Yenikapı ön arıtma tesisi deşarjının kimyasal arıtılabilirliği

Abstract

Halen Yenikapı'da bir ön arıtma tesisi ve derin deniz deşarjı mevcuttur. Bu tesise ilave olarak biyolojik arıtma yapımı planlanmaktadır. Ancak gerek yer problemi ve gerekse işletme zorlukları sebebiyle biyolojik arıtmaya alternatif arama zorunluluğu ortaya çıkmıştır. Söz konusu alternatif kimyasal arıtmadır. İşte bu çalışmada kimyasal arıtılabilirlik düzeyi araştırılmış ve elde edilen sonuçlar irdelenmiştir. Birinci bölümde, yapılan çalışmanın amaç ve kapsamı açıklanmış ve önemi anlatılmıştır. İkinci bölümde Yenikapı Ön Arıtma Tesisi 'nin tanıtımı yapılmıştır. Üçüncü bölümde Yenikapı Ön Arıtma Tesisi deşarjından alman numunelerin analiz sonuçlarına göre karekterizasyon yapılmış ve sonuçlar 1991 yılı çalışması ile mukayese edilmiştir. 4. ve 5. bölümlerde kimyasal arıtmanın prensipleri ile kimyasal fosfor giderimi hakkında bilgi verilmiştir. 6. bölümde koagülanlar için optimum doz tespiti ve optimum dozların karşılaştırılması yapılmış, günlük koagülan tüketimi ile üretilen çamur miktarı hesaplanmıştır. Daha sonra bulunan değerler 1991 yılında yapılan çalışma sonuçları ile karşılaştırılmıştır. 7. bölümde çalışmanın genel bir değerlendirmesi yapılarak elde edilen sonuçlar değerlendirilmiştir.

Istanbul is one of the biggest cities in the world, because of the its population. It accommodates approximately 15 million people. So it has got big problems like as unhealty construction. To solve the sewerage problem several studies have been conducted since years. Some of these studies conducted by Wild, Kehr, DAMOC and Camp-Tekser. In the sewerage project which has been continued at present, settlement areas are divided into eleven seperate sewage collection zones. A complete network of sewer and interceptors ending at 15 different treatment and discharge points are planned. Eight of these involve full biological treatment plants prior to marine discharges, while the remaining seven include only pretreatment consisting of coarse and fine screens and grit removel, then deep marine outfall into lower stream of bosphorus. The information About Yenikapi Pretreatment Plant was given in teh 2nd chapter. At present in the Yenikapi Discharge there are two parallel mechanically cleaned coarse screens with 80 mm size range, a pump station, two fine screens with 200 mm size range, four grit chambers and an effluent pump station. Also there is an ozone system to clean pollutant air in the treatment plant. Im the thirth chapter sampling and analysis methods are explained. The charecterizaion of the grit chamber was made on the 21 samples. These samples are 4 hours composit samples collected with half and hour interval. Also, classification of pollutants in terms of particule size distribution is also shown for each sample in this chapter. The maximum and minimum values of some parameters are shown in Table. 1. In addition to results of 21 samples analysis, these results were considered and statistical evaluation was studied. Also the results compared with the results of 1991. This study shown that the going of the leather industry affected the charecter of the Yenikapi Discharge. Table 1 The charecterization of the Yenikapi Pretreatment Plant Discharge In the fourth chapter princeples of the chemicel treatment are described. Chemicel precipitation, coagulation and effective factors on coagulation process, coagulation steps, nature of particles in wastewater and zeta potential, coagulation substances, coagulation diagrams, pH control and alkalinity, flocculation mechanisms and sludge production were explained. Chemical precipitation was a well-established method of wastewater treatment in England as early as 1870. Chemical treatment was used extensively in the United States in the 1890s and early 1900s, but, with the development of biological treatment the use of chemicals was abondoned and biological treatment was adopted. In the early 1930s, attempts were made to develop new methods od chemical treatment, and a number of plants were installed. In current practice, chemical precipitation is used (1) as a means of improving the performance of primary settling facilities, (2) as a basic step in the independent physical-chemical treatment of wastewater, and (3) for the removal of the phosphorus. Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical state of dissolved and suspended solids and to facilitate their removal by sedimentation. In some cases the alteration is slight, and removal is effected by entrapment within a voluminous precipitate consisting primarily of the coagulant itself. Another result of chemical addition is a net increase in the dissolved constituents in the wastewater. Chemical processes, in conjuction with various physical operations, have been developed for the x v :i. complete secondary treatment of untreated wastewater, including the removal of either nitrogen or phosphorus. Over the years a number of different substances have been used as precipitants. The most common chemicals are Alum, Ferric chloride, Ferric sulfate, Ferrous sulfate and Lime. The degree of clarification obtained depends on the quantity of chemicals used and the care with which the process is controlled. It is possible by chemical precipitation to obtain a clear effluent substantially free from matter in suspension or in the colloidal state. From 80 to 90 percent of the total suspended matter, 40 to 70 percent of the BOD5, 30 to 60 percent of the COD, and 80 - 90 percent of the bacteria can be removed by chemical precipitation. In comparison, when plain sedimentation is used only 50 to 70 percent of the total suspended matter and 30-40 percent of the organic matter settles out. In the fifth chapter chemical phosphour treatment was explained. The purpose in this section is to identify and discuss (1) the chemistry of phosphprus, (2) methods of phosphorus removal, (3) chemical phosphorus removal and reactions, (4) application points, (5) Rapid mixing and flocculation units, (6) settlement tanks, and (7) design methodology. The addition of certain chemicals to wastewater produces insoluble or low - solubility salts when combined with phosphate. The principal chemicals used for this purpose are alum, sodium aluminate, ferric chloride or sulfate, and lime. Ferrous sulfate and ferrous chloride available as by products of steel - making operations (pickle liquor), are also used..Polimers are used effectively in conjunction with alum and lime as flocculant aids. Factors affecting the choice of chemical for phosphorus removal : 1- Influent phosphorus level. 2- Wastewater suspended solids. 3- Alkalinity. 4- Chemical cost. 5- Reliability of chemical supply. 6- Sludge hendlin facilities. 7- Ultimate disposal methods. 8- Compatibility with other treatment processes. Iron or aluminum salts can be added at a variety of different points in the treatment process, but, because XVI 3. polyphosphates and organic phosphorus are less easily removed than orthophosphorus, adding aluminum or iron salts after secondary treatment (where organic phosphorus and polyphosphorus) usually results in the best removal. Some additional nitrogen removal occurs because of better settling due to chemical addition, but essentially not amonia is removed unless chemical additions to primary treatment reduce BOD loadings to the point where nitrification can occur. An increase in total dissolved solids can be excpected because of the added chemicals. In the sixth chapter experimental approaches of the study and experimental results were described. The equipment required to define the optimum operating conditions for coagulation and jartest explained. In the jar test experiments, coagulant solutionts were added to the six beakers and mixed rapidly at 100 rpm for one minute. Then it was flocculated at 25 rpm for 20 minutes and after flocculation paddles were removed it was allowed to settle for 30 minutes. In experiments, in which several coagulants were used to investigate optimum dosage of chemicals. Firstly FeCİ3 was used for chemical coagulation. After addition of the different concentration, optimum dosage for FeCİ3 150 mg/1 was determined. In the second experiment FeCİ3 + polymer were used for chemical coagulation. 2 mg/L Seperan MG205e and at different concentration FeCİ3 were added to the wastewater. Optimum dosage, 100 mg/L was determined. In the thirth study was done with the different concentrations of FeS04 and 200 mg/L was determined as optimum dosage. In the fourth study the different concentrations of alum were used. And for optimum dosage 250 mg/L was sellected. In the fifth experiment the different concentrations of lime and 2 mg/L Seperan were tried. Optimum dosage was obtained as 300 mg/L lime. In the sixth and seventh experiments 2 inorganic polymer were tried. These polymers are polyaluminumchloride, 33% solutions (PAC) and 50% solution aluminumchlorhydrate (sumalchlor) which were developed by Summit Research Labs. xvii :i. Finally all optimum dosages were studied again and compared. The results of these studies were given table. 2. Table 2 Removal efficiencies for different coagulants. At- the end of the sixth chapter daily coagulant consumption and sludge producing were calculated. The results of these calculation were given table. 3. After that the results of 1995 was compared with the results of 1991. Table 3 Daily coagulant consumption and daily sludge production As a result of this comparison, because of moving the leather industries the capital cost and operation and maintenance cost of chemical treatment plant decreased. xix In the seventh chapter, as a result of the study, experimental data was evaluated. The chemical treatment is sufficient for Yenikapi discharge to meet the wastewater standarts of deep marine outfall or receiving water standarts. It can be an alternative treatment method to advanced biological treatment methods