifying material③covering sand ④purifying material （③,④：after removal of sludge）⑤permeating facility①②③④⑤（Ｎａｙａ Bｒｉｄｇｅ）①covering sand ②purifying material③covering sand ④purifying material （③,④：after removal of sludge）⑤permeating facility

14

Monitoring Survey (Benthos survey results)
Investigated at low tide of spring tide Pre-survey Date August 25, 2014
Post-survey Date July 31, 2015

*numbers of sample per 0.025m3
Post-survey
事 後

事 前
Pre-survey
門名

環形動物門

綱名

ゴカイ綱

目名

サシバゴカイ目

科名ゴカイ科

kind of lugworm
スピオ科

スピオ目
ミミズ綱

イトミミズ目

ミズミミズ科種和名②浄化材
Covered
による被覆
with
【石炭灰】

Covered①覆砂with sand

Infiltration
⑤浸透施設
【石炭灰】
facilities

purificationmaterial

カワゴカイ属Polydora 属
エラミミズ
ウチワミミズ属
ユリミミズ属kind of tubifex wormミズミミズ科

トガリミズミミズ属
イトミミズ亜科
ヒル綱吻蛭目

グロシフォニ科

kind of leeche
節足動物門

軟甲綱

ワラジムシ目

ミズムシ科

kind of insects
ユスリカ科

ハエ目（双翅目）

Total kind
合 計number
種 類 数
合 計
個 体数
Total individual
bodynumber40

11155

41,850
144

2

13266

41,89145

ハバヒロビル属
ヌマビル
ミズムシ
セボリユスリカ属

Many organisms are discovered at places
where purification materials had been installed

15

Monitoring Survey (Other view points)
1. Durability of covering
materials against river flowPurification material and sandare covering in stable now.
Continuous observation would
be needed until over flood
season.

2.Deposition of sludge on riverbank
Higher angle of cover materials
for river stream decreases
deposition of sludge.
Higher angle(15%)

Lower angle(5%)

16Monitoring Survey (Summary)
We could see some hopeful changes; COD, ORP and
Benthos for example. But some other viewpoints
like smells couldn’t improve or got worth trend.
So we should hold obvious review at this point.

This survey is just a half year report, andcontinuous monitoring in the long term eyes willbe needed17

■Reservation of Water Source◆Use of Shallow Ground Water
Upstream area of Horikawa River①SanageBridge①

Report of othermeasures

②②③④

⑤③
Meijo

H25.3 瀬古橋上流0.01m3/s④

H16.10 辻栄橋上流0.01m3/s⑤Park

NagoyaCastleH17.11

木津根橋上流0.01m3/s H26.3

猿投橋上流0.01m3/s

H20.3
清水わくわく水0.0005m3/s

18

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

SanageBridge⑥ 志賀橋上流 0.01m3/s
MeijoParkNagoya
Castle19

■Reservation of Additional Water Source（FY2015）◆Upstream of Nakaido Bridge
0.01 m3/s of water will be added （March 2016）

SanageBridge

NakaidoBridge
中土戸橋

中土戸橋上流MeijoPark
NagoyaCastle20

■Improvement of Water Quality◆Removal of Sludge

JR,Meitetsu
BridgeOto Bridge
FY2015
Removalpoint

FY2014
Removalpoint

Sumiyoshi
BridgeFY2013
Removalpoint

KameyaBridge21

■Improvement of Water Quality◆Making shallows and abyss
Setting wooden piles and ripraps generates variable stream on the river for
enforcing river’s self-purification function with growth of plants.
Since FY 2014

fish spawning andplant seed ashore
Change of stream

22■Improvement of Water Quality
H㉒設置箇所（夫婦橋～黒川１号橋）

設置前（H21）

設置後（H25）

H㉔設置箇所（黒川２号橋下流）

設置前（H23）◆Improvement
Variety and amount of fish increased
Benthos increased
Plants growth is promoted

Wild living shown at upstream of Horikawa River

設置後（H25）設置した玉石に群がるオイカワ

H㉕設置箇所（黒川２号橋上流）
淵に集まる
マガモ

設置前（H24）

設置後（H27）

小魚を採る
コサギ

23

■Pollutants removal/inflow reduction◆Control of combined sewer overflow(Rainwater storage facilities)
Construct rainwater storage facilities to reduce pollution load for
Horikawa River in rainy weather by storing high polluted first flush
rainwater temporarily.
Horikawa Ugan Rain- Horikawa Sagan RainOzone stormwater
water Reservior forwater Reservior forreserviorpollution controll
pollution controll

Started operation in 2006

（12,000ｍ3）

Started operation in 2010

（13,000ｍ3）

Under construction（14,000ｍ3）

24

■Pollutants removal/inflow reduction◆Advanced water treatment at Meijo Water Treatment
Center （Started operation in May, 2010）
mg/l

After
introduction

ＢＯＤ

Decreased by 15% Average 4.7
5.5

4.2

5.3

4.5

mg/l
After
introduction

3.3Filter out more minuteSuspeded Solids(SS) intreated water by filteration
devices

ＳＳDecreased by 60%

Average1.3

12125

■Pollutants removal/inflow reduction◆Improvement of the combined sewer system(Installation of the garbage removal device)
Beforeintroduction

Garbageremoval devices

OverflowTo
A water treatment center

After
introduction

Garbage in treated water
overflow with rainwater
Overflow

Rainwater treated by thegarbage removal devices
overflowTo
A water treatment center

Removed garbage istreated with sewage atwater treatment centers

26

■Pollutants removal/inflow reduction◆A Garbage Catcher(Near Johoku Bridge) Introduced in 2006

A garbage basket

An inflow gate

A capturing fence

The accumulation result in 2012

1.1 tons〃in 2013

0.8 tons〃

in 2014

0.7 tons27

■Pollutants removal/inflow reduction◆Changes in garbage accumulation amountby the Garbage Catcher
After the repair（Carried out in March, 2015)（kg）

Changes in garbage accumulation
amount200150

H24
H25
H26
H27

100

50

0
4月
April

5月
May

6月
June28

■Secure the river source◆Reclaimed wastewater supply
Use of reclaimed wastewater treated by the membrane
filtration process at Moriyama Water Treatment Center

Moriyama Water
Treatment Center

Flat membrane units
in aerobic tanks(400 sheets×12 units)

Shonai irrigation channel

The membrane caseof an upper stage(200cartridges inside)

Horikawa River

The membrane caseof a lower stage(200 cartridges inside)

Flat membrane units※Water conveyance period is generally irrigationseasons (from April to October)(except the period for Shonai irrigation channel(from November to March))

29

■Others【Construction of Gojo Bridge River Park】
The river park is under construction on the edgeof Gojo Bridge (right bank of its upstream)
The park with historical explanation boards androofed mud walls suggestive of Minoji Roads
The completion image
The construction status30

Thank you foryour kind attention.

31