聚合氯化铝与粉末活性炭联合强化混凝处理垃圾渗滤液

研究了联合粉末活性炭与聚合氯化铝(PAC)强化混凝对垃圾渗滤液原水的处理效果。结果表明,在原水COD为4 100 mg/L、浊度为147 NTU、UV254为20的条件下,粉末活性炭的加入可以有效增加垃圾渗滤液中有机物的去除率,PAC投加量为0.6 g/L时,投加0.6 g/L粉末活性炭,COD的去除率由21.6%提高到29.1%,UV254去除率由29.8%提高到39.9%,剩余浊度由138 NTU降到133 NTU。该强化混凝过程使原水中溶解性小分子有机物的去除率提高显著,PAC投加量为0.6 g/L时,投加0.6 g/L粉末活性炭,在分子量小于1 kDa的范围内,UV254去除率由2.9%上升为10%。     

水样pH对不同碱度含藻水混凝性能的影响

为探明碱度对混凝去除藻细胞及其分泌有机物的影响,保证饮用水水质。以铜绿微囊藻为研究对象,选用氯化铝(AlCl3·6H2O)作为混凝剂进行混凝实验,考察了不同碱度的含藻水样在pH为6.0~9.0条件下的混凝性能、絮体特性和出水余铝。结果表明：当水样pH=6.0时,相对于低碱度(95、175和245 mg·L−1)水样,碱度较高(330 mg·L−1和415 mg·L−1)的水样Zeta电位趋近于0,可有效降低颗粒间的排斥力,藻细胞的去除率达到74.45%以上(低碱度水样藻细胞去除率在31.64%以下),出水余铝最低为0.003 6 mg·L−1(低碱度时为0.088 9 mg·L−1);当水样pH≥6.5时,碱度较低的水样依靠吸附架桥和网捕卷扫协同作用,使得藻细胞去除率最高达到94.31%,出水余铝可降低至0.035 3 mg·L−1;随着碱度的增加,铝盐水解生成的Al(OH)3胶状沉淀逐渐转变为${{\rm{Al}}\left( {{\rm{OH}}} \right)_4^ -} $,使得网捕卷扫作用减弱,藻细胞去除率有所下降;当水样pH=7.5时,随着碱度增加,平衡时絮体粒径从811.02 μm降低至540.62 μm,絮体强度因子从35.97%降低至24.79%,恢复因子从35.31%增加至47.88%,分形维数从1.586减小到1.372。通过调节水样pH,可有效缓解碱度对含藻水混凝过程的影响,提高藻细胞的去除率。     

高碱度水库水混凝过程中残留铝控制

针对高碱度水库水源的某水厂残留铝超标问题,选取碱化度(B)与Alb含量不同的3种铝盐絮凝剂,研究不同投量与pH值下混凝效果与残留铝浓度水平。结果表明,碱化度和Alb含量显著影响混凝效果。DOC和浊度的去除率随着3种絮凝剂AlCl3(B=0)、PACl-1(B=1.2)、PACl-2(B=2.2)投量增大而升高。3种絮凝剂投量在1.5～2.0 mg/L(以铝计)范围内,总铝和溶解铝含量最低。对于该水厂自制的絮凝剂PACl-2,可通过降低絮凝剂碱化度,或将水的pH值降低至7～7.5之间,以此可以提高PACl-2混凝效果,而且可以降低出厂水残留铝浓度。考虑工程应用可行性,可优先考虑调整絮凝剂生产工艺。     

Effect of Al(III) speciation on coagulation of highly turbid water

In Taiwan, the turbidity of raw water for fresh water treatments can sometimes reach as high as 40 000 NTU due to intensive rainfall, especially in typhoon seasons. In response, water works often apply large quantities of coagulants such as polyaluminium chloride (PACl). In this study, simulated and natural highly turbid water was coagulated with two PACls, a commercial product (PACl-1) and a laboratory product (PACl-E). The Al species distributions of PACl-1 and PACl-E under various pH conditions were determined, and the corresponding coagulation efficiency was evaluated. The PACl-E has a wider range of operational pH, while the efficiency of PACl-1 peaks at around neutral pH. For simulated water up to 5000 NTU, the PACl-E was superior to PACl-1 at low dosage and in the pH range studied. Similar results were discovered with natural water, except that when the turbidity was extremely high, the coagulation efficiency of PACl-E decreased significantly due to the presence of large amounts of organic matter. The coagulation of PACl-E was closely related to the content of polycationic aluminium (Al₁₃) while that of PACl-1 was dictated by the amount of Al_c. The sludge from PACl-E coagulation had better dewaterability when the optimum dosage was applied. The experimental results suggest that for natural water up to 5000 NTU, PACl containing high Al₁₃ species is recommended for coagulation. In cases when the water contains high organic matter, efficient coagulation depends upon enmeshment by amorphous aluminium hydroxide.     

pH对混凝超滤组合工艺性能的影响

在聚合氯化铝(PACl)投加量为4 mg/L条件下,通过调节原水的初始pH值,考察pH条件对混凝超滤组合工艺的净水性能及膜污染的影响。结果表明:当pH为7.5时,组合工艺对CODMn、UV254、DOC的去除率分别为40.2%、35.4%和36.1%;当pH降至4.5时,对应的去除率分别增加至52.9%、52.1%和42.0%。酸性条件下,膜池内絮体的分形维数大,絮体结构密实,膜污染速率较快;当pH等于4.5时,絮体分形维数为1.75±0.15,尺寸大于500 μm的絮体数占总絮体数的9%。中性及偏碱性条件下,絮体分形维数小,絮体结构松散多枝,膜污染速率缓慢;当pH等于7.5时,絮体分形维数为1.37±0.05,尺寸大于500 μm的絮体占65%。针对该水库的水质状况,控制原水pH为7.5有利于混凝超滤膜组合装置的运行。     

联合硅藻土与PAC强化混凝处理含藻微污染原水

研究了联合硅藻土与聚合氯化铝（PAC）强化混凝对原水中藻类、溶解性有机物以及重金属离子的去除效果。结果表明,硅藻土的投加可以有效地改善絮体的沉降性能,增强藻类的混凝沉淀去除效率,PAC投加量为30 mg/L时,投加0.1 g/L硅藻土,叶绿素a去除率由82.5%提高到95.9%。该强化混凝过程使原水中溶解性有机物特别是大分子有机物和重金属离子的去除率有所上升。PAC投加量为30 mg/L,硅藻土投加量为1.5 g/L时,重金属Cu、Pb和Cd的去除率分别达到57.5%、83.7%和22.2%。     

Enhanced removal of heavy metals in primary treatment using coagulation and flocculation.

The goal of this study was to determine the removal efficiencies of chromium, copper, lead, nickel, and zinc from raw wastewater by chemically enhanced primary treatment (CEPT) and to attain a total suspended solids removal goal of 80%. Operating parameters and chemical doses were optimized by bench-scale tests. Locally obtained raw wastewater samples were spiked with heavy metal solutions to obtain representative concentrations of metals in wastewater. Jar tests were conducted to compare the metals removal efficiencies of the chemical treatment options using ferric chloride, alum, and anionic polymer. The results obtained were compared with those from other studies. It was concluded that CEPT using ferric chloride and anionic polymer is more effective than CEPT using alum for metals removal. The CEPT dosing of 40 mg/L ferric chloride and 0.5 mg/L polymer enhanced heavy metals removal efficiencies by over 200% for chromium, copper, zinc, and nickel and 475% for lead, compared with traditional primary treatment. Efficient metals capture during CEPT can result in increased allowable headworks loadings or lower metal levels in the outfall.     

聚硅硫酸铝的形貌结构和絮凝机理

以工业水玻璃、工业硫酸铝为原料制得聚硅硫酸铝(PASS)复合絮凝剂,采用电子显微镜观察了不同,nAl/n(Si)的PASS的形貌,借助倒置式生物显微镜分析了PASS所形成絮体的形貌并用激光粒度分析仪对絮体粒度分布进行了测定,通过红外光谱和X-射线衍射研究了PASS中铝与聚硅酸的相互作用情况,考察了模拟江水中胶体颗粒物和PASS水解物的Zeta电位随pH值的变化,在此基础上探讨分析了PASS的絮凝机理和絮凝过程.结果发现:nAl/n(Si)对PASS的形貌有较大影响,絮体粒度分布的数据印证了该结果;红外光谱图表明PASS中有Si-O-Al振动峰出现,峰强度随nAl/n(Si)减小而增大;X-射线衍射图证实了聚硅硫酸铝不是晶体,而是铝水解产物与聚硅酸共同作用形成的无定型聚合物;吸附架桥及粘结卷裹作用是PASS絮凝时的主导作用.     

聚合氯化铝铁去除微污染水体中藻类的研究

以聚合氯化铝铁(PAFC)为絮凝剂,H2O2为预氧化剂,用正交实验研究了PAFC处理微污染水体中藻类和降低浊度,得出正交实验中各因素的主次关系及对除藻和除浊度的影响,研究表明,ρPAFC是影响除藻和除浊度的重要因素.在最佳处理条件,即ρPAFC为20 mg/L,ρH2O2为6 mg/L,pH为7,搅拌时间为4 min,能使水体中藻细胞街度从9.4×107 cells/L降至3.16×106 cells/L,除藻率为96.6%,浊度降至0.70 NTU,除浊度率达93.0%.     

Pb and Cd binding to natural freshwater biofilms developed at different pH: the important role of culture pH

The effects of solution pH on adsorption of trace metals to different types of natural aquatic solid materials have been studied extensively, but few studies have been carried out to investigate the effect of pH at which the solid materials were formed on the adsorption. The purpose of present study is to examine this effect of culture pH on metal adsorption to natural freshwater biofilms. The adsorption of Pb and Cd to biofilms which were developed at different culture pH values (ranging from 6.5 to 9.0) was measured at the same adsorption pH value (6.5). The culture pH had considerable effects on both composition and metal adsorption ability of the biofilms. Higher culture pH usually promoted the accumulation of organic material and Fe oxides in the biofilms. The culture pH also affected the quantity and species of algae in the biofilms. The adsorption of Pb and Cd to the biofilms generally increased with the increase of culture pH. This increase was minor at lower pH range and significant at higher pH range and was more remarkable for Cd adsorption than for Pb adsorption. The notable contribution of organic material to the adsorption at higher culture pH values was also observed. The profound impacts of culture pH on adsorption behavior of biofilms mainly resulted from the variation of total contents of the biofilm components and were also affected by the alteration of composition and properties of the components.     

Pteris vittata – Revisited: Uptake of As and its speciation, impact of P, role of phytochelatins and S

Pteris vittata is known to hyperaccumulate As but the mechanism is poorly understood. We found an increase of As concentration with increasing soil solution As concentrations, but P application had no impact, although plant P concentrations responded to different rates of P supply. As in fronds was dominantly (82–89%) present in the form of AsIII. In roots we detected 45% as AsIII which is higher than reported in previous studies and supports substantial As-reduction to take place in roots. We detected PC2/3GS–AsIII, PC2–GS–AsIII and (PC2)2–AsIII in increasing amounts with application of As. The total amount of PC was in the range reported previously and far too small to assign a significant role in As detoxification to PCs. The close correlation between S and As in fronds and the lack of data on sulphur uptake and metabolism indicates the need for a detailed investigation on sulphur nutritional status and As metabolism in P. vittata.     

Search for industrial sources of PCDD/PCDFs: II. Metal chlorides

FeCl₃, AlCl₃, CuCl₂, CuCl, SiCl₄ and TiCl₄ were analysed for their content of PCDD/PCDFs and other chloroaromatic compounds. FeCl₃ and AlCl₃ contain OCDF and H₇CDF in ppb- and hexachlorobenzene in ppm-range; CuCl₂ and CuCl contain lower concentrations of OCDF, H₇CDF and additionally OCDD, H₇CDD and hexachlorobenzene in ppb/ppt-range. SiCl₄ and TiCl₄ contain no measurable quantities of PCDD/PCDFs and hexachlorobenzene. A correlation between the PCDD/PCDF - and hexachlorobenzene-content is postulated for products of industrial sytheses involving high temperatures. The origin of the organic substances in a process of inorganic chemistry could be oils on the waste metals which are used in the manufacture of metal chlorides.     

含锌多核聚铝絮凝剂的制备及形态特征

以AlCl3·6H2O和ZnCl2为原料,采用一次加碱法制备了一种新型的改性增效聚合铝类多核无机高分子絮凝剂聚合氯化铝锌(PAZC).通过Al-Ferron逐时络合比色法研究了碱化度(B),Al/Zn摩尔比及陈化时间对铝离子形态的影响.采用混凝实验比较PAZC、PAC的混凝效果.结果表明:在相同B值条件下,PAZC的Ala和Alc少于PAC的Ala和Alc,Alb形态多于PAC中Alb形态,并且PAC中Alb形态最高只有60%,而PAZC中Alb最高达到83%.PAZC具有pH适用范围宽,投药量少以及良好的储存性能.     

The chemical species distribution and transformation of polyaluminum silicate chloride coagulant

The chemical species distributions of polyaluminum silicate chloride (PASC) and polyaluminum chloride (PACl) determined by Al-Ferron complexation timed spectrophotometric and 27Al-NMR methods, respectively, have been compared and analyzed. The experimental results show that the species distribution and transformation of PASC are different from those of PACl, due to the interaction of polysilicic acid and hydrolyzed aluminum species. At the same basicity (B), the contents of, Al(b), Al13 and the monomer species Almono (also determined by 27Al-NMR) in PASC are lower than those in PACl, while the contents of Al(c) and the Alother determined by 27Al-NMR in PASC are higher than those in PACl. The differences between PASC and PACl with respect to these species enlarge as the molar ratio of Al/Si in PASC decreases. Further, in PACl the ratio of Al13 to Al(b) closes to 1.0, indicating that the amount of the two fractions are similar. In PASC, however, such an agreement does not exist at the lower B values and Al/Si molar ratios. When the B value and Al/Si molar ratios increase, however, the amount of Al13 and Al(b) species tends to close. The study findings indicate that polysilicic acid can react with hydrolyzed aluminum species to form an aluminum silicate polymer composite and result in the change in species distribution of PASC.     

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.     

Arsenic release from flooded paddy soils is influenced by speciation, Eh, pH, and iron dissolution

Arsenic (As) is highly mobilized when paddy soil is flooded, causing increased uptake of As by rice. We investigated factors controlling soil-to-solution partitioning of As under anaerobic conditions. Changes in As and iron (Fe) speciation due to flooded incubation of two paddy soils (soils A and B) were investigated by HPLC/ICP-MS and XANES. The flooded incubation resulted in a decrease in Eh, a rise in pH, and an increase in the As(III) fraction in the soil solid phase up to 80% of the total As in the soils. The solution-to-soil ratio of As(III) and As(V) (R_L/S) increased with pH due to the flooded incubation. The R_L/S for As(III) was higher than that for As(V), indicating that As(III) was more readily released from soil to solution than was As(V). Despite the small differences in As concentrations between the two soils, the amount of As dissolved by anaerobic incubation was lower in soil A. With the development of anaerobic conditions, Fe(II) remained in the soil solid phase as the secondary mineral siderite, and a smaller amount of Fe was dissolved from soil A than from soil B. The dissolution of Fe minerals rather than redox reaction of As(V) to As(III) explained the different dissolution amounts of As in the two paddy soils. Anaerobic incubation for 30 d after the incomplete suppression of microbial activity caused a drop in Eh. However, this decline in Eh did not induce the transformation of As(V) to As(III) in either the soil solid or solution phases, and the dissolution of As was limited. Microbial activity was necessary for the reductive reaction of As(V) to As(III) even when Eh reached the condition necessary for the dominance of As(III). Ratios of released As to Fe from the soils were decreased with incubation time during both anaerobic incubation and abiotic dissolution by sodium ascorbate, suggesting that a larger amount of As was associated with an easily soluble fraction of Fe (hydr) oxide in amorphous phase and/or smaller particles.     

高碱度钢渣添加铁尾矿消解f-CaO的机理研究

高碱度钢渣掺唐山石人沟铁尾矿重构,两者在高温环境下熔融反应消解高碱度钢渣中f-CaO。采用正交实验法设计实验方案,考察了铁尾矿掺入量(分别为3%、5%和9%)、反应温度(分别为1 500℃,1 550℃和1 580℃)及恒温反应时间(分别为10 min、20 min和30 min)对消解高碱度钢渣中f-CaO的效果。实验结果表明,铁尾矿能有效消解钢渣中f-CaO,重构渣中f-CaO含量平均值为1.17%,消解率为76.27%。且由正交方法测出了铁尾矿掺入量对f-CaO的消解影响较大,极差值为0.41%;反应温度次之,极差值为0.32%;恒温反应时间影响较小,极差值为0.06%。利用X射线衍射方法测定重构渣中矿物组成,主要为磁铁矿、钙镁橄榄石、硅酸二钙、硅酸三钙、镁铁尖晶石、铁酸钙及铁铝酸钙。     

铁铝盐基离子对土壤中水溶性氟环境效应的影响

氧化物或粘土矿物可吸附氟离子,但磷酸根离子与氟离子存在竞争吸附效应,造成氟的环境存在量、存在形态及生物效应更加复杂,影响了环境中氟污染的治理.试验选用典型贵州黄壤和石灰土,通过向模拟高氟污染土壤中添加铁铝盐基离子和磷酸盐,采用两因素最优设计,研究外源物质对土壤中水溶性氟的影响.结果表明,FeCl3·6H2O或AlCl3·6H2O都能降低土壤中水溶性氟,而KH2PO4使土壤中水溶性氟增加,对黄壤和石灰土中水溶性氟影响效果大小依次为FeCl3·6H2O(AlCl3·6H2O)、KH2PO4.同时表明,采用铁铝盐基离子改变黄壤性质,达到降氟效果仍有很大潜力,而石灰土环境在高添加铁铝盐基离子水平下继续添加FeCl3·6H2O或AlCl3·6H2O降低土壤中水溶性氟的作用较弱.从土壤pH看,黄壤水溶性氟受试验因子影响复杂,土壤pH低水溶性氟不一定低,pH在4～6时,氟元素的形态及有效性尤其复杂,而石灰土中水溶性氟基本随pH降低而降低.     

Changes in speciation and leaching behaviors of heavy metals in dredged sediment solidified/stabilized with various materials

Solidification/stabilization (S/S) of sediments is frequently used to treat contaminants in dredged sediments. In this study, sediment collected from the Pearl River Delta (China) was solidified/stabilized with three different kinds of functional materials: cement, lime and bentonite. Lime primarily acted via induced increases in pH, while cements stabilization occurred through their silicate-based systems and the main function of bentonite was adsorption. The speciation and leaching behaviors of specific heavy metals before and after S/S were analyzed and the results showed that the residual speciation of Cd, Cr, Ni, Pb and Zn increased in all treatments except for Cu, as the exchangeable speciation, carbonate-bound speciation and Fe-Mn-oxide-bound speciation of Cu (all of which could be stabilized) were less than 2 % of the total amount. Pb leaching only decreased when pH increased, while the mobility of Cr and Ni only decreased in response to the silicate-based systems. The leached portion of the Fe-Mn-oxide-bound speciation followed the order Zn?>?Cu?>?Ni/Cd?>?Pb?>?Cr. The leached portion of organic-matter-bound species was less than 4 % for Cd, Cr, Ni and Pb, but 35.1 % and 20.6 % for Cu and Zn, respectively.