Türkiye'de alternatif su kaynaklarının fizibilite analı̇zlerı̇: Yağmur suyu hasadı, gri su kullanımı
Türki̇ye'de alternati̇f su kaynaklarinin fi̇zi̇bi̇li̇te anali̇zleri̇: yağmur suyu hasadi, gri̇ su kullanimi
Yazar: ELİF AYYÜCE KILINÇ
Danışman: PROF. DR. AYŞE GÜL TANIK
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri, Mühendisliği ve Yönetimi Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
Yeryüzündeki tüm canlıların temel yaşam maddesi olan su kaynakları, günümüzde yaşanan hızlı nüfus artışı, kentleşmenin yaygınlaşması, turizm faaliyetlerinin ve endüstrileşmenin yoğunlaşması ve kuraklık, taşkın ve sel gibi iklim değişikliği etkileri sebebiyle tehdit altında bırakılmaktadır. Yıllık kişi başına düşen su potansiyeli (1.322 m³) su stresi sınıfında yer alan ve iklim değişikliği sonuçlarından etkilenebilirliği yüksek bir coğrafyada bulunan Türkiye için suyun döngüselliğini koruyan ve iklim değişikliğine karşı direncini arttırmayı sağlayan yağmur suyu hasadı (YSH) ve grisu kullanımı (GSK) faaliyetleri oldukça önem arz etmektedir.
Bu tez kapsamında YSH ve GSK sistemlerinin ülkemizin önemli turizm kentlerinden olan Antalya ve İzmir illerinde farklı bina tipolojilerinde gerçek projeler üzerinden sistem tasarımları ve fayda-maliyet analizleri çalışılarak uygulanabilirliği değerlendirilmiştir. Sistemlerin tasarımına ilişkin teknik hesaplamalar ile uygulamaya yönelik bir metodoloji sunulmuştur.
Tezin ilk bölümünde, konunun anlam ve önemi vurgulanarak, çalışmanın kapsamı anlatılmıştır.
İkinci bölümde, YSH ve GSK sistemleri; tarihçe, tanım ve terminoloji, yağmur suyu ve grisu sistemi teknolojileri, kalite parametreleri, ulusal mevzuat, tasarım kriterleri, sosyal kabul edilebilirlik, teşvik ve sertifikasyon sistemleri gibi birçok açıdan ele alınmıştır. Ayrıca YSH ve GSK sistem bileşenleri incelenerek tasarım kriterlerine dair bilgiler verilmiştir.
Üçüncü bölüm, YSH ve GSK sistemlerinin fayda-maliyet analizini kapsamaktadır. Otel, konut, sanayi tesisi, alışveriş merkezi, hastane gibi farklı bina tipolojileri üzerinde ayrı ayrı olmak üzere YSH ve GSK sistemlerinin analizi gerçekleştirilmiştir. Ayrıca, Antalya'da projelendirilen bir alışveriş merkezi için YSH ve GSK sistemlerinin birlikte uygulanma durumu incelenmiştir. Yapıların proje ve kullanım aşamalarındaki farklılıklarının analizi için ilave senaryolar değerlendirilmiştir. Seçilen alanlarda toplanabilir yağmur suyu miktarı, geri kazanılabilir grisu miktarı, yeniden kullanım alanları alternatiflerinde ihtiyaç duyulan su miktarları, sistemlerin uygulanması halinde potansiyel su tasarrufu ve ekonomik kazanım hesaplanmıştır. Sistemlerin kazandırabileceği faydalar ve gerektirdiği yatırım-işletme bedelleri hesaplandıktan sonra gereken yatırımın, kazanılan faydalar sayesinde kaç yılda geri ödenebileceği hesaplanmıştır. Teknik ve işletme esaslarına vurgu yapılarak, sistemlerin etkin yönetimi üzerine öneriler sunulmuştur.
Son bölümde, elde edilen bulgular doğrultusunda çıkarılan sonuçlar ve öneriler sunulmuştur.
Bu çerçevede, alternatif su kaynakları sistemlerinin sürdürülebilir su yönetimi açısından önemi vurgulanmış, tasarım kriterleri ve işletme esaslarına dair öneriler ve örnekler sunulmuştur. Tez, sürdürülebilir su kaynakları yönetimi konusundaki literatüre önemli bir katkı sağlamaktadır.

Abstract:
Water resources, which are the essential elements of life for all living bodies on earth, are under threat due to rapid population growth, widespread urbanization, intensification of tourism activities and industrialization, and climate change impacts such as droughts and floods. Due to these factors, the consumption of available water resources increased five-fold in the 20th century, and this increase is expected to continue by 30% in the first quarter of the 21st century. As an effect of this increase, it is projected that by 2025, about 1.8 billion people will live in regions subject to absolute water scarcity and by 2030, almost half of the world's population will struggle to live in regions with high water shortages. Turkey, where the annual per capita water potential is 1,322 m³, is among the countries experiencing water stress. In addition, Turkey, located in the Mediterranean Basin, is in a geography with high vulnerability to the consequences of climate change.
Flood events and dry periods, which we have frequently encountered in the recent years, seriously affect nature, cause loss of life and lead to significant economic damage in our country as well as around the world. Humankind faces various climate change problems such as water resources drying up due to extreme heat, extreme weather events adversely affecting agricultural yields, and thus, economic development.
The fact that the impacts of climate change cannot be prevented in the short-term has increased the importance of climate change adaptation activities, and many national and international studies have been initiated in this regard. In the transition to the "Circular Economy", which is defined as the most important strategy for adaptation to climate change under the EU Green Deal Policy, it has become imperative to ensure the "circularity of water". Rainwater harvesting (RWH) and graywater reuse (GWR) activities have become important methods recommended by the Intergovernmental Panel on Climate Change (IPCC) within the scope of adaptation to climate change. Rainwater harvesting is an effective water management model that allows rainfall to be captured where it falls and used optimally without being dependent on distant water sources. Graywater is defined as domestic wastewater arising from showers, handwashing sinks, laundries and kitchens, excluding toilet waste and food waste from garbage disposals.
Within the scope of this thesis, system designs and cost-benefit analyses of rainwater harvesting and gray water reuse systems were studied on real projects in different building typologies in Antalya and Izmir, which are important tourism cities of our country. The applicability of RWH and GWR systems in different typologies has been analyzed and comparisons have been made.
In the first part of the thesis, the meaning and importance of the subject is emphasized and the scope of the study is explained.
In the second part, the history, definition and terminology, stormwater and graywater system technologies, quality parameters, national legislation, design criteria, social acceptability, incentive and certification systems are discussed. In addition, the system components of RWH and GWR are examined, and information on design criteria is given.
Social acceptability, which is an important issue for alternative water uses, and public perception are also investigated in terms of the RWH and GWR systems. Incentive and certification systems are emphasized, some international examples are  presented and information is given on the certification example applied in our country. The impacts of alternative water resources systems on the society and the difficulties in the dissemination of these systems are discussed.
The third chapter covers the design criteria and cost-benefit analysis of RWH and GWR systems. The design criteria of each system are explained in detail by examining some real projects from different areas of use (hotels, residences, industrial plants, shopping malls, hospitals). Precedents for the design of such reuse systems have been established to initiate such reuse activities in Türkiye, a developing country facing adverse climate change impacts on water resources.
The buildings studied are in 6 different typologies; hotel (2 units), residential building, industrial facility, shopping center and hospital. The feasibility analysis of an hotel, residential site and industrial facility located in Izmir province and another hotel, shopping mall and hospital based in Antalya province were studied. Each building was analyzed in accordance with the technical and financial details for the real application. The buildings selected for each typology reflect the average type of buildings that can be commonly seen in our country reflecting typical examples. Cost-benefit analyses of the RWH and GWR systems have been carried out separately in all selected areas. In addition, for the shopping center in Antalya Province, the case of the combined application of RWH and GWR systems has been studied. In the combined system, the payback period was reduced to 2 years and water savings increased to 69%.
Among the selected buildings, there are areas that are under project design phase and the construction has not yet started. The RWH and GWR systems at the project design stage eliminates the need for installation modifications. An additional scenario has been studied to examine the cost of demolition-construction due to installation changes on the payback period in the case of the applying RWH and GWR systems to existing buildings. In the case that the buildings designed in Izmir Province are the buildings currently in use, the payback period doubles on average for hotels and residential buildings. Therefore, it is concluded that new buildings should be designed in a way to integrate these alternative water resource systems. The cost of demolition-construction did not affect the payback period in the industrial facility. This is due to the fact that the wet areas in industrial facilities are not scattered, and this shows that the applicability of industrial facilities to RWH and GWR systems is high.
In case of implementating RWH and GWR systems; the amount of collectible rainwater, the amount of reusable gray water, water requirement amount in alternative reuse areas, potential water savings and economic savings were calculated in the selected areas. After determining the benefits that the systems can bring and the investment-operating costs,  the years required for the investment to be paid back is also calculated. In addition, technical and operational principles are emphasized and how these systems can be managed effectively is discussed.
In the last section, conclusions and recommendations are presented in line with the findings. 
It is understood that the RWH system is a relatively simple water recovery system in terms of installation and operation. It does not necessarily require high technical expertise and expensive equipment and fittings. In RWH systems, the amount of water harvested depends on the effective roof surface area and the regional rainfall regime. Therefore, the methodology is easy to apply, but it is considered as a system where the water flow rate is spatially and temporally variable. RWH system is regarded as a safer system in terms of quality rather than quantity.
In GWR systems, the amount of water that can be recovered varies depending on the intended use of the building and the number of people residing in it. In hotels serving for tourism where activities such as meetings and events are continuous and serving touristic activities, gray water production is usually high. However, the gray water potential is lower in buildings that are only open at certain hours and do not have uses such as showers and bathtubs (shopping malls, schools, etc.).
In provinces and districts with a large tourism capacity and large population fluctuations in different months of the year, both systems seem to be a suitable solution to the problem of water scarcity. Literature on the use of alternative water sources indicates that payback periods of less than 10 years is quite acceptable. This finding is confirmed through different typologies selected from Izmir and Antalya provinces of Türkiye. According to the results of the analysis, the payback period was found to be below 10 years in all areas except for the Antalya hotel RWH system (16 years). The high payback period in the Antalya hotel is due to the high need for piping and installation due to the dispersed wet areas.
According to the calculated cost components, it is concluded that the treatment system cost constitutes the majority of the investment cost in the GWR systems, while the storage cost constitutes the majority of the investment cost in the RWH system.
The potential for RWH is high in industrial facilities as they generally have larger roof areas. In addition, in industrial buildings, it is advantageous that wet areas are not scattered and pipe costs are low. The cost-benefit analysis for an industrial facility in Izmir showed a payback period of 2 years.
The water saving rates that can be achieved in the identified areas of use with the implementation of the RWH system vary between 3% and 48%. Total water savings through GWR were calculated as 34% for the hospital, 21% for the shopping center and 31% for the hotel. In the case of the shopping center where the combined system of RWH and GWR was studied, the total water saving rate was calculated as 72% from the water needed in the areas of flushing water, green area irrigation water, vehicle washing and cleaning needs.
The savings obtained show that these practices can provide high benefits. In this way, freshwater resources can be used more efficiently, especially in urbanized areas.
In this framework, the importance of alternative water resources systems in terms of sustainable water management is emphasized and recommendations on design criteria and operational principles are presented. This thesis is based on real cases and provides comprehensive examples that can be followed by other scientists and practitioners interested in water reuse in various parts of the world. It is an important contribution to the literature on sustainable water resources management.