The spectroscopic and chemical profiles of commercial and network based drinking waters that are consumed in Istanbul

İstanbul’da tüketilen ticari ve şebeke bazlı içme sularının kimyasal ve spektroskopik profilleri

Abstract

The term drinking water can be briefly defined as all water distributed by any agency or individual, public or private sector, for the purpose of human consumption or which may be used in the preparation of foods or beverages or for the cleaning of any utensil or article used in the course of preparation or consumption of food or beverages for human beings. The term drinking water” also contains the concept that of all the water available for human consumption or used by any institution catering to the public. The municipal drinking water reaches the end-user, through numerous treatment processes covering disinfection, filtration, and chlorination at source with each complying with the current drinking water standards. However, within the process of treatment, mishaps occurring in the infrastructure, i.e. broken or cracked pipes in the network, seepage from wastewater network, can cause detrimental effects on the quality of drinking water. In the recent years İstanbul Water and Wastewater Association (İSKİ) has began taking water samples near 400 points throughout İstanbul and started replacing the existing old pipes with ones manufactured with the newest technologies providing utmost insulation. The safety limit values for drinking water parameters are assigned by Turkish Institute of Standards, however in the last years further global standards for the safety of drinking water, i.e. United States Environmental Protection Agency (USEPA), European Community (EC), World Health Organization (WHO) have also started to be taken into consideration. Considering the fact that Istanbul is one of the highest populated metropolises of the world, provision and maintenance of her drinking water needs and standards faced very big challenges in the last decades. This fact has promoted the commercial drinking water enterprises to rise, which required safety regulations as well. The commercial bottled waters consumed throughout the city are far from being supplied from local sources due to the very high market share threshold in Istanbul. These waters in general have been bottled following the catchments from the sources that are securely protected from anthropogenic pollution. Within the last years, non-spring waters that can fulfill sanitary requirements through rigorous treatment processes such as multiple filtration, uv-treatment, ozonation, and reverse osmosis have started to rank in bottled water market. In this research, alongside commercial bottled waters, tap waters linked to different water reservoirs supplying water for Istanbul were sampled and analyzed in terms of their chemical and spectroscopic properties and their comparisons were presented in order to set a general profile. The chemical properties of samples were monitored by measuring their total hardness, total organic carbon (TOC) and dissolved organic carbon (DOC) content, pH and conductivity, portraying a general outline of the water characteristics. These parameters kept accordance with the UV-vis spectral profiles. The organic content showed an intrinsic relation with the reported total trihalomethane (THM) values that are important in portraying the carcinogenic potential of disinfection by-products. Furthermore, rise of the peak heights were in correspondence with the arrangement of the samples according to their TOC values. The spectroscopic properties were examined through the use of UV/vis and fluorescence spectroscopy. UV/vis spectroscopy in comparison with the commercial bottled water samples yielded approximately doubled absorbance values in the range of 200 – 235 nm range for tap waters. The respective specific UV absorbance values were reported in the range of 0.0179-0.544 L/mg cm for tap waters and 0.063-0.46 L/mg cm for bottled water samples. With its high resolution and peak differentiation, synchronous scan fluorescence spectroscopy yielded explanatory spectrums producing basic peaks at 280 and 356 nm that are most likely representing an organic based component in the tap water. On the other hand, the contourless spectrums reaching maximum at around 450 nm extracted from emission spectroscopy strongly resembled the natural organic matter spectrums adding to the findings of organic content in the sample.

Özet

İstanbul ili, gerek kültürel gerekse ekonomik anlamda Türkiye’nin çekim merkezi olmasının bedelini ağır ödemektedir. Şehrin aldığı yoğun göçlere bağlı olarak oluşan düzensiz kentleşme ve beraberinde getirdiği altyapı sorunları, şebeke suyu kalite parametrelerinin devamlılığını son derece güç hale getirebilmektedir. Bu çalışmada, İstanbul geneline içme suyu sağlayan su kaynaklarını temsil niteliğinde şehrin farklı bölgelerinden rastgele alınan su örnekleri incelenmiş ve yine şehir genelinde içme suyu alternatifi olarak satılmakta olan bazı şişe suları genel kalite parametreleri ile karşılaştırılmıştır. Kimyasal özellik açısından başta tüm örnekler için toplam organik karbon (TOK) ve çözünmüş organik karbon (ÇOK) değerleri olmak üzere, sertlik, iletkenlik, pH değerleri incelenmiş her iki kaynağa ait su örnekleri için de, spektroskopik bulguları doğrular nitelikte değerlerle karşılaşılmıştır. Tüm su örneklerinin UV/görünür bölge spektrumlarına ek olarak floresans spektroskopik özellikleri emisyon ve senkron taramalı emisyon spektroskopisi teknikleri uygulanarak incelenmiştir. Örneklerin UV/görünür bölge spektrumlarına bakıldığında, şişe sularının ultraviyole bölgede organik maddelere işaret eden dalga boylarındaki absorbans (soğurma) değerlerinin şebeke sularına oranla yaklaşık yarı yarıya düşük değerde olduğu gözlenmiştir. Şebeke sularının emisyon floresans spektrumlarında ise belirleyici pikler gözükmemekle birlikte, spektrumların genel görüntüsü doğal organik madde bazlı bileşenlerin varlığını işaret eden konturlar vermiştir. Buna karşın senkron taramalı emisyon spektrumlarında yine organik maddelere işaret eden farklı pik değerleri gözlenmiştir. Şişe sularının floresans spektoskopisiyle elde edilen gerek emisyon gerekse senkron taramalı spektrumlarının ise şebeke suları için elde edilen profillerle karşılaştırılabilir düzeyde oldukları görülmüştür.