Volume 7, Issue 3 (Summer 2018)
Arch Hyg Sci 2018, 7(3): 192-199 |
Back to browse issues page
Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:
Monazami Tehrani G, Molla Mahmoudi M, Borgheipour H, Nezampour A. Evaluation of the Efficiency of Integrated Fixed-Film Activated Sludge reactor for Treatment of Wastewater from Vegetable Oil Industries . Arch Hyg Sci 2018; 7 (3) :192-199
URL: http://jhygiene.muq.ac.ir/article-1-323-en.html
URL: http://jhygiene.muq.ac.ir/article-1-323-en.html
1- Department of Health, Safety and Environment, school of public health and safety, Shahid Beheshti University of Medical Scien ces and Health Services
2- Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences,
3- Department of Environmental Engineering, Central Tehran Branch, Islamic Azad University
4- D epartment of Health, Safety, and Environment, S chool of Engineering, Islamic Azad University, Central Tehran Branch
2- Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences,
3- Department of Environmental Engineering, Central Tehran Branch, Islamic Azad University
4- D epartment of Health, Safety, and Environment, S chool of Engineering, Islamic Azad University, Central Tehran Branch
Keywords: Integrated Fixed-Film Activated Sludge, Attached Growth, Industrial Wastewater, Vegetable Oil Industry, Biological Treatment.
Full-Text [PDF 572 kb]
(875 Downloads)
| Abstract (HTML) (4687 Views)
The vegetable oil production industry is one of the types of food industries, which is developing in our country on an ongoing basis. In addition to the development of this industry, one of the important problems in this field is the dangers of this industry for the discharge of various pollutants into the environment, including polluted wastewater to the environment and groundwater and surface health threats Society (1,2). The entry of wastewater from vegetable oil industries into natural water sources, due to oil and fat contamination, suspended matter, pH and high turbidity, causes them to be contaminated and use these sources unnecessarily. Also, the entry of these wastewater into the sewage collection network and urban wastewater treatment plant causes some problems such as collecting network clogging, disruption of sedimentation unit, reduction in dissolved oxygen, excessive growth of algae and material production, and invisible floating layers, disturbances in microorganisms and, in general, disruptions to the treatment system's work (1,3,4). Therefore, it is necessary to develop a suitable treatment plan for these types of wastewater. One of the methods for solving these problems is the application of hybrid suspended growth and attached growth processes or biofilm processes (5,6).
Since the in this process, the volume required for the basin decreases, it has attracted the attention of most specialists. Based on the medium used in the integrated fixed-film activated sludge (IFAS) process, these systems are divided into two categories of system with fixed media and Scattered Media System (6-10).
Sticking to the bed microorganisms make denitrification possible by increasing cell retention time and increasing sludge age causes less sludge production. Usually attention to attached growth systems is due to the high biomass concentration that can in comparison with suspended growth processes. This action reduces the hydraulic residence time (8,11). The low hydraulic residence time reduces required reactor volume. Particularly when the land is limited to a refinery, this factor can be an important advantage. In these compressed systems, submerged beds are used which the flow can be upward or downward. In fact, in these systems, the performance of wastewater treatment will increase with the attached biomass. On the other hand, with increasing biomass, the resistance of the process increases against organic and hydraulic loading shocks (7,8).
Keramati et al. (2006) conducted a study on Evaluation of the Efficiency of Flotation System with soluble air in reducing pollution load in Naz Isfahan Vegetable Oil Plant. The results showed that the removal rate of COD, oil, total solids, organic solids, mineral solids and suspended solids in 75.85, 78.27, 77.32, 82.47, 73.52 and 85.53 percent respectively (1).
The Varamin Vegetable Oil Plant, located in Rey in Tehran province, Iran, was established in 1950 to produce vegetable oil on an area of 5,500,000 square meters and was put into task in 1951. The factory produces 100 tons of daily cleaning and packaging of edible vegetable oil types.
Aims of the study:
The aim of this study was to evaluate the efficiency of Integrated Fixed-Film Activated Sludge (IFAS) reactor for treatment of wastewater from Varamin vegetable oil industries and to compare its effluent with environmental standards.
The anaerobic and aerobic reactors with sedimentation unit were made from polyethylene and plexiglas sheets with a thickness of 8 mm. The schematic and pilot specifications described in Fig 1 and Table 1 are presented.
Figure 1) Schematic design of IFAS pilot. 1- Anaerobic tank 2-Perestaltic pump 3- Influent 4-Aeration tank 5-Fixed bed media 6- Secondary clarifier 7-Disienfection 8-Effluent 9- Aeration pump 10- Returned activated sludge
The performance of the aerobic biological system is presented in Table 5 to remove the various parameters at different times (4, 6 and 8 hours). Figure 4 also shows the effectiveness of the anaerobic biological system at different times (1, 2, 4, 6 and 8 hours aerobic).
The effluent from the coagulation and flocculation unit at 3, 4, 6, and 8-hours hydraulic times is presented in Table 6. According to the results presented in Table 6, the remaining 2 days of anaerobic, 6-hours aerobic and 2-day anaerobic, 8 hrs aerobic had the best removal efficiency.
The results of the analysis of the chemical properties of effluent from the treatment of wastewater in different time periods (1 and 2 days of anaerobic of 4, 6 and 8 hrs aerobic) are shown in Table 7. The amount of arsenic, barium, cyanide, molybdenum and zinc in the effluent was 0.05 mg/L, iron and manganese levels were also 0.01 mg/L. The concentrations of silver, aluminum, boron, cadmium, cobalt, worm, copper, nickel, selenium, and vanadium in the pilot outlet were less than the ICP detection limit.
The effect of hydraulic retention time of the IFAS reactor on COD removal:
One of the most important parameters in the design and operation of biological reactors is Hydraulic Retention Time (HRT). The COD removal efficiency by anaerobic digestion was investigated at different times of 1 and 2 days HRT, in this study and the results of 2 days HRT showed that the removal efficiency was greater than 1 day. Which is consistent with the study by Li et al. (2012) (13). In their study, the removal rate of COD from the IFAS reactor increased with increasing HRT. The increment in efficiency can be explained by the fact that the longer the amount of HRT in the digester is, the greater the time available for the removal of organic pollutants in the microorganisms, as well as by increasing the amount of settled sedimentation time suspended solids also increases. The maximum removal rate of COD in the digester was 63.10 % at a HRT of 2 days.
Also, the results showed that in the HRT of low anaerobic digestion (1 day), the efficiency of COD removal in the IFAS reactor was low. Therefore its outlet concentration was high. In general, the anaerobic HRT 1 day anaerobic 4 hrs aerobic and 2 days anaerobic 8 hrs aerobic were respectively the lowest and the highest removal efficiency in the total reactor, which was 92.1% and 97.9%, respectively. This is consistent with the study by Azimi et al (2013). Azimi et al. used the IFAS to treatment Amol food industry wastewater and obtained the efficiency of removal COD by about 98% to 99% (14).
The results showed that, during the 4, 6 and 8 hrs HRT, the COD removal efficiency was >97.7%, >97.3%, and >97.7%, respectively. During all HRT, the IFAS reactor managed to bring the COD to the lowest (<5 mg/L). Comparison of the results of the removal efficiency in the pilot study with actual data obtained from the wastewater treatment plant of the vegetable oil plant showed that the use of IFAS was associated with increased COD removal efficiency.
Anaerobic digestion efficiency and IFAS system in removing BOD and TSS:
The purpose of industrial wastewater treatment is to eliminate or reduce the concentration of organic or inorganic compounds, the compounds in these sewage systems are toxic to microorganisms, are decomposable, not decomposable and easy to decompose. Organic or inorganic materials are soluble, colloid and suspended. Using the biological units for units for the removal of biological pollutants is appropriate whilst wastewater has decomposable organic compounds. The wastewater of the vegetable oil of Varamin has a high BOD/COD ratio, which means that the use of biological processes is suitable for the treatment of this wastewater. Total suspended solids in the effluent can intrude with the reuse of wastewater. The results showed that with decreasing HRT (from 2 days of anaerobic 8 hrs aerobic to 1 day anaerobic 4 hrs aerobic), the removal of BOD also decreased, resulting in a higher concentration of outlet BOD from the system. In the total system (anaerobic reactor and IFAS), the minimum and maximum removal efficiency of BOD is related to the HRT of 1 day anaerobic 4 hours aerobic and 2 day anaerobic of 8 hrs aerobic. The reduction of HRT has had a significant effect on the removal efficiency of BOD by anaerobic reactors, IFAS and the total system.
Also, the highest amount of removal of suspended solids occurred during a HRT 2-day of 8 hrs aerobic. Due to the continuous flow of wastewater inside the system and the constant volume of the secondary sedimentation unit, the increase in TSS removal was increased by increasing the HRT in the basin. The highest and lowest removal rate of TSS was obtained for 2 days of anaerobic 8 hrs aerobic (98.8%) and 1 day anaerobic 4 hrs aerobic (94.7%). Comparison of the results of the removal BOD and TSS pilot with actual data from the refinery shows that the use of IFAS was associated with a tangible decrease in these parameters. According to the results, the BOD value at the pilot outlet in three times the hydraulic, 4, 6, and 8 hours was less than 3 mg/L. The efficiency of removal of this parameter is higher than 97% at all times.
Anaerobic digestion and IFAS system efficiency in removing TKN and phosphorus:
The results showed that by decreasing the HRT (from 2 days of anaerobic 8 hrs aerobic to 1 day anaerobic 4 hrs aerobic), the removal of TKN decreased, and as a result, the TKN concentration increased from the system. The minimum and maximum removal efficiency of TKN is related to the HRT of 1 day anaerobic 4 hrs aerobic and 2-day anaerobic of 8 hrs aerobic. The reduction of HRT has had a significant effect on the efficiency of removal of TKN by anaerobic reactors, IFAS and the system total. Which is consistent with the study by Regmi et al. (2011) (15). In the study of Regmi et al., TKN increased with time. A study by Veuillet et al. (2014) also showed that, as time increases, the efficiency of removal of TKN did not increase, which is consistent with the present study (16).
According to the results, the highest and lowest removal rate of phosphorus was in HRT 2 days anaerobic 8 hrs aerobic (62.5 %) and 1 day anaerobic 4 hrs aerobic (36.1%). Due to the high concentration of phosphorus in the effluent, the anaerobic process may need to be changed, or the hydration time of the anaerobic digester should be increased. For HRT 2-days anaerobic of 8 hrs aerobic, the concentration of phosphorus from the outlet system was the lowest (3.98 mg/L). The highest and lowest removal efficiency of phosphorus was 6 hrs aerobic (65.9%) and 4 hrs aerobic (45.2%). Which is consistent with the study by Dargahi et al (2017) (17). In a study by Dargahi et al., Which used anaerobic pond system to treatment wastewater, the results showed that by increasing the time, the removal rate of phosphorus increased. In order to provide the standard output of phosphorus, COD to phosphorus ratio, which is an important parameter in phosphorus removal, is about 40 or more. In this study, the ratio of COD to phosphorus at the inlet of the system was equal to or greater than 100, but, despite the proper fit of COD/P, there was no increase in efficiency from 6-hours aerobic to 8-hours aerobic increase, because of this incidence could be the reason for the loss of the balance of phosphorus degrading bacteria should be noted. If using a small anaerobic unit before the IFAS reactor, it can achieve the phosphorus removal efficiency to the required standard.
Chemical analysis of other pollutants at the output of the IFAS reactor:
The effluent from the coagulation and flocculation unit arrived at the 3, 4, 6, and 8-hours HRT. At all times, the amount of treatment was optimum. Owing to the results, the effluent from the pilot plant has the standard of the industrial water (group third and fourth). Standard TDS in groups 1 and 2 and chloride in group 1 are not provided with the proposed treatment in this project, but with the use of advanced treatment such as reverse osmosis, these standards can also be achieved.
For the most part, the results confirmed that industrial wastewater treatment methods using the IFAS biological system is a suitable method for the removal of pollutants. In addition to acceptable costs, appropriate technology and acceptable energy consumption, this method plays an important role in environmental conservation and can be replacing with conventional methods. Moreover, the efficiency of removing COD, BOD and TSS from the plant was at the optimum level by this system.
Acknowledgments:
This article is an excerpt from the Master's Thesis from Islamic Azad University.
Conflict of Interest:
The authors declared no conflict of interest.
Full-Text: (1008 Views)
|
Background
|
The vegetable oil production industry is one of the types of food industries, which is developing in our country on an ongoing basis. In addition to the development of this industry, one of the important problems in this field is the dangers of this industry for the discharge of various pollutants into the environment, including polluted wastewater to the environment and groundwater and surface health threats Society (1,2). The entry of wastewater from vegetable oil industries into natural water sources, due to oil and fat contamination, suspended matter, pH and high turbidity, causes them to be contaminated and use these sources unnecessarily. Also, the entry of these wastewater into the sewage collection network and urban wastewater treatment plant causes some problems such as collecting network clogging, disruption of sedimentation unit, reduction in dissolved oxygen, excessive growth of algae and material production, and invisible floating layers, disturbances in microorganisms and, in general, disruptions to the treatment system's work (1,3,4). Therefore, it is necessary to develop a suitable treatment plan for these types of wastewater. One of the methods for solving these problems is the application of hybrid suspended growth and attached growth processes or biofilm processes (5,6).
Since the in this process, the volume required for the basin decreases, it has attracted the attention of most specialists. Based on the medium used in the integrated fixed-film activated sludge (IFAS) process, these systems are divided into two categories of system with fixed media and Scattered Media System (6-10).
Sticking to the bed microorganisms make denitrification possible by increasing cell retention time and increasing sludge age causes less sludge production. Usually attention to attached growth systems is due to the high biomass concentration that can in comparison with suspended growth processes. This action reduces the hydraulic residence time (8,11). The low hydraulic residence time reduces required reactor volume. Particularly when the land is limited to a refinery, this factor can be an important advantage. In these compressed systems, submerged beds are used which the flow can be upward or downward. In fact, in these systems, the performance of wastewater treatment will increase with the attached biomass. On the other hand, with increasing biomass, the resistance of the process increases against organic and hydraulic loading shocks (7,8).
Keramati et al. (2006) conducted a study on Evaluation of the Efficiency of Flotation System with soluble air in reducing pollution load in Naz Isfahan Vegetable Oil Plant. The results showed that the removal rate of COD, oil, total solids, organic solids, mineral solids and suspended solids in 75.85, 78.27, 77.32, 82.47, 73.52 and 85.53 percent respectively (1).
The Varamin Vegetable Oil Plant, located in Rey in Tehran province, Iran, was established in 1950 to produce vegetable oil on an area of 5,500,000 square meters and was put into task in 1951. The factory produces 100 tons of daily cleaning and packaging of edible vegetable oil types.
Aims of the study:
The aim of this study was to evaluate the efficiency of Integrated Fixed-Film Activated Sludge (IFAS) reactor for treatment of wastewater from Varamin vegetable oil industries and to compare its effluent with environmental standards.
|
Materials & Methods
|
The anaerobic and aerobic reactors with sedimentation unit were made from polyethylene and plexiglas sheets with a thickness of 8 mm. The schematic and pilot specifications described in Fig 1 and Table 1 are presented.
Figure 1) Schematic design of IFAS pilot. 1- Anaerobic tank 2-Perestaltic pump 3- Influent 4-Aeration tank 5-Fixed bed media 6- Secondary clarifier 7-Disienfection 8-Effluent 9- Aeration pump 10- Returned activated sludge
Table 1) Specifications of the reactors used in this study
| The sedimentation basin | Aerobic reactor | Anaerobic reactor | Parameter | ||
| Rectangular cube | Rectangular cube | Cylinder | Diagram | ||
| 20 | 40 | 200 | Useful volume (L) | ||
| 6.6-10 | 6.6-10 | 0.55-1.6 | Incoming current (L.hr) | ||
| Horizontal | First downward and then upward | Horizontal | Flow direction | ||
| 2, 3, 4 | 4, 6, 8 | 24-48 | HRT (hr) | ||
According to Fig. 1, the aerobic tank is composed of three distinct parts. The two parts were as an aeration basin, and the third part was a clarifier for separating the floc from the fluid phase. The two sections of the aeration basin were modified using packing media.
After the construction, installation and drainage of reactors, the system was launched. To launch the reactors, first the seeding was done. For this purpose, the reactors were filled with sludge from the return flow of aeration basin to the human wastewater treatment plant. The IFAS reactor was packed with ratio 70% by Honeycomb packing F 19-1. The honeycomb hatching specification F 19-1 is presented in Table 2.
Table 2) specifications honeycomb packing F 19-1
The IFAS reactor was aerated for 25 days to provide a good biofilm on packing media. After completing this period of aeration, synthetic wastewater was injected into the system with specifications similar to the wastewater of the plant to be adapted to the biological system. This operation continued until the quality of the effluent of the pilot plant did not change significantly during the course. Aeration was used to provide dissolved oxygen of 2 to 4 mg/L and liquid mixing.
After stabilizing the system and full biofilm growth on the packaging media, the main wastewater was injected. Pre-coagulation and flocculation wastewater samples used in this study were prepared from the equalization tank wastewater treatment plant. Pilot was launched by three Hydraulic retention time (HRT), 4, 6, and 8 hr. In each step, the inlet and outlet wastewater characteristics were analyzed. The chemical compounds used for the synthesis of wastewater were including starch (1,2 mg/L), glucose (952 mg/L), NH3Cl (56 mg/L), KH2PO4 (12.2 mg/L) and Na2CO3 (1.6 mg/L). Table 3 shows the input raw wastewater specifications to the IFAS reactor.
Table 3) Specifications of synthetic raw wastewater entering the reactor examined
During the startup of the anaerobic reactor, the HRT was kept constant for 1 day by setting the flow rate. Synthetic wastewater was used together with the return sludge to feed the system continuously. To create optimal growth conditions for microorganisms in anaerobic digestion, the COD/N/P ratio was adjusted to 300/5/1. Phosphorus required for bacteria were provided from the dissolution of potassium dihydrogen phosphate. For injection of wastewater based on the desired flow rate from the raw wastewater storage tank and plant wastewater to the anaerobic reactor, and from the anaerobic reactor to the aerosol reactor, the pump was AQUA model of HC 1 made in Italy. In order to supply the required air in IFAS and mixing in this reactor, an aerated aquarium with a capacity of 45 liters of compressed air per minute was used. The chlorination of the polyethylene tanks wastewater was embedded at the end of the system. In addition to collecting pilot wastewater, this basin was used as a disinfection basin at the system stability stage (system operators in various detention times). All stages of inspecting and testing in this think about were carried out in understanding with the standard method (12). Sampling and analysis of the parameters were performed at the time of system stability at different times from the pilot outlet (at least three times for each retention time). It is noteworthy that measuring parameters such as pH, temperature, dissolved oxygen, and every day was needed to allow for treatment conditions to be avoided and prevent disruption of the purification process.
The results of the raw wastewater entering to the anaerobic and aerobic system and its effluent in different time periods (1, 2 days anaerobic and 4, 6, and 8-hr aerobic) are shown in Table 4.
After the construction, installation and drainage of reactors, the system was launched. To launch the reactors, first the seeding was done. For this purpose, the reactors were filled with sludge from the return flow of aeration basin to the human wastewater treatment plant. The IFAS reactor was packed with ratio 70% by Honeycomb packing F 19-1. The honeycomb hatching specification F 19-1 is presented in Table 2.
Table 2) specifications honeycomb packing F 19-1
| Property | Parameter | |
| PVC | Materials | |
| ~145 | Special level (m2/m3) | |
| 19 | Air passageway (mm) | |
| 1200-2400 | Length (mm) | |
| 6300-600 | Width (mm) | |
| 300-600 | Height (mm) | |
| 60 | Operating temperature (ºC) | |
| Black | Color |
After stabilizing the system and full biofilm growth on the packaging media, the main wastewater was injected. Pre-coagulation and flocculation wastewater samples used in this study were prepared from the equalization tank wastewater treatment plant. Pilot was launched by three Hydraulic retention time (HRT), 4, 6, and 8 hr. In each step, the inlet and outlet wastewater characteristics were analyzed. The chemical compounds used for the synthesis of wastewater were including starch (1,2 mg/L), glucose (952 mg/L), NH3Cl (56 mg/L), KH2PO4 (12.2 mg/L) and Na2CO3 (1.6 mg/L). Table 3 shows the input raw wastewater specifications to the IFAS reactor.
Table 3) Specifications of synthetic raw wastewater entering the reactor examined
| Concentration | Parameter |
| 2000 | COD (mg/L) |
| 100 | N-NH3 (mg/L) |
| 20 | P (mg/L) |
| 7.3 | pH |
| 18-22 | Temperature (ºC) |
|
Results
|
The results of the raw wastewater entering to the anaerobic and aerobic system and its effluent in different time periods (1, 2 days anaerobic and 4, 6, and 8-hr aerobic) are shown in Table 4.
Table 4) Wastewater characteristics of influent and effluent of IFAS in different times
Table 5) The efficiency of the aerobic biological system to remove the various parameters at different times
Table 6) Comparison of wastewater effluents from the IFAS system for industrial wastewater treatment
with industrial water standards
Table 7) Chemical analysis of effluent from IFAS system at different times
Figure 4) Efficiency of the biological treatment system. a) 1 day anaerobic COD, b) 2 day anaerobic COD, c) 1 day anaerobic BOD and d) 2 day anaerobic BOD
| Aerobic effluent | Anaerobic outlet and Aerobic influent | Anaerobic inlet | Parameter | |||||||
| HRT (hr) | ||||||||||
| 8 | 6 | 4 | 8 | 6 | 4 | 8 | 6 | 4 | ||
| 125 | 216 | 290 | 1624 | 1677 | 1647 | 3503 | 3731 | 3684 | 1 day anaerobic | COD (mg/L) |
| 76 | 110 | 127 | 1359 | 1448 | 1435 | 3627 | 3663 | 3457 | 2 day anaerobic | |
| 58 | 128 | 149 | 844 | 922 | 857 | 2207 | 2276 | 2321 | 1 day anaerobic | BOD5 (mg/L) |
| 38 | 68 | 65 | 761 | 782 | 732 | 2176 | 2271 | 2213 | 2 day anaerobic | |
| 6.28 | 7.01 | 9.46 | - | - | - | 34.7 | 28.4 | 24.5 | 1 day anaerobic | TKN (mg/L) |
| 1.19 | 1.93 | 11.89 | - | - | - | 27.6 | 30.1 | 33.2 | 2 day anaerobic | |
| 5.15 | 5.58 | 6.20 | - | - | - | 9.40 | 9.60 | 9.71 | 1 day anaerobic | Phosphate (mg/L) |
| 3.98 | 4.24 | 5.70 | - | - | - | 10.60 | 9.90 | 10.10 | 2 day anaerobic | |
| 56 | 97 | 107 | - | - | - | 2850 | 3033 | 2001 | 1 day anaerobic | TSS (mg/L) |
| 125 | 216 | 290 | - | - | - | 3503 | 3731 | 3684 | 2 day anaerobic | |
| 76 | 110 | 127 | - | - | - | 3627 | 3663 | 3457 | 1 day anaerobic | pH |
| 58 | 128 | 149 | - | - | - | 2207 | 2276 | 2321 | 2 day anaerobic | |
Table 5) The efficiency of the aerobic biological system to remove the various parameters at different times
| Aerobic effluent | Aerobic influent | ||||||
| HRT 8 (hr) |
HRT 6 (hr) |
HRT 4 (hr) |
HRT 8 (hr) |
HRT 6 (hr) |
HRT 4 (hr) |
Parameter | |
| 5 | 5 | 5 | 213 | 183 | 188 | COD (mg/L) |
|
| 3 | 3 | 3 | 128 | 112 | 120 | BOD (mg/L) |
|
| 0.2 | 0.8 | 1.2 | 6.2 | 6.3 | 6.6 | TKN (mg/L) | |
| 0.66 | 0.50 | 0.88 | 1.54 | 1.48 | 1.60 | Phosphate (mg/L) | |
| 5 | 5 | 5 | 208 | 192 | 236 | TSS (mg/L) |
|
| 7.87 | 7.61 | 7.09 | 7.79 | 7.85 | 7.54 | pH | |
Table 6) Comparison of wastewater effluents from the IFAS system for industrial wastewater treatment
with industrial water standards
| 2 day anaerobic and 8 hr aerobic | 2 day anaerobic and 6 hr aerobic | HRT (hr) | Parameter | ||
| 8 | 6 | 4 | |||
| <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | Fe (mg/L) |
| <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | Mn (mg/L) |
| 8.01 | 7.7 | 7.87 | 7.61 | 7.09 | pH |
| 76 | 110 | <5 | <5 | <5 | COD (mg/L) |
| 34 | 61 | <5 | <5 | <5 | TSS (mg/L) |
| 738 | 667 | 538 | 458 | 483 | TDS (mg/L) |
| 137 | 133 | 78 | 75 | 93 | CL (mg/L) |
Table 7) Chemical analysis of effluent from IFAS system at different times
| F (mg/L) | Fats and oils (mg/L) | SO4 (mg/L) | Mg (mg/L) |
Ca (mg/L) | Color (Pt-Co) |
TDS (mg/L) |
Cl (mg/L) | HRT |
| 0.5 | 1.91 | 134 | 6 | 87 | 95 | 728 | 116 | 1 day anaerobic and 4 hr aerobic |
| 0.56 | 1.2 | 120 | 6 | 95 | 107 | 657 | 133 | 1 day anaerobic and 6 hr aerobic |
| 0.53 | 4.6 | 146 | 7 | 94 | 73 | 684 | 129 | 1 day anaerobic and 8 hr aerobic |
| 0.68 | 5.2 | 108 | 4 | 87 | 51 | 545 | 146 | 2 day anaerobic and 4 hr aerobic |
| 0.61 | 5.4 | 116 | 8 | 83 | 47 | 667 | 133 | 2 day anaerobic and 6 hr aerobic |
| 0.57 | 3 | 106 | 5 | 90 | 60 | 738 | 137 | 2 day anaerobic and 8 hr aerobic |
The performance of the aerobic biological system is presented in Table 5 to remove the various parameters at different times (4, 6 and 8 hours). Figure 4 also shows the effectiveness of the anaerobic biological system at different times (1, 2, 4, 6 and 8 hours aerobic).
The effluent from the coagulation and flocculation unit at 3, 4, 6, and 8-hours hydraulic times is presented in Table 6. According to the results presented in Table 6, the remaining 2 days of anaerobic, 6-hours aerobic and 2-day anaerobic, 8 hrs aerobic had the best removal efficiency.
The results of the analysis of the chemical properties of effluent from the treatment of wastewater in different time periods (1 and 2 days of anaerobic of 4, 6 and 8 hrs aerobic) are shown in Table 7. The amount of arsenic, barium, cyanide, molybdenum and zinc in the effluent was 0.05 mg/L, iron and manganese levels were also 0.01 mg/L. The concentrations of silver, aluminum, boron, cadmium, cobalt, worm, copper, nickel, selenium, and vanadium in the pilot outlet were less than the ICP detection limit.
|
Discussion
|
The effect of hydraulic retention time of the IFAS reactor on COD removal:
One of the most important parameters in the design and operation of biological reactors is Hydraulic Retention Time (HRT). The COD removal efficiency by anaerobic digestion was investigated at different times of 1 and 2 days HRT, in this study and the results of 2 days HRT showed that the removal efficiency was greater than 1 day. Which is consistent with the study by Li et al. (2012) (13). In their study, the removal rate of COD from the IFAS reactor increased with increasing HRT. The increment in efficiency can be explained by the fact that the longer the amount of HRT in the digester is, the greater the time available for the removal of organic pollutants in the microorganisms, as well as by increasing the amount of settled sedimentation time suspended solids also increases. The maximum removal rate of COD in the digester was 63.10 % at a HRT of 2 days.
Also, the results showed that in the HRT of low anaerobic digestion (1 day), the efficiency of COD removal in the IFAS reactor was low. Therefore its outlet concentration was high. In general, the anaerobic HRT 1 day anaerobic 4 hrs aerobic and 2 days anaerobic 8 hrs aerobic were respectively the lowest and the highest removal efficiency in the total reactor, which was 92.1% and 97.9%, respectively. This is consistent with the study by Azimi et al (2013). Azimi et al. used the IFAS to treatment Amol food industry wastewater and obtained the efficiency of removal COD by about 98% to 99% (14).
The results showed that, during the 4, 6 and 8 hrs HRT, the COD removal efficiency was >97.7%, >97.3%, and >97.7%, respectively. During all HRT, the IFAS reactor managed to bring the COD to the lowest (<5 mg/L). Comparison of the results of the removal efficiency in the pilot study with actual data obtained from the wastewater treatment plant of the vegetable oil plant showed that the use of IFAS was associated with increased COD removal efficiency.
Anaerobic digestion efficiency and IFAS system in removing BOD and TSS:
The purpose of industrial wastewater treatment is to eliminate or reduce the concentration of organic or inorganic compounds, the compounds in these sewage systems are toxic to microorganisms, are decomposable, not decomposable and easy to decompose. Organic or inorganic materials are soluble, colloid and suspended. Using the biological units for units for the removal of biological pollutants is appropriate whilst wastewater has decomposable organic compounds. The wastewater of the vegetable oil of Varamin has a high BOD/COD ratio, which means that the use of biological processes is suitable for the treatment of this wastewater. Total suspended solids in the effluent can intrude with the reuse of wastewater. The results showed that with decreasing HRT (from 2 days of anaerobic 8 hrs aerobic to 1 day anaerobic 4 hrs aerobic), the removal of BOD also decreased, resulting in a higher concentration of outlet BOD from the system. In the total system (anaerobic reactor and IFAS), the minimum and maximum removal efficiency of BOD is related to the HRT of 1 day anaerobic 4 hours aerobic and 2 day anaerobic of 8 hrs aerobic. The reduction of HRT has had a significant effect on the removal efficiency of BOD by anaerobic reactors, IFAS and the total system.
Also, the highest amount of removal of suspended solids occurred during a HRT 2-day of 8 hrs aerobic. Due to the continuous flow of wastewater inside the system and the constant volume of the secondary sedimentation unit, the increase in TSS removal was increased by increasing the HRT in the basin. The highest and lowest removal rate of TSS was obtained for 2 days of anaerobic 8 hrs aerobic (98.8%) and 1 day anaerobic 4 hrs aerobic (94.7%). Comparison of the results of the removal BOD and TSS pilot with actual data from the refinery shows that the use of IFAS was associated with a tangible decrease in these parameters. According to the results, the BOD value at the pilot outlet in three times the hydraulic, 4, 6, and 8 hours was less than 3 mg/L. The efficiency of removal of this parameter is higher than 97% at all times.
Anaerobic digestion and IFAS system efficiency in removing TKN and phosphorus:
The results showed that by decreasing the HRT (from 2 days of anaerobic 8 hrs aerobic to 1 day anaerobic 4 hrs aerobic), the removal of TKN decreased, and as a result, the TKN concentration increased from the system. The minimum and maximum removal efficiency of TKN is related to the HRT of 1 day anaerobic 4 hrs aerobic and 2-day anaerobic of 8 hrs aerobic. The reduction of HRT has had a significant effect on the efficiency of removal of TKN by anaerobic reactors, IFAS and the system total. Which is consistent with the study by Regmi et al. (2011) (15). In the study of Regmi et al., TKN increased with time. A study by Veuillet et al. (2014) also showed that, as time increases, the efficiency of removal of TKN did not increase, which is consistent with the present study (16).
According to the results, the highest and lowest removal rate of phosphorus was in HRT 2 days anaerobic 8 hrs aerobic (62.5 %) and 1 day anaerobic 4 hrs aerobic (36.1%). Due to the high concentration of phosphorus in the effluent, the anaerobic process may need to be changed, or the hydration time of the anaerobic digester should be increased. For HRT 2-days anaerobic of 8 hrs aerobic, the concentration of phosphorus from the outlet system was the lowest (3.98 mg/L). The highest and lowest removal efficiency of phosphorus was 6 hrs aerobic (65.9%) and 4 hrs aerobic (45.2%). Which is consistent with the study by Dargahi et al (2017) (17). In a study by Dargahi et al., Which used anaerobic pond system to treatment wastewater, the results showed that by increasing the time, the removal rate of phosphorus increased. In order to provide the standard output of phosphorus, COD to phosphorus ratio, which is an important parameter in phosphorus removal, is about 40 or more. In this study, the ratio of COD to phosphorus at the inlet of the system was equal to or greater than 100, but, despite the proper fit of COD/P, there was no increase in efficiency from 6-hours aerobic to 8-hours aerobic increase, because of this incidence could be the reason for the loss of the balance of phosphorus degrading bacteria should be noted. If using a small anaerobic unit before the IFAS reactor, it can achieve the phosphorus removal efficiency to the required standard.
Chemical analysis of other pollutants at the output of the IFAS reactor:
The effluent from the coagulation and flocculation unit arrived at the 3, 4, 6, and 8-hours HRT. At all times, the amount of treatment was optimum. Owing to the results, the effluent from the pilot plant has the standard of the industrial water (group third and fourth). Standard TDS in groups 1 and 2 and chloride in group 1 are not provided with the proposed treatment in this project, but with the use of advanced treatment such as reverse osmosis, these standards can also be achieved.
|
Conclusion
|
For the most part, the results confirmed that industrial wastewater treatment methods using the IFAS biological system is a suitable method for the removal of pollutants. In addition to acceptable costs, appropriate technology and acceptable energy consumption, this method plays an important role in environmental conservation and can be replacing with conventional methods. Moreover, the efficiency of removing COD, BOD and TSS from the plant was at the optimum level by this system.
|
Footnotes
|
Acknowledgments:
This article is an excerpt from the Master's Thesis from Islamic Azad University.
Conflict of Interest:
The authors declared no conflict of interest.
Type of Study: Original Article |
Subject:
Environmental Health
Received: 2018/03/11 | Accepted: 2019/03/27 | Published: 2018/10/7
Received: 2018/03/11 | Accepted: 2019/03/27 | Published: 2018/10/7
References
1. Keramati H, Parvaresh A, Movahedian Attar H. Survey of dissolved air flotation (DAF) system efficiency for reduce of pollution of Naz vegetable oil factory's wastewater in Isfahan. Horizon Med Sci. 2006; 12 (3) :33-37.
2. Mohamadi N, Ali Dadolahi S. A Study on the Effects of Food Industry Sewage on the Agricultural Water in Dezful. JEST. 2012;14(4):55-62.
3. Khosravi M, Hassani AH, Khani MR, Yaghmaeian K. Synthetic Analysis of Nitrogen and Phosphorous Removal from Municipal Wastewater Using Sequencing Batch Bio-film Reactor with Fixed Bed. JEST. 2016;17(4):59-73
4. Bajaj M, Gallert C, Winter J. Biodegradation of high phenol containing synthetic wastewater by an aerobic fixed bed reactor. Bioresource Technology. 2008;99(17): 8376–8381.
5. Xin Z, Yanming W, Zhengfang Y. Oil field wastewater treatment in biological aerated filter by immobilized microorganisms. Process Biochemistry. 2006;41(7): 1475-1483.
6. Yen-Hui L. Kinetics of nitrogen and carbon removal in a moving fixed bed biofilm reactor. Applied Mathematical Modeling. 2008;32(11): 2360–2377.
7. Mahendran B, Lishman L, Liss S.N. Structural, physicochemical and microbial properties of flocs and biofilms in integrated fixed-film activated sludge (IFFAS) systems. water research. 2012; 46: 5085-5101.
8. Azimi A.A, Hooshyari B, Hradi N.M, Didendi Gh. Enhanced COD and Nutrienent removal efficiency in a hybrid integrated fixed film activated. Iranian Journal of Science & Technology, Transaction B, Engineering. 2007; 31(B5): 523-533.
9. Borghei S, Sharbatmaleki M, Pourrezaie P, Borghei G. Kinetics of organic removal in fixedbed aerobic biological reactor. Bioresource Technology. 2008;99(5): 1118-1124.
10. APHA. AWWA. WEF. Standard Methods for the Examination of Water and Wastewater”. 20th Ed. Washington APHA. 1998.
11. Li C, Li X. L, Ji M, Liu J. Performance and microbial characteristics of integrated fixed-film activated sludge system treating industrial wastewater. Water Science & Technology. 2012;66(12):2785-2792.
12. Azimi N, Taheriyoun M. The Performance of Integrated Fixed Film Activated Sludge in Wastewater Treatment of Food Industry (Case Study: Amol Industrial Park Wastewater Treatment Plant). J water and wastewater. 2013;24(3)80-87.
13. Regmi P, Thomas W, Schafran G, Bott Ch, Rutherford B, Waltrip D. Nitrogen removal assessment through nitrification rates and media biofilm accumulation in an IFAS process demonstration study. Water Res. 2011;45:6699-6708.
14. Veuillet F, Lacroix S, Bausseron A, Gonidec E, Ochoa J, Christensson M, Lemaire R. Integrated fixed-film activated sludge ANITA™Mox process – a new perspective for advanced nitrogen removal. Water Science & Technology. 2014;69(5): 915-922.
15. Dargahi A, Mohammadi M, Amirian F, Karami A, Almasi A. Phenol removal from oil refinery wastewater using anaerobic stabilization pond modeling and process optimization using response surface methodology (RSM). Desalination and Water Treatment. 2017;87:199-208.
Send email to the article author
| Rights and permissions | |
 |
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. |
Owned by Qom University of Medical Sciences
Published by Qom University of Medical Sciences Press
eISSN: 2322-4916
pISSN: 2251-9203
Email: arch.hygiene[at]muq.ac.ir
arch.hygiene[at]gmail.com
