Küçük sahil yerleşimlerinde su temininde çoklu karar analizleriyle desalinasyon teknolojisinin entegrasyonu
Integration of desalination technology in small coast towns' water supply with multi criteria analyses
Yazar: MURAT SÖNMEZ
Danışman: PROF. DR. İLHAN TALINLI
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
Günümüzde insanlar tarafından su çevrimine göre suyun kullanımı ihtiyacı doğal koşullar ve jeolojik yapı ile ilişkili olarak önemli oranda farklılıklar göstermektedir. Yüzeysel su kaynakları açısından fakir olan bölgeler ve yerleşim yerlerindeki hızlı nüfus artışı bu problemin temelini oluşturmaktadır. Bu problemde mühendisleri su temininde farklı çözümler bulmaya yönlendirmiştir. 20. yüzyılın sonundan itibaren sürekli gelişim göstermekte olan desalinasyon teknolojisi ise su temininde yaşanan sıkıntıyı giderebilecek önemli bir gelişmedir. Bu proses farklı fiziksel, kimyasal yöntemler kullanarak miktar açısında hiç sorun teşkil etmeyen deniz suyunun tatlılaştırılmasını yani tuzunun giderilmesini sağlamaktadır. 
Özellikle sahil bölgelerinde bulunan küçük yerleşim yerlerinde yaz dönemlerinde nüfus patlaması sonucu artmakta olan su ihtiyacını karşılamak için deniz suyundan çok kademeli ani damıtma (MSF), çok etkili damıtma (MED), ters osmoz (RO), vb. desalinasyon teknikleri ile yüzeysel su kaynaklarını destekleyerek su temini için bir model oluşturmak amacıyla bu çalışma ortaya konmuştur. Ele alınan senaryodaki hangi seçeneğin uygun olabileceği yapılan çok kriterli analizler ile bulanık analitik hiyerarşi prosesi (FAHP) yöntemi kullanılarak tespit edilmiştir. Bu şekilde karar verecek olan kişiye ya da kurumlara yardım edileceği düşünülmektedir. Bu amaç çerçevesinde bu çalışmanın kapsamında ise öncelikle ikinci bölümde su temini için gerekli olan su alma yapıları ve iletimi konusunda inceleme yapılmıştır. Ardından ise tuzdan arındırma seçeneği üzerinde üçüncü bölümde ayrıntılı bir şekilde bahsedilmiştir. Bu bölümde öncelikle desalinasyon teknolojisinin tarihçesi ve dünya üzerindeki kapasitesi hakkında bilgi verildikten sonra deniz suyu özellikleri hakkında inceleme yapılmıştır. Bundan sonrada termal ve membran teknolojiler hakkında bilgi verilmiş olup enerji tüketimi ve çevresel etkileri üzerinde durulduktan sonra bahsedilen desalinasyon tekniklerinin karşılaştırılması ile bu bölüm sonlandırılmıştır. Desalinasyon hakkında bilgi verildikten sonra ise dördüncü bölümde bu çalışmada uygulanacak olan yöntemin temeli olan bulanık mantık ve analitik hiyerarşi prosesi hakkında açıklamalarda bulunulmuştur. Beşinci bölümde ise bu çalışmada kullanılacak olan FAHP yöntemi hakkında ayrıntılı bir şekilde açıklamalarda bulunulmuş olup uygulamada izlenecek çözüm yaklaşımının verilmesiyle bu bölüm sonlandırılmıştır. Ardından altıncı bölümde ise FAHP yöntemi ile Antalya'nın Kaş ilçesi için bir su yönetim modeli oluşturulmuştur. Bu model neticesinde hangi seçeneğin ilçede uygulanmasına yönelik bir tercih sıralaması elde edilmiş olup sadece desalinasyon ile su temininin uygun olacağı görülmüştür.

Abstract:
According to water cycle, people's water consumption need shows important differences due to the change of natural conditions and geological structure. This problem consists of two basic causes; the poor areas about surface water sources and high population growth rate in towns. It's directed engineers to find new solutions for water supply. Together with the end of 20. century, desalination technology has showed great development and in this way, it is a significant chance that can remove trouble in the water supply. This process that uses several physical and chemical methods remove salt from seawater that is unlimited source.
In this work, firstly, it is told how water is important for the sustainability of life together with water cycle. After that, information is given about various water intake structures (from surface water and groundwater). Then, if it is necessary after treatment, it is told how water is transported from sources to people and is stored. After the information about water supply is given, how it is treated in the third chapter.
Water is the most significant element of the life and therefore, it's not surprised that many people believe that distillation technologies have been used so as to produce fresh water since the fourth – century BC. This technology is started to spread out while growing owing to the water crisis especially in Middleast and the other countries in the World together with the end of 20. century. The capasity of desalination has reached to the peak level due to high population growth rate and changing climate conditions in the 21. century. It is thought that this is continued in this way. Nevertheless, increasing demand for this technology decreases it's cost. Approximately % 97 of the water sources in the World is found in the seas and oceans that cover approximately % 70 of the earth surface. Hence, it is obliged to use this source in order to survive. In addition, removal of salt from seawater is hard compared to solid particles because overcoming of the osmotic pressure is required and therefore, the requirement for energy is higher according to the other treatment processes. Through the principle of the sustainable life, for this necessity, if renewable energy sources are used, the increasing climate change worries would be removed. In this work, this technology is investigated as two titles; thermal and membrane technologies. Thermal technologies is based on the principle of evaporation of seawater and then production of pure water with the condensation of vapor produced. There are various thermal processes such as multistage flash distillation (MSF), multiple effect distillation (MED) and vapor compression (VC). Membrane technologies is based on the principle that some ions are selectively permitted or minimized through semi – permeable membranes. There are various membrane technologies such as reverse osmosis (RO), nanofiltration (NF), elektrodialysis (ED) / electrodialysis reversal (EDR) and etc. Nevertheless, RO is the most widespread technology among the others. After the information about these technologies is given in this chapter, the product of desalination processes is assessed. Forward treatment follows desalination processes not only to stable it but also to make it compatible with the distribution system. After that, these technologies from the point of view of energy consumption and environmental impacts are investigated and then a comparison is made among them.            
Life is full of uncertainties that are not perceived in the same way by the people. The results of them aren't estimated, they don't consist of objective data and maybe they can be expressed as abstract. For instance, When you make a decision to buy a house, there are a lot of uncertainties such as where you can live, how you transport, how the situation of ground of the house is, etc. In situations like this, how to prefer the right option is tough with classical logic and also is impossible. However, Prof. Dr. Lotfi A. Zadeh who is a professor at the University of California, Berkeley developed the theory of fuzzy sets in 1965. In this way, expression of this uncertainties is provided. Owing to the fact that human brain thinks as verbal across the uncertainties, certain comments shouldn't be waited. Nevertheless, fuzzy logic that is developed by Zadeh takes into consideration grey tones between black and white like human thinking system. This helps decision makers during decision – making processes. In classical logic, there are two situations that are white and black. Then, a situation is wrong or true. There is no other options. But, fuzzy logic gives decision makers a chance to rank the options. Nowadays, applications of fuzzy logic are too many. After that, making a best decision inside a decision set by a decision maker is defined as multi – criteria decision problem. In this situation, there are a lot of methods that help decision makers such as analytic hierarchy process (AHP) that is told and used in this work. AHP was developed by Thomas L. Saaty who is a professor at the University of Pittsburgh in 1965. This significant method that is flexible and easy applicable and also not only quantitative but also qualitative all criterias are assessed in this method. Therefore it helps decision makers in the solution of a lot of hard problems. In this method, firstly, problem is exactly defined and then criterias and/or subcriterias are determined about this problem. After that, alternatives are designated. In this way, a hierarchy frame is conducted. Then, criterias and/or subcriterias are compared as pairwise. Finally, alternatives are compared as pairwise with themselves according to every criteria and/or subcriteria. Lastly, best option or best ranking is determined. 
AHP that is one of the multi – criteria decision making methods can't remove exactly uncertainty due to the usage of crisp values especially for abstract concepts. Therefore, classical AHP is combined with fuzzy logic and then fuzzy analytic hierarchy process (FAHP) is acquired. In this process, fuzzy numbers are used. In this way, intermittent assessment can be done that is reliable. A lot of studies are found in literatüre about this process. One of them was developed by Laarhoven ve Pedrycz in 1983. The other study is Buckley's approach (1985). Nevertheless, in this work, the approach that was developed by Chang in 1996 is used. Detailed information about this approach is given in the fifth chapter. After that, solution approach that is applied in this work is told. This approach was developed by Srdjevic and Medeiros in 2007. This is called as fuzzy decision making (FDM) approach.        
The FDM approach that is told in the fifth chapter is applied in order to form a water management model for Kaş, Antalya. When it's strategic plan that was published in 2014 is investigated, it is established that their surface water resources are being decreased. Therefore, a model is formed to assess the alternatives that supply water. With this model, especially in summer term, three options are proposed to meet increasing water demand owing to tourism so as to support their own surface water resources. These options are water supply with water conveyance, water supply with treatment of seawater and water supply together with water conveyance and treatment of seawater.
Nowadays, how water is important for the sustainable of life is an incontrovertible truth. Especially,  in small towns, in summer term, high population growth rate and decreasing surface water resources lead engineers to find new sources for water supply. In this way, treatment of seawater that is an unlimited source with desalination technology is a precious solution. With this technology, supporting surface water sources in these towns, a water management model is established. After that, this model is applied for Kaş, Antalya. For this town, with this model that uses FAHP method with multi – criteria analyses, three options are compared. These options are water convayence, water convayence and treatment of seawater and just only treatment of seatwater. The application results that treatment of seawater is best option. Nevertheless, RO process is chosen for desalination technology because of the fact that this process is more productive in small towns compared to MSF and MED. However, If the renewable energy and less (environmental friendly)/none chemical substance is used for this process, the environmental performance of the process is well. In addition, with this work, fuzzy version of AHP that is called as FDM approach is proposed. Owing to the performed tests, it can be said that the FDM approach is flexible and robust. It's been recommended as a reliable support tool for decision makers to use in real situations.