Combined alkaline and ultrasonic pretreatment of sludge before aerobic digestion

Alkaline and ultrasonic sludge disintegration can both be used as pretreatments of waste activated sludge (WAS) for improving the subsequent anaerobic or aerobic digestion. The pretreatment has been carried out using different combination of these two methods in this study. The effect was evaluated based on the quantity of soluble chemical oxygen demand (SCOD) in the pretreated sludge as well as the degradation of organic matter in the following aerobic digestion. For WAS samples with combined pretreatment, the released COD was in high level than those with ultrasonic or alkaline treatment. When combined with the same ultrasonic treatment, NaOH treatment resulted in more solubilization of WAS than Ca(OH)2. For combined NaOH and ultrasonic treatments with different sequences, the released COD were in the order: simultaneous treatment > ultrasonic treatment following NaOH treatment > NaOH treatment following ultrasonic treatment. For simultaneous treatment, low NaOH dosage (100 g/kg dry solid), short duration (30 min) of NaOH treatment, and low ultrasonic specific energy (7 500 kJ/kg dry solid) were beneficial for sludge disintegration. Using combined NaOH and ultrasonic pretreatment with the optimium parameters, the degradation efficiency of organic matter was increased from 38.0% to 50.7%, which is much higher than with ultrasonic (42.5%) or with NaOH pretreatment (43.5%) in the subsequent aerobic digestion at the same retention time.     

Metal chlorides loaded on activated carbon to capture elemental mercury

Activated carbon (AC) was considered to be an effective sorbent to control mercury in combustion systems. However, its capture capacity was low and it required a high carbon-to-mercury mass ratio. AC loaded with catalyst showed a high elemental mercury (Hg0) capture capacity due to large surface area of AC and high oxidization ability of catalyst. In this study, several metal chlorides and metal oxides were used to promote the sorption capacity of AC. As a result, metal chlorides were better than metal oxides loaded on AC to remove gaseous mercury. X-ray diffractometer (XRD), thermogravimetric analyzer (TGA) and specific surface area by Brunauer- Emmett-Teller method (BET) analysis showed the main mechanisms: first, AC had an enormous surface area for loading enough MClx; second, Cl and MxOy were generated during pyrogenation of MClx; finally, there were lots of active elements such as Cl and MxOy which could react with elemental mercury and convert it to mercury oxide and mercury chloride. The HgO and HgCl2 might be released from AC’s porous structure by thermo regeneration. A catalytic chemisorption mechanism predominates the sorption process of elemental mercury. As Co and Mn were valence variable metal elements, their catalytic effect on Hg0 oxidization may accelerate both oxidation and halogenation of Hg0. The sorbents loaded with metal chlorides possessed a synergistic function of catalytic effect of valence variable metal and chlorine oxidation.     

A2/O工艺中好氧污泥絮体的分形结构与理化特征分析

采用图像法和沉降柱法分别研究了A²/O工艺中好氧污泥絮体的形貌、粒度分布、低维分形维数和沉降速率、有效密度、空隙率以及质量分形维数,并尝试探讨了上述相关性质与这些污泥宏观操作性质(沉降、压缩、脱水和稳定性)相关的各种理化指标以及胞外高分子物质(EPS)的含量之间的变化关系.结果表明,污泥絮体呈现不规则的形貌,表面具有空隙.其有效密度一般随着其粒径的增加而降低,而空隙率和沉降速率却呈现与有效密度相反的变化趋势,这些均表明了污泥絮体的分形结构的存在.2次所采集的污泥絮体的中位直径分别为248.81、 332.86 μm,有效密度的平均值分别为0.004 0、 0.007 2 g·cm^-3,自由沉降速率的平均值分别为2.67、 4.79　mm·s^-1,空隙率的平均值分别为0.94、 0.89,一维分形维数分别为1.03、 1.19,二维分形维数分别为1.64、 1.84,采用基于Logan经验公式的有效密度-最大直径的双对数关系确定的质量分形维数分别为1.74、 2.29.尽管第2次所采集的污泥絮体较为密实,但其表面粗糙程度却比第1次的低.此外,研究中发现絮凝能力较高或负电荷较高的A²/O好氧污泥絮体具有高的SVI和ZSV值;分形维数较低的污泥具有高的剪切敏感性和低絮体强度,相应的污泥稳定性低;EPS总量高的污泥脱水性能差,EPS中蛋白质含量高的污泥其表面电荷也较高.     

水源水中典型化学品突发污染的应急处理

针对被典型化学品双酚A(BPA)与邻苯二甲酸二乙酯(DEP)污染原水的应急处理工艺进行了研究.结果表明,活性炭吸附可有效去除双酚A和DEP.拟二级动力学模型和Elovich模型较好地描述粉末活性炭对原水中BPA和DEP的吸附过程.中试条件下,50 mg/L的粉末活性炭可分别将原水中浓度约为500 μg/L的双酚A和3.3 mg/L的DEP处理达标.炭砂滤柱对2种化学品的动态吸附表明,BPA和DEP的去除率受它们初始浓度的影响较小,在滤速为5.1～15.3 m/h的范围内BPA和DEP的去除率基本不受滤速的影响.当同时采用粉末活性炭和炭砂滤柱工艺时, PAC的吸附过程是去除污染的主要阶段,炭砂滤柱可以作为粉末活性炭的有效补充保证一定的安全系数.KMnO₄和Cl₂均不能氧化DEP,3 mg/L的KMnO₄和1.5 mg/L的Cl₂可几乎完全氧化水中浓度为850　μg/L的BPA,BPA的氯化产物和KMnO₄的氧化产物及其毒性有待于进一步研究.　1.5 mg/L高锰酸钾和PAC联用对去除DEP无协同作用,对去除BPA有促进作用.     

生物因子控制反冲洗对BEAC滤池优势菌稳定性影响研究

针对用于生物增强活性炭工艺(BEAC)中的6株优势菌,利用生物因子研究反冲洗对优势菌群在活性炭表面稳定性的影响,确定适合的反冲洗方式及强度.中试试验表明,气冲强度对BEAC生物膜的影响作用要比水冲洗大,通过比较反冲洗前后优势菌群生物量,确定BEAC滤池启动期采用单独水反冲洗,稳定期采用气水联合反冲洗,优势菌群在活性炭表面的平均生物损失量为15.47%;利用生物量和生物活性的乘积(生物需氧量,BRP)确定最佳反冲洗气强度为8～10 L/(m~2·s),反冲洗前后的生物量和生物活性变化最小;扫描电镜和PCR-DGGE图片结果表明,启动期采用气水联合反冲洗导致优势菌数量减少,稳定期采用气水联合反冲洗可保持优势菌的稳定性,反冲洗前后优势菌在活性炭表面数量变化较小.     

基于批式呼吸计量法的溶解性COD组分划分

利用批式好氧呼吸计量法结合溶解性慢速水解COD(S_H)水解动力学拟合提出了溶解性COD(SCOD)的组分划分方案.上海2个污水处理厂进水的SCOD组分划分结果表明,A厂沉砂池出水(典型生活污水)的SCOD中含有43.5%～58.6% S_H、 21.8%～35.2%易生物降解COD(S_S)和15.4%～30.9%溶解性惰性COD(S_I); B厂沉砂池出水(长距离输送的合流制污水)SCOD中含有34.5%～45.2% S_H、 29.3%～37.7% S_S和25.6%～31.2% S_I. 9组不同水样的试验拟合结果表明,一级动力学能够很好地描述S_H的水解过程,A厂和B厂进水S_H的水解速率常数分别为28.00～39.77 d^-1和26.48～29.52 d^-1.该组分划分方案能够实现S_S积分区域的理论划分,并消除溶解性微生物产物对S_I测定的影响.     

一种测定活性污泥中高等微生物活性的方法

采用机械破碎方式灭活活性污泥中高等微生物,并通过测定破碎前后泥样耗氧速率(OUR)之差别间接计算高等微生物的活性作用.实验结果表明,以分散机破碎活性污泥,高等微生物均可被有效地破碎灭活,且再培养138h后不再恢复.与此同时,对酵母菌破碎实验显示,机械破碎并未对其数量、形态以及活性产生太大影响,这表明机械破碎亦不会对个体尺寸比酵母菌更小的细菌构成任何影响.为使破碎前后活性污泥絮凝体形态基本一致,将破碎后的泥样经离心处理,以尽可能使絮凝体恢复如初(以SVI衡量).通过比较破碎前后泥样的OUR并计算可知,高等微生物活性相对于活性污泥总活性约占12%～14%.     

活性炭滤池中微生物特征及其对溶解性有机碳的去除作用

采用异养菌总数计数（HPC）法检测了北京地区J水厂活性炭滤池中微生物量,并分析了活性炭滤池进出水中有机物的组成、活性炭的吸附作用及微生物作用对溶解性有机碳(DOC)去除的贡献率.结果表明,不同炭龄、不同运行周期活性炭滤池中的微生物量有显著的差异.由于溶解性可生物降解有机碳（BDOC）占溶解性有机碳（DOC）的比例较小,且受微生物数量、活性等因素的影响,微生物对DOC的去除效果极为有限,在1.5年和5年炭龄活性炭滤池中对DOC的去除率仅占总去除率的18.8%和26.4%.此外,微生物对较为敏感的嗅味物质2-MIB和geosmin去除作用也不显著,去除率在15%以下（初始浓度为100ng·L-1）;在使用5年活性炭滤池中,微生物对2-MIB和geosmin去除率为12%和14%,分别占总去除率的32%和29%.因此,北京地区地表水净水厂活性炭滤池中微生物对有机物控制的贡献率较低,对DOC的去除主要以活性炭的吸附为主.     

铜藻基载铁活性炭的制备及其对亚甲基蓝的吸附特性研究

以一种大型海藻——铜藻为原料,Fe Cl3·6H2O为活化剂,采用超声浸渍-原位合成法制备了铜藻基载铁活性炭(Fe/SAC),并以活性炭得率和亚甲基蓝吸附值为指标,通过正交法考察了活化温度、活化时间和浸渍比的影响.同时,采用X射线衍射、扫描电镜和比表面积分析仪对最优结果进行表征,并考察了Fe/SAC吸附亚甲基蓝的热力学与动力学特性.结果表明,Fe/SAC的最优制备工艺条件为活化温度600℃、活化时间1 h、浸渍比1∶1,此时的活性炭得率为39.5%,亚甲基蓝吸附值为255.67 mg·g~(-1);最优工艺条件下制得的Fe/SAC比表面积为558.31 m2·g~(-1),其负载的铁组分主要为Fe3O4和Fe O;亚甲基蓝在Fe/SAC上的吸附过程符合准二级动力学模型,Langmuir等温吸附模型能够很好地描述吸附平衡过程,该吸附是熵增加的自发吸热(ΔS0、ΔG0、ΔH0)过程,升温有利于吸附.     

驯化活性污泥SBR工艺处理乳制品废水研究

乳制品废水直接采用生物法处理在现有研究中较少,为验证处理效果,将4阶段驯化后的活性污泥投加到SBR中,进行了低浓度乳制品废水的直接生物降解试验,主要考察了对COD、NH4-N的去除效果,结果显示:活性污泥驯化期间,COD、NH4-N平均去除率分别为93%、90%;驯化后的活性污泥处理效果稳定,当进水COD为1654 mg/L、NH4-N为115 mg/L时,出水COD、NH4-N分别为66 mg/L、2 mg/L,达到《污水综合排放标准》(GB 8978-1996)一级排放标准,证明了用驯化活性污泥直接处理低浓度乳制品废水是可行的.