细微泥沙粒径对活性污泥产率的影响及其计算公式

针对我国城镇污水处理厂进水SS/BOD5值普遍偏高,在取消初沉池后出现泥沙淤积、污泥浓度提高和污泥MLVSS/MLSS(f)值下降等问题,利用实验室SBR研究了不同粒径的细微泥沙对活性污泥产率的影响,并在对国内外现有污泥产率公式进行具体分析的基础上,提出了对于污泥产率公式的优化方法,并借此推导出f值的预测表达式。结果表明:当在进水中分别掺入体积平均粒径为19.8、72和118.6 μm的细微泥沙300 mg/L时,在系统运行36 d后,污泥浓度从启动初期的3 450分别提高至7 898、5 389和3 742 mg/L,MLVSS/MLSS则从0.67分别下降为0.33、0.48和0.59;活性污泥产率由0.498分别提升至1.257、0.813和0.575 kg MLSS/kg BOD5,利用悬浮系数ω对ATV污泥产率公式进行优化修正,计算值与实测值的相对误差分别由修正前的46.1%、125.8%和219.3%降至修正后的8.4%、8.9%和3.5%,所得的产率更贴近实际;通过修正后的ATV产率公式建立f值的预测表达式,计算值与实测值的相对误差分别为18.3%、12.6%和4.4%。

Calculation formulas of activated sludge yield and impact of fine sediment size in wastewater treatment systems

The high suspended solids/biochemical oxygen demand (SS/BOD5) of influent and the cancellation of primary sedimentation result in serious sediment deposition, a high sludge concentration, and a low mixed liquor volatile suspended solids/mixed liquor suspended solids (MLVSS/MLSS) (f) ratio in many wastewater treatment plants in China.This study investigated the effects of fine sediment with different particle sizes on the sludge yield from a sequencing batch reactor (SBR).Based on the analysis of the formulas of sludge yield domestically and abroad, methods to optimize the formula were proposed and the prediction expression of MLVSS/MLSS was derived.The results showed that when the influent was combined with 300 mg/L of different fine sediments with average volume sizes of 19.8, 72 and 118.6 μm, respectively, the sludge concentration, MLVSS/MLSS, and sludge yield changed after 36 d.Sludge concentrations increased from 3 450 to 7 898, 5 389, and 3 742 mg/L, respectively.The values of MLVSS/MLSS decreased from 0.67 to 0.33, 0.48, and 0.59.The values of sludge yield improved from 0.498 to 1.257, 0.813, and 0.575 kg MLSS/kg BOD5.After the suspension coefficient ω was used to modify and optimize the ATV formula of sludge yield, the relative errors of the calculated value and measured value decreased from 46.1%, 125.8%, and 219.3% to 8.4%, 8.9%, and 3.5%, respectively;thus, the results were closer to actual figures.According to the modified ATV formula of sludge yield, the prediction expression of MLVSS/MLSS was established and the relative errors of prediction value and measured value were 18.3%, 12.6%, and 4.4%, respectively.