Document Details
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Document Type |
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Thesis |
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Document Title |
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IMPROVEMENT OF WASTE WATER SLUDGE TREATMENT AND BIOGAS PRODUCTION USING INTEGRATED PHOTO CATALYSIS- ANAEROBIC DIGESTION. تحسين معالجة حمأة مياه الصرف وانتاج الغاز الحيوي باستخدام تقنيتي التحفيز الضوئى والهضم اللاهوائي. |
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Subject |
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Faculty of Meteorology, Environment and Arid Land Agriculture |
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Document Language |
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Arabic |
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Abstract |
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With rapid industrialization and economical growth, reasonable numbers of wastewater treatment plants have been established, producing a huge amount of waste activated sludge (WAS). Industrial sector in Saudi Arabia, has made momentous progress during last four decades where the number of operating units has increased from 198 to 7007 between 1974 to 2015. Industries are using enormous amount of fresh water ≈ 7.1 x 108 m3/year, and generating an excess of wastewater ≈1238 tons of WAS per day from treatment plants. The WAS from secondary treatment of wastewater exerts a significant pressure to its disposal and stabilization. WAS processing and disposal entails high expenditure that accounts 50 % of the total operating cost of wastewater treatment plant. The management of WAS is considered as one of the most significant environmental problems in the current scenario.
Among various approaches to WAS disposal, anaerobic digestion is a prefered treatment option and has attracted much attention due to its low expenditure and high energy recovery in the form of biogas. However, the efficiency of this process in WAS is hindered due to the presence of complex organics, rate limiting microbial flocs, extracellular polymeric substances, and various toxic compounds. To overcome these rates limiting factors, a pretreatment step can be applied prior to the anaerobic digestion process. Photocatalysis is considered the most effective, environmentally friendly, and advanced oxidation technology that can be used as a pre-treatment for WAS disintegration. It is a promising option in the context of low energy requirement due to the use of solar light, and high economic feasibility.
In the present study various types of novel visible light active photocatalysts composites such as ZnO-ZnS@PANI, ZnO-ZnS/Ag2O-Ag2S, Cr2O3/C3N4 and C3N4/TiO2 NTs were successfully fabricated and analysed for their morphology and structure characteristics by using various techniques i.e. XRD, SEM, EDS, XPS, Raman spectroscopy and FTIR etc. Each material was evaluated for multiple environmental applications i.e. degradation of organic pollutants (to analyse photocatalytic activity of the material using the 2-Chlorophenol as model pollutant) and disintegration (solubilization) of WAS by photocatalysis (visible light + catalyst) to improve biogas production during the aerobic digestion process. The results showed that the composite materials achived the highest degradation (>80 %) of 2-Chlorophenol as compared to the respective parent materals. The optimum operating conditions were achieved for pollutant concentration of 30-50 mg/l. catalyst dose of 0.5 g/l and pH 3-7. The efficient degradation was achieved due to the formation of composites of photocatalysts that shifted the high energy band gap to the visible region. Moreover, the catalyst showed high stability and retained its photocatalytic activity up to the maximum level even after multiple reuses.
In case of sludge, photocatalysis using visible light catalyst accelerated the hydrolysis of WAS and increased the sCOD by > 6 times after 6 h and transform tCOD into bioavailable sCOD. In a subsequent anaerobic digestion of pretreated sludge, a significant removal of organic matter and tCOD was achieved in photocatalytic pretreated sludge as compared to raw sludge. Similarly, the methane production was improved as much as 1.6 folds higher compared to the raw sludge. Moreover, the photocatalysis decrease the onset of methanogenesis by up to 12 days while achieve the maximum conversion rate of reducing sugars into organic acids (precursor of methane) at that time. These results suggested that photocatalysis is an efficient pretreatment method and visible light composites photocatalysts can degrade sludge efficiently for enhance biogas production in anaerobic digestion process. Overall, this study determined the significance of photocatalysis for sludge treatment and cleaner energy production, while providing a useful reference for its industrial applications. |
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Supervisor |
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Prof. Dr. Mohamed Abu El-Fetouh Barakat |
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Thesis Type |
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Doctorate Thesis |
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Publishing Year |
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1439 AH
2018 AD |
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Added Date |
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Tuesday, February 13, 2018 |
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Researchers
| مزمل انجم | Anjum, Muzammil | Researcher | Doctorate | |
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