Backwash Optimization for Drinking Water Treatment Biological Filters

A lab scale study was conducted to examine the impacts of backwashing on biofiltration performance. Collapse pulsing resulted in significantly higher DOC removals (21%) compared to the water only backwash (13%). Three backwash procedures were investigated under nutrient supplemented conditions. Employing a lower bed expansion of 20% compared to the 30% reference bed expansion lead to similar DOC removals (30%). However, employing a 40% bed expansion lead to significantly lower DOC removals (24%). A backwash strategy that reduced the backwash water volume usage by about 20% resulted in similar DOC reductions observed with the reference backwash. The investigated backwash procedures were also terminated by the extended terminal subluidization wash (ETSW). ETSW demonstrated no impact on DOC removals, however, ETSW successfully eliminated the filter ripening sequence. Phospholipids and adenosine tri-phosphate methods showed no correlation with DOC removal. On the other hand, dissolved oxygen uptake showed a direct correlation with DOC removals.