Applying Life Cycle Assessment to Drinking Water Treatment

W.Takashima*, S.Takizawa**and M. Fujiwara* *Japan Water Research Center, Minato-ku, Tokyo, 105-0001, Japan

(takashima@jwrc-net.or.jp) ** University Of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan Keywords: CO2 emission, energy consumption, LCA (Life Cycle Assessment), water treatment INTRODUCTION Although LCA (Life Cycle Assessment) is being implemented in many industrial sectors, so far there have been few examples of LCA research or practical applications in waterworks. We applied LCA method to drinking water treatment in order to collect fundamental data and show specific examples of the process for implementation of LCA in selection, planning, and maintenance of water treatment systems at purification plants. This report shows how energy consumption and CO2 emission depend on each process and stage, i.e. the stage of construction, operation and maintenance, and disposal, of drinking water treatment system through LCA research. The study forms a part of the "Research Into Water Treatment and Pipe Technology Aimed at Establishment of a Safe Water Cycle" subsidized by the Ministry of Health, Labour and Welfare. METHODS Water treatment types covered by this study were flocculation + sedimentation + sand-filtration, membrane filtration, ozonation, and activated carbon treatment. Major specifications of the respective facilities are listed in Table 1. Reference information about weight/volume of materials and equipment was collected from design specifications used for actual purification plant construction. The figures for energy consumption and CO2 emission per unit weight/volume for each material are based on available published databases and other reference documents. Some figures were directly from some related manufacturers.

Table 1 Main specification of facilities Item Specifications

Capacity Max. 21,000 m3/d Flocculation＋sedimentation＋sand-filtration Flocculation basin

Vertical baffled channel flocculator

Sedimentation basin Horizontal flow plate settler

Sand filtration basin Self backwashing type filter

Chemical feeding Intermediate chlorination: ratio (Average) 2 mg/l

Post-chlorination: 1 mg/l Coagulant(PACl): 20 mg/lActivated carbon absorption Filtering type Fixed bed gravitational

filtering Activated carbon Granular activated carbon Linear velocity 190 m/day Ozonation Ozone feeding ratio 2.0 mg/L Contact time 13.2 minutes Contact method Vertical baffle type flow,

Diffusing pipe feeder Membrane filtration

RESULTS A series of case studies were implemented by applying LCA methods mentioned above. The results are as follows: 1) Flocculation + Sedimentation

+Sand-filtration Figure 1, 2 shows LC-E (Life Cycle Energy consumption) and LC-CO2 (Life Cycle CO2 emission) amounts for this treatment system for 58 years operation. In construction stage, load caused by civil engineering for concrete structures, etc., makes up the highest figure. The LC-E and the LC-CO 2 in operation stage

Membrane module

Ultra filtration (organic membrane)

Filtering type Dead end filtering Flow rate 1.7 m3/m2/day Driving method Pump pressurization

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accounts for the most part of whole energy consumption and CO2 emission. Especially chemical feeding results in very high values. It includes those on the production of the chemicals, e.g. coagulant, chlorine. The electric power for feeding pumps, etc also causes to high LC-E and LC-CO2 values. If the chemicals are used continuously for as long as 58 years, it is likely that a considerable load will be produced. Consequently this area offers the potential for important energy savings and reduction of CO2 emission.

0 20 40 60 80 100 120

Construction

Operation

Renewal

Disposal

Law water

Flocclation

Sand-filter

Chemicals

Discharge

Electricity

LC-E　（106MJ/58ｙ）

Fig.1 LC-E for Flocculation + Sedimentation + Sand-filtration

0 1 2 3 4 5 6 7 8 9

ConstructionOperation

RenewalDisposal

Law water

Flocclation

Sand-filter

Chemicals

Discharge

Electricity

LC-CO2　（106Kg-CO2/58ｙ）

Fig.2 LC-CO2 for Flocculation + Sedimentation + Sand-filtration 2) Membrane Filtration The majority of LC-E and LC-CO2 appear in operation stage. The result is due to electric power for pumping the raw water into the membrane. In addition, a chemical, sodium hypochlorite, for back-washing and disinfection accounts for relatively large part. This system has relatively low LC-E and LC-CO2 amounts in construction stage. This might be due to the compact facilities of membrane filtration system. 3) Ozonation The majority of LC-E and LC-CO2 appear in operation stage. Electric power for ozone

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generation and injection accounts for the majority of both in operation stage. This part is highly subject to energy saving according to equipments and control system required. 4) Granular activated carbon (GAC) treatment The majority of both appear in renewal stage. This is due to activated carbon which is assumed to be replaced to new one for every four years in this study. This is due to activated carbon itself. The CO2 emission from GAC production is large because of heat processing. So it is likely that LC-CO2 reduction in operation stage is relatively small. 5) Flocculation + Sedimentation + Ozonation + GAC + Sand-filtration An approximation was carried out on an advanced treatment system based on the previous results. The major part of LC-E and LC-CO2 appear in operation stage. Electric power for intermediate pumps accounts for one third or a half of LC-E and LC-CO2 amounts in the stage. It is important to consider the whole system so that the power requirement like this should be minimized. CONCLUSIONS By applying LCA to drinking water treatment it became apparent that 1) LC-E and LC-CO2 amounts in operation stage are generally large and 2) they are mainly due to electric power for pumps and some chemicals for treatments. The important point is that the quantitative and long-term evaluation can be helpful when aiming for lasting improvements in pump operation methods and in use of consumables like chemicals, etc. In future, we expect that increasing examples of similar LCA implementation will contribute towards making water treatment system more energy efficient.

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Japan Water Research Center(JWRC)Director of Water Treatment Engineering Dept.

Mr. WATARU TAKASHIMA

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The present situation

The first commitment period of Kyoto Protocol has begun since 2008.Much more efforts toward reducing environmental impacts have been required in every field of society.

Water supply services also shouldcut the impacts in their activities.

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How do energy consumption and CO2emission depend on each drinking water treatment process and stage, i.e. construction stage, operation stage and disposal stage?

Life Cycle Assessment

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A Simple definition of LCA

Life cycle assessment determines the environmental impacts of products or services, thorough production, usage, and disposal.

As actual procedures, calculating Energy consumption (LC-E) or Carbon dioxide emission (LC-CO2)

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Calculation method of LCA1) As to one material

Unit energy consumption or unit CO2 emission

× Amount of materials used２） As to all materials

Summing up with all materials

Easy to understand but, a lot of work

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Calculation example（１）ー CO2 emission per Kw of motor

1) CO2 emission (kg-CO2) of 5.5KW motor (weight 116kg) in a raw material procurement stage

= 285.67kg-CO2

2) CO2 in a production stage = 400kg-CO2/motor-ton

3) CO2 a motor of 5.5kw= 285.67+(400×116/1000) =332.1kg-CO2/a

motor4) CO2 per kw

= 332.1kg-CO2/5.5kw = 60.38kg-CO2/kw6

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Calculation example(2)ー CO2 emission of motors

Installation of pumps in a construction stage1) Unit CO2 emission of motors : 60.38kg-CO2/kw2) Power of a motor : 15 kw/unit３）The number of motors : 2 units

Total CO2 emission in a construction stage.= 60.38 kg-CO2/kw ×15 kw/unit×2 units=1,811.4 kg-CO2

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Service lifeBuildings:58years, Pipes:38yearsElectric apparatus and

Machine:16years

Items SpecsFlocculation + Sedimentation +Sand-Filtration

Flocculation basin Vertical baffled channel flocculator

Sedimentation basin Horizontal flow plate settler

Sludge scraper

Sand-filtration basin Self backwashing type

Chemical feeding Intermediate Cl：2mg/l

（Average） Post Cl：1mg/l

PACl ：20mg/l

Activated carbon absorptionFiltering type Fixed bed gravitational

filtering

Activated carbon GAC , Depth 2.4m

Filter area/basin 110.8m2

Linear velocity 190m/d

Items Specs

OzonationOzone feeding rate 2.0mg/L

Contact time 13.2min

Contact method Vertical baffle, Diffusing pipes

Number 2 basins

Membrane filtrationMembrane module Ultra filtration（Organic)

Filtering type Dead end filtering

Flow rate 1.7m3/m2/d

Driving method Pump pressurization

Table 1 Main specification of facilitiesCapacity Max. 21,000m3/d

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Water treatment typesfor case studies

1) Flocculation + Sedimentation + Sand-filtration

2) Membrane Filtration3) Ozonation4) Granular Activated Carbon treatment5) Advanced treatment system

(Flocculation + Sedimentation + Ozonation + GAC + Sand-filtration)

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Fig.1 Grouping of Flocculation + Sedimentation + Sand-filtration

Flocculation+ Sedimentation Sand-filtration

Coagulant Post Cl

Raw water

Chemicals

【Treatment 】

Intermediate Cl

Washing waste water

Thickening

Electric equip.

【Common】

【Discharge】 (Sludge treatment）

(Abstraction)

(Transmission)

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0 20 40 60 80 100 120

Construction

Operation

Renewal

Disposal

Law water

Flocclation

Sand-filter

Chemicals

Discharge

Electricity

LC-E　（106MJ/58y)

Fig.2 LC-E for Flocculation+ Sedimentation + Sand-filtration

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0 1 2 3 4 5 6 7 8 9

ConstructionOperation

RenewalDisposal

Law water

Flocclation

Sand-filter

Chemicals

Discharge

Electricity

LC-CO2　（106Kg-CO2/58y)

Fig.3 LC-CO2 for Flocculation+ Sedimentation + Sand-filtration

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Receiving wellPipes,ValvesFloor pumps

Sub totalMixing basinMixersFlocculation basinWeirSedimentation basinInclined plate settlerScraperDischarge troughSludge equipments Electric equipments

Sub totalSand filtersDischarge troughFilter mediaCollectorInlet equipmentsDischarge equipmentswashing equipmentsPipes,ValvesElectric equipments

Sub totalFeeding chamberSodium hypochloriteCoagulant(PACl)Pipes,ValvesElectric equipments

Sub totalDranage basinPumpsPipes,ValvesRacksThicknerSludge scraperPumpsPipes,ValvesRacksElectric equipments

Sub totalReceiving & transformer Receiving & transformer

Monitoring equipmentsInsrumentation

Emergency power supply GeneratorSub total

Sludgetreatment

Drainage basin

Thickner

Raw water

FlocculationSedimentatio

n

Mixing basin

Buffle type flocculation

Horizontal-flow sedimentation basin

with inclined plate settler

Sand-filtration

Receiving well

Chemicals feeding

Feeding equipments

Sand filters

ElectricMonitoring & contorl

eqipments

0 20 40 60 80 100 120

Construction

Operation

Renewal

Disposal

LC-E　（106MJ/58y)

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Fig.4 Details of LC-E for F+S+S-f

Receiving wellPipes,ValvesFloor pumps

Sub totalMixing basinMixersFlocculation basinWeirSedimentation basinInclined plate settlerScraperDischarge troughSludge equipments Electric equipments

Sub totalSand filtersDischarge troughFilter mediaCollectorInlet equipmentsDischarge equipmentswashing equipmentsPipes,ValvesElectric equipments

Sub totalFeeding chamberSodium hypochloriteCoagulant(PACl)Pipes,ValvesElectric equipments

Sub totalDranage basinPumpsPipes,ValvesRacksThicknerSludge scraperPumpsPipes,ValvesRacksElectric equipments

Sub totalReceiving & transformer Receiving & transformer

Monitoring equipmentsInsrumentation

Emergency power supply GeneratorSub total

Sand-filtration

Sand filters

Raw waterReceiving well

FlocculationSedimentatio

n

Mixing basin

Buffle type flocculation

Horizontal-flow sedimentation basin

with inclined plate settler

ElectricMonitoring & contorl

eqipments

Chemicals feeding

Feeding equipments

Sludgetreatment

Drainage basin

Thickner

0 1 2 3 4 5 6 7 8 9

Construction

Operation

Renewal

Disposal

LC-CO2　（106Kg-CO2/58y)

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Fig. 5 Details of LC-CO2 for F+S+S-f

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Fig.6 Grouping of Membrane Filtration

Waste water tank Thickener

Sodiumhypochlorite

Rawwater Membrane

Electric eqip.

Buildings

【Common】【Discharge】

【Treatment 】

(Abstraction)

Chemical washingChemical tank

Washingwater tank

ChemicalWaste tank

ConditioningCoagulant

Reducing agent

(Sludge treatment)

(Discharge)

NeutralizationReducing

(Transmission)

(Sewer pipe)

0 2 4 6 8 10 12 14 16 18

Construction

Operation

Renewal

Disposal

Ｍｅｍｂｒａｎｅ

Ｄｉｓｃｈａｒｇｅ

Ｅｌｅｃｔｒｉｃｉｔｙ

Ｂｕｉｌｄｉｎｇ

LC-CO2　（106Kg-CO2/58y)

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0 1 2 3 4 5 6 7 8

Construction

Operation

Renewal

Disposal

LC-CO2　（106Kg-CO2/58y)

Contact basin Contact basinOzon generator unit

Air compressorHeat exchanger

Cooling water pumpExahaust ventilation fan

InstrumentationMonitoring panel

Decomposing towerCatalyst

Ozone generatorchamber Ozone generatorchamberTotal

Ozone

Feeding facilities

Exhaust ozone

Fig. 8 LC-CO2 for Ozonation

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0 2 4 6 8 10 12 14

Construction

Operation

Renewal

Disposal

LC-CO2　（106Kg-CO2/58y)

AdsorptionbasinTroughAvtivated carbonFilter mediaCollecting equipmentsInlet equipmentsDischarge equipmentsWeirWashing equipmentsPipes,valvesExhaust ozone facilitiesIncidental FacilitiesBuilding

Total

Adsorption basin

Fig. 9 LC-CO2 for GAC

Notice: GAC is supposed to be renewed every four years.18

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FlocculationSedimentation Sand-filtrationGACOzone

Waste water tank

Thickener

CoagulantPost Cl

Rawwater

Chemicals

Electric eqip.

Others(Intermediate

pumps)

【Common】

【Discharge】

【Treatment】

Intermediate Cl

（Sludge treatment）

(Abstraction)

（Transmiss

Fig.10 Grouping of Advanced Treatment (F + S +Oz +GAC +S-f)

0 10 20 30 40 50 60

Construction Operation Renewal Disposal

Intermediate pump

LC-CO2　（106Kg-CO2/58y)

Advanced treatment

Fig. 11 LC-CO2 for F+S+Oz+GAC+S-f

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LC-CO2

0 5 10 15 20 25

Sand Fil.

Membrane Fil.

106Kg-CO2/58Years

Construction Operation Renewal Disposal

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Conclusion 1) LC-E and LC-CO2 in operation stage

are generally large.

2) Both of them are mainly due to electric power for pumps and some chemicals for treatments.

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Recommendations1) Consider the electric energy saving in

planning and designing.2) Paying much attention to proper

injection rate of chemicals in daily operation.As one of measures, avoiding abstracting

highly turbid water would contribute to the reduction of energy and CO2 emission.

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Thank you for your kind attention.ありがとうございました。

JWRC24

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