生化池中不同粒径细微沙的悬浮特性

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≤73 μm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≤73 μm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>33 μm的细微沙不易被活性污泥卷捕,呈自由悬浮态势；粒径≤33 μm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. 

Suspension Properties of Fine Grit with Different Particle Sizes in Bioreactors

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/(12.27x+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.