الفهرس 
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Abstract
This study was made to check the suitability of DBAF system as a biological treatment preceded by a chemical precipitation as new technique to treat industrial wastewater of tannery industry.
DBAF plant designed by others was erected by a contractor in Sahien tannery factory that lies in el Max industrial zone in Alexandria city, with capacity of 30 m3/day wastewater flow in 8 hours operation one turn/day. The study also measured the characteristics of the primary treated wastewater through the chemical precipitator and the biological treated wastewater through the DBAF system. The analysis of the plant influent and effluent was during the period from April 2007 to August 2008.
The study concluded the following:
1. The success of DBAF system for treating such industry wastewater type with suitable removal efficiencies.
2. The DBAF unit reducing the required area to about 20% and reducing the required power supply to about 10% of the activated sludge system and minimizing the control needs to its minimal value.
3. The DBAF achieved less cost in initial by 50% and in running 60% with reducing 53% in total cost compared with activated sludge system which applied in this industrial wastewater treatment in Egypt.
4. The results for chemical treatment using sodium sulphate addition followed by precipitation in settling tank shows that this treatment was effective in achieving Cr removal ratio by 98.85%.
5. The chemical precipitation succeeded in decreasing the BOD & COD loads on the biological unit by ratios varied between 16.0 & 23.6 % for BOD and 26.7 & 39.4% for COD.
6. The TSS load was decreased by chemical precipitation to about 50%.
7. The DBAF system achieves high removal efficiency for BOD, COD, TSS & Cr ;the BOD & COD loads were high than domestic sewage but the DBAF unit had succeeded in removing it by average removal ratios 88.05% for BOD and 85.50% for COD.
8. The TSS and Cr resulted good removal efficiencies in the DBAF system and produced effluent concentrations below the law limits