Experimental Study on Bio-slow Filtration System for Treating Micro-polluted Water:A Comparison of Two Fillers
The characteristics of fillers determine the removal efficiency of various pollutants in bio-slow filtration systems.However,research on the comparison of purification performance and microbial community differences in bio-slow filtration systems using different fillers is limited both domestically and internationally.In this study,quartz sand and activated carbon were chosen as fillers in the bio-slow filtration system,and their differences in pollutant removal and microbial community were compared.Backwashing experiments were conducted using a self-designed bio-slow filtration device when the fillers became clogged.The results showed that both columns required 26 days for biofilm formation.After biofilm formation,the average removal rates of turbidity,CODMn,and ammonia nitrogen by the activated carbon column were 92.18％,65.53％,and 99.37％,respectively,while those by the quartz sand column were 91.89％,42.91％,and 98.87％,respectively.The activated carbon column showed better removal efficiency compared to the quartz sand column.During biofilm formation,both the quartz sand and activated carbon columns exhibited accumulation of nitrite nitrogen and nitrate nitrogen.The dominant bacterial groups in the quartz sand column were A0839 and Rhodobacter,while in the activated carbon column,the dominant bacterial groups were Ramlibacter,Pseudomonas,and Leptospirillum.This microbial community analysis provided an explanation for the superior removal efficiency of organic matter and total nitrogen in the activated carbon column compared to the quartz sand column.The penetration depth of activated carbon filter media is greater than that of quartz sand filter media.In the quartz sand column,clogging mainly occurs in the first 40 cm of the filler,while in the activated carbon column,clogging occurs in the first 60 cm of the filler.At a filter media expansion coefficient of 30％,the backwash intensities for the quartz sand column and the activated carbon column were 6.83 L·m-2·s-1 and 3.16 L·m-2·s-1,respectively.The activated carbon column required 53.7％less backwash water compared to the quartz sand column.This study provides technical basis for selecting filter media in rural slow filtration systems and offers economically viable solutions for addressing clogging issues.It also provides technical support for the application of this technology in rural water supply,benefiting rural communities.
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