Azo boyası içeren tekstil atıksuyunun anaerobik olarak arıtılması ve renk giderimi

Abstract

Günümüzde çevre kirliliği insan sağlığını ve doğayı tehdit eden önemli sorunlardan biridir. Temiz su kaynaklarının, hızla yok olduğu veya kirlendiği düşünülürse atık su arıtımı modern dünyanın önemli gereksinimlerinden biridir. Atıksuların renkli olması suyun ışık geçirgenliğini engelleyerek sudaki canlıların fotosentez yapmasını önler, Bunun sonucunda ekolojik denge bozulur. Günümüzde atıksu arıtımında yaygın alarak kullanılan aerobik mikroorganizmalar atık sulara renk veren azo boyalarını parçalamaya elverişli değillerdir. Bu nedenle, yapılan çalışmada azo boyası içeren tekstil atık suyunun anaerobik arıtılması ve işlem sırasındaki renk giderimi incelenmiştir. Bir boyama tesisinden elde edilen Kimyasal Oksijen İhtiyacı (KQİ) değeri 1010 mg/lt, kirlilik % si 33, berr saklık % si 26. B olan, baskın olarak D-Kentaş Kahverengi M ve D-İlkim Barı 5G azo boyalarını içeren atık su beş gün boyunca anaerobik olarak arıtılmış ve sonuçta KOİ'nin %57. 6 azaldığı, berraklığın % 10 arttığı ve kirliliğin % 12 azaldığı saptanmıştır. Atık sudaki boyaların ve non-iyonik ıslatıcının etkisinin tespit edilmesi amacıyla, biyokütle miktarı sabit tutulup çeşitli oranlarda boya ve non-iyonik ıslatıcı içeren sentetik karışımlar hazırlanıp arıtılabilirlik ve renk giderimleri incelenmiştir. Bu karışımlarda boya miktarları arttıkça KOİ giderimi azalmıştır. Boya miktarları arttıkça çamurdan gelen renk kirliliği etkinliğini kaybetmekte, boya miktarı azaldıkça ise çamurdan gelen kirlilik öne çıkarken % giderim değerleri azalmaktadır. Berraklık ve kirlilik parametrelerindeki değişiklik başlangıçtan itibaren ilk iki saatte olmakta daha sonra sabit bir değer almaktadır.

Technological development, rapid urbanization and increasing population have led to the pollution of the environment and are threatening the scarce mater resour ces. Today wastewater treatment has became a very important issue providing the reuse of water and preventing pollu tion of the water resources by municipal and industrial discharges. The textile industry and the dyestuff manufacturing industry arethe major sources for the release of dyes into the environment. Dyeing and finishing processes are two important steps in the textile manufacturing process. These steps involve the dyeing of man-made or natural fibers to the desired permanent colors and processing of these fibers into final commercial products. Hence dyeing and finishing processings have become an integral part the textile manufacturing process. However, in the dyeing and finishing processes, a considerable amount of wastewater is generated. The most notorious part of textile waste water is its strong color. Depending on the type of dyestuff usBd, the color of the textile wastewater varies from red, brown, blue, purple and black due to the their intensified and dark varieties. Textile wastewater can change color from day to day, or even several times a day because the dyestuff used in the dyeing process changes frequently due to customers requirements. The variation of color also causes frequent fluctuation in the DOD content of the textile wastewater. Such a strong color, if unt reated, would have a marked negative impact on the environ ment of the receiving water body. The large pH swing in the textile wastewater is another strong negative point. The pH variation is primarily caused by different kinds of dyestuff used in the dyeing process. In comparison to most industrial wastewaters, the temperature of textile wastewater is unusually high. Other important pollutant of textile wastewater may consist of small amounts of polyvinyl alcohol, carboxymethyl cellulose and starch used for sizing of the chemical or man-made fibers. The sizing VI agents have a very high COD content of over 1DDÜD mg/1, depending an their concentrations. They enter the waste water after the desizing process and contribute signifi cantly to the COD content of the textile wastewater. The color in the wastewater usually varies in inten sity according to the above strength classification. But in many circumstances, the low or medium strength waste water may also have a very strong color. Compared to other industrial wastewaters, textile wastewater entering the environment is large. In general basic parameters in wastewater characterization are physical, chemical and biological properties. Basic parameters in water characterization are below: 1 )j- Physical properties a- Tempetature range b- Insoluble components (colloidal, settleable, floatable) c- Color d- Odor e- Radioactivity f- Foamability g- Dissolved oxygen hH Corrosiveness 2)- Chemical Properties a- Organic and inorganic components b- Chemical oxygen demand, total carbon, extrac- tables c- pH, acidity, alkalinity d- Oxidizing or reducing agents e- Chloride, ion f- Hardness (Calcium and magnesium) g- Nitrogen and phosphorus h- Surfactants 1- Total dissolved salts j- Phenol k- Grease and hydrocarbons 3)- Biological Effects a- Biochemical oxygen demand b- Pathogenic bacteria c- Chemical toxicity The treatment techniques choise must be based on characteristics of the waste effectiveness of treatment processes and economics of the individual situation vii wastewater treatment is based on chemical and biological treatment, followed f locculation, settling, filtration, carbon adsorbtion, reverse osmosis, electrodialysis. Biological treatment systems are commonly used in treatment of textile industry waste waters. Biological treatment of industrial waste has been successful for wastewater treatment. Biological treatment systems has been classified as aerobic and anaerobic processes. Biological treatment in aerobic methods includes logooning, biological filtration and activated sludge process. The aerorobic processes in biological systems have been extensively applied due to their treatment efficiencies, low hydraulic retention times and they are easy to operate and control. However., their high operat ing costs and practical problems which have been appeared especially in high strength wastewaters, have increased the interest in anaerobic wastewater treatment. Anaerobic wastewater treatment processes are being used for the treatment of high strength municipal and industrial wastewaters for over a century. The processes convert organic materials into methane and carbondioxide in the absence of oxygen through a complex series of micrahial interactions. In such processes most of the chemical energy in the initial substrate is released as methane and can be recovered where as in aerobic processes the aerobic bacterial metabolism releases most of the original chemical energy from the organic matter by oxidizing them to carbondioxide and water. Bacterial cell (sludge) production is high in aerobic systems com pared to anaerobic ones, the reason being higher growth rate of aerobic bacteria because of high energy production in the aerobic route. Anaerobic processes are advantageous in making pos sible the recovery of an energy-rich product such as methane, the production of less sludge compared to aerobic systems, the possibility of high organic loading rate, the requirement of less energy and nutrients and no neces sity of oxygen supply. But these processes are very sen sitive to external stimulations such as changes in tempe rature, pH, mixing, hydraulic retention time etc. and therefore require continuous monitoring and attention. Dne other disadvantage of the anaerobic systems is the slow proceeding of the process during growth and start up periods compared to aerobic ones (Table 1). vm TABLE 1. Advantages And Disadvantages of Anaerobic Processes Advantages of Anaerobic Processes -Making possible the recovery of an energy-rich product -Production of less sludge -High organic loading rate possibility -Requirement of less energy Disadvantages of Anaerobic Processes -Sensitivity to external stimulations -Requirement of continuous monitoring and attention -Slom proceeding of the process with respect to aerobic systems. Since wastewaters consist of complex organic matters and it is not possible to measure the organic content each of them individually, it is necessary to use collec tive parameters such as chemical oxygen demand(COD), bio chemical oxygen demand, (BGD), volatile fatty acids(vTA). CDD is used as a measure of the oxygen equivalent of the organic matter content of a sample that is sus- pectible to oxidation by a strong chemical oxidat. To determine the influent characteristics, one of the most commonly used parameter is COD. In the textile wastewaters, color has been viewed by many as a parameter that would have little impact on the biota of a receiving stream or a sewage treatment plant. However, the discharge of highly colored waste is not only aesthetically unacceptable, but also impedes light penetration. Spent chemicals from dyeing repre sent one of the significant sources of textile pollution and there are several thousand dyes and other chemicals used in dyeing. Substantial quantities of these dyes are known azodyes. The azo linkage of this large and econo mically important group of dyes is considered to be axeno- biotic structural element as are the aromatic sulfo groups found in many commercial âzo dyes. It is therefore not suprising that azo dyes are not degraded in biological waste treatment plants. A certain proportion of azo dyes is eliminated from waste streams by adsorbtion to sludge. The major part, however, is found unchanged or modified in the effluent. Under anaerobic conditions azo dyes are reduced to colorless aromatic amines. Since these com pounds are carcinogenic, their formation must be preven ted, preferably by establishing conditions that lead to aerobic mineralization of azo dyes, or by establishing microbial strains that metabolize the dyes. IX In this study, anaerobic biological treability of a textile factory wastewater union is consist of azo dyes was experimentally investigated under anaerobic conditions. And the fate of azodyes in anaerobic con ditions was studied. Begining of the study the textile wastewater's properties are determined. These values are given below; CDD-1010 mg/1 pH-7.5 TS-1DQ mg/1 Dirty(%)-33 Luminance(%)-26.B In the experimental study, first of all any of the leaks in the anaerobic reactor were prevented. All experiments were done in fixed temperature (37DC) and mixing velocity (BOrpm /min). The anaerobic reactor has two liters volume and in the all experiments the anaero bic reactor was fed with wastewater (1.25 1) and anaero bic sludge (G.2 1). The biogas formation in anaerobic treatment was measured with a gas measure system. In this system biogas accumulated on the mineral oil and replaced with oil. Begining of all experiments 10 mi's of samples were taken in the system, in order to deter mine CDD, UFA,TS, TSS, TDS and color parameters. The treatment operation was continued until the COD value decreasing BOO mg/1. The pH value was observed between 6.5-7.5 all experiments. For this reason the pH control wasn't done during the treatment operations. Furthermore, the new synhtetic solutions were pre-i pared in order to investigate the non-ionic wetting matter and azo dyes effect on the treatment, and anaero bic treatability and color removal were investigated. The COD removal efficiency was achieved from 1100mg/l to BBO mg/1 in the original wastewater in five days. In the other synhtetic sollutions, if the quantity of dyes in these solutions were increased, COD values and COD removal with time would increase. The results of this study showed that the anaerobic treatment process can be successfully applied to the textile wastewater which con tain azo-dyes. The investigations showed that the removal of color in anaerobic processes is more effective. These values are best determined from the light transmission charac teristics of the filtered sample by means of a spectraphometer. The relative of dye is determined using the spectropohDtometer and a 1i cm path-length cell. In this study spectre-photometric method was used to read transmitance characteristics. In this method, the sample having original pH uas centrifuged to remove excessive quantities of suspended materials. 0.1 g filter aid (celite) uas mixed in a 1 D ml portion of centrifuged sample and filtered to form a precoat in the filter. Then G.04 g. filter aid uas mixed in a 35 ml. portion of centrifuged sample. The clean sample uas collected 25 ml. for the transmittance determination. Ue observed, the dyes uare reduced uithin Z-k hour under anaerobic conditions.