生化池中不同粒径细微沙的悬浮特性

Suspension Properties of Fine Grit with Different Particle Sizes in Bioreactors

进入生化池的沙粒受粒径影响,或沉积或悬浮在生化池,粒径≤73μm的细微沙容易悬浮在污泥混合液中,导致活性污泥ρ(MLVSS)/ρ(MLSS)(生物有机质所占的比例)下降.以粒径≤73μm的沙粒为对象,研究生化池中不同粒径细微沙对活性污泥ρ(MLVSS)/ρ(MLSS)的影响,探讨细微沙的可悬浮性和悬浮态势,揭示细微沙对污泥活性的影响,以期为污水厂的运行管理提供理论基础.通过显微观察发现,粒径>33μm的细微沙不易被活性污泥卷捕,呈自由悬浮态势;粒径≤33μm的细微沙容易被活性污泥絮体卷捕,呈卷捕附着态势.细微沙粒径越小,悬浮比(悬浮在污泥混合液中的细微沙占生化池进水中细微沙总量的比例)越大,活性污泥ρ(MLVSS)/ρ(MLSS)越低,悬浮比与细微沙粒径呈显著线性相关(y=0.996-0.010x),活性污泥ρ(MLVSS)/ρ(MLSS)与悬浮比相关性显著〔y=2.84/(12.27x+3.06)〕.研究显示,细微沙不影响污泥中微生物的活性,污水厂可结合活性污泥ρ(MLVSS)/ρ(MLSS)调控ρ(MLSS),保证ρ(MLVSS)的稳定,有利于实现污水处理系统的稳定运行.

Grit particle size affects whether grit is deposited at the bottom of bioreactors or suspended in activated sludge. Fine grit with a particle size of ≤73 μm is easily suspended in activated sludge and directly results in a decrease in the ratio of mixed liquor volatile suspended solids（ ρ（ MLVSS）） to mixed liquor suspended solids（ ρ（ MLSS））. With fine grit of ≤73 μm as the research object,this paper investigated the effect of fine grit with different particle sizes on the ρ（ MLVSS） /ρ（ MLSS） of activated sludge,discussed the suspensibility and suspension modes of fine grit,and further revealed the influence of fine grit on the activity of activated sludge,in order to provide a theoretical basis for the operation and management of wastewater treatment plants（ WWTPs）. Microscopic observations showed that fine grit with a particle size of 〉33 μm was freely suspended in activated sludge. Fine grit of ≤33 μm was picked up and bound by activated sludge flocs. A smaller particle size corresponded to a larger suspension ratio,which defined the proportion of fine grit brought in by influent that was suspended in the activated sludge,and a smaller ρ（ MLVSS） /ρ（ MLSS） of activated sludge. The suspension ratio was linearly related to the particle size of fine grit（ y = 0. 996-0. 010x）. The ρ（ MLVSS） /ρ（ MLSS） of activated sludge and the suspension ratio were significantly correlated（ y = 2. 84 /（ 12. 27 x ＋ 3. 06））. The present study further revealed that fine grit is an inert substance and has no influence on microorganism activity. WWTPs can adjust ρ（ MLSS） based on ρ（ MLVSS） /ρ（ MLSS） to ensure the stability of ρ（ MLVSS）,which is conducive to the stable operation of WWTPs.