Journal of Environmental Protection and Ecology 11, No 1, 7–19 (2010) Water pollution
Decolourisation ofazo dyes containing wastewater by Phanerochaete chrysosporium in a rotating biological contactor G. Demir Faculty of Engineering, Department of Environmental Engineering, Bahcesehir University, 34 349 Besiktas, Istanbul, Turkey E-mail:
[email protected] Abstract. In this study, removal efficiencies of colour, COD, copper and aromatics in different concentrations of Remazol Yellow RR gran, Remazol Red RR gran and Remazol Blue RR gran were analysed using white rot fungus, namely Phanerochaete chrysosporium. Colour and COD removal efficiency values were compared with respect to EN ISO 7887 standards and Turkish water pollution and control legislation limit values. Colour measurements were made using values of the index of transparency parameter. Values of index of transparency = DFZ (DurchsichtsFarbZahl), in accordance with the EN ISO 7887 standards, were obtained by taking absorbance in 436, 525 and 620 nm. DFZ values were calculated from these measurements. The reactor hydraulic retention time was kept at 4 days (1ml/min of continuous flow rate) and 2 days (2 ml/min of continuous flow rate) with a 10 mg l–1 concentration of Remazol mixture and the disc rotating speeds were 10 and 15 rpms. The optimum reactor hydraulic retention time was determined to be 4 days. After the determination, experiments were carried out at the dye concentrations of 5, 10, 15, 20, 25 mg l–1 and disc rotation speeds of 5, 10, 15 rpms. As a result, disc rotation speed and removable dye concentration were determined to be 10 rpm and 10 mg l–1, according to the EN ISO 7887 standards for Remazol mixture and the specific type of reactor used. Keywords: textile wastewater, azo dyes, biodegradation, Phanerochaete chrysosporium, rotating biological contactor, decolourisation.
aims and background When coloured wastewater is discharged directly to the environment, the already toxic dyes cause the formation of more toxic wastes, especially in anaerobic conditions and this creates significant environmental problems1. Nowadays, the most common and standard treatment applied to textile wastewater involves biological and chemical methods2. Dyes can not be reduced to CO2 by adsorption, but instead pass from liquid phase to solid phase. Degradation of dyes can only be realised by chemical or biological oxidation. Since synthetic dyes are resistive to biological degradation, colour removal by biological processes is difficult. Colour removal is generally realised by adsorption of dyes on bacteria rather than oxidation in aerobic systems. Literature has shown that some of the anaerobic microorganisms degrade dyes by reducing their nitrogen bonds, but toxic and carcinogenic
compounds might be formed as final products as a result of the biological degradation3,4. Nevertheless, colour can be regained through contact of anaerobic degradation products with oxygen5. Using bacteria, these problems restrict the colour removal in large amounts. Because of the above-explained problems, faced with active sludge systems or aerobic, anaerobic bacteria during colour removal, colour and organic load removal with white rot fungi was studied in this study. It has been shown that white rot fungus has the ability to degrade many substances which are difficult to degrade, such as lignin, chlorinated aromatic and aliphatic hydrocarbons, and dyes by using extracellular enzyme systems1,6. The most commonly used white rot fungus types are Phanerochaete chrysosporium, Coriolus versicolor and Trametes versicolor. White rot fungus has a more active biological degradation in nutrition media where nitrogen is limited7–9. For this reason, by using a nitrogen-limited nutrition media in the study, the goal has been to make the white rot fungus take the nitrogen necessary for their microbiological activities from the nitrogen existing in the structure of the azo dyes. In the existing literature, there have been studies related to colour removal with white rot fungus in wastewater containing only one dye8,10,11. From this point of view, in this study, colour, COD, aromatic group and Cu removal using one of the white rot fungi has been investigated. The white rot fungi used was Phanerochaete chrysosporium, in a model wastewater containing certain concentrations and mixtures of Remazol Blue RR gran, Remazol Red RR gran and Remazol Yellow RR gran, which have been produced by the Dyster company and are of the widely used azo dyes because they are new. The obtained biological degradation efficiencies were compared with limit values in the legal regulations12,13. During colour measurements, a new colour parameter called Index of transparency parameter (DFZ = DurchsichtsFarbZahl) was used in accordance with the European Norm EN ISO 7887 (Refs 14 and 15). COD values were interpreted with respect to Water Pollution Control Legislation discharge limit values. As a result, in case of Remazol Yellow RR gran, Remazol Red RR gran, Remazol Blue RR gran, which have wide range of utilisation areas in the textile sector, exist in aquatic environments separately or together. The treatability of the colour and pollution load by one of the white rot fungi Phanerochaete chrysosporium, has been investigated. experimental Material and Methods
Microorganism. Phanerochaete chrysosporium ME 466 was first isolated by forest products laboratory in USA (Ref. 16).
Cultivation conditions. Cultivation conditions of Phanerochaete chrysosporium culture were performed according to the method used by Demir12. Decolourisation medium. In the studies, the medium suggested by Zang et al.17 was used as basic nutrition medium. Nutrition medium components, which existed in very small amounts, were initially prepared as stock solutions. Later, the abovestated amounts were used from these stock solutions. The same procedure was also followed while adding the dyes. Azo dyes. Three Remazol group dyes, namely; Remazol Yellow RR gran, Remazol Red RR gran and Remazol Blue RR gran, produced by Dystar company were used both separately and together in order to analyse the colour removal efficiency. Reactor. The reactor was used in all the experiments designed for this study. The system can be seen in Fig. 1 (Ref. 12).
Fig. 1. Schematic diagram of operating system: 1 – entering water tank; 2 – exiting water tank; 3 – biodisc unit; 4 – peristaltic pump; 5 – heater with thermostat; 6 – electrical motor; 7 – air filter; 8 – flowmeter; 9 – air compressor; 10 – control panel
Sterilisation and colonisation. The reactor was filled with 70% methanol for sterilisation up to the working volume before being commissioned12,18. In order to see the biological adsorption effect of the dyes on the fungi, distilled water containing the same concentration of dye and fungi, but without nutrition substance, was used to make checks in the batch reactor and was incubated at the same conditions with the biological degradation experiments18. Analytical Methods
Colour measurements. In the studies, DFZ parameter was chosen in accordance with the standards determined by the European Norm EN ISO 7887. DFZ limit values
determined according to European norm, are 7 m–1 for 436 nm, 5 m–1 for 525 nm and 3 m–1 for 620 nm (Refs 13–15). DFZ calculation was made according to: DFZ= 100 (Eλ/d)
where Eλ is extinction (at a known wavelength), and d – the thickness of sample in cm. COD analysis. COD experiments were realised according to the standard method (open reflux, titrimetric method) stated in APHA 5220 B (Ref. 19). Aromatic group analysis. Aromatic group analyses were realised by using a Jenway type 6105 UV/visible spectrophotometer at 280 nm after the wastewater sample, which passed colour removal process, was passed from the processes stated in Section Colour Measurements20. Biomass measurement method. The formed biomass amounts were determined by making dry weight measurement experiments21,22. For the changes of biomass formed on the reactor disc surface, samples having a certain area (about 1cm2) were taken from the surface23. Metal analysis. In order to determine the removal ratio of copper existing in the structure of the Remazol Blue RR gran in 2%, an UNICAM 929 AA atomic adsorption equipment was used20. Results and Discussion Colour, COD and Aromatic Group Removal in Biodisc at Various Dye Concentrations
First of all, the optimum hydraulic retention time was determined for the biodisc system by studying colour removal at different hydraulic retention times (hydraulic retention time 4 days = feed flow rate 1ml/min, hydraulic retention time 2 days = feed flow rate 2 ml/min) using the treatable dye concentration of 10 mg l–1 (10 mg l–1 R. mixture, 10 mg l–1 R. Yellow, 10 mg l–1 R. Red, 10 mg l–1 R. Blue), which was determined for batch system13. Using the model wastewater of 10 mg l–1 R. mixture when the reactor hydraulic retention time was kept at 4 days (1 ml/min) and disc rotation speed was kept at 10 rpm, it has been observed that all dyes provided the required EN ISO 7887 discharge limit values (λ(1)= 436 nm (Yellow) 7 m–1, λ(2)= 525 nm (Red) 5 m–1, λ(3)= 620 nm (Blue) 3 m–1). After these values had been determined, colour removal efficiency of 10 mg l–1 1 R. mixture at hydraulic retention time 2 days (2 ml/min flow rate) and disc rotation speed at 10 rpm was determined. It can be seen that both R. Red and R. Yellow values are above the desired values of 5 and 7 m–1. It has been known that passage speed and amount of oxygen in water can be increased by increasing disc rotation speed in a surface ventilated reactor. From 10
suspended biomass amount in biodisc (mg/20 ml)
this point of view, hydraulic retention time was kept 2 days and disc rotation speed was increased to 15 rpm in order to see the effect on the removal efficiency. However, this modification did not have a significant positive effect on the treatment efficiency. Nevertheless, some breaks were observed due to the increase in the disc rotation speed. Limit discharge values required by EN ISO 7887 could not be attained at dye concentrations of 10 mg l–1 both for R. Red and R. Blue. The required limit discharge value (7 m–1) was attained for 10 mg l–1 of R. Yellow. Whenever the hydraulic retention time was kept at 4 days (1 ml/min flow rate), 200–300 mg l–1 of COD values required by Water Pollution and Control Legislation were attained with all dyes (10 mg l–1). However, when the hydraulic retention time was 2 days (2 ml/min), COD values were observed to be as high as 400–450 mg l–1 for all dyes (10 mg l–1). These results are above the Water Pollution and Control Legislation limit discharge values, which are 200–300 mg l–1. During the colour removal experiments, changes in suspended microorganism amount and the amount of biomass clinged to the disc surface were also observed. The suspended microorganism amount in the reactor initially dropped, then decreased for a while, but increased after a period. Since there were some breaks in the biofilm formed on the biodisc surface due to thickening, if the biofilm suspended, microorganism amount increased (Fig. 2). One of the most important characteristics of the white rot fungi is that they grow very well on the surfaces. Due to the substrate, the microorganism showed significant growth on the surface during the disc surface growth. Later, biofilm thickness reached to a certain amount and breaks were faced, and thus the biofilm thickness decreased (Fig. 3). This fact is supported by the information gathered from treatment of toluene in a reactor cultivated with petrochemical wastewater in a laboratory scaled biodisc system23. 3.5
R. Yellow R. Red R. mixture - 1 ml/min R. mixture - 2 ml/min R. Blue
3 2.5 2 1.5 1 0.5 0
0
20
40
60 80 time (hour)
100
120
Fig. 2. Suspended biomass changes in removal of R. Yellow, R. Red, R. Blue and R. mixture dyes with biodisc system. Hydraulic retention time for R. Yellow, R.Red, R. Blue and R. mixture 4 days (feed volume flow rate 1ml/min); hydraulic retention time for R. mixture 2 days (feed volume flow rate 2ml/min); in all experiments ventilation flow rate 1.5 l/min, disc rotation speed 10 rpm, total dye feed concentration 10 mg l–1
11
biomass amount on disc surface in 2 biodisc (cm /mg)
3
R. Yellow R. Red R. mixture – 1 ml/min R. mixture – 2 ml/min R. Blue
2.5 2 1.5 1 0.5 0
0
20
40
60
80
100
120
time (hour)
Fig. 3. Biomass changes on disc surface in removal of R. Yellow, R. Red, R. Blue and R. mixture dyes with biodisc system. Hydraulic retention time for R. Yellow, R.Red, R. Blue and R. mixture 4 days (feed volume flow rate 1ml/min); hydraulic retention time for R. mixture 2 days (feed volume flow rate 2ml/min); in all experiments ventilation flow rate 1.5 l/min, disc rotation speed 10 rpm, total dye feed concentration 10 mg l–1
During the experiments carried out with 10 mg l–1 R. mixture and 10 mg l–1 R. Blue, removal of copper consisting in the structure of the R. Blue dye was investigated at a hydraulic retention time of 4 days. 0.2 ppm of copper exists in 10 mg l–1 of Remazol Blue dye concentration. It has been determined that 39% of this copper could be removed during a process of 105 h. Up to the 45th hour, copper removal rate increased progressively. After that time, it has been observed that removal percentage decreased. The reason for this fact is that copper in the wastewater loaded to the reactor was tolerated by the microorganisms up to a certain time and used for conversion to the biomass. However, with a high concentration of 0.2 ppm for copper and a continuous flow rate of 1 ml/min, copper entering continuously to the system could not be totally transformed to biomass and also had some toxic effects. Aromatic group measurements were carried out in the UV region at 280 nm wavelength on the samples taken during the colour removal operations. As a result of the measurements, it has been revealed that there has been non-degraded aromatic group in the wastewater used for colour removal processes12. However, the Dystar company that supplied the dyes did not give any detail about the chemical composition of the dyes. For this reason, there could not be a clear conclusion about the type of the aromatic groups contained in the wastewater after the processes. After trial experiments carried out at 10 mg l–1 dye concentration using the biodisc, studies were continued with making trials at dye concentrations of 5, 15, 20 and 25 mg l–1 and at various disc rotation speeds (5, 10, 15 rpm). The obtained results are gathered in the Tables 1–6. Using the model wastewater of 5 mg l–1 R. mixture, when the reactor hydraulic retention time was kept at 4 days (1 ml/min) and disc rotation speed was kept at 5, 10 and 15 rpm, colour removal was observed (Table 1). It has been observed that all dyes provided the required EN ISO 7887 discharge limit values (λ(1)= 436nm (Yellow) 7 m–1, λ(2)= 525 nm (Red) 5 m–1, λ(3)= 620nm (Blue) 3 m–1). 12
Table 1. Colour removal values (DFZ m–1) of 5 mg l–1 of R. mixture dye at various disc rotation speeds
Time (h) 0 12 22 36 44 59 67 83 91 105 DFZ removal efficiency (%)
5 rpm 10 rpm 15 rpm R. Y. R. R. R. B. R. Y. R. R. R. B. R. Y. R. R. R. B. 4.9 5 1.5 4.9 5 1.4 5 4.9 1.5 2.5 3.2 0.9 2.1 2.5 0.8 3 3 0.8 2.6 3.3 0.5 2 3 0.6 2.9 3.1 0.7 2.5 3.2 0.7 2 3 0.6 3 3.1 0.7 2.6 3.4 0.9 2.1 3.1 0.7 2.8 3 0.8 2.5 3 1 2.2 3.1 0.7 2.8 3.2 1 2.7 3.4 0.9 2 3 0.7 2.6 3.3 0.8 2.6 3.4 1 2.1 3.1 0.6 2.8 3.2 0.9 2.6 3.2 0.9 2.2 3 0.7 2.9 3.2 1 2.6 3.2 0.9 2.2 3 0.6 2.9 3.2 1 46 36 40 55 40 57 42 35 33
EN ISO 7887 discharge limit values (λ(1)= 436 nm (Yellow) 7 m–1, λ(2)= 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1).
Using the model wastewater of 10 mg l–1 R. mixture when the reactor hydraulic retention time was kept at 4 days (1 ml/min continuous flow rate) and disc rotation speed was kept at 5, 10 and 15 rpm, colour removal was observed. As it can be seen in Table 2, R. Yellow has given 4.8 DFZ exit value from 9.2 DFZ start value at a disc rotation speed of 5 rpm. With this value, 48% of DFZ removal efficiency was obtained. This DFZ value provides standard discharge value, which is 7 m–1. R. Red has given a DFZ value of 5.2 m–1 after an initial DFZ value of 9 m–1. This has resulted in a removal efficiency of 42%. This DFZ value, however, does not provide standard discharge value. R. Blue has given a DFZ value of 1.9 m–1 after an initial DFZ value of 2.4 m–1. This has resulted in a removal efficiency of 21% and correspondingly provided the standard discharge value of 3 m–1 (Table 2). In the experiments carried out using 10 mg l–1 R. mixture model wastewater at disc rotation speed of 10 rpm, DFZ value of R. Yellow decreased from its initial value of 9 m–1 down to 4.2 m–1. 53% of removal efficiency has been obtained from this value. It has been observed that reactor exit DFZ value has provided the discharge standard value, which is 7 m–1. DFZ value of R. Red decreased from its initial value of 9 m–1 down to 4.8 m–1. 47% of removal efficiency has been obtained from this value. Besides, it has been observed that reactor exit DFZ value has provided the discharge standard value, which is 5 m–1. DFZ value of R. Blue decreased from its initial value of 2.3 m–1 down to 1.6 m–1. 30% of removal efficiency has been obtained from this value and it has been observed that reactor exit DFZ value has provided the discharge standard value that is 3 m–1 (Table 2). 13
Table 2. Colour removal values (DFZ m–1) of 10 mg l–1 of R. mixture dye at various disc rotation speeds
Time (h) 0 12 22 36 44 59 67 83 91 105 DFZ removal efficiency (%)
5 rpm 10 rpm 15 rpm R. Y. R. R. R. B. R. Y. R. R. R. B. R. Y. R. R. R. B. 9.2 9 2.4 9 9 2.3 9.1 9 2.4 5 5.5 1.9 4.3 4.5 1.6 5 5.2 2 4.8 5.2 1.8 4.8 4.7 1.5 4.5 5.1 1.7 5 5.3 1.8 5 5 1.5 4.6 5.3 1.6 4.5 5 1.7 4.3 4.8 1.5 4.6 5.2 1.6 4.5 5.1 1.8 4.8 4.8 1.7 4.7 5.2 1.7 5 5 1.8 4.7 4.9 1.7 4.8 5.2 1.8 4.9 5.2 1.9 4.5 4 1.6 4.2 5.2 1.7 4.8 5 1.8 4.5 4.9 1.6 4.8 5.3 1.6 4.8 5.2 1.9 4.2 4.8 1.6 4.8 5.2 1.7 48 42 21 53 47 30 47 42 29
EN ISO 7887 discharge limit values (λ(1) = 436 nm (Yellow) 7 m–1, λ(2)= 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1).
In the experiments carried out using 10 mg l–1 R. mixture model wastewater at disc rotation speed of 15 rpm, DFZ value of R. Yellow decreased from its initial value of 9.1 m–1 down to 4.8 m–1. 47% of removal efficiency has been obtained from this value. It has been observed that reactor exit DFZ value has provided the discharge standard value that is 7 m–1. DFZ value of R. Red decreased from its initial value of 9 m–1 down to 5.2 m–1. It has been calculated that 42% of removal efficiency could be obtained from this value. It has been observed that reactor exit DFZ value did not provide the discharge standard value, which is 5 m–1. DFZ value of R. Blue decreased from its initial value of 2.4 m–1 down to 1.7 m–1. It has been calculated that 29% of removal efficiency could be obtained from this value. Reactor exit DFZ value has provided the discharge standard value, which is 3 m–1 (Table 2). DFZ removal values of 15 mg l–1 of R. mixture dye can be seen in Table 3. It has been observed that R. Yellow has provided the EN ISO 7887 standard value of 7 m–1 with its DFZ values 6.3, 5.7 and 6.9 m–1 at disc rotation speeds of 5, 10 and 15 rpm, respectively. One of the other dyes constituting the mixture, namely R. Blue, provided the standard value of 3 m–1 while R. Red did not provide the standard value of 5 m–1. DFZ removal values of 20 mg l–1 of R. mixture can be seen in Table 4. It has been observed that R. Yellow, which is one of the dyes in the mixture, provided the standard 7 m–1 value of EN ISO 7887 at disc rotation speeds of 5 and 10 rpm with DFZ resulting values of 6.8 and 6.5 m–1, respectively, while it did not provide the standard value at 15 rpm with resulting DFZ value of 7.5 m–1. One of the other 14
dyes constituting the mixture, namely R. Blue, provided the standard 3 m–1 value of EN ISO 7887 at disc rotation speeds of 5 and 10 rpm with DFZ resulting values of 2.6 and 2.4 m–1, respectively, while it did not provide the standard value at 15 rpm with resulting DFZ value of 3.2 m–1. On the other hand, all DFZ values of R. Red were above the standard value of 5 m–1. Table 3. Colour removal values (DFZ m–1) of 15 mg l–1 of R. mixture dye at various disc rotation speeds
Time (h) 0 12 22 36 44 59 67 83 91 105 DFZ removal efficiency (%)
5 rpm 10 rpm 15 rpm R. Y. R. R. R. B. R. Y. R. R. R. B. R. Y. R. R. R. B. 14 13 3 14 13 3 14 13 2.9 6.5 8 2.1 7 7 2 8 8 2.4 6.6 7 2 6.5 6.8 1.9 7 7.8 2.3 6.3 7 2.2 6 6.8 1.8 7.1 7.3 2.2 6.2 7.2 2 5.5 7 1.7 7 7.5 2.4 6 7.3 2 5.6 7.1 1.6 6.9 7.5 2.4 6 7.3 2.2 5.8 7 1.6 6.9 7.6 2.3 6.1 7.2 2.2 5.8 7.1 1.6 6.8 7.4 2.2 6.3 7.1 2.3 5.7 7 1.7 7 7.5 2.3 6.3 7.1 2.2 5.7 6.8 1.7 6.9 7.5 2.4 55 45 27 59 47 43 51 42 17
EN ISO 7887 discharge limit values (λ(1) = 436 nm (Yellow) 7 m–1, λ(2) = 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1). Table 4. Colour removal values (DFZ m–1) of 20 mg l–1 of R. mixture dye at various disc rotation speeds
Time (h) 0 12 22 36 44 59 67 83 91 105 DFZ removal efficiency (%)
5 rpm 10 rpm 15 rpm R. Y. R. R. R. B. R. Y. R. R. R. B. R. Y. R. R. R. B. 17 17 4.4 17 17 4.3 17 17 4.3 6.8 10 2.4 9 8.6 2.4 10 11 3.3 6.5 8.1 2.5 6.5 7.5 2.1 9 9 3 6.5 8.2 2.5 6.4 7.8 2 7.5 8.4 3 6.8 7.9 2.4 6.5 7.8 2.2 7.7 8 3.1 6.7 7.8 2.6 6.5 7.6 2 7.6 7.9 3.3 6.8 7.4 2.6 6.6 7.6 2.3 7.4 7.6 3.2 6.8 7.4 2.6 6.3 7.7 2.4 7.5 7.5 3.2 6.7 7.5 2.7 6.2 7.6 2.3 7.5 7.9 3.2 6.8 7.4 2.6 6.5 7.7 2.4 7.5 7.9 3.2 60 56 41 61 54 44 56 54 26
EN ISO 7887 discharge limit values (λ(1) = 436 nm (Yellow) 7 m–1, λ(2) = 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1).
15
Table 5 shows that all DFZ values of all dyes constituting 25 mg l–1 or R. mixture were above the standard values determined by EN ISO 7887. Table 5. Colour removal values (DFZ m–1) of 25 mg l–1 of R. mixture dye at various disc rotation speeds
Time (h) 0 12 22 36 44 59 67 83 91 105 DFZ removal efficiency (%)
R. Y. 20 12 11.5 11 12 12 12 12.1 12.1 12 40
5 rpm R. R. R. B. 21 5.4 14 4.8 14 4.3 13.1 4.2 16 4.3 15 4.5 14.8 4.7 14.8 4.6 14.7 4.3 14.5 4.5 31 22
R. Y. 20 11 11 11.5 12 11 11.1 11.2 11.1 11.2 44
10 rpm R. R. R. B. 21 5.4 13 4.3 13.5 4.1 13.5 4 14 4.6 14 4.3 14.3 4 14.3 4.1 14 4 13.8 4.2 34 17
R. Y. 20 13 13.2 13 13 12.5 12.7 14 14.2 14.3 29
15 rpm R. R. R. B. 20 5.3 14.2 4.6 14.1 4.3 13.9 4.3 13.5 4.4 13.5 4.6 14 4.6 14.6 4.7 14.5 4.7 14.7 4.6 27 13
EN ISO 7887 discharge limit values (λ (1)= 436 nm (Yellow) 7 m–1, λ(2) = 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1).
Table 6 shows the DFZ removal efficiencies corresponding to the first 12 h after the loading which was done after the reactor reached the steady state. The removal efficiencies for R. Yellow, R. Red and R. Blue obtained for disc rotation speed of 5 rpm were 46, 39 and 21%, respectively, for 10 rpm – 52, 50 and 30% and for 15 rpm – 45, 42 and 17%. Table 6. Colour removal (DFZ m–1) of 10 mg l–1 R. mixture dye during the first 12 h at various disc rotation speeds
Time (h) 0 2 4 6 8 10 12 DFZ removal efficiency (%)
5 rpm 10 rpm 15 rpm R. Y. R. R. R. B. R. Y. R. R. R. B. R. Y. R. R. R. B. 9.2 9 2.4 9 9 2.3 9.1 9 2.4 8 8 2.2 7.5 7.6 2 8 8 2.2 6.8 7.5 2.1 6.7 7 1.8 7.3 7.5 2 6 7 2 5.8 6.5 1.6 5.5 7 1.9 5.5 6.5 2 5.3 5.3 1.5 5.2 6 1.9 5.3 6 1.9 5 5S 1.4 5 5 2 5 5.5 1.9 4.3 4.5 1.6 5 5.2 2 46 39 21 52 50 30 45 42 17
EN ISO 7887 discharge limit values (λ(1) = 436 nm (Yellow) 7 m–1, λ(2)= 525 nm (Red) 5 m–1, λ(3) = 620 nm (Blue) 3 m–1).
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It can be observed that the resulting COD values provided the required discharge limit of 200–300 mg l–1 for all disc rotation speeds after 44–59th hours after the system was run continuously (1 ml/min continuous flow rate) at dye concentrations of 5, 10 and 15 mg l–1, when the COD removal values of R. mixture dyes are compared with the limit discharge values of Water Pollution and Control Legislation. For dye concentrations of 20 and 25 mg l–1, however, the limit discharge values of 200–300 mg l–1 were exceeded. It has been known that heavy metals affect the cellular enzymatic reactions positively or negatively. If the concentration is low, the living thing can tolerate this and even use it for metabolic activities, but causes death if it is high. For this reason, the removal of copper existing at 2% in the structure of R. Blue RR gran by fungi during the experiments carried out in the biodisc. For the R. mixtures of 5 mg l–1 (0.012 ppm copper), 10 mg l–1 (0.024 ppm copper), 15 mg l–1 (0.036 ppm copper), 20 mg l–1 (0.048 ppm copper) and 25 mg l–1 (0.06 ppm copper) the arithmetic average of the copper removal values at 5, 10 and 15 rpm are 97, 90, 73, 51 and 48%, respectively. It has been determined that toxicity showed effect or at least microbial activities were slowed down with increasing concentration. Conclusions For dye concentrations of 10 mg l–1, which was determined for batch reactors, both separate and mixture of the Remazol dyes were used for the experiments with the biodisc system initially. Discharge standards were attained for 10 mg l–1 of R. Yellow according to the EN ISO 7887 at hydraulic retention time of 4 days, disc rotation speed of 10 rpm, but could not be attained for the dyes R. Red and R. Blue. When the hydraulic retention time was 4 days and the disc rotation speed was 10 rpm, all dyes provided the discharge limit values of EN ISO 7887 at 10 mg l–1 R. mixture. When the hydraulic retention time of 10 mg l–1 of R. mixture was kept at 2 days (2 ml/min flow rate) and disc rotation speed at 10 rpm, both Remazol Red and R. Yellow have been observed to be above the required limit discharge values when colour removal efficiencies have been analysed. When the results of the experiments at different disc rotation speeds were analysed, it has been observed that increasing the disc rotation speed to 15 rpm decreased the colour removal efficiency. It has been determined that this decrease was due to the breaks from the biofilm. For this reason, it has been revealed that disc rotation speed of 10 rpm is the proper one for a pilot reactor used in the studies. All values were observed to be above the standards for R. mixture concentration of 25 mg l–1 using the biodisc. During colour removal processes, aromatic group measurements were taken in UV region at 280 nm wavelength for experiments carried out both in batch re17
actors and on biodisc. As a result of these measurements, it has been revealed that there was non-degraded aromatic group in the model wastewater used for colour removal experiments at the end of the process. This fact is supported by other literature studies20. The great portion of the COD of the wastewater is composed of glucose, which is used to prepare the wastewater, and is a component of the nutrition media. For this reason COD removal has been realised by the white rot fungi rapidly. This fact is supported by the other literature results24. References 1. K. I. Kapdan, F. Kargi, G. Mcmullan, R. Marchant: Comparison of White Rot Fungi Cultures for Decolorization of Textile Dyestuffs. Bioprocess Engineering, 22, 347 (2000a). 2. I. A. Balcioglu, I. Arslan: Treatability of Textile Industry Wastewater by Photocatalytic Oxidation Method. Gebze Institute of Technology, Environmental Pollution Symposium, Vol. 2, Turkey, 1997, 193–199. 3. M. A. Brown, S. C. Devito: Predicting Azo Dye Toxicity. Critical Reviews in Environmental Sciences and Technology, 23, 249 (1993). 4. K. T. Chung, S. J. R. Stevens: Decolorization of Azo Dyes by Environmental Microorganism and Helmiths. Environmental Toxicology Chemistry, 12, 2121 (1993). 5. J. S. Knapp, P. S. Newby: The Microbiological Decolorization of an Industrial Effluent Containing a Diazo-linked Chromophore. Water Research, 29, 1807 (1995). 6. J. A. Bumpus, S. D. Aust: Studies on the Biodegradation of Organopollutants by a White Rot Fungus. In: Intern. Conference on New Frontiers for Hazardous Waste Management, 1985, 404–410. 7. D. C. Eaton: Mineralization of Polychlorinated Biphenyls by Phanerochaete chrysosporium – a Lignolytic Fungus. Enzyme Microbial Technology, 7, 194 (1985). 8. F. Zhang, J. T. Yu: Decolorization of Acid Violet 7 with Complex Pellets of White Rot Fungus and Activated Carbon. Bioprocess Engineering, 23, 195 (2000). 9. F. Zhang, J. S. Knapp, K. N. Tapley: Decolorization of Cotton Bleaching Effluent in a Continuous Fluidized Bed Bioreactor Using Wood Rotting Fungus. Biotechnology Letters, 20 (8), 717 (1999b). 10. K. I. Kapdan, F. Kargi: Biological Decolorization of Textile Dyestuff Containing Wastewater by Coriolus versicolor in Rotating Biological Contactor. Enzyme and Microbial Technoloy, 30, 195 (2001). 11. F. C. Yang, J. T. Yu: Development of a Bioreactor System Using an Immobilized White Rot Fungus for Decolorization. Bioprocess Engineering, 16, 9 (1996). 12. G. Demir: Decolorization of Textile Wastewaters Containing Azo Dyes by White Rot Fungus (Phanerochaete chrysosporium). Ph. D. Thesis, Istanbul University, Institute of Science and Technology, Department of Environmental Engineering, 2002. 13. G. Demir, M. Borat, C. Bayat: Decolorization of Remazol Red RR Gran by the White Rot Fungus Phanerochaete chrysosporium. Fresenius Environmental Bulletin, 13 (10), 979 (2004). 14. Europa Norm. 1994. EN ISO 7887. 15. T. Akgun: Color Removal from the Textile Wastewater by Adsorption Techniques. Msc Thesis, Istanbul University, Institute of Science and Technology, 1999. 16. G. R. J. Mileski, J. A. Bumpus, M. A. Jurek, S. D. Aust: Biodegradation of Pentachlor phenol by the White Rot Fungus Phanerochaete chrysosporium. Applied and Environmental Microbiology, 54, 2885 (1988).
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17. F. Zhang, J. S. Knapp, K. N. Tapley: Decolourisation of Cotton Bleaching Effluent with Wood Rotting Fungus. Water Research, 33, 919 (1999a). 18. K. I. Kapdan, F. Kargi, G. Mcmullan, R. Marchant: Effect of Environmental Conditions on Biological Decolorization of Textile Dyestuff by C. versicolor. Enzyme and Microbial. Technology, 26, 381 (2000b). 19. Apha-Awwa-Wpcf: Standard Methods for the Examination of Water and Wastewater. 17th ed. New York, 1989. 20. A. Heinfiling, M. Bergbauer, U. Szewzyk: Biodegradation of Azo and Phthaloccynine Dyes by Trametes versicolor and Bjerkandera adusta. Applied Microbiology Biotechnology, 48, 261 (1997). 21. G. Demir: Degradation of Some Chlorinated Organic Materials by White Rot Fungus (Phanerochaete chrysosporium) in Waters. Msc Thesis, Istanbul University, Institute of Science and Technology, Department of Environmental Engineering, 1996. 22. G. Demir, H. Barlas, C. Bayat: Degradation of Some Chlorinated Organic Materials by White Rot Fungus (Phanerochaete chrysosporium) in Waters. Fresenius Environmental Bulletin, 7, 927 (1998). 23. I. Alemzadeh, M. Vossoughi: Biodegradation of Toluene by an Attached Biofilm in a Rotating Biological Contactor. Process Biochemistry, 36, 707 (2001). 24. H. Cao: Decolorization of Textile Dyes by White Rot Fungi. Ph.D. Thesis, University of Georgia, Faculty of Graduate, USA, 2000. Received 29 May 2009 Revised 1 July 2009
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