PHD theses : Engineering

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Author: search.filters.author.Alfatih Awad Mohamed YasseenSubject: search.filters.subject.Chemical Engineering

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    Cleaner Production in Tanning Processing (Case Study: Afrotan Tannery)
    (Al Neelain University, 2016) Alfatih Awad Mohamed Yasseen
    Afrotan tannery was established in 1983, in Albagair Area- AlGazira State - Sudan. It tans about 20000 hide per day. It has four units of wastewater treatment. The wastewater of soaking, deliming, fleshing (washing water) and cleaning processes is treated in general waste water treatment unit. The wastewater of un hairing and liming processes is treated in liming recovery unit. The wastewater of tanning processes is treated in chromium recovery unit. The sludge precipitated in sedimentation tanks of these units is treated in sludge treatment and dewatering unit. The objective of this study is to evaluate the efficiency of the methods of treatment and recycling applied in these four units and to assess the environmental impact for these units. The analysis was carried out by using the standards methods for the Examination of Water and Waste Water, Edition 20, (1998). The results showed that, the general wastewater treatment unit receives 1000 m3/day of wastewater. 300 m3/day of this quantity is precipitated as sludge in sedimentation tanks. 700 m3/day is the amount of treated water. 280 m3/day of this treated water is reused in production line and the remaining (420 m3/day) is ditched in land. The removal rates of deliming process substances and chlorides are very low. The removal of deliming process substances in biological oxidation tank increases the treatment cost. The study recommended that waste water of deliming process should be separated, treated and recycled directly. The liming recovery unit receives 300 m3/day of spent liming liquor. 140 m3/day of the quantity is floated and precipitated as sludge. 60 VIII m3/day of this sludge is directly burred in landfills contaminating the soil with sulphide. 160 m3/day of the quantity is the amount of treated liming liquor which is mixed with fresh makeup solution and recycled. The study recommended that further studies to reduce organic loads should be conducted and all sludge should be sent to the sludge treatment unit. The results showed that the chromium recovery unit receives 40 m3/day of spent chromium liquor. Just 1.2 m3 /day of the quantity is recovered and converted to basic chromium sulphate which is reusable. The remaining 38.8 m3/day is supernatant which is sent to general waste water treatment unit and the chromium is precipitated with sludge in sedimentation tanks. For proper chrome treatment, it is recommended that chrome recovery method must be replaced by the direct chrome recycling method. The sludge treatment unit receives 380m3/day of slurry sludge. After treatment and dewatering, 80m3/day of sludge is burred in landfills which it contains chrome, sulphides, chloride and others. The study recommended that sludge should not burred in landfills and also further studies should be conducted to utilize this sludge as fertilizer or in any other purposes. The results showed that there is no contamination by tannery wastewater in the tannery drinking water wells. The study recommended that periodic tests for tannery drinking water must be regularly run and the samples should be taken directly from the well.