6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Optimization method for sustainablewastewater treatment systems
in the population declining society
Takeshi Ishikawa, Ryo Matsumoto, Tsuyako Fujii, Hiromasa Yamashita
National Institute for Land and Infrastructure Management , Japan
17 May 2018

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Introduction (Wastewater treatment of Japan)

Local governments have adopted thewaste water treatment system , which
are suitable for their regional condition.
• The wastewater treatment service
ratio is 90.4%.
• Service population is about 115 million
people (Total population 127million)6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Introduction (Population declining of Japan)
The overall population of Japan is expected to fall from thepresent level of around 130 million to around 88 million in 2065.

88million

The service population of wastewater treatment
and then its sewage inflow also will decrease.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

The sustainability of the wastewater treatment service is
now on crisis.
•••••

The operation efficiency of the facilities could be decreased.
The revenue from user-fee would also be decreased.
The shortage of financial resources
The shortage of technical staff
Demand for the reconstruction / renewal of aged facilities inthe near future…..

It’s necessary to introduce sustainable wastewater
treatment system under the population declining
society.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“15-18 May 2018, Munich, Germany

Our research
The optimization method of wastewater treatment
systems• Collected and created cost functions• Clarified the relation between the operating rate
and the maintenance cost
• Developed the estimation method of themaintenance cost in population declining society• Evaluated for technical and environmental points

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Target facilities in this research
Target on the small to medium-sized treatment plants which
would be sensitively affected due to decrease in inflow.
Facility(Occupy approximately
90% of the total)

Capacity(Small to medium)

Process(Those of accounted forabout 80%)

Sewerage(piping, urban area)

10,000 m 3 / dayor less

Oxidation ditch process(OD) , Conventional
activated sludge
process (CAS)

Agriculturalcommunity effluent(piping, rural area)

1,000 m 3 / dayor less

JARUSⅠ,Ⅲ,ⅩⅠ,ⅩⅡ,ⅩⅣ(Japanese standard)

Human waste
treatment(non-piping)100kl/day or lessAll

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

The optimization method of wastewater treatmentsystems(outline)
Basic survey and setting prerequisites• Basic information (population, inflow, service situation etc.)

Setting representative integration scenarios• (no integration, full integration, partial integration)

Comparison of economics• Calculate life cycle cost(consider operating rate)• Confirm the most economical one

Technical and environmental evaluation• Facility capacity, Energy consumption etc.

Comprehensive evaluation• Select the integration scenario→ Sustainable wastewater treatment system

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Representative integration scenario 1
No integration(Downsizing separately)
Original capacity
Downsizing tothe appropriatecapacity(each facility)

Efficiency could be improved by reducting the facility size
(downsizing) to appropriate facility capacity based on thefuture inflow prediction.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Representative integration scenario 2
Full integration(Unify treatment areas)
Treatment areaATreatment area
BTT

Decommission wastewater
treatment plant and connect toanother ones

Efficiency could be improved by decommissioning one oftreatment facility and unifying treatment areas.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Representative integration scenario 3
Partial integration(Unify sludge treatment function)
Wastewater
treatment plant
which accept othersludge

Decommission
only sludge
treatment
facilitieswater
treatment
Sludgetreatment

Efficiency could be improved by decommissioning thefunction of sludge treatment in one of treatment facility
and unifying it.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Collection and creation of cost functions (some example)
facilities , equipment

variable (x)usable rangefunction(y)●overall※m3/day10,000～50,000m3/day

mechanical●overall※m3/daym3/daym3/daym3/day1,000～10,000m3/day
1,000～10,000m3/day～299m3/day
300～1,300m3/day●overall※m3/day1,400～10,000m3/day

mechanical(water treatment)

m3/day1,000～10,000m3/day
y = 2271.2x0.6663
y = 237,636x0.4571
20～100kl/day

1.reconstruction / renewal cost [thousand JPY]CAS

mechanical(water treatment)●overall※sewerage
OD

agricultural community effluent ●overall

human waste
treatment

pipe

over allpretreatment
standard processequipment
standard process

construction●manhole type pumping station●gravity system●pressurized sewer●small scalepersonkl/daykl/day20～100kl/day

pointmmm-

y = 1,550,000（x/1,000）0.58
×(103.3/101.5)
y = 72,734x0.26
y = 978x0.59
y = 14,680x0.49
y = 505,000（x/1,000）0.64
y = 1,380,000（x/1,000）0.42×(103.3/101.5)
y = 1,580x0.66

y = 57,548x0.5274
y =9,200x
y =63xy =45xy =56x

2.maintenance cost ［thousand JPY/year］●overallm3/dayagricultural community effluent ●overall

personoverallover allpretreatment
overallequipment

kl/day1,000～10,000m3/day
10,000m3/day～
300～1,300m3/day
1,400～10,000m3/day
20～100kl/day

kl/day20～100kl/day

point
mm

-

seweragehuman waste
treatment

pipe

CASOD

overall●overall●manhole type pumping station●pipe（standard）●pipe（small scale）●The function described in the past document※Including structures, machinery and electrical equipment

m3/dayy = 2,468x0.382
y = 18,800（x/1000）0.69×(103.3/101.5)
y = 19,000（x/1000）0.78
y = 28,600（x/1000）0.58×(103.3/101.5)
y = 37.811x0.6835
y = 17,845x0.57
y = 6,716x0.2692
y =220xy =0.060x
y =0.031x

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

The relation between the operating rate andthe maintenance cost
Operating rate x＝ (Average inflow volume) (m3/day)/ (The facility capacity) (m3/day)
The facility capacity

Average inflow

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

The relation between the operating rate andthe maintenance cost
• Arranged the maintenance costas M-coefficient ”km”.
• “km” indicates the maintenance cost per unit
inflow at a certain operating rate.
Maintenance cost
per unit inflow(certain operating rate)

The larger “km” indicateskm (ratio) the more inefficient
operation situation.
Referance value(Fixed)(ones at max operating rate)

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany“km” is increased as the operating rate decline.
2.47

1.00
28%

The maintenance costdoesn’t decrease,even if the inflowdecreases.
(km isn’t constant)70%

Difficult tocontrol
aeration(singlechannel) etc.

Fig. Relation between the operating rate and M-coefficient (Sewerage:OD)

The lower the operation rate, the worse the operation
efficiency of the facility.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

The future maintenance cost estimation(an example)
Condition
Facility type

Sewerage(OD)

Current maintenance cost

65,000,000JPY/year

Current inflow

1,000,000m3/year

Current operating rate

70％

Future inflow (estimate)

600,000m3/year

Future operating rate

42％

・km’s ratio (current and future)

1.65 / 1.00 = 1.65

・Future maintenance cost(per unit inflow) 65 × 1.65 = 107.25 JPY / m3
・Future maintenance cost(total) 107.25 × 600,000 = 64,350,000 JPY / year
Reference: Estimated results without considering operating rate65(using current unit of maintenance cost) × 600,000

Big difference= 39,000,000 JPY / year

The cost estimation would be more accurate by this method.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Pipe

Whether the flow velocity is satisfied or not
How often the pipe cleaning is required

Whether the pumping capacity
is satisfied or not
Wastewater Whether the capacity is satisfied or not
pumpingstation

treatmentplant

In the case of acceptance of night soil etc.,
its receiving ratio
In particular, Notice when the ratio
exceeds 10%.

Essential points

Some important points for the examination in case of theintegration is listed for technical evaluation.
problems that must be checked
Sort
Whether the flow capacity is satisfied or not6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Environmental evaluation (some example)• Calculation the energy
consumption andgreenhouse gas(GHG)
emissions from the power
consumption.

(example)• The merit of sludge concentration by integration
increase of digested gas generation amount, etc.
Increased digested gas

E.g. Collect of sludge by integration.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Comprehensive evaluation by optimization method(example)
Factors

scenario 1

scenario 2

scenario 3

Overview

no integration

full integration

partial integration

5,879

4,368

5,016

Life cycle cost
[million JPY]

Technologicalevaluation-the capacity of the the capacity of thepipe etc.
treatment plant etc.

Environmental evaluationEnergy consumption[Mega joules]

120 million

109 million

116 million

GHG emissions[t-CO2]

16,732

15,11616,144

Evaluation results

most efficient

In this example, Scenario2 (full integration) was found to be
the most efficient.

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, Germany

Considering the renewal schedule of each facility(treatment plant,pipes of A,B) for the selected scenario,
optimum stepwise construction plan was developed.
6,000

Annual cost [million JPY]

800600

Maintenance cost(A)Maintenance cost(B)

4,000"A" Treatment plant renewal cost
400

Construction cost of pipes for integration

cumulative cost200

maintenance cost of A
doesn’t increase much

2,00000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Integrated on the 6th year

Increasing operating
rate after integration

Cumulative cost[million JPY]

Optimum stepwise construction plan（Unify treatment area B to A）

6th EWA / JSWA / WEF Joint Conference„The Resilience of the Water Sector“
15-18 May 2018, Munich, GermanySummary
 Developed into the coefficients from the relation
between the operating rate and the maintenancecost. It enable us to estimate the maintenance costin the future.
 Confirmed the tendency that the maintenancecost per unit inflow ”km” increase as theoperating rate declines each facilities.
 Developed the optimization method forsustainable wastewater treatment systems in thepopulation declining society.