混凝过程絮体开始形成和开始沉降时间研究

以不同浊度高岭土水样为研究对象,运用激光测试技术对3种混凝剂(聚合氯化铝(PAC)、硫酸铝和三氯化铁)混凝过程絮体开始形成时间和开始沉降时间进行测定,初步研究了混凝剂投药量对浊度的影响,投药量、pH和浊度对絮体开始形成和开始沉降时间的影响.结果表明:(1)PAC、硫酸铝和三氯化铁最佳投药量为4.8、6.4、8.0 mg/L;(2)PAC和硫酸铝混凝过程在pH为7时絮体开始形成和开始沉降时间均最短,但PAC混凝过程絮体开始形成和开始沉降时间(分别为27.4,51.0 s)都比硫酸铝混凝过程絮体开始形成和开始沉降时间(分别为51.5、85.4 s)短,三氯化铁混凝过程在pH为6时絮体开始形成和开始沉降时间均最短,分别为50.0、84.0 s;(3)随投药量的增大,絮体开始形成和开始沉降时间均逐渐缩短;(4)随浊度的增大,絮体开始形成和开始沉降时间总体上缩短.     

氢氧化镁混凝性能及絮体特性

以氢氧化镁作为混凝剂,不同浊度高岭土水样为研究对象,运用iPDA在线监测技术对混凝过程絮体形成进行监测,探求了操作条件对絮体特性和混凝过程的影响;同时讨论了FI值和浊度去除的关系。结果表明,当浊度分别为5、10和20 NTU时,最佳投加量分别为21.6、14.4和3.6 mg/L;随着pH的升高,FI指数增大,同时混凝剂的最佳投加量也逐步减小;随着慢速搅拌转速的增大,絮体破碎过程明显,FI指数降低;当转速为60 r/min时,浊度去除率最高。     

高藻水中新生态三价铁混凝行为及其对絮体生长的影响

通过阐释新生态三价铁活性高的机制从而提出混凝剂的连续投加方式对混凝除藻效果的促进作用。与高锰酸钾-铁混凝过程相比,高锰酸钾-亚铁混凝过程初期絮体粒径较小;但经过一段时间后,后者絮体粒径将明显大于前者。Mn(VII)投量为1.7μmol/L时,混凝进行到720 s之前高锰酸钾-亚铁混凝过程中絮体粒径均低于200μm,反应进行到990s时絮体粒径稳步增大到239μm。形成对比的是,高锰酸钾-铁混凝过程进行到720 s和990 s时絮体粒径分别为198μm和204μm。在混凝过程中,亚铁逐步转化生成新生态三价铁,相当于向系统中持续投加混凝剂。在混凝剂总量相同(197.4μmol/L)的情况下,分次连续投加Fe(III)比一次性投加Fe(III)所生成的絮体粒径要大32%。     

聚合铝水解形态对混凝效果及絮体特性的影响

采用微量滴定法制备不同碱化度的聚合铝,并测定其铝形态分布,通过其对腐殖酸-高岭土水样进行烧杯实验,依据絮体的Zeta电位、浊度、UV254及絮体强度因子及恢复因子等参数,以综合评价聚合铝水解形态的混凝机理及其絮体特性。结果表明:聚合铝投加前后铝形态分布存在很大差异,碱化度越低影响越明显,碱化度为0.5的聚合铝中Ala含量由原来的69.57%变为4%左右,而其Alc由9.36%变为50%左右;预制铝的中聚体和高聚体形态在混凝过程中相对比较稳定,而低聚合度的Ala变化显著;Alb电中和能力强,对溶解性有机物去除效果好,其絮体成长速度慢但絮体强度高;Alc具有较强的吸附架桥能力,能促进浊度的去除;预制Alc的吸附架桥能力强于水解生成的Alc,但其絮体恢复性能差。     

加药量和水力搅拌速度对雨水混凝效果的影响

为降低分流制雨水中悬浮颗粒物及其他污染物浓度,减轻城市景观河道的水体富营养化程度,对取自泵站的雨水进行混凝沉淀工艺优化实验。以PAC为混凝剂,采用Zeta电位仪、激光粒度仪和iPDA在线监测技术对混凝过程进行监测,考察了混凝剂投加量和水力搅拌速度对絮体形成和分流制雨水处理效果的影响,结果表明,混凝剂投加量和混合水力搅拌速度直接影响絮体Zeta电位和聚沉特性;混合搅拌速度控制混凝反应速率,絮凝速度梯度影响絮体形成粒径。FI曲线特征参数对控制混凝工艺具有指导意义。PAC投加量为35 mg/L,混合阶段搅拌速度800 r/min,搅拌30 s,絮凝阶段采用150、108和60 r/min的转速各自搅拌5 min,沉后水中剩余颗粒总数最少,浊度、COD和总磷去除效果最佳。     

絮体性状实时图像检测系统的开发与应用

概述了水处理絮体性状(包括絮体粒度、分形维数及表观强度)在线图像检测系统的开发,结合实验室条件下的混凝实验考查了该实时图像检测系统的应用情况.结果表明,利用该图像检测系统获取的数据符合一般混凝实验的结果,且对混凝慢速搅拌时间、原水浊度及混凝剂投加量有不同程度的敏感性.在进一步研究的基础上,该图像检测系统可在水处理混凝过程的自动控制中加以应用.     

PAM复配混凝剂对高岭土体系混凝过程的影响

为了解决无机混凝剂在混凝过程中的不足选用AlCl_3及其与2种不同阴离子度的PAM复配的混凝剂对高岭土体系进行混凝实验研究。结果表明:使用AlCl_3做混凝剂,当投加量(以Al计)为0.1 mmol·L~(-1)时,剩余浊度达到最低;平衡时粒径达到700μm且随着破碎时间的延长,絮体再生长结束后的粒径逐渐减小在破碎时间为6.O min时,絮体粒径最终能恢复到300左右。以PAM4复配的AlCl_3为混凝剂在投加量为0.1 mmol·L~(-1)时,剩余浊度最低;经慢速搅拌10 min絮体平衡时的粒径较使用AlCl_3作混凝剂时略小,但随着PAM4浓度的増大,絮体破碎后的恢复能力逐渐増大。当PAM4与Al的比例为10%破碎1.0 min时絮体粒径最终可以恢复到600μm左右。以PAM-2复配的AlCl_3为混凝剂时,由于PAM-2的阴离子度过高需要更多的混凝剂中和体系中存在的负电荷,所以在混凝剂浓度为0.2 mmol·L~(-1)时,剩余浊度才达到最低。     

混凝工艺水力条件的优化与絮体尺寸特性的研究

制造更优的混合和絮凝设备,其核心技术在于设备所提供的水力条件是否更加有利于絮体的形成、是否更加有利于水质处理效果的提高。以成都市府南河水为原水,在不同的快搅强度和不同的快搅时间下进行混凝杯罐实验,混凝剂为硫酸铝、氯化铁,采用激光粒度仪Mastersizer 2000测量絮体平均粒径随时间的变化过程,以去除浊度为目标,分析最优水力条件。实验得到如下结论:(1)快搅强度对氯化铁混凝剂水质处理效果有着明显的影响,快搅时间对硫酸铝和氯化铁混凝剂水质处理效果均有明显影响;(2)以浊度为去除目标,对于硫酸铝通过实验确定快速搅拌强度为250 r/min时,快速搅拌时间为60 s时,水质处理效果最好;(3)以浊度为去除目标,对于氯化铁确定快速搅拌强度为300 r/min时,快速搅拌时间为60 s时,水质处理效果最好。     

氯化镁复配硫酸铝混凝性能及絮体特性

在研究氢氧化镁混凝特性的基础上,复配氯化镁和硫酸铝作为混凝剂,以高岭土配水水样为研究对象,运用iPDA在线监测技术对混凝过程絮体形成进行监测,探讨了单独使用氯化镁和硫酸铝以及二者复配使用的混凝效果和絮体特性,确定复配使用的各种条件。结果表明,对于浊度20 NTU,pH 11.5的高岭土配水水样,氯化镁、硫酸铝最佳投加量分别为7.2 mg/L(Mg2+计)和3 mg/L(Al3+计);硫酸铝跟氯化镁复配使用时,先投加硫酸铝,间隔30 s后投加氯化镁,混凝效果较好;在镁离子最佳投加量7.2 mg/L时,铝和镁最佳质量比在1∶3~1∶2之间;镁铝复配时其FI值明显大于单独作用时,即絮体尺寸大小:二者复配硫酸铝氯化镁,而且复配条件下Zeta电位值在零电势左右浮动,浮动范围小,更利于聚集沉淀;镁铝复配时发生了协同效应,弥补了单独使用氯化镁混凝过程的不足。     

不同混凝剂处理低温低浊水

针对低温低浊水处理难度大的问题进行了一系列的混凝实验,实验结果表明,随着混凝剂投加量的增加,剩余浊度呈现先降低后升高的趋势,单独使用HPAC时,剩余浊度在投加量为14 mg/L时达到最低(2.39 NTU)。pH值对余铝含量具有重要的影响,3种铝系混凝剂均在pH=7.0时余铝含量达到最低。Al Cl3对水中有机物的去除率较其他3种混凝剂低。絮体形成与破碎受搅拌强度的影响很大,当破碎强度增加到50 r/min,使用PACl、HPAC、Fe Cl3作混凝剂时絮体粒径下降不明显,当破碎强度增加到100 r/min时,絮体粒径有明显的下降。破碎结束后,絮体粒径有所恢复,但是并不能增长到破碎前的粒径。PACl、HPAC以及Fe Cl3形成的絮体的沉降性较好,上覆水浊度下降较快,经过3 h的沉降后,剩余浊度分别达到1.82、1.44和0.97 NTU。     

Comparison of hydrolysis/coagulation behavior of polymeric and monomeric iron coagulants in humic acid solution

Fluorescence quenching is commonly used to study the extent of metal binding to humic acid or fulvic acid. By studying this phenomenon, the hydrolysis and precipitation behaviors of polymeric and monomeric iron coagulants in the coagulation of humic acid were evaluated. Combined measurements of fluorescence intensity and dissolved organic carbon were performed to distinguish the hydrolysis and organic matter binding of polymeric and monomeric iron salts in coagulating high molecular weight organic compounds. Experimental results showed that ferric chloride had lower fluorescence quenching than polyferric sulfate (PFS), indicating more rapid hydrolysis of the monomeric ferric ion in the coagulation and dilution process. The less fluorescence quenching was caused by the lower residual concentration of Fe-humic acid complexes in the filtrate. There was no clear difference in adsorption ability and fluorescence quenching, which indicated that the physical and chemical properties of Fe(OH)3 flocs formed from PFS and FeCl3 coagulation were similar. From the pH study, we found that sludge formed from PFS coagulation was more stable than that from FeCl3 coagulation.     

溶气气浮过程动力学模型的分形观

凝聚/絮凝过程中形成的絮体通常具有分形几何结构,导致絮体的密度、渗透性发生了变化,从而对于固液分离过程(沉淀、气浮和过滤)带来很大的影响。本文基于前人对于絮体分形的研究成果,建立了絮体与微气泡之间接触碰撞的动力学方程、絮体/微气泡聚集体在水中上升的分形速率方程。絮体与微气泡间的相对尺度和流态的不同会有不同的碰撞机制,相应的动力学方程式与絮体的分形维数也有不同的关系。     

Evaluation of Al30 polynuclear species in polyaluminum solutions as coagulant for water treatment

Polyaluminum coagulant with a content of 76.8% of Al30 (PACAl30) was prepared. Its coagulation behaviors were compared with high Al13 content polyaluminum coagulant (PACAl13) and AlCl3. The species stability was studied using Al-Ferron method and 27Al NMR. The coagulation performances were investigated by studying the rate of flocs development, the turbidity removal efficiency and charge neutralization capacity under fixed pH conditions and uncontrolled pH conditions. The effect of pH on coagulation was also studied. The results show that PACAl30 are stable for using as coagulant. PACAl30 causes less pH depression than PACAl13. The charge neutralization capacity of PACAl30 is slightly lower than that of PACAl13 at pH6.8 and higher at pH 6.5. PACAl30 achieves the most effective turbidity removal in these three coagulants. And it acts effectively within a much broader dosage range and a wider pH range when compared with PACAl13. PACAl30 achieves the highest turbidity removal due to its strong flocs formation capacity. The results verify that Al30 is another highly active coagulation/flocculation species for turbidity removal.     

Comparison of coagulation performance and floc properties of a novel zirconium-glycine complex coagulant with traditional coagulants

A new inorganic-organic hybrid material zirconium-glycine complex (ZGC) was firstly used as a coagulant in a coagulation process to treat Pearl River raw water. Its coagulation performance was compared with commonly used aluminum (Al) coagulants such as aluminum sulfate (Al₂(SO₄)₃) and polyaluminum chloride (PAC), in terms of water quality parameters and floc properties. ZGC coagulation achieved higher removal of turbidity (93.8 %) than other traditional coagulants. Charge neutralization was proven to act as a dominant mechanism during ZGC coagulation. The aggregated flocs with ZGC showed the fastest growth rate and good recovery ability compared with the other coagulants and achieved the largest floc size within 5 min. The ZGC coagulant can decrease the hydraulic retention time and increase removal efficiency.     

纳米SiO2对微污染物HA、SDS及NH3-N的助凝特性研究

以聚合氯化铝PAC为混凝剂，纳米SiO₂为助凝剂，对含有下列微污染物：十二烷基硫酸钠（SDS）、氨氮（NH₃-N）或腐植酸（HA）的高岭土悬浊液进行混凝沉降实验。借助形态学理论、电镜观察与图像分析技术，研究纳米SiO₂对微污染物的助凝作用效果、吸附特性与絮体结构的形态学特征。结果表明：（1）在含有HA、SDS、NH₃-N的模拟原水中，污染物去除率与浊度去除率的相关性随污染物分子量的增大而增强；（2）纳米SiO     

Enhanced coagulation of ferric chloride aided by tannic acid for phosphorus removal from wastewater

Phosphorus removal from wastewater is of great importance. In the present study, ferric chloride was selected as the coagulant, and tannic acid (TA), a natural polymer, as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus recovery from different types of wastewater. The results showed that TA can accelerate the settling speed by forming flocs with large size, reduce the residual Fe(III) to eliminate the yellow color caused by Fe(III), and slightly increase the phosphorus removal efficiency. The precipitate formed by TA-aided coagulation showed the advantage of releasing phosphorus faster than ferric phosphate, indicating the possibility of phosphorus recovery from wastewater as slow release fertilizer. To further understand the structural characteristics of the precipitate, analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry were employed. The analytical results indicated that TA–Fe–P complex was formed during the coagulation/flocculation processes. Solid phase in the precipitate consisted of TA–Fe–P complex, Fe–TA complex and/or ferric hydroxyphosphate.     

正交实验优化超声波预处理污泥的工况研究

在污泥浓度为9 915 mg/L时,选取超声频率、超声声强和超声时间3个因素设计正交实验,以污泥破解度(DDSCOD)、污泥好氧率(SOUR)和脱氢酶(DHA)活性作为指标,对超声波预处理的工况进行了优化。研究结果表明,最佳的超声预处理参数组合为:超声频率28 kHz,声能密度0.15 W/mL,超声时间10 min。此外,研究还发现不同浓度的污泥,对应的最佳超声组合参数也不同。     

Removal of algal blooms from freshwater by the coagulation–magnetic separation method

This research investigated the feasibility of changing waste into useful materials for water treatment and proposed a coagulation–magnetic separation technique. This technique was rapid and highly effective for clearing up harmful algal blooms in freshwater and mitigating lake eutrophication. A magnetic coagulant was synthesized by compounding acid-modified fly ash with magnetite (Fe₃O₄). Its removal effects on algal cells and dissolved organics in water were studied. After mixing, coagulation, and magnetic separation, the flocs obtained from the magnet surface were examined by SEM. Treated samples were withdrawn for the content determination of chlorophyll-a, turbidity, chemical oxygen demand (COD), total nitrogen, and total phosphorus. More than 99 % of algal cells were removed within 5 min after the addition of magnetic coagulant at optimal loadings (200 mg L^?1). The removal efficiencies of COD, total nitrogen, and phosphorus were 93, 91, and 94 %, respectively. The mechanism of algal removal explored preliminarily showed that the magnetic coagulant played multiple roles in mesoporous adsorption, netting and bridging, as well as high magnetic responsiveness to a magnetic field. The magnetic–coagulation separation method can rapidly and effectively remove algae from water bodies and greatly mitigate eutrophication of freshwater using a new magnetic coagulant. The method has good performance, is low cost, can turn waste into something valuable, and provides reference and directions for future pilot and production scale-ups.     

Hydrodynamic treatment of wastewater effluent flocs for improved disinfection

Hydrodynamic forces generated by an orifice plate under low pressure were examined as a means of disrupting flocs, in order to improve disinfection of treated wastewater effluents. Changes in cavitation conditions were found to have little impact on the extent of particle breakage in this experimental setup. The rate of strain (flow rate divided by the hole radius cubed), however, was found to be the best predictor of floc breakage. Floc breakage was not affected by changes in floc concentration, but was very sensitive to differences between flocs collected from different sources. Larger flocs (90 to 106 microm) were broken apart to a greater extent than smaller ones (53 to 63 microm). Hydrodynamic treatment decreased the viability of bacteria associated with large flocs, and also increased the ultraviolet dose response by up to one log unit (i.e., a factor of ten). Subjecting final effluent wastewaters to hydrodynamic treatment, therefore, provides a treatment strategy for conditions in which the presence of flocs limits the level of disinfection that can be achieved.