Experimental study on the removal of organic pollutants and NH₃-N from surface water via an integrated copolymerization air flotation-carbon sand filtration process

Micro-polluted surface water sources contain organic pollutants and NH₃-N contents that exceed the limits, and the effluent from conventional water plant operations poses a threat to water supply safety. In this paper, countercurrent-cocurrent dissolved air flotation (CCDAF) and carbon sand double-layer filtration were integrated to produce a copolymerization air flotation-carbon sand filtration process. The results of the pilot studies show that the average removal percentage for COD_Mn and UV₂₅₄ reached 47.86% and 58.80%, respectively, and the removal efficiency of UV₂₅₄ was better than that of COD_Mn using the air flotation unit. The removal of COD_Mn was also better than the removal of UV₂₅₄ using the filtration unit, and the organic matter removal primarily occurred in the activated carbon layer. The total removal percentage of trihalomethane formation potential (THMFP) was 24.43%. The average removal percentage of NH₃-N was 27.50%, and the removal percentage of the filter unit for total nitrogen (TN) and NH₃-N was 15.00% and 54.00%, respectively. The sufficient dissolved oxygen content in the floating filter enhanced the removal of the organic matter and nitrogen, and the advantages of the direct filtration process were obvious as the influent pollutant load increased.