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: [email protected] (or [email protected])
Comfortable living through water supply systems for children in future