Biofiltration is a process in which an otherwise conventional granular filter is designed to remove not only fine particulates but also dissolved organic compounds through microbial degradation. Biofiltration can reduce the need for chemicals in drinking water treatment and thus improved applications of biofiltration in drinking water treatment can be viewed as green or sustainable engineering technology. Recent trends in biofiltration technology for drinking water treatment have or have attempted to extend the performance of biofilters through gaining a better understanding of operational constraints. This review articles summarizes important operational parameters influencing biofiltration performance such as hydraulic loading, empty bed contact time (EBCT), temperature, media type, and backwashing conditions. In addition, recent advancements in biofiltration operations including, ozonation, ammonia removal and the influence of nutrient (nitrogen, phosphorous) supplementation to facilitate carbon removal are explored.
Analysis of the impacts of nitrogen, phosphorus and potassium supplementation on biofilter performance for organic carbon removal was studied on laboratory-scale biofilter columns. Three dual media biofilter columns were fed with synthetic raw water C:N:P ratios of 546:24:1, 100:10:1, and 25:5:1 (w/w) to simulate nutrient limited and two nutrient supplemented conditions, respectively. Research found that air-scour versus water only backwash improved the nutrient limited dissolved organic carbon (DOC) removal by 8%. In addition, nutrient supplementation and backwash alteration improved DOC removals by 19% for the 25:5:1 column and 14% for the 100:10:1 column. Potassium supplementation with the 25:5:1 C:N:P ratio column had no discernible effect on DOC removal. No correlation with phospholipid (7–474 nmol P/g media) and adenosine triphosphate (ATP) (0.6 × 105–32.74 × 105 pg ATP/g media) values with DOC removal were found. Nutrient availability was found to influence DOC removal, demonstrating its importance when utilizing biofiltration for treatment of source waters.
Three lab scale dual media columns filtering synthetic raw water were monitored for dissolved organic carbon removal under nutrient limited (nitrogen, phosphorous deficient) and nutrient enhanced (nitrogen, phosphorous supplementation) conditions. The effects of different types of backwash procedures were also observed. Overall, nitrogen and phosphorous enhancement improved DOC removals by 14% -18.5%. As well, the addition of air scour to the backwash procedure increased DOC removal by 8% for the nutrient limited control column. Besides nitrogen and phosphorous, the effects of potassium addition were also studied. Potassium enhancement did not improve DOC removal but an increase in phospholipid biomass values was observed. Following this increase, a biomass sloughing event was observed that may have been a result of the potassium enhancement.No clear correlations could be drawn between biomass phospholipid or ATP values and DOC removal. Final top of the filter biomass values ranged from 7 -474 nmol P/g media and 0.6 × 10 5 -32.74 × 10 5 pg ATP/g sample for the phospholipid and ATP values respectively.iii
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