活性污泥法处理高钙废水中污泥特性的变化

通过单级SBR法处理模拟高钙废水,研究了活性污泥法处理高钙废水的过程中钙离子对COD,MLVSS,MLSS,SVI,污泥增长速率,污泥形态结构及生物相的影响,揭示活性污泥法处理高钙废水的过程中污泥量巨大的原因。采用逐步增加钙离子浓度的方法,检测到在污泥培养期([Ca2+]=0 mg/L),COD去除率为98.1%,MLVSS和MLSS稳定在4 900~5 500mg/L,污泥增长速率为67 mg/(L·d),SVI为55~60 mL/g;在驯化处理期([Ca2+]=120~2 400 mg/L),COD去除率降至87.37%,MLVSS降至2 500 mg/L,MLSS增加至19 300 mg/L,污泥增长速率为212.31 mg/(L·d),SVI降至25 mL/g;在冲击期([Ca2+]=4 000 mg/L),COD去除率降至69.23%,MLVSS降至1 600 mg/L,MLSS迅速增加至24 200 mg/L,污泥增长速率为816.67 mg/(L·d),SVI降至14 mL/g。经显微镜观察发现,污泥絮体由松散变得密实,生物相由钟虫等指示性微生物变为不适应环境的胞囊结构。结果表明,随Ca2+浓度的增加,COD去除率下降,MLSS迅速增加,MLVSS和SVI急剧缩小,说明活性污泥中的活性微生物逐渐减少,而无机物组分逐渐增多;钙离子的加入促使系统碳酸平衡向右移动,使离子状态的钙大部分转化为难降解的碳酸盐,并附着于污泥絮体上,污泥绒粒被压缩,使污泥颗粒密实度及MLSS迅速增加,导致污泥排放量巨大。

Change of sludge characteristics in high cacium wastewater by activated sludge process

We studied the influences of different Ca²⁺ concentrations on the COD removal rate and sludge characteristics, such as MLVSS, MLSS, SVI, sludge growth rate, sludge morphology, and sludge biophase during the process of treating high calcium wastewater with a single sequencing batch reactor, and revealed the causes of huge sludge deposition in this process. Through gradually increasing Ca²⁺ concentrations, it was detected that in sludge cultivation stage ([Ca²⁺]=0 mg/L), the COD removal rate was 98.1%, MLVSS and MLSS was around 4 900~5 500 mg/L, sludge growth rate was 67 mg/(L·d), and SVI was 55~60 mL/g; in sludge domestication and disposal stage ([Ca²⁺]=120~2 400 mg/L), the COD removal rate dropped to 87.37%, MLVSS reduced to 2 500 mg/L, MLSS increased to 19 300 mg/L, the sludge growth rate became 212.31 mg/(L·d), and SVI dropped to 25 mL/g. In the shock stage ([Ca²⁺]=4 000 mg/L), the COD removal rate fell to 69.23%, MLVSS reduced to 1 600 mg/L, MLSS increased to 24 200 mg/L rapidly, sludge growth rate turned to 816.67 mg/(L·d), and SVI reduced to 14 mL/g. The microscopic observation showed that the structure of sludge flocs turned from loose to compact, and biofacies changed from epistylis to cytocyst. The results indicate that with the increase of Ca²⁺ concentration, the COD removal rate decreases, MLSS increases rapidly, and MLVSS and SVI drop sharply, which reveals that active microbes reduce and inorganic components increase gradually in the activated sludge; and that the increase of Ca²⁺ causes the carbonate balance equilibrium of system move to rightwards, and the majority of Ca²⁺turns into refractory carbonates. These carbonates then attach to the sludge flocs and meanwhile compress them, which leads to the rapid increase of compactness of sludge granules and MLSS. A huge amount of sludge is thus produced.