The relationship between chemical parameters and toxicity in effluent-dependent and effluent-dominated systems

Endüstrileşmenin hızlı olduğu bölgelerde, akışı sürekli olmayan, tatlı su miktarı genellikle yağışlarla orantılı olan ve deşarjlar için alıcı ortam olarak kullanılan nehir ve dereler atıksu kanalları haline gelebilmektedir. Bu su kaynakları deşarj-bağımlı ve deşarj-ağırlıklı sistemler olarak sınıflandırılarak, farklı şekilde yönetilmesi gereken sistemlerdir. Bu çalışma, böyle nehir ve nehir kollarına sahip, endüstrileşmenin çok hızlı gerçekleştiği ve yaklaşık 1000 endüstrinin arıtılmış veya arıtılmamış deşarjlarını alan Ergene Nehri ve kollarında yapılmıştır. Çok karmaşık özellikteki birçok deşarjı alan bu nehir ve nehir kollarının, kirlenme durumlarına bağlı olarak zehirliliklerinin belirlenmesi sürdürülebilir kullanımlarının sağlanabilmesi ve yönetimlerinin doğru şekilde yapılması için önemli bir veri sağlayacaktır. Bu çalışmada bu nehir ve nehir kollarından numuneler alınmış ve kirletici parametreler ile Vibrio fischeri organizmasına zehirlilik etkileri ölçülmüştür. Çalışma sonuçlarında, bölgedeki özellikle deşarj-bağımlı sistemlerin kimyasal parametreler ve zehirlilik açısından oldukça etkilenmiş oldukları görülmüştür. Referans bölge olarak seçilen su kaynağının kimyasal parametreler ve zehirlilik açısından kirletilmediği, en çok kirlenmiş bölgenin tekstil ağırlıklı organize sanayi ve deri organize sanayi ile daha birçok endüstrinin deşarjlarını birlikte alan ve deşarj-bağımlı bir sistem olan Çorlu Deresi ile bir kolu olan Sinandede Deresi olduğu görülmüştür. Vibrio fischeri test organizmasının zehirliliğine neden olan parametreler istatistiki analizler yapılarak belirlenmiş ve çoklu regresyon analizi kullanılarak regresyon modeli kurulmuştur. Kurulan regresyon modeline göre zehirlilik ölçütlerinden olan EC10 değeri en çok Çözünmüş Oksijen (ÇO), Kimyasal Oksijen İhtiyacı (KOİ) ve Toplam Çözünmüş Maddelerden(TÇM) etkilenmiştir. Anahtar Kelimeler: Deşarj-bağımlı sistemler, deşarj-ağırlıklı sistemler, Vibrio fischeri, zehirlilik.Effluent - dependent and effluent -dominated systems here we call them effluent - dependent / dominated systems are defined as surface water consist primarily of discharge wastewater and/or runoff from urban and agricultural areas. An effluent - dominated stream contains more effluent than receiving water (> 50% effluent). An effluent - dependent stream is 100 % effluent and would cease flow if anthropogenic sources were to stop discharging. Effluent - dependent / dominated systems have many different properties than natural water bodies as most characteristics of them are dependent on human activities. Mostly without the human generated flow, some effluent - dependent / dominated rivers would be ephemeral. The two major characteristics of such these systems are an increase in pollution and an increase in dry weather base flow. Effluent - dependent / dominated rivers described in this study are in heavily industrialized area. The study area-Ergene River Basin- is situated in the north west of Turkey in Thrace Region. This basin is one of the biggest basins in the region. It has 11.325 km2 drainage areas and Ergene River and its branches collects waters of the watershed and discharges and this basin have effluent -dependent and effluent - dominated streams. In the basin, rapid industrialization caused many problems to environment quality of the waters in recent years. Total about 1000 industries wastewater effluents in the region are flushed directly into the river and streams. Some branches of the river have intermittent flow in dry seasons. So sometimes these streams receive little or no upstream dilution and effluents may comprise the majority of stream flows. In the basin, Ergene River is effluent - dominated and Çorlu and Sinandede streams are effluent - dependent streams. Çorlu stream and Ergene River are important, because they collect complex discharges of textile and leather industries, various industries wastewaters and municipal wastewaters. A field survey is conducted to detect a relationship between chemical parameters and toxicity in the river and streams samples. Understanding relationship of these systems is critical for maintaining water quality and offers challenges in regulatory permitting and monitoring. And these data could be used for proper management of such these systems in similar basins. In the current study toxicity of samples were determined with reconstituted freeze-dried bacteria called Vibrio fischeri. All calculations to determine percent inhibition effect (INH %) was performed with the BiotoxTM Software (Aboatox, Turku, Finland). Chemical parameters for wastewater samples included pH, Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Temperature (T), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Phosphate (TP), Total Sulfide (TS), Ammonium Nitrogen (NH3-N), Total Suspended Solids (TSS) and heavy metals were determined. After the results of the experiments, cause-effect relationship between chemistry and toxicity, ambient quality of effluent - dependent / dominated systems and degree of necessity of toxicological data for point sources pollution control were determined in effluent - dependent / dominated systems. For all cases data are presented as mean ± S.E. After assessment of the data it is found that Çorlu and Sinandede stream are the most polluted waters regarding to chemical and toxicological parameters. It is supposed that toxicity is caused by complex discharges. Because those streams collected the textile organized and the leather organized areas and lots of the other industries wastewaters. The Ergene stream which is chosen as reference ambient water wasn't polluted in respect of chemical parameters and, because of this result, it is supposed that it didn't show toxicity to Vibrio fischeri. Statistical analyses were conducted to understand chemistry-toxicity relationship between EC10 and various chemical parameters. Statistical analyses are done by using SPSS 13.0 statistic pragramme. Significant correlations were observed between EC10 values and COD, DO and TDS. The present study suggested that COD and TDS can be assumed as a good indicator of the potential toxicity of ambient waters of such these effluent - dependent / dominated systems. After multiple regression analyses, the data of COD, DO and TDS which have smaller than 0.01 P-values elected for setting multiple regression model. R2 of the model was 0.95. It was concluded that toxicity testing is a useful tool supplementing chemical analyses of the potential hazard from point sources in effluent - dependent / dominated rivers. Keywords: Effluent - dependent systems, effluent -dominated systems, Vibrio fischeri, toxicity