水泥及其外加剂固化淤泥的试验研究

为了改善武汉东湖疏浚淤泥的物理力学性能,在传统水泥固化处理方法的基础上,掺入外加剂氢氧化钠(NaOH)和石膏,对100多组淤泥固化土试样进行了室内无侧限抗压强度试验,进行固化效果和固化机理的分析。结果表明:在疏浚淤泥固化过程中水泥占主导地位,对固化效果影响最为显著;NaOH促进了水泥的水化作用,增强了淤泥固化土的无侧限抗压强度,表现在固化淤泥早期强度的快速提高;石膏有利于固化淤泥早期强度的形成,其作用持续于整个淤泥固化过程。在水泥掺入比一定时,NaOH和石膏都存在最佳掺量,超过了最佳掺量,强度就会降低。3种固化剂的正交试验得出最佳配比为实际工程的应用提供依据。     

稻壳灰水泥固化淤泥土试验研究

为拓宽稻壳灰和淤泥土等固废资源处理途径,基于传统水泥固化处理方法,提出稻壳灰-水泥固化处理淤泥土技术。通过室内击实、无侧限抗压强度(UCS)和电镜扫描(SEM)试验,分析稻壳灰-水泥土强度特性及微观机理。结果表明:稻壳灰对淤泥固化土强度增强效果显著,并且15%稻壳灰+8%水泥掺量效果最佳,稻壳灰加入显著提高淤泥固化土韧性,其破坏应变在3%~5%左右,变形系数E₅₀与抗压强度近似呈线性递增关系,E₅₀可取(19~50)q_u。微观分析表明:水化硅酸钙生成是稻壳灰-水泥固化淤泥强度提高的主要来源,其填充孔隙、胶结作用使土体更加密实,提高强度。基于试验结果,提出了稻壳灰-水泥固化淤泥微观演变机制分析模型。     

水泥固化温州污染土的力学性质和微观结构特性

在不同水泥掺量和龄期条件下对NaCl、油脂、Pb(NO_3)_2污染的温州软土进行水泥固化处理后,土体的强度得到改善。为进一步得出水泥固化处理对于不同污染土的处理效果,对水泥固化稳定不同的污染土进行了无侧限抗压强度试验和微观结构研究。分析了不同污染物类型、污染物掺入量、水泥掺入量以及养护龄期对水泥固化污染土强度特性的影响以及不同污染物浓度下水泥固化土微观结构的差异。试验结果表明:NaCl在一定范围内促进了水泥固化土早期强度的提高;油脂使水泥固化土的强度明显降低,压缩性增大;Pb(NO_3)_2掺入到土体中后,水泥固化土的强度总体上略有降低,掺入量与强度之间大致呈线性关系。随着水泥掺入量及龄期的增加,水泥固化污染土的强度会有显著提高。扫描电镜(SEM)结果分析得出:由于污染物的作用,污染物浓度的增加使固化土中孔隙增多,结构变得疏松。     

ISS—水泥联合固化淤泥的微观机理研究

采用离子土固化剂(ISS)、水泥、碱化剂NaOH对福建宁德海相淤泥进行单掺、复掺、碱化复掺等不同方式的化学固化。在对固化前后的淤泥样品开展无侧限抗压强度、24h固结压缩等力学试验的基础上,通过SEM、XRD、XRF等微观测试,分析不同固化方式下淤泥的固化效果;研究不同形态酸、碱固化剂相互作用的定性和定量关系;探讨ISS—水泥联合固化淤泥的微观机理。试验结果表明:在相同水泥掺量下,NaOH碱化ISS—水泥联合固化淤泥效果优于单掺水泥固化淤泥效果,且二者都好于酸性ISS—水泥联合固化淤泥的效果。     

碱激发钢渣粉淤泥固化土性能研究

在淤泥土等不良土质中水泥固化存在抗压强度低、水泥消耗量大等问题,分析了钢渣粉掺量、养护龄期、激发剂等对固化土抗压强度的影响规律。结果表明:当钢渣粉掺量超过10%,固化土7 d抗压强度快速降低,28 d抗压强度逐渐提高;NaOH和Na2CO3对钢渣基淤泥固化土影响类似,低掺量效果有限,20%掺量固化土28 d抗压强度分别提高至1.33 MPa和1.67 MPa。复合碱激发材料对固化土的抗压强度提高效果优于单一碱激发材料,10%NaOH复合10%Na2CO3固化土28 d抗压强度达到2.37 MPa。SEM表明,复合碱激发材料的掺入可促使淤泥固化土内部产生更多的硅酸钙凝胶,减少孔隙,提升整体密实性,从而提高了固化土抗压强度。     

复合固化剂固化某淤泥质土的试验研究

为了改善青弋江分洪道工程淤泥质土地基的物理力学性能,选用普通硅酸盐水泥、粉煤灰、水玻璃以及木质素磺酸钠组成的水泥基复合固化剂,以青弋江芜湖段典型淤泥质土样作为试验土样,进行了室内固化试验研究,分析了固化剂掺量、淤泥质土初始含水率以及养护龄期的改变对固化土无侧限抗压强度和抗剪强度参数的影响关系。研究结果表明:对于提高青弋江淤泥质土强度,试验所用固化剂作用效果明显,90d龄期养护条件下,掺入复合固化剂处理的固化淤泥质土无侧限抗压强度最高为单掺水泥条件下固化土无侧限抗压强度的4.2倍,同时前者抗剪强度也明显大于后者;固化土无侧限抗压强度随固化剂掺量增加而提高,但增长速率逐渐减缓,同时还随着养护龄期的增加而提高,两者呈明显的对数关系。     

滨海淤泥固化土在路基回填中的应用研究

为实现滨海淤泥资源再利用，通过承载比（CBR）、无侧限抗压强度和抗压回弹模量试验探究了不同固化剂及其掺量对滨海淤泥固化性能的影响，并基于现行规范对滨海淤泥固化土用于路基填筑的可行性进行了分析。结果表明，滨海淤泥固化土的CBR值、无侧限抗压强度和抗压回弹模量均随着固化剂掺量的增加而增大；相同掺量下，偏硅酸钠对石膏的激发作用大于对水泥的激发作用，水泥掺入偏硅酸钠后，淤泥固化土的CBR值增大了3.4%～12.5%，而石膏掺入偏硅酸钠后，固化土CBR值增大了9.4%～41.7%；当固化剂A、固化剂C和固化剂D的掺量超过4%，固化剂B的掺量超过6%时，滨海淤泥固化土的CBR值能够满足《公路路基设计规范》中路基填筑用土CBR≥8%的要求；当固化剂A、固化剂C和固化剂D的掺量≥6%，固化剂B掺量≥8%时，抗压回弹模量能够满足《公路沥青路面设计规范》给出的路基填筑用土的抗压回弹模量要求。     

稻壳灰-水泥固化淤泥土力学特性及微观机理研究

我国许多地区河道湖泊环境受损,淤泥淤积速度加快,淤泥质软土地区易发生严重的地基或边坡失稳,通过固化/稳定化技术对淤泥土进行资源化利用具有重要意义。提出利用稻壳灰和水泥进行淤泥固化处理,通过无侧限压缩试验、三轴固结不排水试验评价固化土力学特性;并结合核磁共振、X射线衍射和电子显微镜扫描试验,分析稻壳灰掺量对固化土孔隙尺寸、矿物成分、微观形貌的影响规律,揭示稻壳灰-水泥固化淤泥土的机理。研究表明：稻壳灰能显著提高固化淤泥土强度,稻壳灰-水泥土强度随稻壳灰掺量的增加先增后减,随龄期的增长而增加;当水泥掺量8%时,稻壳灰最优掺量为15%,稻壳灰-水泥土应力应变曲线为应变软化型,抗剪强度参数随着养护龄期增大而增大。稻壳灰-水泥土养护28d试样的XRD图中出现水化硅酸钙(CSH)衍射峰,而T2分布曲线中大孔峰值及面积明显降低,同时观察到SEM图中大量网状水化硅酸钙凝胶,该凝胶能够起到填充土体孔隙、联结土颗粒的作用。     

侵蚀性环境下纳米矿粉—水泥固化滩涂淤泥的强度特性研究

将性能优异的纳米SiO_2和纳米Al_2O_3混合共掺应用于滩涂淤泥固化土的强度改性。通过室内试验,探讨了不同龄期、不同纳米矿粉掺入比时标准养护、不同浓度SO_4~(2-)溶液和海水养护条件下的水泥固化土的无侧限抗压强度变化规律,分析了纳米矿粉对水泥固化土强度的改善效果以及抗侵蚀能力。试验结果表明,标准养护条件下,混合掺入纳米SiO_2和纳米Al_2O_3后,各龄期的固化土强度均不同程度提升;纳米矿粉表现出了良好的抗硫酸盐侵蚀效果,当纳米矿粉的掺入比较大时,不同浓度SO_4~(2-)溶液养护条件下的固化土强度反而出现一定程度的增长;海水养护使得固化土强度明显降低,而掺入纳米矿粉后,起到了良好的抗侵蚀效果,掺入比较大时,固化土的中后期强度提高更加明显。研究结果为高含水率淤泥的固化处理以及侵蚀性环境下固化土桩的应用问题奠定了试验研究基础。     

粉煤灰生石灰加固吹填淤泥质土的试验研究

在吹填淤泥质黏土中掺入不同比例的生石灰和粉煤灰,对不同掺入比的固化土进行无侧限抗压强度试验,分别测定不同龄期固化土强度。根据结果分析加固效果、确定合理的掺灰比,并与常用固化剂比较加固效果。结果表明,当生石灰的掺量一定时,粉煤灰的掺量在15%左右时无侧限抗压强度达到峰值,粉煤灰掺量一定时固化土无侧限抗压强度随着生石灰掺量增大而增大。替代水泥、生石灰等常用固化剂,采用掺入15%粉煤灰与10%生石灰混合固化剂加固吹填淤泥加固效果明显,粉煤灰与生石灰混合加固是一种既经济又环保的加固吹填淤泥方法。     

Effect of extra polymeric substance removal on sludge reduction potential of Bacillus licheniformis at its optimised pH condition

The effect of extracellular polymeric substances (EPSs) on the solubilisation of municipal wastewater sludge by protease‐secreting bacteria was investigated. The untreated sludge is an environmental menace, so sludge management techniques are introduced to treat and dispose sludge in a proper way. Sludge pretreatment is needed to increase the solubilisation and the efficiency of treatment methods. The present study deals with sludge solubilisation by bacterial enzymatic pretreatment. The EPS present in the sludge was removed by sodium hydroxide and formaldehyde to enhance solubilisation and increase the bacterial enzymatic activity. After the removal of EPS with different normalities of NaOH, there was about 11–18% sludge solubilisation and about 8–16% sludge reduction during bacterial pretreatment. Bacterial enzymatic pretreated sludge was further treated using aerobic digesters. From the results obtained in aerobic digestion, 0.06 N NaOH was chosen as the optimal concentration to remove EPSs.     

Experimental studies simulating potential phosphorus release from municipal sewage sludge deposits

In a laboratory experiment, artificial rainwater was passed through Fe- and Al-precipitated sludge. The release of phosphorus (P) at different temperatures and different oxygen conditions was studied up to 160 d. Under anaerobic conditions and at a temperature of 20°C, 95% of the total P in sludge was released as phosphate. In contrast, in an aerobic environment at the same temperature, only between 20 and 30% of the total phosphorus was released. Water oxygen status and flow size through the sludge were found to be the main factors controlling the P release. Phosphorus fractionations demonstrated that 75% of the total P in sludge initially was found in the NaOH extractable fraction representing P adsorbed to Fe compounds, for example. After passage of oxygenated artificial rainwater, a transformation to more inert P-compounds occurred (HCl extractable and inert P) while only 10% remained in the NaOH extractable fraction. The risk of increasing non-point pollution of P from P-accumulating sludge deposits is discussed.     

利用剩余污泥制备泡沫灭火剂的试验研究

以武汉市某污水处理厂的剩余污泥为材料,在不同酸、碱浓度以及不同时间条件下对其进行水解,以制备含水解蛋白质、脂肪酸、糖类等可溶性有机物及无机物的混合液,并分析、测定了所制备混合液的蛋白质含量,探讨了影响剩余污泥水解的因素.试验结果表明,当采用NaOH水解剩余污泥时,所产水解液为膏状,不能过滤,因而不适合采用;而HCl可水解剩余污泥,且pH值为1.0时的水解效果最好,蛋白质含量高（59.2%）,但所制备的蛋白质混合液的发泡倍数相对较小（7.0倍）;CaO水解剩余污泥的效果较好,所制备蛋白质混合液的发泡倍数较高（7.6倍）,但所需时间较长,且蛋白质含量不高、CaO用量较大;将CaO（25%,相对于干污泥的投加量）与NaOH（5%,相对干污泥的投加量）混合使用的效果最好,不仅水解时间短,而且所得水解液可过滤、蛋白质含量高.经过测定同一蛋白质样品在不同水解时间下的灭火参数发现,水解时间越短则其发泡倍数越高.通过测定不同混合液与粘度、沉淀物、发泡倍数、90%火焰控制时间、灭火时间、抗烧时间等灭火指标的关系,分析了剩余污泥水解液的灭火机理.结果表明,剩余污泥水解液属于空气泡沫灭火剂,其灭火指标达到了国家标准（GA 219-1999）.此技术可实现剩余污泥的再利用,既避免了剩余污泥的二次污染,又可克服使用化学泡沫灭火剂时对环境的污染.     

The feasibility of coagulant recycling by alkaline reaction of aluminium hydroxide sludges

Coagulant recycling appears to be economically attractive as much by the reduction of fresh chemical dosing as by the simplification of the sludge disposal. The present paper has studied the feasibility of aluminium coagulant recovery by an alkaline treatment of sludge. The study was carried out on sludge obtained from the drinking-water treatment plant of the Brussels' Intercommunal Waterboard located at Tailfer on the river Meuse. The general conditions are summarized as follows and given as guidelines:

• to limit the starting sludge concentration to a threshold below 20 g l⁻¹ dry wt concentration;

• to optimize the alkalisation process which means a pH between 11.4–11.8 for NaOH and 11.2–11.6 for Ca(OH)₂;

• to choose between NaOH and Ca(OH)₂ is optional but heavy metals contained in the sludge are reduced by a factor of 10–15 by using lime instead of NaOH;

• to use a settling process to recover the supernant before recycling and therefore best limit the recovery to 25–30% of the coagulant even though when using sodium hydroxide, an 80% recovery is possible.

When restricting the recycling to less than 50% of the coagulant (for instance 25–30%) no detrimental effect on the treatment performance was detected in conditions of this laboratory investigation.     

Comparison of dried sludge and sludge ash for phosphorus recovery with acidic and alkaline leaching

Nowadays, the recovery of phosphorus has been in the spotlight due to its importance for food security and depleting sources. In this study, phosphorus recovery from dried sewage sludge and sludge ash by acid and alkaline leaching was evaluated. Optimum extraction time and temperature were determined as two hours and ambient temperature. Results showed the superiority of strong acidic conditions for leaching; 75 ml/g with 0.4N HCl and 25 ml/g with 0.6N HCl were determined as optimum conditions to achieve efficient phosphorus dissolution from sludge ash (94.6%) and dried sludge (91.1%), respectively, with the lower heavy metal concentrations. Lower L/S ratio put forward the dried sludge as a more advantageous resource for phosphorus extraction. Besides, by alkaline leaching of sludge ash and dried sludge, 60.3 and 70.3% phosphorus dissolutions were achieved with 75 ml/g and 1N NaOH; and the leachate was a suitable product for phosphorus precipitation due to its high pH.     

Effects of chemical sludge disintegration on the performances of wastewater treatment by membrane bioreactor

A new wastewater treatment process combining a membrane bioreactor (MBR) with chemical sludge disintegration was tested in bench scale experiments. In particular, the effects of the disintegration treatment on the excess sludge production in MBR were investigated. Two MBRs were operated. In one reactor, a part of the mixed liquor was treated with NaOH and ozone gas consecutively and was returned to the bioreactor. The flow rate of the sludge disintegration stream was 1.5% of the influent flow rate. During the 200 days of operation, the MLSS level in the bioreactor with the disintegration treatment was maintained relatively constant at the range of 10,000-11,000 mg/L while it increased steadily up to 25,000 mg/L in the absence of the treatment. In the MBR with the sludge disintegration, relatively constant transmembrane pressures (TMPs) could be maintained for more than 6 months while the MBR without disintegration showed an abrupt increase of TMP in the later phase of the operation. In conclusion, a complete control of excess sludge production in the membrane-coupled bioreactor was possible without significant deterioration of the treated water quality and membrane performances.     

Fractional, biodegradable and spectral characteristics of extracted and fractionated sludge extracellular polymeric substances

Correlation between fractional, biodegradable and spectral characteristics of sludge extracellular polymeric substances (EPS) by different protocols has not been well established. This work extracted sludge EPS using alkaline extractants (NH₄OH and formaldehyde + NaOH) and physical protocols (ultrasonication, heating at 80 °C or cation exchange resin (CER)) and then fractionated the extracts using XAD-8/XAD-4 resins. The alkaline extractants yielded more sludge EPS than the physical protocols. However, the physical protocols extracted principally the hydrophilic components which were readily biodegradable by microorganisms. The alkaline extractants dissolved additional humic-like substances from sludge solids which were refractory in nature. Different extraction protocols preferably extracted EPS with distinct fractional, biodegradable and spectral characteristics which could be applied in specific usages.     

铝离子浓度对厌氧处理城市污水混凝污泥的影响

通过实验室小试,考察了城市污水经混凝处理所产污泥的厌氧消化性能.结果表明,与单独采用聚合氯化铝混凝的初沉污泥和剩余污泥相比,经聚合氯化铝与聚丙烯酰胺联合混凝的污泥,其厌氧消化性能更理想.通过产甲烷毒性试验、毒性驯化与毒性恢复试验,可以推断混凝剂中铝离子对甲烷菌产甲烷活性的影响类别为代谢毒素类;铝离子对产甲烷菌的50%活性抑制浓度为0.4 mg/L,相当于聚合氯化铝的投加量为40～60 mg/L.建议采用聚丙烯酰胺类絮凝剂与铝类混凝剂联合处理的方法来降低铝的用量,以提高混凝污泥后续处理的效率.     

Test for assessing shear sensitivity of activated sludge flocs: a feasibility study

Sludge deflocculation can cause, like excessive growth of filamentous bacteria, activated sludge wastewater treatment failure. Yet, unlike the latter cause, there exists no widely accepted tool to assess the flocculation level of activated sludge and to predict sludge deflocculation. In this study, a test procedure is proposed to assess the sensitivity of activated sludge flocs to shear. The test consists in subjecting sludge sample to a shear treatment followed by a sludge volume measurement (SV(30)), with reference to a control. The ratio (%) obtained by dividing the SV(30) of the sheared sample by the SV(30) of the control is used to express the shear sensitivity. In a first series of experiments using two types of sludge, the test was shown to be able of ranging sludge samples in a correct order of shear sensitivity. Applying this so-called shear-SV test procedure to a series of sludge samples allowed to distinguish amorphous sludges (SV(30) ratio> or =100%) from normal sludges (SV(30) ratio<100%). The test was shown to be repeatable and simple. It requires only basic laboratory equipment and implies minimum cost. It can be used as framework for the assessment of activated sludge shear sensitivity in practice.     

Microstructure and Leaching Characteristics of Sludge Treated with Low Alkalinity Additives

The prospect of reusing sludge treated by solidification/stabilization prompts this technique and makes it attractive. However, the reuse of solidified/stabilized sludge must deal with the increasing concern of environmental impact in terms of heavy metals leaching, alkaline migration control and acid neutralization. This paper presents the results of an experimental study to investigate the suitability of a new low alkalinity additive (mainly gypsum and polymer). Assessment of two types of treated sludge was conducted through unconfined compression strength (UC) test, microstructure analysis (X-ray diffraction, scanning electron microscopy), pH test, acid neutralization capacity (ANC) test and chemical analysis for Pb leaching.Results of UC test and microstructural analysis show a solidification effect on the treated sludge with the development of new components, mainly hydrated gypsum, and to a lesser extent, hydrated cement products. pH variation measured during 28 days indicates the effectiveness of treatment by a low alkalinity additive. pH values were found to be lower than 9 and influenced by the type of sludge and curing conditions (with and without air contact). ANC was found to be different for raw sludge and was enhanced by the treatment especially in the case of sludge treated with the highest amount of additives. ANC appears to involve dissolution of Ca, Mg, Al, Na and Si containing components. Although an increase of Pb release was observed with the increase of acid addition due to matrix dissolution and pH drop, measured concentrations were seriously reduced after treatment by the additive in treated sludge.