May 2014
JOINT RESEARCH PROJECT between U of Peradeniya and NSC

Approach for Improving Water Quality in Sanaru Lake
○Michihiro MURATA, Koichi MATSUBARA, Riota ADACHI, Tatsuya TOBE

Contents

1. Introduction
2. Feature of Water Pollution based on Monitoring
3. Water Quality Simulation Model
4. Evaluation of Purification Measures
5. Conclusion

21. Introduction
Feature of the Lake

Legend Shizuoka prefecture, upstreamof Hamana Lake
 Brackish-water lake

Paddy
Dry Field
Fruit Farm
Urban Area
ForestWater Area

JapanObjective Area

 Salt water flow into the Lake
through the downstream riverfrom Hamana Lake, PacificOcean Lake area ; 1.2km2

Pacific Ocean Lake depth ; 2.5m(deepest point) Downstream river length ; 6km

Hamana Lake

Feature of the Basin in 2007

Sanaru Lake
Downstream River Basin area ; 58km2
 Urban area ; 40km2 (70%)
 Population ; 164,400 people Sewage coverage ; 90%

Pacific Ocean
31. Introduction
Water Quality in Sanaru Lake
The water quality had deteriorated from the 1960s, because of the rapid urbanization andindustrialization in the watershed.
Yealy Average COD [mg/L]

Sanaru Lake

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Most polluted lake in Japan from 2001 to 2007
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105

Target of the Local Committee 8.0mg/L
Enviromental Standard 5.0mg/L

01975

1980

1985

1990

1995

2000

2005

Purpose of Study
To figure out the feature of water pollution, and evaluate the effect of purification measures bydeveloping and applying the simulation model based on the feature of water pollution in Sanaru
lake.
42. Feature of Water Pollution based on Monitoring

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3. Water Quality Simulation Model
Divided Mesh Distribution
Altitude [T.P. m]

Sanaru Lake

Hamana Lake &Pacific Ocean

Downstream RiverVertically Two-Dimensional
鉛直2次元メッシュモデル Model

Three-DimensionalModel
3次元メッシュモデル

Sanaru Lake

Downstream River

This NSC original model can calculate the complicated feature of the water quality in brackish
or closed water body with accuracy.
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3. Water Quality Simulation Model
Hydraulic Model

Water Quality Model

Equation for Continuity

Equation for Salinity Balance Vertical flow velocity
 Water level (water volume) Advection and diffusion
Equation for Temperature Balance

Equation for Conservation ofMomentum

 Advection and diffusion
 Sunshine and heat loss in watersurface

 Horizontal flow velocity

Equation for Ecological Model

Equation for Shear Stress Advection and diffusion
 Chl-a (Phytoplankton)
 DO
 COD (Dissolved and Particulate) Nitrogen and Phosphorus(Inorganic and Organic) Bottom layer Water surface by wind
Equation for Density

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3. Water Quality Simulation Model
Ecological Model

83. Water Quality Simulation Model
Model Reliability

SalinityCl- （mg/l） 佐鳴湖 湖心 H19年
10,000

観測値
Observation

計算値
Calculation

計算値（日変動幅）
Cal.
Value (daily range)

8,000
6,000
4,000
2,0000H19.4.1
2007.4.1

H19.5.1 2007.6.1
H19.6.1 2007.7.1
H19.7.1
2007.5.1

COD
COD(mg/l)
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H19.9.1 2007.10.1
H19.10.1 2007.11.1
H19.11.1 H19.12.1
2007.12.1 H20.1.1
2008.1.1 H20.2.1
2007.9.1
2008.2.1 H20.3.1
2008.3.1

H19.8.1
2007.8.1

Observation
COD観測値
Valueof COD

佐鳴湖 湖心 H19年

Observation
D-COD観測値
Valueof D-COD

Calculation
COD計算値
Valueof COD

Calculation
D-COD計算値
Valueof D-COD

計算値（日変動幅）
Cal.
Value (daily range)

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201510502007.4.1
H19.4.1

H19.5.1 2007.6.1
H19.6.1
2007.5.1

H19.7.1
2007.7.1

H19.8.1
2007.8.1

H19.9.1 2007.10.1
H19.10.1 2007.11.1
H19.11.1 2007.12.1
H19.12.1 2008.1.1
H20.1.1
2007.9.1

H20.2.1 2008.3.1
H20.3.1
2008.2.1

94. Evaluation of Purification Measures
Purification Measures
In the River or Lake
Dredging in River

Improvement of Purification Facilityin LakeOutlet

Lake

Inlet

Plant

Nitrogen Removalin Upper Stream

Oxidation
Facility

Pond

Oxidation
Material

In the Watershed
Improvement and Connection toSewerage in Domestic Drainage

Installation of Advanced Domestic
Wastewater Treatment Tank

Connection to Sewerage inIndustrial Drainage
104. Evaluation of Purification Measures
Effect of Purification Measures by Applying the Model
COD [mg/L]
10.0Measure

9.0

8.0

Effect
1.29
9.28
7.99

7.0

6.0
Before Measures

After Measures

EffectDredging in River

0.37 mg/L

Improvement of Purification
Facility in Lake

0.02 mg/L

Nitrogen Removal in Upper Stream

0.11 mg/L

Subtotal In the River or Lake

0.50 mg/L

Improvement and Connection toSewerage in Domestic Drainage

0.66 mg/L

Connection to Sewerage inIndustrial Drainage

0.10 mg/L

Installation of Advanced Domestic

 Yearly average COD value inWastewater Treatment Tank
Sanaru lake became under 8.0mg/L Subtotal In the Watershedin 2007 condition by carrying outTotal
the all purification measures.

0.03 mg/L
0.79 mg/L
1.29 mg/L

114. Evaluation of Purification Measures
Before Measures
Existing Situationin 2007

After Measures

Yearly Average
COD
9.28mg/L

Yearly Average
COD
7.99mg/L

In fact, the actual water quality in Sanaru Lake has become under 8.0mg/L andachieved water quality target of the Local Committee in 2009 and 2011.
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5. Conclusion The approach of Monitoring-Modeling-Evaluation is important tocarry out the water purification effectively.
Monitoring Periodical and effective monitoring Feature of water pollution by monitoring results
 Check of progress on purification measures
Modeling
ExecuteMeasures Construction of simulation model based on feature Reliability check of simulation model

Evaluation
 Evaluation of purification measures by applying
simulation model Figure out effective purification measures
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Educational Activity in Sanaru Lake
Environmental Education

Water Survey by Basin Residents

Garbage Clean up by Basin Residents

Holding some Events14

Educational Activity in Sanaru Lake
Distributing Pamphlet for Publicity Activities
Connection to Sewerage

Installation of Advanced Domestic
Wastewater Treatment Tank

Kind Treatment in Domestic Drainage

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Effect of water quality improvement
For water supply resources- Take stable water regarding water quantity and quality
Algal Bloom- Cause odor problem for water supply

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Effect of water quality improvement
For public water body
- Improvement of ecological service- Improvement of recreation and scenery
Ecological Service
Fish and Fishing

Plant

Bird

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Effect of water quality improvement
Recreation and Scenery
Easy Access and Activity

Beautiful Scenery18

Approach for Improving Water Environment in KANDY LAKE

(1) Water Quality Monitoring Implement the water quality monitoring regularly andcontinuously in Kandy Lake under the collaboration withUniversity of Peradeniya and NWSDB (or possibly CEA orIWMI), and Nihon Suido Consultants Co., Ltd. in Japan.

(2) Water Quality Modeling Develop a water quality simulation model considering data
availability and independent simulation use in Sri Lankan
agencies.
 Apply the water quality simulation model to evaluate thewater quality improving effect by various options (e.g.
Wastewater disposal project, vegetation…).
19• Thank you very much for your kind attention.

Acknowledgement
Special thanks to Shizuoka Prefecture, Hamamatsu City, andLocal Committee of Water Renaissance in Snaru Lake.
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