粉煤灰在水厂污泥处理和处置中的作用研究

在水厂污泥水中加入电厂粉煤灰,不需再添加其他材料,即可以很好地改善水厂污泥的脱水性能.细粉煤灰最佳投加量为20%,粗粉煤灰最佳投加量为30%,不但可以节约能耗,粉煤灰有了新的出路,干化污泥对环境友好,而且还能制成低热值燃料作焚烧处置,回收部分热能.     

粉煤灰替代石灰进行污泥深度脱水的中试研究

采用板框压滤机在中试规模下,以粉煤灰替代工业石灰,对污泥进行调质脱水实验研究,从而考察粉煤灰替代石灰进行污泥调质脱水的可行性。结果表明:粉煤灰投加后可降低污泥p H,降低其二次污染危害,但污泥进料量却降低14.3%~15.2%,脱水能力下降;针对不同有机质含量的污泥,粉煤灰的替代性并不相同,对于低有机质含量污泥,采用粉煤灰替代工业石灰具有一定可行性,且随着粉煤灰投加量的加大,污泥热值逐步上升,而对于高有机质含量污泥,粉煤灰并不适用于其深度脱水过程。     

剩余污泥浓缩脱水投药量优化和模型建立

应用高分子阳离子絮凝剂（CPF-100）和聚丙烯酰胺（PAM）对污水厂剩余污泥进行浓缩脱水实验，研究表明：CPF-100的浓缩脱水效果优于PAM；当CPF-00投加量为1．16‰时，污泥沉降性能改善程度为37．51％；且在CPF-100投加量逐渐增大的初始阶段，污泥沉降性能改善程度随投加量的增加而增大，但CPF-100投加量也不宜过大，当CPF-100投加量超过1．16‰后，反而会使浓缩脱水效果变差。同时，建立了污泥沉降性能改善程度与絮凝剂CPF-100投加量、沉降时间之间的数学模型，其能较好地反映污水厂剩余污泥的浓缩脱水效果。     

改性粉煤灰与过氧化氢联合作用深度处理皂素生产废水的研究

利用改性粉煤灰与过氧化氢(H2O2)联合的方法对二次处理过的皂素生产废水进行深度处理,研究了pH、改性粉煤灰投加量、H2O2投加量、反应时间对皂素生产废水脱色率和COD去除率的影响,分析了其作用机制.结果表明,试验最佳条件为:pH=6、反应时间60 min、改性粉煤灰投加量10 g/L、H2O2投加量4 mL/L.在最...     

Fe(Ⅱ)活化过硫酸盐改善污泥脱水性能

针对污水处理厂剩余污泥脱水困难的问题,采用Fe~(2+)活化过硫酸钾高级氧化法提高剩余污泥脱水性能,使用污泥含水率和污泥比阻对调理前后污泥脱水效果进行分析;研究了过硫酸钾投加量、Fe~(2+)投加量、pH和反应时间对污泥调理效果的影响;探究了过硫酸盐调理污泥过程中溶解性有机物质和胞外聚合物(extracellular polymeric substance,EPS)的变化特性。结果表明:过硫酸钾调理的最佳反应条件为pH=7.5,反应时间为20 min,过硫酸钾和Fe~(2+)的最佳投加量分别为15 mmol·L~(-1)和18 mmol·L~(-1),在此条件下,污泥含水率和污泥比阻值分别可达78.89%和0.3×10~(12) m·kg~(-1);污泥含水率和比阻的变化可能与污泥调理后絮体结构形态变化有关;调理污泥后,上清液中溶解性有机物质含量与过硫酸钾投加量呈显著正相关关系,而EPS不同组分中蛋白质和多糖含量在Fe~(2+)投加后均减少,表明Fe~(2+)的投加可以破坏污泥絮体,分解胞内物质;利用Fe~(2+)激活过硫酸钾所生成的硫酸根自由基可极大改善污泥的脱水性能。     

过硫酸盐氧化法对污泥脱水性能的影响

以污水处理厂浓缩池污泥为研究对象,用污泥比阻、污泥含水率和污泥粘度评价污泥脱水性能,研究亚铁离子活化过硫酸盐氧化法对污泥脱水性能的影响。结果表明,单独投加过硫酸钾时,污泥比阻和含水率随过硫酸钾投加量的增加稍有下降。投加硫酸亚铁和过硫酸钾时,温度对污泥脱水性能影响不大。污泥脱水性能最佳的条件:在常温下,污泥p H为7,硫酸亚铁投加量为1.5 mmol/g VSS、过硫酸钾投加量为1.2 mmol/g VSS,亚铁离子和过硫酸根的摩尔比为1.25∶1,污泥的比阻从5.36×1012m/kg降低到1.9×1011m/kg,含水率从97.0%降低到81.6%,粘度从178 m Pa·s降低到102 m Pa·s。     

微生物絮凝剂的制备及其对城市污水厂污泥的脱水

研究利用甘蔗渣作为廉价原材料制备微生物絮凝剂并探讨其对城市污泥的脱水性能。按0.5%最佳接种量接种,并利用发酵罐进行批式发酵培养,培养60 h后的发酵液具有最佳絮凝效果,投加量为5.0 mg/L时较优,污泥脱水率从75.60%提高到84.2%,污泥含水率从95.82%降至76.21%。此时絮凝剂粗产量为1.16 g/L。培养108 h后,发酵液仍具有显著的絮凝效果,能使污泥含水率维持在76.81%左右。补料发酵实验表明,恒pH培养会抑制微生物分泌絮凝剂,最佳絮凝效果为72 h的发酵液,投加量5.0 mg/L,污泥含水率降至76.47%。通过补料以及不控制pH后,发酵液絮凝效果迅速上升,投加不同量的发酵液使污泥的含水率保持在76.22%~75.60%之间。综合来说,补料在能减少原料浪费的同时也可以有效地提高絮凝剂的絮凝效果。     

市政污泥深度脱水药剂优化研究简

污泥含水率高影响污泥后续处置。利用化学药剂对污泥进行深度脱水处理可使污泥减量化、稳定化。为提高深度脱水效果，对添加剂进行了种类和添加量的优化研究（石灰、工业石灰、粉煤灰、硅藻土、十二烷基磺酸钠和飞灰；5%、10%、15%、20%、25%和30%），另外，还进行了复合投加实验。研究结果表明，石灰、工业石灰、粉煤灰的深度脱水效果最好；复合添加中，25%石灰+5%粉煤灰，20%石灰+10%粉煤灰，10%石灰+20%粉煤灰的深度脱水效果最好。5%的石灰或者工业石灰的添加剂量使干化污泥pH值达到12.25，粉煤灰、硅藻土、十二烷基磺酸钠和飞灰的添加对干化污泥pH值影响相对要小。     

低温胁迫下Ca2+对厌氧氨氧化污泥脱氮效能影响研究

为了解决厌氧氨氧化(ANAMMOX)污泥在低温下脱氮效能较低的问题,采用上流式厌氧污泥床(UASB)反应器,通过投加不同浓度的Ca~(2+),考察低温胁迫下Ca~(2+)对ANAMMOX污泥脱氮效能及特性的影响。结果表明:低温胁迫下ANAMMOX污泥脱氮效能明显降低,当Ca~(2+)投加量为0mmol/L时,氨氮、亚硝态氮去除率分别降至50%、54%,UASB反应器的TN去除负荷最低为0.094kg/(m~3·d);投加一定Ca~(2+)对ANAMMOX反应有正面促进作用,在最佳Ca~(2+)投加量(0.04mmol/L)下,氨氮、亚硝态氮去除率可分别提高至65%、68%,TN去除负荷提高至接近0.200kg/(m~3·d),脱氮效能是未投加Ca~(2+)时的2倍左右,但Ca~(2+)投加量大于0.04mmol/L时,脱氮效能开始呈现下降趋势。投加Ca~(2+)可以增大污泥颗粒粒径,提高污泥的混合液悬浮固体(MLSS)、混合液挥发性悬浮固体(MLVSS)浓度,但对污泥活性的提升不明显。     

粉煤灰基混凝剂制备及处理印钞废水研究

将粉煤灰经过超细球磨后再采用微波处理，用于制备粉煤灰基混凝剂。结果表明，超细和微波处理能明显增加混凝剂的产率和性能。通过正交实验确定了去除印钞废水中浊度的粉煤灰基混凝剂的最佳制备工艺条件：粉煤灰/酸比为1∶4（w/v），粉煤灰/碱比为1∶3（w/v），熟化温度为40℃。当投加量为5 mL/100 mL时，粉煤灰基混凝剂对印钞废水处理的浊度去除率为98.37％。对粉煤灰基混凝剂的混凝机理进行了分析。     

改性粉煤灰处理低浓度含磷废水的研究

以酸改性粉煤灰为吸附剂,处理低质量浓度(1 mg/L左右)磷酸盐溶液,探讨了改性剂的种类、改性剂用量、吸附剂用量、反应时间、pH以及温度对除磷效果的影响.结果表明:(1)经过酸改性后粉煤灰的磷去除率显著提高,而且硫酸改性粉煤灰的除磷效果更好,磷去除率最高可达97.68％.(2)最佳条件:选择硫酸用量为5 mL/g进行改性,硫酸改性粉煤灰投加量为2.0g,反应时间为60 min,pH为7.2～10.8,温度为25℃(即室温).(3)改性粉煤灰对磷的吸附更符合Freundlich吸附等温模型,既有物理吸附,也有化学吸附,并以Ca、Mg氧化物与磷形成磷的沉淀物为主.     

Chlorobenzenes removal from municipal solid waste incineration fly ash by surfactant-assisted column flotation

The organic contaminants in municipal solid waste incineration (MSWI) fly ash, including chlorinated aromatic compounds and polycyclic aromatic hydrocarbons, have high toxicity and a potential negative impact on the environment. An effective and low energy consumption technique to remove the organic contaminants from MSWI fly ash is required urgently. Organic contaminants, such as chlorobenzenes (CBzs), in MSWI fly ash are known to become enriched in the unburnt carbon (UC) fraction. It is proposed that removal of UC from fly ash will result in the effective removal of most organic micropollutants. In this research, we use a technique of surfactant-assisted column flotation to decontaminate MSWI fly ash by removal of the CBzs-enriched UC from MSWI fly ash. We find that 39.8% of CBzs can be removed from fresh MSWI fly ash with 61.7% UC removal efficiency, whereas only 33.2% of CBzs can be removed from weathered MSWI fly ash with a low UC removal efficiency of 33.7%. By adding a mixture of two kinds of surfactants: sorbitan mono-oleate and polyoxyethylene (20) sorbitan mono-oleate to the weathered fly ash, 47.0% of CBzs were removed at the hydrophile lipophile balance value of 13.5, while the UC removal efficiency increased to 49.0%. The results show that surfactants can enhance CBzs and UC removal efficiencies during the column flotation process. Higher CBzs and UC removal efficiencies can be expected by further optimizing the conditions of surfactant-assisted column flotation.     

Speciation and mobility of cadmium in straw and wood combustion fly ash

Two fly ashes from biomass combustion have been analysed regarding cadmium speciation and mobility. A fly ash from straw combustion contained 10 mg Cd/kg dry matter, and around 50% of the cadmium was leachable in water. The possible main speciation of cadmium in this fly ash was CdCl2. When adding this fly ash to agricultural soil a threat for groundwater contamination and plant uptake is existing. A fly ash from wood chip combustion had 28.6 mg Cd/kg dry matter. In this fly ash, the cadmium was bound more heavily, with only small amounts of cadmium leached in mild extractants. A possible speciation of cadmium in this fly ash was as oxide or as CdSiO3. Long-term effects and accumulation of cadmium could be a problem when adding this fly ash to agricultural or forest soils.     

粉煤灰对水溶液中磷的吸附性能及机理

以粉煤灰为吸附剂去除溶液中的磷,考察了其吸附除P动力学特征、热力学特征以及溶液初始pH和粉煤灰投加量对吸附除P效果的影响,并对其吸附除P机理做了初步探讨。结果表明,在给定实验条件下,粉煤灰对P具有较好的去除效果,随着初始P浓度从10 mg/L升高到80 mg/L,平衡吸附量为0.46～2.44 mg P/g粉煤灰,吸附效率从92.2%降低至61.1%;对不同浓度的含P溶液,粉煤灰最适用量为0.6～1.5 g粉煤灰/mg P;相同反应条件下,当温度由25℃升高到45℃时,P初始吸附速率提高了3倍;粉煤灰对P的吸附过程能够较好地拟合Langmuir、Freundlich及D-R吸附等温模型,相关系数均在0.98以上。通过对吸附饱和的粉煤灰进行解析实验发现,初始P浓度较低(<50 mg/L)时,以化学吸附为主,而在初始P浓度较高(>80 mg/L)时,则以物理吸附为主。     

Improving phosphate removal of sand infiltration system using alkaline fly ash

Septic tank effluent is customarily disposed of by soil infiltration. Coarse, sandy soil such as those found in Perth, Western Australia, exhibit low attenuation capabilities for phosphate (PO4(3-)) during effluent infiltration. Amendment of such soil with different amounts of alkaline precipitator and lagoon fly ashes was investigated as a means of reducing phosphorus (P) leakage to ground water. Alkaline precipitator fly ash possessed the highest P sorption capacity in terms of its Langmuir and Freundlich isotherm parameters during initial batch tests. The test materials were repeatedly contacted with fresh PO4(3-) solutions over 90 contacting cycles to gain a better indication of long-term P sorption capability. Again, precipitator fly ash exhibited higher P sorption capacity than lagoon fly ash and Spearwood sand. Column studies assessed the influence of various application rates of alkaline precipitator and lagoon fly ashes on the P removal of septic tank effluent. Septic tank effluent was applied at the rate of 4 cm/day to the column for 12 weeks. Concentrations of P were monitored in the column effluent. All the fly ash columns were more efficient in reducing P migration compared to the sand column. Increased levels of fly ash in the soil columns resulted in increased P attenuation. Lagoon fly ash was inferior to precipitator fly ash for P removal; high application rates of fly ash caused clogging of the infiltration bed apparently due to their lower permeability. It is reasoned that 5-15% precipitator fly ash, and less than 30% lagoon fly ash could be added to coarse sands to produce an infiltration bed, which would result in a better quality effluent than can be obtained with untreated sand alone.     

The effects of temperature and oxygen content on the PCDD/PCDFs formation in MSW fly ash

In this study, the effects of the temperature, oxygen content in the gas stream and carbon content in ash particles on PCDD/Fs formation on the fly ash surface were investigated. The optimum temperatures for dioxin formation were found at 350 degrees C for boiler ash, 300 degrees C for cyclone ash and 250 degrees C for ESP ash, respectively. Preliminary results indicate that the optimum temperature will decrease as the particle size decreases. When the O2 concentration is varied between 0% and 100%, the optimum oxygen content for PCDD/Fs formation is found to be at 7.5% for cyclone ash, and the PCDD/PCDF ratio increases with the increase of oxygen content. Dioxin formation is observed even for the gas containing no oxygen passed through the fly ash. Hence, other reacted routes that do not need O2 for dioxin formation take place on fly ash. The carbon content in fly ash is varied between 0% and 20% in this study, and the results have indicated that the maximum dioxin formation is to be found at 5%. The precursors are not injected into the fly ash or gas stream in all formation experiments, however, dioxin is still formed in fly ash. Consequently, other chlorinated routes besides Deacon reactions may take place on the fly ash surface.     

Immobilization and volume reduction of heavy metals in municipal solid waste fly ash using nano-size calcium and iron-dispersed reagent

This study was conducted to examine the synthesis and application of novel nano-size calcium/iron-based composite material as an immobilizing and separation treatment of the heavy metals in fly ash from municipal solid waste incineration. After grinding with nano-Fe/Ca/CaO and with nano-Fe/Ca/CaO/[PO₄], approximately 30 wt% and 25 wt% of magnetic fraction fly ash were separated. The highest amount of entrapped heavy metals was found in the lowest weight of the magnetically separated fly ash fraction (i.e., 91% in 25% of treated fly ash). Heavy metals in the magnetic or nonmagnetic fly ash fractions were about 98% and 100% immobilized, respectively. Additionally, scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDS) observations indicate that the main fraction of enclosed/bound materials on treated fly ash includes Ca/PO₄-associated crystalline complexes. After nano-Fe/Ca/CaO/[PO₄] treatment, the heavy metal concentrations in the fly ash leachate were much lower than the Japan standard regulatory limit for hazardous waste landfills. These results appear to be extremely promising. The addition of a nano-Fe/Ca/CaO/PO₄ mixture with simple grinding technique is potentially applicable for the remediation and volume reduction of fly ash contaminated by heavy metals.

Implications: After grinding with nano-Fe/Ca/CaO and nano-Fe/Ca/CaO/[PO₄], approximately 30 wt% and 25 wt% of magnetic fraction fly ash were separated. The highest amount of entrapped heavy metals was found in the lowest weight of the magnetically separated fly ash fraction (i.e., 91% in 25% of treated fly ash), whereas heavy metals either in the magnetic or nonmagnetic fly ash fractions were about 98% and 100% immobilized. These results appear to be very promising, and the addition of nano-Fe/Ca/CaO/PO₄ mixture with simple grinding technique may be considered potentially applicable for the remediation and volume reduction of contaminated fly ash by heavy metals.     

Sorption of metolachlor and atrazine in fly ash amended soils: comparison of optimized isotherm models

Adsorption of metolachlor and atrazine was studied in the fly ash (Inderprastha and Badarpur)- amended Inceptisol and Alfisol soils using batch method. Results indicated that sorption of both the herbicides in soil+fly ash mixtures was highly nonlinear and sorption decreased with a higher herbicide concentration in the solution. Also, nonlinearity increased with an increase in the level of fly ash amendment from 0-5%. Three two-parameter monolayer isotherms viz. Langmuir, Temkin, Jovanovic and one imperical Freundlich models were used to fit the experimental data. Data analysis and comparison revealed that the Temkin and the Freundlich isotherms were best-suited to explain the sorption results and the observed and the calculated adsorption coefficient values showed less variability. The study suggested that sorption mechanism of metolachlor and atrazine involved the physical association at the sorbate surface and the nonlinearity in the sorption at higher pesticide or fly ash concentration was due to a decrease in the heat of adsorption and higher binding energy.     

Effect of fly ash on metsulfuron-methyl sorption and leaching in soils

This investigation was undertaken to determine the effect of amendment of two fly ashes [Kota and Inderprastha (IP)] on sorption behavior of metsulfuron-methyl in three Indian soil types. Kota fly ash (5%) did not show any effect on herbicide sorption while IP fly ash significantly enhanced the sorption. Further studies on metsulfuron-methyl sorption-desorption behavior in 0.5, 1, 2, and 5% IP fly ash-amended soils suggested that effect of fly ash varied with soil type and better effect was observed in low organic carbon content soils. The sorption-desorption isotherms fitted very well to the Freundlich sorption equation and, in general, slope (1/n) values less than unity were observed. Metsulfuron-methyl sorption in the IP fly ash-amended soils showed strong correlation with the fly ash content and compared to the Freundlich sorption constant (K _f), K _FA values (sorption normalized to fly ash content) showed less variation. Metsulfuron-methyl leaching studies suggested greater retention of herbicide in the application zone in IP fly ash-amended soils, but effect varied with soil type and no herbicide leaching was observed in 5% fly ash-amended soils. The study suggested that all coal fly ashes are not effective in enhancing the sorption of metsulfuron-methyl in soils. However, one which enhanced herbicide sorption, could play an important role in reducing its leaching losses.