Seawater Desalination for Water SupplyFriday Lecture（#32） 17th Jun, 2016

Isao MORI (JICA Expert Team/Water supply & Sewerage)

Project for Formulation of Comprehensive Development Master Plan in the Mombasa Gate City

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Contents 1. Introduction 2. Water Demand Forecasting 3. Technology of Seawater Desalination 4. Issue of Seawater Desalination 5. Proposal and Discussion

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Abbreviations WTP: Water Treatment PlantWWTP: Wastewater Treatment PlantUF: UltrafiltrationMF: Membrane FilterRO: Reverse Osmosis

1. Introduction 1-1. Background Mombasa County does not have any surface water sources

and therefore it depends on water sources from outside thecounty. (E.g. from Mzima, Baricho, Marere and Tiwi)

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Apart from these,some residents alsoreceived its waterfrom many shallowwells, springs, waterpans and tubewellsoperated by privateinvestors and NGOs.

Water Supply Plan (source: KMP ISUD PLAN-2035)

1. Introduction 1-2. Issue of Water Supply Now the major water supply issues are

considered: Old or low level of water supply facilities Salinity and pollution of groundwater High Non Revenue Water levels

And, Water demand in future. Based on the forecast of future

population by Mombasa master plan, the water demand will increase in future.

And the water source will lack a lot.

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2. Water Demand Forecasting 2-1. Population Projection

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Mombasa County Population Projection to 2040(source: JICA Expert Team)

143,128 Island, 215,700

380,055

Mainland North, 1,520,800

250,179

Mainland West, 568,000

166,008

Mainland South, 447,000

939,370

Night-time population

2,751,500

995,732

Day-time population

3,026,650

-

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

2009 2015 2020 2025 2030 2035 2040

2. Water Demand Forecasting 2-2. Water Demand Projection (Draft)

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Mombasa Water Demand Projection to 2040(source: JICA Expert Team) Note: Under study

186,098 221,213 

262,952 

312,567 

371,545 

442,992 

 ‐

 50,000

 100,000

 150,000

 200,000

 250,000

 300,000

 350,000

 400,000

 450,000

 500,000

2015 2020 2025 2030 2035 2040

Domestic Water (m3/day) No‐n Domestic Water (m3/day)

Total Water Demand (m3/day)

2. Water Demand Forecasting 2-3. Development of Water Source Extension of the existing water source Development of Mwache Dam Recycled Water Rainwater Harvesting Seawater Desalination

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Development of Mwache Dam(source: CWSB)

Seawater Desalination(source: www.taprogge.com)

3. Technology of Seawater Desalination

3-1. Seawater Desalination Processes It is a process that removes or separates salts from saline

water to give fresh water, at the expense of energy. Desalination Processes can be broadly classified into two

groups: 1. Thermal Desalination (Flash Distillation) 2. Membrane Desalination

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Flash Distillation (MED)(source: ikcorp.biz)

Membrane Desalination(MF and RO)(source: global.kawasaki.com)

3. Technology of Seawater Desalination

3-2. Seawater Desalination in World

9 NIPPON KOEIVarious countryʼs usage of desalination (source: 12.000.scripts.mit.edu)

3. Technology of Seawater Desalination

3-3. Seawater Desalination in Africa （１）

Sojitz Completes Construction and Begins CommercialOperation of Desalination Plant in Republic of Ghana

Total project cost: US$126 million

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Desalination Plant in Republic of Ghana (source: www.sojitz.com)

Water production capacity: Maximum of 60,000 tons per day (equal to drinking water for approximately 500,000 people)

Facilities: Reverse osmosis membranes (RO membranes)

3. Technology of Seawater Desalination

3-3. Seawater Desalination in Africa （2） Toyota Tsusho Corporation announces that it has signed a

MOU with Mombasa County, the Republic of Kenya, to conducta feasibility study on supplying desalinated water to theMombasa district. (12 Dec 2013)

Construction of a 100,000m3/d desalination plant using a BOTcontract model. Target of operations: 2017 (current plan)

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Toyota Tsusho to invest billions in Kenyaʼs energy sector(source: capitalfm.co.ke)

3. Technology of Seawater Desalination

3-4. Seawater Desalination in Japan Uminonakamichi Nata Seawater Desalination Center

(MAMIZU PIA) in Fukuoka District, Japan (2005) Technique: UF + Reverse Osmosis Maximum product water volume: 50,000m³/d

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Desalination Plant in in Fukuoka District, Japan (source: www.f-suiki.or.jp)

4. Issue of Seawater Desalination 4-1. High Electricity Consumption Energy consumption of seawater desalination has more than

3 kWh/m3, including pre-filtering and ancillaries.

Since composition of the substance in which SeawaterDesalination Water has melted compared with fresh waterfrom River or Spring is different, this water is Not tasty .

For this reason, after adding some mineral etc. and adjustingthe taste, that produced water is supplied.

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Desalination Method (source: en.wikipedia.org)

Multi-stage Flash MSF

Multi-Effect Distillation MED

Mechanical Vapor Compression MVC

Reverse Osmosis RO

Electrical energy (kWh/m3) 4–6 1.5–2.5 7–12 3–5.5Thermal energy (kWh/m3) 50–110 60–110 None None

Electrical equivalent of thermal energy (kWh/m3) 9.5–19.5 5–8.5 None None

Total equivalent electrical energy (kWh/m3) 13.5–25.5 6.5–11 7–12 3–5.5

4. Issue of Seawater Desalination 4-2. Impact on Environment (around sea) Desalination plant discharges salt, chemical, heat, etc. which

were removed from seawater. It discharges 8.7% of condensing salt water against 3.5% of

the salt density of usual sea water. In the shore area, the impact on environment happens by

high salt density or high temperature water.

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5. Proposal and Discussion Solution for the Issue? 1) The newest technology is

installed for to cut down electricity consumption.

2) The condensing salt water is discharged to the deep sea more distant than the coast.

3) The treated water from WWTP is added to high salt water, and it is diluted.

4) Do you have any ideas?

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Desalination Plan in Mombasa (source: KMP ISUD PLAN-2035)

Thank you for your attention!

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Isao MORI Professional Engineer, Japan (Water supply and Sewerage)NIPPON KOEI CO.,LTD.Mobile Phone: +254-7-3189-2212 (Mombasa, Kenya)E-mail: t2278@n-koei.co.jp (or t2278@tamano.co.jp)

Comfortable living through water supply systems for children in future