Nanofiltrasyon ve granül aktif karbon ileri su arıtma yöntemlerinin karşılaştırmalı maliyet analizi
Comparative cost analysis of nanofiltration and granular activated carbon methods in advanced water treatment
Yazar: İLKAY UTKU
Danışman: PROF. DR. İSMAİL KOYUNCU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Mühendislik Bilimleri = Engineering Sciences ; Çevre Mühendisliği = Environmental Engineering
Dizin: Arıtma maliyeti = Treatment cost ; Birim maliyetleri = Unit costs ; Granüler aktif karbon = Granular activated carbon ; Su arıtma = Water treatment ; Ters osmoz yöntemi = Reverse osmosis method ; Yatırım maliyeti = Investment cost ; İçme suyu arıtma = Drinking water treatment ; İçme suyu arıtma tesisleri = Drinking water treatment plants ; İşletme maliyeti = Operation cost

Özet:
Yüzeysel su kaynaklarının arıtılarak içilebilir kalitede insanların kullanımına sunulması su idareleri için hedeflerin başında yer almaktadır. Ülkemiz denizlerle çevrili olmasına rağmen tatlı su kaynakları konusunda zengin değildir. Özellikle iç bölgelerde yaşayan vatandaşlara temiz ve güvenilir içme suyu temini hususunda ciddi sıkıntılarla karşılaşılmaktadır.
Mevcut su kaynaklarının etkili olarak kullanılması ve modern yöntemlerle arıtılması için her geçen gün yeni çalışmalar yapılmaktadır. İstanbul'un su ihtiyacı İSKİ'nin arıtma tesislerinde içilebilir kalitede kesintisiz olarak sağlanmaktadır. Arıtılan suyun kalitesinin arttırılarak tüketiciler tarafından içilmesini sağlayacak bir lezzette sunmak için araştırmalar ve yatırımlar yapılmaktadır.
İleri su arıtma yöntemleri, konvansiyonel metodlarla istenilen miktarda giderilemeyen toplam organik karbon, pestisitler, dezenfeksiyon yan ürünleri, tat ve koku gibi bazı parametrelerin etkili olarak arıtılmasını sağlamaktadır. Bu kapsamda İSKİ Elmalı İçmesuyu Arıtma Tesisi için ileri arıtma yöntemlerinden olan granül aktif karbon filtre ve nanofiltrasyon membran prosesleri bu çalışma kapsamında detaylı olarak ele alınmıştır. 
Yapılan tasarımlarda 23.000 m3/gün işletme kapasitesi için nanofiltrasyon prosesi ve granül aktif karbon filtre prosesi tasarlanmıştır. Proseslerin tasarımında Dünya'da daha önce yapılan ve işletilen ileri arıtma yöntemlerine sahip tesisler incelenmiş ve bu tesislerin tasarımlarından faydalanılmıştır. Nanofiltrasyon prosesi 15.000 m3/gün süzüntü suyu debisine göre tasarlanmış olup, 23.000 m3/gün debi ihtiyacı için suyun şebekeye verilirken %65 oranında paçallanması düşünülmüştür. granül aktif karbon filtre prosesi işletme kapasitesine göre dizayn edilmiş ve ozonla birlikte biyolojik aktif karbon filtresi olarak çalıştırılması planlanmıştır. 
Bu prosesler detaylı olarak incelenerek Elmalı İçmesuyu Arıtma Tesisine entegre edilmesi halinde karşılaşılacak olan maliyetlerin analizleri ayrıca yapılmıştır. Proseslerin kurulum aşamasında karşılaşılacak ilk yatırım maliyetleri alt başlıklara ayrılarak incelenmiş ve piyasadaki güncel fiyatları toplanmıştır. Bu çalışmada kurulması planlanan nanofiltrasyon veya granül aktif karbon filtre proseslerinin beş yıl süreyle işletilmesi halinde karşılaşılacak olan işletme maliyetleri hesaplanmıştır. Elde edilen maliyetler ile arıtılacak su miktarı oranlandığında birim üretim başına toplam maliyetler elde edilmiştir. Bu maliyetler kıyaslanarak iki farklı ileri arıtma yöntemi hakkında ekonomik açıdan bir sonuç ortaya koyulmuştur.

Abstract:
Treatment of surface water resources and providing potable water for people is one of the most important objectives of water administrations. Although Turkey is surrounded by seas, it is not rich in fresh water resources. In particular, citizens living in the inner regions are faced with serious difficulties in terms of clean and safe drinking water supply.
Advanced treatment technologies are not widely used in Turkey and conventional methods are utilized to treat parameters such as pesticides, organic carbon, softening, taste and odor. Studies conducted around the world provide new findings related to pollutants that threaten human health, and the limit values of these pollutants in drinking water are being reevaluated.
Many techniques have already been developed in water treatment and new techniques continue to be developed. The quality of the water to be used is primary for determination of the appropriate treatment method. Pollution in water can be eliminated physically, chemically and biologically. Water treatment plants rarely consist of a single unit and usually several processes are brought together because of the different pollutants in the water.
It is essential to determine the treatment method based on the statutory quality parameters determined by countries. Conventional treatment methods can be used in this regard, as well as advanced treatment methods based on eliminating specific pollutants and producing better quality of water.
New studies are being carried out every passing day in order to use existing water resources efficiently and to treat these resources with modern methods. İstanbul Water and Sewerage Administration (İSKİ) treatment plants continuously provide drinkable water to meet the water need of İstanbul. Studies and investments are being made to increase the quality of the treated water and provide high quality drinkable water to citizens.
Advanced water treatment methods provide effective treatment of some parameters such as TOC, pesticides, DBP's, taste and odor that cannot be effectively removed by conventional methods. In this context, granular activated carbon filters and nanofiltration membrane processes, which are advanced treatment methods used in İSKİ Elmalı Potable Water Treatment Plant, are discussed in details in this study.
If the quality of the water resource is good, water treated in conventional facilities is drinkable. However the taste perception of people varies among cultures. In some cases, advanced treatment methods need to be applied to treat the parameters affecting the taste of water. In this study, cost analysis of two different advanced treatment processes being added to a conventional treatment plant with a capacity of 23.000 m3/day will be performed. Based on the results of the study, economically critical issues will be identified for nanofiltration or granular activated carbon processes that will be planned in the future.
Nanofiltration is one of the most effective processes in the removal of inorganic contaminants in surface waters. The removal of multivalent ions involves electrostatic interactions. NF membranes have high permeability for monovalent salts. However, they can hold multivalent salts to a large extent so that the method is effective in removing the hardness caused by ions such as calcium and magnesium.
Nanofiltration (NF) process is used for the treatment of organic substances which lead to the formation of DBP's due to the low energy requirement compared to reverse osmosis. When surface water is treated with NF membranes, natural organic compounds are removed by the sieve mechanism since they have larger molecules than the pore size.
NF membranes are used in treatment of whey, recovery processes from dairy industry waste products, in color and organic matter removal in textile industry, and in organic matter and salt removal in pharmaceutical sector. There are applications for treatment of industrial wastewater where NF membranes are integrated with UF and RO membranes.
Adsorption is one of the processes commonly used in water treatment. Adsorption is the process where an atom, ion or molecule in a substance accumulate or stick to another substance. Adsorption occurs through accumulation between two different phase surfaces (solid-liquid or solid-gas). Substances that accumulate or stick to the surface of the other substance are called adsorbates, whereas the solid substance that accumulates adsorbates on its surface is called adsorbent. The main adsorbents commonly used in water treatment are activated carbon species, ion exchange resins and metal oxides.
Adsorption process has an important role in increasing the quality of treated water. Activated carbon is widely used for the removal of natural organic substances which cause the formation of organic molecules and DBP's that cause undesired taste and odor in water.
Activated carbon is used as an adsorbent for removal of natural organic substance in groundwater and surface water resources. Activated carbon particles used in water treatment are called as granular or powdered according to their sizes and there is no significant difference in their adsorptive properties.
The main reason for the widespread use of granular activated carbon (GAC) in water and wastewater treatment is that most of the carbon it contains can be reused by being subjected to a regeneration process. Activated carbon becomes saturated with the adsorbate substances accumulated in its pores and fails to adsorb new substances, and it adsorption capacity decreases considerably. For this reason, regeneration process becomes necessary so that GAC particles can be reused. If regeneration is not applied, the use of GAC can be economically costly.
The most common regeneration method used for GAC is thermal reactivation. In this process, the activated carbon that becomes saturated is heated in the furnace at high temperatures and the adsorbate materials are thrown out and burned. On the other hand, the system is kept under control to prevent activated carbon from burning and oxidation. After the reactivation process, GAC is ready for reuse.
Bacteria and other microorganisms occur naturally in water resources. The number of bacteria present at the outlet of sand filters is very low but the number of bacteria found in GAC filters in treatment plants where GAC is used is very high. Granular activated carbon surfaces and pores provide a suitable environment for microorganisms to survive.
Biofilm forms on GAC surfaces due to processes such as adsorption, desorption, adhesion, microbial growth and deaths. Biofilm is a gel-like medium consisting of microbial cells and extracellular polymeric substances. In the studies conducted, it was observed that spontaneous bioactivity occurred and developed on GAC during drinking water treatment. GAC with bioactivity observed on its surface is used for advanced water treatment and the biofilm layer on its surface is very effective for the biological removal of dissolved organic matter. This process is described as biologically activated carbon (BAC).
BAC process is commonly used together with ozone. As a result of the ozonation process, organic carbon species that cannot be biologically removed are degraded and converted into structures that are biodegradable. BAC process works like a two stage bioreactor together with adsorption of activated carbon. The organic matter adsorbed on activated carbon is biodegraded to allow the BAC filter to serve for a longer time and reduces the need for regeneration which is a relatively expensive process.
The Elmalı potable treatment plant is located within the borders of Göztepe neighborhood of Beykoz . The water treated in this facility supplies the coastal regions of this district. Studies are conducted by İSKİ to provide potable water to the region which requires 23.000 m3 of treated water per day.
With the rapidly increasing population in Istanbul, the present location of the facility is now within city limits. Uncontrolled urbanization has formed shanties and neighborhoods in the reservoir areas and it has been determined that this situation negatively affected some parameters in water quality.
In order to reduce the amount of organic carbon and DBP's found in the effluent water of the treatment plant, it is planned to establish a granular activated carbon filter process in the facility. The removal of ammonia, geosmin and MIB parameters found in reservoir water by biologically activated carbon process is one of the research topics of İSKİ.
İSKİ has been conducting studies on advanced treatment methods in order to increase the quality of the effluent water in Elmalı potable water treatment plant and to provide drinkable water to citizens. Based on the results of the membrane pilot plant established at Ömerli potable water treatment plant, the installation of a nanofiltration process at the outlet of the filter unit of Elmalı potable water treatment plant is considered as one of the alternative methods of advanced water treatment.
Nanofiltration process is used worldwide in removal of organic matter, pesticide, hardness, taste and odor in drinking water treatment. It is also preferred because it reduces the use of chlorine and minimizes the formation of DBP's. It is predicted that the amount of organic matter in the effluent water will significantly decrease with the NF process to be established in Elmalı potable water treatment plant and accordingly the need for chlorine will decrease.
In the designs made, a nanofiltration process and a granular activated carbon (GAC) filter process were designed for an operating capacity of 23,000 m3/day. In the design of the processes, facilities having advanced treatment methods which were constructed and operated in the world were examined and the designs of these facilities were utilized. The nanofiltration process was designed for 15,000 m3/day filtrate water flow, with a 65% blending rate when water is supplied to the network for a flow rate requirement of 23,000 m3/day. Granular activated carbon process was designed according to the operating capacity of the facility and it was planned to operate as a biologically activated carbon filter together with ozone.
These processes have been analyzed in details and the costs that would be encountered if they were integrated into Elmalı Potable Water Treatment Plant were also analyzed. The initial investment costs to be encountered during the installation phase of the processes were examined by dividing them into subheadings and current market prices were summed up. In this study, five year operating costs of nanofiltration or granular activated carbon filter processes planned to be installed were calculated. Total costs per unit production were obtained when the costs obtained were divided by the amount of water to be treated. By comparing these costs, conclusions were made on two different advanced treatment methods in terms of their cost effectiveness and economic performance.