Phosphorus removal effect enhanced by magnetic seeds loading in pure membrane MBBR process at low temperature
When iron salts were added to the effluent of pure MBBR process for phosphorus removal at low temperature,the phosphorus removal rate was low due to the poor setting performance of the fine phosphorus-contained flocs.In this study,ferric chloride was taken as coagulant to investigate the enhanced phosphorus removal effect by magnetic seeds with different particle sizes at 10 ℃.The results showed that in comparison with that of FeCl3 coagulation without magnetic powder addition,TP removal rates increased by 8.52％and 5.12％after addition of 18 μm or 58 μm magnetic powder,respectively.This was mainly attributed to the enhanced removal of fine phosphorus-contained flocs.By comparing the fractal dimensions of the flocs formed after adding five kinds of magnetic powders,the smaller the particle size for magnetic powders of 18～58 μm,the larger the fractal dimension,and the more compactness of formed flocs.When the size of magnetic powders exceeded 58 μm,the fractal dimension of formed flocs decreased rapidly,and their compactness became worse.The anti-shear test of flocs showed that the strength and settling ability of phosphorus-contained flocs after addition of 18 μm magnetic powders were better than them after addition of 58 μm magnetic powders.The study confirmed that the addition of magnetic powders with small particle size at low temperature could form the dense flocs with magnetic seeds as the core,and good settling ability and capture ability for fine phosphorus-contained particles of flocs can improve the phosphorus removal rate of the MBBR process.
magnetic seedsMBBRremoval of phosphoruslow temperaturefloc structure
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