Precipitation Removal of Fluoride from Semiconductor Wastewater

Chemical precipitation method utilizing calcium salts has been extensively used to treat fluoride-containing wastewater from semiconductor manufacturers. The major objective of this study was to investigate coagulation-flocculation of calcium fluoride precipitates (CaF2). Residual fluoride concentration of lower than 15?mg/L, the effluent standard, was found when molar ratio of calcium to fluoride, [Ca2+/F?], was 0.5 and pH ranged from 6.5 to 8.5. The fine precipitates of CaF2 were further flocculated by polyaluminum chloride (PAC) and anionic polyelectrolyte, polyacrylic acid (PAA) with different molecular weight, to facilitate better solid-liquid separation. Experimental results indicated that both PAC and PAA with low to medium molecular weight could remove CaF2 precipitates effectively. Satisfactory removal efficiency was achieved at lower dosage when PAC and PAA were used in combination. Recycling of CaF2 precipitates or CaF2 sludge did not enhance removal of fluoride or CaF2 precipitates. Reaction mechanisms were discussed based on zeta potential and particle size distribution.     

CaCl2-PAC絮凝法处理含氟废水的研究

文章绘制了水溶液中总氟与游离钙离子和pH值的关系图,并结合氯化钙、PAC混凝剂处理含氟废水,分别考察了氯化钙的加入量和PAC加入量对除氟的影响.结果表明,在氯化钙加入量为I00mg/L时,水样中氟离子残余量为10.2 mg/L,在溶液pH值为6.5,PAC加入量为400mg/L时,水样中残余氟离子浓度为3.62 mg/...     

Boron Removal via Formation of Magnesium Silicate Solids during Precipitative Softening

Precipitative softening is an option to remove silicon and boron from natural waters. Silicon was removed from hard waters by precipitative softening when the molar ratio of Mg:Si was less than 6:1 by the formation of an amorphous magnesium silicate. This solid had an apparent solubility product constant of 10?25.66 and was stoichiometrically similar to the mineral forsterite, Mg2SiO4. Boron removal was consistent with sorption to this amorphous magnesium silicate and could be roughly described by a Freundlich isotherm: Bsorb/Mg2SiO4(s) = 21×Bsol0.51.     

Laccase-Catalyzed Removal of Phenol and Benzenediols from Wastewater

A two-step process for the removal of phenol and benzenediols, namely catechol, resorcinol, and hydroquinone, from buffered synthetic wastewater was investigated. The proposed process comprised laccase catalyzed conversion of these substrates using laccase from Trametes villosa followed by the removal of products generated using alum as coagulant. The effects of pH, laccase concentration, substrate concentration, and the presence of a hydrophilic polymer additive [polyethylene glycol (PEG)] to achieve ≥ 95% removal of the substrate in a 3-h reaction period at room temperature were determined. The parent compound, phenol, required the most enzyme, followed by resorcinol, catechol, and hydroquinone. PEG showed no effect on any of the substrate conversions. Substrate conversion and enzyme inactivation were monitored over the reaction period. As phenol and benzenediols might coexist in industrial effluents, enzymatic treatment of an equimolar mixture of these four substrates was examined. Except for hydroquinone, the proposed enzymatic treatment method is a viable alternative means to remove phenol and benzenediols from industrial wastewaters.     

非金属矿物材料处理含磷废水的研究现状

介绍了膨润土、凹凸棒石、沸石、硅藻土、蛭石等非金属矿物材料的结构和性质,对其在含磷废水中的应用现状进行了综述,并对其应用前景进行了展望.     

Use of Immobilized Bentonite in Removal of Heavy Metals from Wastewater

Bentonite is known to adsorb toxic metal ions from aqueous solutions. In this study bentonite was immobilized in a polymer matrix of polysulfone in the form of spherical beads to remove cadmium and copper ions. For this purpose a bead-producing unit was fabricated. The procedure for making beads is described. The beads exhibited a porous surface and surface area of up to 20 m2∕g. 99.4% of beads were retained on a sieve size of 1.18 mm and were finer than 2.36 mm. Batch adsorption data was adequately described by the Freundlich isotherm model. The beads were able to remove more than 99% of copper and cadmium ions in the column mode. These beads can find application as filter media in the removal of toxic heavy metal ions from aqueous solutions.     

转炉污泥处理含磷废水的实验研究

研究转炉污泥对模拟含磷废水脱磷的一般规律,实验结果表明,转炉污泥对磷有较好的去除效果。影响转炉污泥除磷的主要因素有污泥用量、pH值、吸附时间和原水含磷浓度。在污泥用量大于1 5mg/100ml,pH<4,脱磷时间5h时,磷的去除率达88%以上。     

脱氨剂去除稀土废水氨氮的研究

采用脱氨剂去除稀土废水氨氮,并对处理的影响因素进行了探讨。试验结果表明,投加量脱氨剂为1000 mg/L、反应时间为60min、反应pH为9时,可将稀土废水中的NH3-N从14436mg/L降低到2435mg/L,去除率达到83.13%,并可大大降低处理成本,因此,该方法可以作为稀土废水的前处理方法。     

Precipitative Removal of As, Ba, B, Cr, Sr, and V Using Sodium Carbonate

Sodium carbonate softening at pH 10.3 is a viable method of removing the inorganic contaminants arsenic, barium, chromium, strontium, and vanadium from drinking water sources. A broad survey revealed that removals varied widely and were dependent on solution composition. Median removals of As, Ba, Cr, Sr, and V were 24, 100, 92, 99, and 60%, respectively. Linear and nonlinear empirical models were fit for crudely estimating the removal of these contaminants in the presence of other elements that are typically removed in the softening process (i.e., calcium, magnesium, silicon, iron, and aluminum). Boron was removed to a much lesser extent (median removal 2%) indicating soda ash softening is not a promising treatment option for this purpose.     

湿法炼锌中氟氯去除方法的研究

分析了湿法炼锌体系中氟、氯的来源及氟、氯的存在对生产设备和电积的危害,从火法和湿法两个方面阐述了湿法炼锌中氟、氯的去除方法,火法中重点介绍了多膛炉和回转炉焙烧脱氟氯;湿法中重点介绍了吸附法、沉淀法、絮凝沉淀法脱氟和铜渣、氧化铋、离子交换法脱氟氯。     

离子交后液回收钨废水中MnO除磷的研究

目前离子交后液回收钨冶炼废水中磷含量普遍高于国家排放标准,亟待开发出高效、低成本的除磷工艺.研究提出了采用MnO从钨冶炼废水中吸附除磷工艺,考察了液固比、pH、温度、反应时间和搅拌速度对含磷模拟液除磷效果的影响.优化后的结果表明,在液固比为67:1、废水初始pH值为2、反应时间为50 min、反应温度为40℃、搅拌速度...     

Simultaneous Removal of Carbon and Nitrogen from Swine Wastewater Using an Immobilized-Cell Reactor

A single-stage phosphorylated polyvinyl alcohol immobilized-cell reactor with three operation modes was employed to investigate the efficiency of simultaneous carbon/nitrogen removal from raw swine wastewater. In continuous aeration mode, the removal efficiency of chemical oxygen demand (COD) and total nitrogen (T-N) exceeded 70 and 8%, respectively, at hydraulic retention time of 10?days. In intermittent aeration (IA) mode, the removal efficiency of COD and T-N was more than 85 and 46%, respectively, when the reactor was set at 50% aeration duration to cycle time to operate at three aerobic-anoxic cycles per day. When oxidation-reduction-potential control was adopted to control the duration of the anoxic period in the real-time controlled (RTC) IA mode for a 4?h aeration period, the total cycle time was reduced by about 20% with a slight increase in removal efficiency of COD (87%) and T-N (47%). The system with no extra chambers required is efficient in simultaneous carbon/nitrogen removal.     

Application of Natural Clayey Soil as Adsorbent for the Removal of Copper from Wastewater

Use of clayey soil has been explored in the laboratory scale experiment as a low cost adsorbent for the removal of copper from wastewater. The influence of metal ion concentration, weight of adsorbent, stirring rates, influence of temperature, pH are also evaluated and the results are fitted using adsorption isotherm models. From the experimental results it is observed that almost 90–99% copper can be removed from the solution using clay at optimized pH 5.5. Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm model have been used to describe the distribution of copper between the liquid and solid phases in batch studies and it has been observed that Langmuir isotherm better represents the phenomenon. From the experimental results rate constant, activation energy, Gibbs free energy, enthalpy, and entropy of the reaction are calculated to determine the mechanism of the sorption process. Thomas, Adams-Bohart, and Yoon-Nelson models are applied to the experimental data to determine the characteristic parameters of the column for process design.     

Modeling of Cadmium Removal from Domestic Wastewater in Constructed Wetlands Using STELLA Simulation Program

A mathematical model was developed to simulate cadmium removal from wastewater in free water surface (FWS) and subsurface flow (SF) constructed wetlands using STELLA simulation program. The model simulated the accumulation of cadmium in soil (Cds), uptake by plants (Cdp), and residual concentration in effluent (Cdww_eff). The model was calibrated using one-half of the experimental data for the adjustment of the coefficients and the remaining data for model verification. The comparison of simulated and experimental values of Cds, Cdp, and Cdww_eff showed good agreement. The results indicated that the developed mathematical model could be useful for predicting the fate of cadmium when treating domestic effluents in constructed wetlands.     

Simultaneous Nitrogen and Phosphorus Removal from High-Strength Industrial Wastewater Using Aerobic Granular Sludge

Aerobic granular sludge technology was applied to the simultaneous nitrogen and phosphorus removal from livestock wastewater that contains high concentrations of nitrogen and phosphorus (TN: 650?mg/L; TP: 125?mg/L). A lab-scale sequencing batch reactor was operated in an alternating anaerobic/oxic/anoxic denitrification mode. Granular sludge was first formed using synthetic wastewater. When livestock wastewater was diluted with tap water, the shape and settleability of aerobic granular sludge were maintained even though livestock wastewater contained suspended solids. Simultaneous nitrification, denitrification, and phosphate uptake were observed under an aerobic condition. However, when nondiluted livestock wastewater was used, the diameter of granular sludge and the denitrification efficiency under an oxic condition decreased. When the concentrations of nitrogen and phosphorus in wastewater increased, hydraulic retention time (HRT) increased resulting in a decrease in selection pressure for granular sludge. Therefore, the sustainment of granular sludge was difficult in livestock wastewater treatment. However, by applying a new excess sludge discharge method based on Stokes’ law, the shape of granular sludge was maintained in spite of the long HRT (7.5?days). To select large granular sludge particles, excess sludge was discharged from the upper part of settled sludge because small particles localized there after settling. Finally, excellent nitrogen and phosphorus removal was accomplished in practical livestock wastewater treatment. The effluent concentrations of NH4–N, NOx–N, and PO4–P were <0.1, 1.4, and 1.2?mg/L, respectively.     

Use of a Sequencing Batch Reactor for Nitrogen and Phosphorus Removal from Municipal Wastewater

In this study, a suspended growth sequencing batch reactor (SBR) and an attached cum suspended growth SBR were used to investigate the performance characteristics of nitrogen and phosphorus (NP) removal from municipal sewage. The effects of three controlling factors, namely batch loading rate, feed pattern (initial feed or step feed), and mixing/aeration ratio, on NP removal were investigated under nine different experimental conditions. Owing to a large number of possible combinations among the controlling factors and different experimental conditions, it is very difficult to enumerate all the available combinations experimentally. In view of this, the Taguchi method, a cost-effective technique for design of experiments, was exploited for estimating the optimal operating condition. This study also evaluated the difference between the suspended growth SBR and the attached cum suspended growth SBR. The total nitrogen (TN), total phosphorus (TP), total biochemical oxygen demand (TBOD)5, and suspended solids (SS) removal efficiencies were 90.2, 83.9, 98.6, and 93.0%, respectively, for the suspended growth SBR. The corresponding values for the attached cum suspended growth SBR were 92.6, 82.1, 98.3, and 93.1%, respectively. It was observed that the batch loading rate influenced the efficiencies in terms of TN removal. It was also noted that step feed and mixing/aeration ratio had significant impact on TP removal performance. The optimal operating condition for the suspended growth SBR system in terms of batch loading rate, feed pattern, and mixing/aeration ratio were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 1-to-1, respectively. The associated TN, TP, TBOD5, and SS removal efficiencies for the suspended growth SBR were 93.8, 98.2, 99.6, and 98.5%, respectively. The corresponding results for the attached cum suspended growth SBR system were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 3-to-1, respectively. Similarly, the corresponding removal efficiencies for the attached cum suspended growth SBR were 94.7, 97.8, 99.3, and 98.8%, respectively.     

Combined System for Biological Removal of Nitrogen and Carbon from a Fish Cannery Wastewater

A combined system composed of three sequentially arranged reactors, anaerobic-anoxic-aerobic reactors, was used to treat the wastewater generated in the tuna cookers of a fish canning factory. These wastewaters are characterized by high chemical oxygen demand (COD) and nitrogen concentrations. The anaerobic process was performed in an upflow anaerobic sludge blanket reactor operated in two steps. During Step I different influent COD concentrations were applied and organic loading rates (OLRs) up to 4 g COD/(L?d) were achieved. During Step II hydraulic retention time (HRT) was varied from 0.5 to 0.8 days while COD concentration in the influent was constant at 6 g COD/L. The OLRs treated were up to 15 g COD/(L?d). When HRTs longer than 0.8 days were used, COD removal percentages of 60% were obtained and these values decreased to 40% for a HRT of 0.5 days. The denitrification process carried out in an upflow anoxic filter was clearly influenced by the amount of carbon source supplied. When available carbon was present, the necessary COD/N ratio for complete denitrification was around 4 and denitrification percentages of 80% were obtained. The nitrification process was successful and was almost unaffected by the presence of organic carbon (0.2–0.8 g TOC/L), with ammonia removal percentages of 100%. Three recycling ratios (R/F) between the denitrification and nitrification reactors were applied at 1, 2, and 2.5. The overall balance of the combined system indicated that COD and N removal percentages of 90% and up to 60%, respectively, were achieved when the R/F ratio was between 2 and 2.5.     

Simultaneous Removal of Nitrogen and Phosphorous from Municipal Wastewater Using Continuous-Flow Integrated Biological Reactor

A pilot-scale experiment was carried out to study the simultaneous removal of nitrogen and phosphorous from municipal wastewater by an innovative continuous-flow integrated biological reactor (CIBR) process. A three-phase separator was used in the CIBR process, which not only saved energy consumption of sludge returning, but also solved the sludge–gas separating problem. The optimal working condition was 2?h aeration, 1?h agitation, and 1?h settling, with an energy consumption of 0.23?kW?h/m3. The average removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), total nitrogen (TN), and total phosphorus (TP) under the optimal conditions were 72.87, 75.23, 61.25, and 68.25%, respectively. The distributing rules of dissolved oxygen, pH, mixed liquid suspended solid, COD, NH4+–N, NO3?–N, TN, and TP in each phase of CIBR was studied. It was indicated that the appropriate condition was created for the simultaneous removal of nitrogen and phosphorus in the integrated reactor. The study demonstrated the feasibility of using CIBR process for simultaneous removal of nitrogen and phosphorus at the average temperature 12.2°C.     

烧结机头烟气除氟脱硫系统高效化运行的探索

文章根据包钢炼铁厂四烧机头烟气净化系统采用石灰石—石膏湿法除氟脱硫工艺,在一年运行中出现的问题,提出了通过技术改造、参数控制等手段来提高净化效率和稳定性的措施,取得良好效果。     

贵溪冶炼厂废水除砷工艺优化

以贵溪冶炼厂废水处理工艺为例,研究了铁离子对外排水指标的影响,并结合生产实际,用硫化滤液对废铁进行溶解,提升废酸铁离子浓度。实施后,石膏滤液Fe~(2+)由44mg/L上升到200mg/L,外排水含砷由0.07mg/L降低至0.02mg/L,年节约生产成本54.6万元,取得了良好的效果。