Membran teknolojisinin çevre mühendisliğinde kullanım potansiyeli ve ters osmoz ile amonyum iyonu giderimi

Abstract

Günümüzde, artan su fiyatı, çevrenin kirlenmesi, atıksu uzaklaştırma maliyetlerinin yüksek olması gibi nedenlerle atıksuyun arıtılıp tekrar kullanılması ekonomik hale gelmiştir. Ayrıca su kaynaklarının giderek kısıtlı hale gelmesi ve kalite bozulmaları, deniz suyundan tatlı su eldesi v.b. ileri arıtma yöntemlerini gündeme getirmiştir. Bunda da başvurulan yol membran teknolojisi olmuştur. Evsel ve endüstriyel atıksularda, azot bileşikleri toplu halde, en önemli kirleticilerdendir. Azot bileşikleri, alıcı ortamda meydana getirdiği zararlı etkilerden dolayı, biyolojik ve fiziko-kimyasal arıtma yöntemleri ile arıtılmaktadır. Membran prosesler de, azot bileşiklerinin arıtılmasında, özellikle deşarj standartlarının çok sıkı uygulandığı bölgelerde, yaygın olarak kullanılmaya başlamıştır. Aynı zamanda, elde edilen konsantre kısmının da ayrı olarak değerlendirilmesi söz konusudur. Konsantre kısımda, azot bileşiklerinin yüksek konsantrasyonlarında olması, gübre olarak değerlendirilmelerini gündeme getirmiştir. Bu çalışmada, membran proseslerin teorisi ve çevre mühendisliğindeki kullanılma potansiyeli geniş bir biçimde araştırılmış, uygulamalardan örnekler verilmiştir. İki aşamadan oluşan deneysel çalışmada, ilk olarak konsantrasyonları farklı sularda, ultrafiltrasyon ve ters osmoz membranları, ikinci aşamada, amonyum iyonunun ters osmoz membranları ile arıtılabilirliği araştırılmıştır. Zamanla akı, enerji maliyeti ve verim değerlerinin değişimi incelenmiştir. Bu maksatla, laboratuvarda teşkil edilen membran proses pilot tesisi ile sentetik numuneler üzerinde, bir seri deneyler yapılmıştır. Tezin birinci bölümünde tezin kapsamı, anlam ve önemi açıklanmıştır. İkinci bölümde, membran ile ayırma mekanizması ve membranların yapısı hakkında bilgi verilmiştir. Üçüncü bölümde, membran proseslerden ve membranların performansında düşüş meydana getiren, konsantrasyon polarizasyonu, jel polarizasyonu ve tıkanmadan bahsedilmiştir. Dördüncü bölümde, azot giderme yöntemleri ve ters osmoz ile amonyum iyonu giderme konusunda yapılmış literatür çalışmaları verilmiştir. Beşinci bölümde, bu tezde kullanılan membran proses pilot tesisi, çalışma prensibi, izlenen parametreler ve pilot tesiste yapılan deneyler ve deneysel çalışmanın aşamalarından bahsedilmiştir. Altıncı bölümde, bu çalışmada elde edilen sonuçlar değerlendirilmiş, ilgili grafikleri verilmiştir. Yedinci bölümde, sonuç ve öneriler belirtilmiştir. xvii

Human beings have faced with drinking water and wastewater treatment problems as a result of uncontrollable overpopulation, technological development and urbanization. They have been directed towards alternative production processes because natural sources have been reduced and become less and less. Concepts of recycling, controling at source and maximazing beneficial usage have been very important lately. Principles of sources are global concern and development is indispensable. "Protection of environmental values" and "Sustainable development" have become the agenda, so that to provide next generations needs. First applications of membrane processes have been done during the late 1950's. Fresh water has been obtained by filtering salty water through a semipermeable membrane under high pressure. This process was called "Reverse Osmosis". Osmotic pressure is prevented by using high pressure in this system. Various pore sizes have been developed in the semipermeable membrane material that are named as nanofiltration, ultrafiltration and microfiltration depending on their pore sizes. These systems work as a pressure driver. Membrane technologies have been used in advanced water treatment in Turkey since 1980 at which Turkish Water Pollution Control Regulation was published. Studies have been continuing to expend applications of this technology to get lower first investment and higher efficiency among research centers, universities and industries. Nitrogen and nitrogen forms are very important pollutants in domectic and industrial wastewaters. Nitrogen compounds have been treated by using biological and physico-chemical treatment systems because of their harmful impacts on receiving waters. Membrane processes have been extensively used to treat nitrogenous compounds especially in the regions of the discharge standarts strictly applied. The concentrated part of wastes should be considered differently from the liquid part of the wastes. The concentrated part of the wastes can be used as a fertilizer in agriculture because of their high nitrogen concent. In this study, first literature has been extensively researched. Second, the theory of membrane processes and its aplication in environmental engineering has been researched and pratical examples were given. Third, the experimental studies have been divided into two parts. In the first part, treatibility studies of different concentrated waters and the second part, treatibility studies of ammonium ions have been researched using reverse osmosis and ultrafiltration membrane processes. Finally; for this purpose, synthetis samples were prepared and the xvm membrane processes pilot system was established in the laboratory for the experimental studies. The results of these experiments were given below. a) First Stage Experiments: First stage of experiments were completed with distilled water, tap water and salty water. a-1) The flux, proportionally increased with pressure. Correlation coefficients (which explain this relation) reached over 90 %. The results of BW membrane experiments were given in figure 1. a-2) The cost of energy changed with increased pressure. Correlation coefficient reached over 90%. a-3) Filtrate concentration exponentially changed with increased pressure. Correlation coefficient reached over 90%. Figure 1. The results of BW membrane experiments xix b) Second Stage Experiments: In these experiments, NH4OH and Fe(NH4)2-(S04)2.H20 synthetic samples were used. b-1) Examining flux changes In filtration with BW membrane, there wasn't important effect of concentration variations on the flux value. The feeding tank and the flux values were approximately constant at 65 lt/m2*hour. In filtration with SW membrane, concentration variations in the feeding tank didn't cause important change on the flux value which was approximately constant at 56 lt/m2*hour. In Fe(NH4)2. (S04)2.H20 Solution ; In filtration with BW membrane, changes in the concentration in the feeding tank effected on the flux a little. The flux value decreased to 57 lt/m2*hour from 65 lt/m2*hour when the concentration was increased to 30 mg /It. In filtration with SW membrane, the changes in the concentration in the feeding tank effected the flux. The flux value decreased to 53 lt/m2*hour from when the concentration was increased to 100 mg/1. b-2) Analyzing Energy Coast In NH4OH Solution; In filtration with BW membrane, the changes of the concentration in the feeding tank effected the energy coast a little, was stable around 12 KWH/m3. In filtration with SW membrane, the changes of the concentration in the feeding tanf effected the energy coast a little, was stable around 26 KWH/m3. ]nFe(NH4)2.(S04)2.H20 Solution ; In filtration with BW membrane, the changes of the concentration in the feeding tank didn't cause significant energy coast changes that it was approximately 13.5 KWH/m3. In filtration with SW membrane, the changes of the concentration in the feeding tank didn't cause significant energy coast changes that it was approximately 25 KWH /m3. xx b-3) Analyzing Treatment Efficiency In NH4OH Solution; In filtration with BW membrane increase in the concentration in the feeding tank decreased the treatment efficiency. The efficiency decreased to 5% from 55 % when the concencration was increased to 186 mg/1. The reason for the low treatment efficiency might be NH4 ions passed easily through pores of the membrane because their diameters are not changed but they come more frequently on the membrane pores. So the treatment efficiency decreased and is inversely proportional with the concentration. In filtration with S W membrane, the changes of the concentration in the feeding tank effected the treatment efficiency. The efficiency decreased to 30% from 45 % when the concencration was increased to 90 mg/1 at 2 mg/1 treatment efficiency. The reason for this might be ions come more frequently on the membrane pores. So the treatment efficiency decreased when the concentration was increased. In Fe(NH4)2. (S04)2H20 Solution ; In filtration with BW membrane the efficiency increased when the concentration was increased in the feeding tank. The efficiency at 1 mg/1, increased to 98 % from 83 % percent when concentration was increased to 30 mg/1. The reason for this might be the pore size of NH/ ions was increased with making a ferrious comlex so the ions could not pass through the membrane pores. In filtration with SW membrane the efficiency increased when the concentration was increased in the feeding tank. The efficiency at 1 mg/1, increased to over 99 % from 88 % percent when concentration was increased to 100 mg/1. The reason for this might be same for BW membrane which it was increased the pore size of NHU"1" ions was increased with making a ferrious comlex so the ions could not pass through the membrane pores. Figure 2 shows the relation between time and the efficiency for BW membrane. xxi