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Feasibility of Providing Media for Multi-Media Filter Bed in Treatment

Shojae Ghias, Masoumeh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41095 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Hashemian, Jamaleddin
  7. Abstract:
  8. In Iran, the technical issues are not considered when changing or replacing the bed of filter. In this regard, less attention is paid for the properties of the materials (e.g. shape, aggregation, effective size and uniform coefficient of grains, etc.) used in the replaced bed of filter. Therefore, the performance of the replaced filter is not good from treated water quality, water production, and backwash interval points of view. In this project, Light Expanded Clay Aggregate, LECA, was chosen as a suitable material to be used in the bed of filter because of its favorable grain shape. The performance of LECA has been examined in both “Single- Media Filter” and “Dual-Media Filter” for improving the treatment quality. Light weight LECA with diameter of 2.36-4 mm was used in a bed of single media filter with up flow, while heavy weight LECA with diameter of 1.18-2.36 mm was used as the second layer placed in top of a sand layer with diameter of 0.85-1.18mm in a bed of Dual Media Filter for wastewater treatment. The performance of our dual media filter consisting of LECA and sand was also compared with a dual media filter consisting of Anthracite and sand for water treatment. Our experimental results showed that the removal percentage of wastewater quality parameter in the Single-Media Filter has been increased by decreasing the filtration rate and using coagulant as in-line pre-treatment ahead of filtration. By using alum dosage of 4mg/lit at the filtration velocity of 5m/h, removal percentage of turbidity, TSS, COD in waste water treatment were found to be 58.4%, 68.9%, 34.7%, respectively. In the filtration cycle, the average removal efficiencies of turbidity, TSS and COD were found to be 56.6%, 34.7% and 56.8% when using a filter consisting of sand and LECA without pretreatment in waste water treatment. In this case, duration of filtration cycle was 50 h and 15 min, in which the filtration cycles were determined by the hydrostatic head build up. At filtration velocity of 5m/h, we conclude that sand/LECA filter produced better effluent quality with a slower build up than the anthracite/sand filter in water treatment. The optimal dosage of coagulant was found to be at 2mg/lit while the removal percentage of turbidity for LECA and Anthracite were found to be 96.2% and 95.6%, respectively. Our experimental result showed that the LECA grains have a great potential to be used in replacement of filter bed throughout the country concerning the following factors: grain shape, availability, ease of accessibility, surface roughness (for biofilm grows and particle trapping), different specific weight, different grain size distributions, lower cost (than conventional media) and producing relatively better water quality with slower head build up compared to Anthracite
  9. Keywords:
  10. Light Expanded Clay Aggregate (LECA) ; Water Treatment ; Grain Shape ; Waste Treatment ; Single and Multi-Media Filter ; In-Line Filtration

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