Removing Humic Acid In Water By The Integrated Processes Of Micro-eddy Flocculation (MEF)-counter Current Dissolved Air Flotation (CCDAF)-nanofiltration (NF)

Humic acids in the water are one kind of the most important natural organic matter NOM which affect the water quality stability and nowadays that have become the focus of notice in worldwide research. This paper mainly studied the characteristics and the removaling of humic acid in water by the integrated processes of micro-eddy flocculation (MEF) - counter current dissolved air flotation (CCDAF) -nanofiltration (NF) when using PAC and PFC as flocculant, and the dynamic running characteristics of MEF - CCDAF - NF integrated process were studied, combined with micro-eddy flocculation (MEF), counter current dissolved air flotation (CCDAF) and nanofiltration (NF). The main results showed as follows:1. The results showed that water quality of MEF - DAF process matched the requirement of pre-unit for membrane system at optimum dosages of PAC and PFC flocculant. These dosages were less than these in flocculation-sediments processes. The MEF - CCDAF - NF integrated processes could remove most of humic acids in water, and Flowage one with Q5633 NF unit had better performance than Flowage two with M-N1812A. It could be demonstrated by the better quality of effluent water after Flowage one (0.243-0.473 mg L^-1 of TOC, 0.77-0.77 mg L^-1 of COD_Mn, 0-0.0033 of UV₂₅₄nm) than after Flowage two (about 1.0 mg L^-1 of TOC, 0.82 -0.92 mg L^-1 of COD_Mn , 0.008-0.012 of UV₂₅₄nm) when using PAC as flocculant. When using PFC as flocculant also demonstrated the better quality of effluent water after Flowage one (0.418⁰.554mg L^-1 of TOC, 0.60⁰.69mg L^-1 of COD_Mn, no UV₂₅₄nm absorbance) than after Flowage two (0.932-1.0 mg L^-1 of TOC, 0.95-1.2 mg L^-1 of COD_Mn, 0-0.011 of UV₂₅₄nm) there was only 5% residual TDS after with Q5633 NF unit ,but high TDS content after with M-N1812A NF unit. So, Flowage four is the best Flowage when producing drinking water, but Flowage three is the best when removing the most of natural organic matter . Moreover, the NF permeat quality could be improved when activated carbon (AC) unit following MF, but some kinds oforganics in water could be absorbed by both AC and NF units. These led leading to decreasing the stepwise removal rate for organics in water by NF unit. When using PAC as flocculant. the dso of particle size distribution (PSD) in flocculated water and floated one are 10¹4u.m and 8¹3|im for Flowage one, and the dso of particle size distribution (PSD) in flocculated water and floated one were 21u.m and 16u.m when using PFC as flocculant, respectively. Sometimes particles in water with several microns of dso, could still be found after MF or MF-AC units, no particles exist in NF permeat.2. The dynamic running characteristics of MEF - CCDAF - NF integrated process were studied, combined with micro-eddy flocculation (MEF), counter current dissolved air flotation (CCDAF) and nanofiltration (NF). Its running period was about 72 hours when used to remove humic acid in three different kinds of raw water. The results showed that the MEF - CCDAF - NF integrated processes could remove most of humic acids in water, but Flowage one with Q5633 NF unit performed better than Flowage two with M-N1812A one. When treating raw Water two with PAC flocculant in the integrated processes, the better quality of effluent water after Flowage one was 0.45mgL'' of CODMn, fluctuated UV254nm value around 0.0033, and only 5% residual TDS , and the effluent water quality after Flowage two was OJSmgL"1 of CODMn , much less than 0.0075 of UV254nm, and sometimes no detected, and still existed 94%⁹0% TDS. Moreover, when treating raw Water one and Water three, the effluent water quality after Flowage two was 0.0054 of average UV254nm, higher than that for raw Water two with 0.0033 of average UV254nm. A little better effluent water quality was found for the integrated processes with PFC flocclant than with PAC, this could be attributed to better PFC performance in MEF - CCDAF processes for humic acids removal and higher quality pre-treated water. However, the integrated processes could have a stronger ability for buffering the change of raw water quality when PAC as flocculant. The activated carbon unit in the integrated processes improved its NF permeat quality, but didn't prolong its running period. These demonstrated that membrane pollution mainly accredited to inorganic matters.