Enhancing sewage sludge dewaterability by bioleaching approach with comparison to other physical and chemical conditioning methods

The sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition of inorganic or organic chemicals. Here we report that bioleaching, an efficient and economical microbial method for the removal of sludge-borne heavy metals, also plays a significant role in enhancing sludge dewaterability. The effects of bioleaching and physical or chemical approaches on sludge dewaterability were compared. The conditioning result of bioleaching by Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans on sludge dewatering was investigated and compared with the effects of hydrothermal (121℃ for 2 hr), microwave (1050 W for 50 sec), ultrasonic (250 W for 2 min), and chemical conditioning (24% ferric chloride and 68% calcium oxide; dry basis). The results show that the specific resistance to filtration (SRF) or capillary suction time (CST) of sludge is decreased by 93.1% or 74.1%, respectively, after fresh sludge is conditioned by bioleaching, which is similar to chemical conditioning treatment with ferric chloride and calcium oxide but much more effective than other conditioning approaches including hydrothermal, microwave, and ultrasonic conditioning. Furthermore, after sludge dewatering, bioleached sludge filtrate contains the lowest concentrations of chroma (18 times), COD (542 mg/L), total N (TN, 300 mg/L), NH₄⁺-N (208 mg/L), and total P (TP, 2 mg/L) while the hydrothermal process resulted in the highest concentration of chroma (660 times), COD (18,155 mg/L), TN (472 mg/L), NH₄⁺-N (381 mg/L), and TP (191 mg/L) among these selected conditioning methods. Moreover, unlike chemical conditioning, sludge bioleaching does not result in a significant reduction of organic matter, TN, and TP in the resulting dewatered sludge cake. Therefore, considering sludge dewaterability and the chemical properties of sludge filtrate and resulting dewatered sludge cakes, bioleaching has potential as an approach for improving sludge dewaterability and reducing the cost of subsequent reutilization or disposal of dewatered sludge.     

红土复合聚合氯化铝以及三氯化铁去除水华藻类的研究

采用红土复合聚合氯化铝（PAC）以及三氯化铁（FeCl3）制得的复合絮凝剂对水样中的藻类絮凝沉降效果进行了研究。结果表明,与PAC复合FeCl3混凝剂不同,红土的加入可增加絮体的密实度,加快絮体沉降速度,沉淀后的絮体在微扰动下不再漂浮上升从而有效提高除藻效果。采用正交试验探讨了复合絮凝剂除藻的最优配比,用混凝剂（红土：PAC：FeCl3=50mg：8．75mg：17．5mg）处理水样,1h后水样浊度由22．35NTU降至1．85NTU,浊度去除率为91．72％。讨论了温度、pH值等因素对除藻效果的影响,并对除藻机理进行了初步的探讨。     

混凝工艺去除合流污水中有机物及营养元素

通过系列杯罐试验混凝处理合流污水,采用硫酸铝（Al₂(SO₄)₃）、硫酸铁（Fe₂(SO₄)₃）、聚合氯化铝（PAC）和聚合氯化铝铁（PAFC）4种混凝剂均能有效去除污水中的 TP、PO^3-₄-P、SS和COD。聚合金属盐（PAC和PAFC）混凝处理效果优于金属盐（Al₂(SO₄)₃和Fe₂(SO₄)₃）,达到相同的处理效果的投加量明显低于后者。助凝剂采用聚丙烯酰胺（PAM）、聚乙烯醇（PVA）、自制的高分子聚合物（AN）和活化硅酸（AS）,在保持较低混凝剂投加量的条件下可明显提高污水处理效果;添加助凝剂对强化PO^3-₄-P的去除作用不明显,PO^3-₄-P的去除仅与混凝剂的投加量相关。混凝剂和助凝剂对污水中NH₃-N的去除作用相对不显著。SS去除率随混凝剂投加量的变化趋势说明混凝的机理较为复杂,可能存在多种混凝机理共同作用。     

基于IPLV指标测算建筑空调能耗的方法研究

提出一种在建筑节能评估工作中基于IPLV指标测算空调能耗的新方法。通过对同一多层建筑物采用面积指标法和IPLV指标法进行空调能耗的测算,并对比利用e QUEST模拟软件的计算结果,发现面积指标法与模拟结果误差高达30%以上,而IPLV指标计算法与模拟结果误差在10%左右,且IPLV指标法计算过程简便,更适合在实际节能评估过程中使用。     

城市溢流雨水的磁絮凝净化初步研究

采用磁絮凝方法处理城市溢流雨水,以自制的絮凝剂PSFS和磁种为原料做絮凝试验,研究了磁场、絮凝剂投加量、磁种投加量、废水pH等参数对絮凝效果的影响.实验结果表明,磁场可以改变絮凝剂的理化性质,增强絮凝剂的净水效果.通过实验确定了最佳实验条件,在场强为8000 Cs,磁种投加量为200mg/L,絮凝剂投加量为4 mL/L...     

混合碳源制备生物絮凝剂的絮凝效能及产量预测模型

为实现混合底物的高效定向转化,以产絮菌根癌农杆菌(Agrobactrium tumefaciens)F2为研究对象,考察不同单一碳源及不同初始浓度对菌体生长、絮凝效能及絮凝剂产量的变化规律,采用BP算法构建絮凝效能及产量预测神经网络.产絮菌F2利用葡萄糖时的絮凝效能和产量分别为88.98%和2.20 g·L-1,过低的初始浓度将影响产量,不低于7.5 g·L-1为佳.以D-(+)-葡萄糖、D-半乳糖和D-甘露糖3种单糖为混合碳源,构建网络结构为3-5-2的产絮效能及絮凝剂产量预测模型,对两个输出层的预测误差范围均在4%以内,预测葡萄糖、半乳糖、甘露糖浓度的最优解为6.59 g·L-1、1.32 g·L-1、3.57 g·L-1,经验证混合碳源发酵产絮可使絮凝效能和产量比单一葡萄糖发酵时分别提高6.87%和26.82%,本文为产絮菌F2利用含糖有机质废液发酵产絮凝剂提供数据参考.     

聚合氯化铝-壳聚糖复合絮凝剂对腐殖酸的絮凝特性研究

研究了聚合氯化铝-壳聚糖(PAC-CTS)絮凝剂的絮凝特性,进行了聚合氯化铝-壳聚糖复合絮凝剂和单独聚合氯化铝对水中溶解态腐殖酸的去除实验。结果表明:复合絮凝剂在投加量为80 mg/L时即可达到与单独聚合氯化铝投加量为150 mg/L时的去除效果,同时前者适应的pH值范围更宽;与投加量和pH值相比,水样浊度和絮凝搅拌速度是影响絮凝效果的次要因素;另外红外光谱分析发现复合絮凝剂中壳聚糖与聚合氯化铝之间存在相互作用。     

Taylor-Couette流场数值模拟及絮凝效果研究

通过流体力学中的Fluent软件模拟了Taylor-Couette反应器的速度矢量分布、湍动动能分布和有效能耗分布,同时实验研究了TaylorCouette反应器不同内筒转速下三氯化铁对高岭土悬浊液的絮凝效能.结果表明,内外筒环隙间存在亚微尺度的涡旋,当转速为30～60 r·min-时,涡旋形状闭合完整,相互分离,涡旋内部速度梯度较小,湍动动能k在0.00010 ～0.00023 m2·s-2的范围内,有效能耗ε在0.00057 ～0.00189 m2·s-3的范围内,絮凝效能达到最大(80％以上),湍动动能和有效能耗过大或过小均不利于形成完整闭合的涡旋,絮凝效能较差.     

微生物絮凝剂MBFGA1的结构鉴定及絮凝机理研究

以对高岭土的絮凝率为指标对GA1发酵液中各组分的絮凝活性进行预分析,确定MBFGA1精产品为该絮凝剂的核心有效成分.通过丙酮沉淀法提取MBFGA1粗产品,经Sevage试剂纯化后得到MBFGA1精产品,采用全波长扫描、苯酚-硫酸法及考马斯亮蓝法鉴定精产品为多糖类物质,并经2次凝胶过滤层析分离获得MBFGA1-1和MBFGA1-2两组分;分别使用电镜(ESEM)、红外光谱(FTIR)、高效液相色谱(HPLC)以及气相色谱(GC)对MBFGA1、MBFGA1-1和MBFGA1-2进行检测分析.结果显示MBFGA1为线性长链状分子结构,多糖主链上单糖间的连接主要为α-型糖苷键,含有羟基,羧基,甲氧基等有利于絮凝的基团;高效液相色谱和气相色谱测定MBFGA1-1分子量为1.18′106D,单糖组成为0.3木糖:1甘露糖:1.09葡萄糖,另含有少量鼠李糖;MBFGA1-2分子量为3.08′103D,单糖组成为0.68鼠李糖:0.28木糖:1.82甘露糖:1半乳糖:3.73葡萄糖.根据分析结果推测絮凝机理主要为吸附架桥,其中MBFGA1的大分子量以及所含的极性基团使得絮凝剂长链结构分子能够充分伸展,较好地发挥吸附架桥作用.     

Influential factors of formation kinetics of flocs produced by water treatment coagulants

The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process.The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality.Experimental conditions such as alum dosage,pH value for coagulation,stirring intensity and initial turbidity were extensively examined.The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants(alum and polyaluminium chloride) could be taken as a two-phase process:slow and rapid growth periods.Operating conditions with higher coagulant doses,appropriate pH and average shear rate might be particularly advantageous.The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity.The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages.Under the same operating conditions,the alum showed a higher grow rate,but with smaller floc size.