Investigation of the change in the water quality of the Kehli Stream before and after the discharge of the urban wastewater

Evsel atıksu deşarjı öncesinde ve sonrasında Kehli Deresi’nin su kalitesi değişiminin incelenmesi

Abstract

Water pollution is most commonly associated with the discharge of effluents from sewers or sewage treatment plants, drains and factories. Pollutants that may exist in untreated water include microorganisms such as viruses and bacteria, inorganic pollutants such as salts and metals, pesticides and herbicides, organic pollutants and radioactive pollutants. Water quality objectives provide the basis for pollution control regulations and for carrying out specific measures for the prevention, control or reduction of water pollution and other adverse impacts on aquatic ecosystems. Water quality criteria for surface waters have been widely established for a number of conventional water quality variables such as pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and nutrients. The main aim of this study is to examine the change in the quality of Kehli Stream, which flows into Keban Reservoir with the distance and determine the quality class according to Water Pollution Control Regulation. For this reason, water samples were taken from a station before the effluent of Elazığ Municipal Wastewater Treatment Plant which is discharging into the Kehli Stream and from five different stations after the effluent was discharged into the Kehli Stream between April and June, 2006. DO and temperature, pH and electrical conductivity (EC) were carried out by using a WTW Oxi 330 Analyzer, Orion SA 729 Analyzer and Jenway 4075 Analyzer. Hardness, chloride, total solids (TS), suspended solids (SS), total kjeldahl nitrogen (TKN), ammonium nitrogen $(NH_4-N)$, COD, total coliform (TC) and fecal coliform (FC) parameters were analysed according to Standard Methods. At the station before the discharge, it was determined that DO, pH, temperature and EC values varied in the range of 6.66-9.71 mg/L, 7.58-7.74, 14.0-25.9 oC and, 350-860 $mu mhos/cm$, respectively. COD, BOD5, TKN, $NH_4-N$, TP, TS, SS, hardness and chloride values varied in the range of 10-55 mg/L, 3-35 mg/L, 0.47-3.36 mg/L, 0.33-3.18 mg/L, 1.84-3.18 mg/L, 470-750 mg/L, 300-360 mg/L, 212-356 mg CaCO3/l and 4.5-87.97 mg/L, respectively. TC and FC values were found between 3-24x$10^4$ MPN/100mL and 11-60x$10^3$ MPN/100mL, respectively. After the effluent was discharged, it was determined that DO, pH, temperature and EC values varied in the range of 0.9-8.45 mg/L, 7.09-8.77, 14.9-31.2 oC and 390-1600 $mu mhos/cm$, respectively. COD, $BOD_5$, TKN, $NH_4-N$, TP, TS, SS, hardness and chloride values varied in the range 80-420 mg/L, 65-225 mg/L, 4.92-41.16 mg/L, 4.2-40.0 mg/L, 7.23-23.93 mg/L, 460-960 mg/L, 120-560 mg/L, 152-344 mg CaCO3/L and 24.49-120.96 mg/L, respectively. TC and FC values were found between 5-90x$10^6$ MPN/100ml and 23-280x$10^5$ MPN/100mL, respectively. According to the results obtained, Kehli Stream is negatively affected by domestic discharges and agricultural drainage. The concentration of pollutants in the receiving water after disharge of the effluent is initially high, decreasing as the distance from the point of discharge increases. When wastewater containing high concentration of nutrients was discharged to the aquatic environment, these nutrients can be lead to the growth of undesirable aquatic plants. Results obtained were evaluated according to Water Pollution Control Regulation. With respect to organic parameters, at the station before the discharge of the effulent, it was determined that while Kehli Stream had the first class water quality in April, it was of the fourth class water quality level in May and on the second class water quality in June. While it was the first class quality water in April, it was of the fourth class water quality in May and June according to physical and inorganic-chemical parameters. In terms of bacteriological parameters, it was the fourth class for the monitoring period (three months). At all the stations after the discharge, it was determined that it was on the fourth class water quality level for all three months according to physical and inorganic parameters, organic parameters and bacteriological parameters. In summer, as the flowrate of the stream decreased, it hardly had the capacity to assimilate the pollutants. During the period the study carried out, it was determined that a portion of the wastewater of the city was discharged into the stream after treatment and the remaining part of the wastewater was discharged into the stream without any treatment. In this way, much of the pollution was discharged into Keban Reservoir.

Özet

Bu çalışmada Keban Baraj Gölü’ne dökülen Kehli Deresi’nin su kalitesinin mesafeyle değişimini incelemek amacıyla su kalitesi parametreleri Nisan ve Haziran 2006 tarihleri arasında analiz edilmiştir. Su örnekleri; Elazığ Kenti Atıksu Arıtma Tesisi çıkış suları Kehli Deresi’ne deşarj edilmeden önce bir noktada ve deşarj edildikten sonra beş farklı noktadan alınmıştır. Tesis çıkış suları deşarj edilmeden önceki noktada Kimyasal Oksijen İhtiyacı(KOİ), Toplam Kjeldahl Azotu(TKN) ve Toplam Fosfor(TP) değerleri sırasıyla 10-55 mg/L, 0.47-3.36 mg/L ve 1.84-3.18 mg/L arasında değişirken, deşarjdan sonra KOİ, TKN ve TP değerleri sırasıyla 80-420 mg/L, 4.92-41.16 mg/L ve 7.23-23.93 mg/L arasında değişmiştir. Tesis çıkış sularının deşarj edilmeden önceki noktada organik kirlilik açısından Nisan ayında I. sınıf kaliteli su iken Mayıs ayında IV. ve Haziran ayında II. sınıf kaliteli bir su seviyesinde olduğu tespit edilmiştir. Deşarjdan sonra bütün noktalarda her üç ayda da IV. sınıf kaliteli su seviyesinde olduğu görülmüştür. Bakteriyolojik parametreler açısından deşarjdan önce ve deşarjdan sonra bütün noktalarda IV. sınıf kaliteli bir su seviyesi gözlenmiştir. Yaz aylarında derenin debisi çok azaldığından kirleticileri özümleme kapasitesi hemen hemen bulunmamaktadır. Çalışmanın yapıldığı dönemde kentin atıksularının bir kısmının arıtılarak bir kısmının da arıtılmadan dereye verildiği tespit edilmiştir. Bu şekilde büyük miktarda kirlilik yükü Keban Baraj Gölü’ne ulaşmaktadır.