Optimization of coagulation–flocculation process for papermaking-reconstituted tobacco slice wastewater treatment using response surface methodology

A coagulation–flocculation process was used to treat papermaking-reconstituted tobacco slice wastewater with polyaluminium chloride (PAC) as coagulant and a cationic polyacrylamide (CPAM) as flocculant. To maximize the reduction of chemical oxygen demand (COD) and color, the jar tests were carried out in the experiments and response surface methodology (RSM) was applied to optimize the process. A central composite design, i.e., a standard approach in RSM, was used to evaluate the effects and interactions of three factors, i.e. PAC dosage, CPAM dosage and pH on the treatment efficiency. Results revealed that the maximum reduction of COD and color could be achieved at an optimal conditions, i.e., PAC = 715 mg/L, CPAM = 4.8 mg/L and pH = 6.6, from which the reduction of COD and color were 67.8% and 77.7%, respectively. The study also showed that the regression equations could be used as the theoretical basis for coagulation–flocculation process of papermaking-reconstituted tobacco slice wastewater. They will be very helpful to flexibly select the appropriate process parameters in the engineering applications     

混凝-Fenton法对中晚期垃圾渗滤液预处理研究

利用混凝-Fenton法对中晚期垃圾渗滤液进行预处理研究。首先以PAC为混凝剂,PAM为助凝剂对垃圾渗滤液进行混凝处理,然后对混凝后渗滤液进行Fenton氧化。考察混凝剂用量,起始pH值,H2O2/FeSO4·7H2O投加比,Fenton试剂投药量和搅拌速度对垃圾渗滤液COD去除的影响,并进行正交试验分析。结果表明:混凝法的最佳投药量为1 L渗滤液投加1.5 g PAC和5 mg PAM;Fenton法的最佳条件为:起始pH值为3,H2O2/FeSO4·7H2O投加比为8∶1,Fenton试剂投药量为135 g/L,搅拌速度为150 r/min;各因素对Fenton试验影响大小为:起始pH值Fenton试剂投药量搅拌速度。在最佳条件下,混凝-Fenton法对垃圾渗滤液COD去除率可达91.41%。     

Statistical optimization of process conditions for photocatalytic degradation of phenol with immobilization of nano TiO<Subscript>2</Subscript> on perlite granules

Response surface methodology (RSM) using D-optimal design was applied to optimization of photocatalytic degradation of phenol by new composite nano-catalyst (TiO₂/Perlite). Effects of seven factors (initial pH, initial phenol concentration, reaction temperature, UV irradiation time, UV light intensity, catalyst calcination temperature, and dosage of TiO₂/perlite) on phenol conversion efficiency were studied and optimized by using the statistical software MODDE 8.02. On statistical analysis of the results from the experimental studies, the optimum process conditions were as follows: initial pH, 10.7; initial phenol concentration, 0.5 mM; reaction temperature, 27 °C; UV irradiation time, 6.5 h; UV light intensity, 250 W; catalyst calcination temperature, 600 °C; and TiO₂/perlite dosage, 6 g/L. Analysis of variance (ANOVA) showed a high coefficient of determination (R²) of 91.8%.     

Sequencing coagulation–photodegradation treatment of Malachite Green dye and textile wastewater through ZnO micro/nanoflowers

Sequencing coagulation–photodegradation over ZnO micro/nanoflowers was assessed for Malachite Green (MG) dye removal and followed by the MG-containing textile wastewater treatment. The ZnO micro/nanoflowers were prepared using a facile reflux route and analyzed by various characterization techniques. The flower-like morphological structures of ZnO were witnessed through microscopy analyses. X-ray diffraction findings showed that the prepared ZnO samples were highly crystalline with hexagonal wurtzite structure. The operational parameters including type of coagulant, coagulant dosage, solution pH, photocatalyst dosage and light power exerted their individual influences on the removal of MG dye. The CaCO₃ was the best coagulant among the three coagulants tested due to its high formation of precipitates and adsorption of cationic dye molecules. Using CaCO₃ as a coagulant, 88.3% MG removal was obtained at coagulant dosage of 160?mg and solution pH of 9.0. Complete removal of MG was found with 0.5?g?L^?1 ZnO micro/nanoflowers and 105?W light power. The kinetic analysis showed that a Langmuir?Hinshelwood model was in good agreement with dye removal data. Moreover, a complete removal of MG dye and 80.0% of chemical oxygen demand removal over sequencing coagulation–photodegradation were observed for MG-containing textile wastewater treatment. The sequencing coagulation–photodegradation process using ZnO micro/nanoflowers indicated much promise to be an attractive method for textile effluent treatment applications.     

混凝沉淀预处理洗浴废水试验研究

采用混凝沉淀法预处理洗浴废水,探讨混凝搅拌强度、混凝剂投加量、废水pH值及沉淀时间等因素对CODCr及浊度去除率的影响,研究混凝沉淀工艺的最佳运行条件。试验结果表明,混凝沉淀的最佳运行条件为:中速搅拌(100 r/min)2 min,慢速搅拌(30 r/min)5 min,沉淀时间为15 min;PAC和PAM投加量分别为40、2.5～3.5 mg/L,pH值为6～9。在此条件下,废水中CODCr和浊度的去除率分别达到76%和81%。采用混凝沉淀预处理,可以大大减轻后续处理单元的负荷,为洗浴废水处理后回用提供了保障。     

强化混凝去除二级生化出水中磷的研究

对强化混凝去除二级生化出水中磷的可行性进行了研究。研究结果表明，在磷质量浓度较高（约10mg／L）的情况下，聚合硫酸铁和聚合氯化铝不宜作为除磷的混凝剂；而自制931型复合混凝剂的处理效果较好。在931投加量160mg／L、阴离子型聚丙烯酰胺（PAM）投加量0．5mg／L、pH值6．5的条件下，混凝效果最佳，出水中磷的质量浓度在1．0mg／L以下，可满足GB18918—2002规定的一级排放标准的要求，且处理效果稳定，重现性较好。成本核算显示，总运行成本约0．33元／m^3，运行成本合理，具有较高的应用价值。     

Removal of chemical oxygen demand from textile wastewater using a natural coagulant

A biomaterial was successfully synthesized from Plantago ovata by using an FeCl₃-induced crude extract (FCE). The potential of FCE to act as a natural coagulant was tested for the pretreatment of real textile wastewater. Tests were performed to evaluate the effects of FCE quantity, salt concentration, and wastewater pH on chemical oxygen demand (COD) reduction during a coagulation/flocculation process. Experimental results indicated that the wastewater could be effectively treated by using a coagulation/flocculation process, where the BOD₅/COD ratio of the effluent was improved to 0.48. A low coagulant dose, 1.5mg/L, achieved a high COD removal percentage, 89%, at operational conditions of neutral pH and room temperature. The experimental data revealed that the maximum COD removal occurred at water pH<8. Increasing the salt promoted the COD removal. The settling and filterability characteristics of the sludge were also studied. Scanning electron microscopy and energy dispersive spectroscopy studies were conducted to determine the sludge structure and composition, respectively. Overall, FCE as an eco-friendly biomaterial was revealed to be a very efficient coagulant and a promising option for the removal of COD from wastewaters.     

Kinetics and neuro-fuzzy soft computing modelling of river turbid water coag-flocculation using mango (Mangifera indica) kernel coagulant

This study investigates kinetics and Adaptive Neuro-Fuzzy Modeling (ANFM) of river turbid water coagulation-flocculation (CF) process using mango kernel coagulant (MKC). CF experiments were performed using jar test apparatus and the process kinetic-transport parameters (coagulation rate constant, half-life time, and particle diffusivity) were determined using kinetic-transport models. Grid-partitioning neuro-fuzzy programming codes were written and implemented in Matlab 9.2 software environment for the development of neuro-fuzzy architecture. The ANFM input data include initial water pH, initial water turbidity, biocoagulant dosage, CF time, and turbidity removal percentage (TRP) as output data. Generalized bell membership function was optimally selected for fuzzification of input variables and a hybrid algorithm was considered for the learning method of input-output data with constant output membership type. The minimum turbidity (0.51 NTU) of treated water was achieved at pH 12 and coagulant dosage of 2.5?mg/L with coagulation rate constant, half-life (t_1/2) and particle diffusivity 0.0194?s^?1, 10.01?min, and 7.267?×?10^?14 m²/s, respectively. The correlation coefficient (R²) between the experimental and neuro-fuzzy predicted values was 0.9924 and the ratio (K) of training error to testing error was 0.68. Thus, this study shows that ANFM can be used as a reliable tool for modeling river water CF and kinetic-transport parameter results are useful in process design, optimization, and control.     

Preparation of a composite coagulant: Polymeric aluminum ferric sulfate (PAFS) for wastewater treatment

A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80 °C) and time (30–50 min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80 °C, 40 min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45 mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250 rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids.     

还原-混凝法回收低浓度含金废水中的金

采用还原一混凝法回收低浓度含Au废水中的Au,考察了还原剂的投加量、反应时间、混凝剂类型、混凝剂投加量、混凝时间等因素对Au回收率的影响。最佳工艺条件为：还原剂的投加量为1．2g／L．还原反应时间为35min;混凝剂为聚合氯化铝铁,投加量为O．2g／L,混凝时间为6min;絮凝剂为0-4％聚丙烯酰胺,投加量为2mL／L,在此条件下废水中Au的回收率超过92．86％,处理后滤液中Au的质量浓度小于0．02mg／L。该方法具有工艺简单、操作简便、Au回收率高等特点。     

Silver recovery from radiographic film processing effluents by hydrogen peroxide: Modeling and optimization using response surface methodology

The recovery of silver from X-ray film processing effluents by precipitation using hydrogen peroxide as the precipitating agent was studied. Response surface methodology (RSM) and central composite design (CCD) were applied to achieve optimum conditions. Linear, square and interactions effects between parameters to study of a second order polynomial equation were obtained. Optimum condition included the volume of H₂O₂ 0.8 ml/min, pH=5.5, ethylene glycol 9 ml in the experimental condition. In these conditions silver recovery percentage was predicted as 92.8%. The experiment was conducted in triplicate under optimized conditions. Silver recovery percentage and average of precipitate were obtained as 91.5% and 423.19mg, respectively, which were close to the predicted amount achieved by the model.     

三种絮凝剂除藻效果的比较

以合肥市环城河为研究对象,采用聚合氯化铝（PAC）、聚合氯化铝铁（PAFC）、聚合硫酸铝铁（PAFS）三种絮凝剂对该含藻水体进行强化混凝除藻、除浊的试验研究,考察了絮凝剂种类及添加量、水样的pH、助凝剂的种类以添加量等因素对强化混凝效果的影响。结果表明：在相同添加量时,聚合氯化铝的除藻、除浊效果最好,当添加量为27 mg/L时,叶绿素a的去除率为87.46%,浊度的去除率为92.74%,添加高分子助凝剂PAM、HCA对原水的浊度、叶绿素a有一定的去除效果,助凝剂与絮凝剂的配合使用可改善絮凝剂的的混凝去除效果,助凝剂PAM的效果较好,当PAM的投加量为2 mg/L时,叶绿素a的去除率可提高5.91%,浊度的去除率可提高1.70%。     

泥渣回流强化混凝沉淀再生水处理工艺条件优化

以北方某城市再生水厂原水为研究对象,通过泥渣回流强化混凝沉淀工艺进行再生水处理,研究了泥渣回流浓度、泥渣回流量、助凝剂投加量、泥渣回流位置、搅拌强度等参数对该工艺的运行效果影响.结果表明,经泥渣回流强化混凝沉淀后,再生水处理效果良好.在进水流量为200L·h~(-1)时,优化后工艺运行参数分别为:PAc投加量10mg·L~(-1),PAM投加量0.3 mg·L~(-1),泥渣回流质量浓度10 000～16 000 mg·L~(-1),泥渣回流量200 mg·L~(-1),混合池搅拌强度G=328 S~(-1),絮凝池搅拌强度G=22 S~(-1),泥渣回流位置在混合池.在最佳工艺运行条件下,出水水质达到了景观环境用水水质(GB/T 18921-2002)的要求.     

新型高分子硅铁混凝剂深度处理腈纶废水研究

采用自制新型氧化混凝药剂——无机氧化性高分子硅铁混凝剂(PSF)对腈纶废水生化出水进行处理,并与聚合硫酸铁、聚合氯化铝的混凝效果进行对比试验;以出水COD去除率为评价指标,通过单因素试验优化确定出适宜条件。结果表明,在初始pH为9、CaO投加量为1.0 g/L、PSF和聚丙烯酰胺投加量分别为900、6 mg/L的条件下,出水COD去除率可达到30%以上。采用PSF新型混凝剂可以有效去除腈纶废水生化出水中的溶解性大的难降解有机污染物,效果明显优于其它2种混凝剂,可以作为腈纶废水深度处理的一种新型预处理药剂。     

处理造气废水混凝药剂选择的研究

研究了不同的混凝药剂对造气废水处理的效果,考察了药剂组合、投加量的影响因素,分析了运行的经济成本,确定了最佳药剂及其投量。混凝剂PAC的最佳投加量为140mg/L,此时,COD和SS的去除率分别为29.6%和60.1%;助凝剂PAM和DC-491都可以提高PAC的混凝效果,当PAC的投加量为140mg/L时,PAM和DC-491的最佳投加量分别为2mg/L和4mg/L;单独使用SX-P时,最佳投加量为160mg/L,此时的COD和SS去除率分别为41.8%和71.5%,混凝效果优于PAC与助凝剂的联用。因此,实际工程中选择SX-P作为混凝剂,并取得了良好的运行效果。     

最佳混凝投加量和pH去除水中有机物的研究

对强化混凝去除黄浦江水的有机物进行了试验研究。尽管增加混凝剂投加量和降低pH都能有效地提高去除有机物的效果，但降低pH去除有机物更有效。不同的pH，达到最佳有机物去除效果所需的混凝投加量是不同的，pH越低，所需的投加量就越少。就黄浦江水来说，达到最佳有机物去除效果的硫酸铝投加量为8mg/L（以Al计），pH在5．5，DOC和UV254的去除率可分别达到46％和57％，较常规处理方法，去除率可提高1倍。强化混凝也能有效地去除消毒副产物。     

Optimization of acrylonitrile removal by activated carbon‐granular using response surface methodology

A statistical Box–Behnken design of experiments was performed to evaluate the effects of individual operating variables and their interactions on the acrylonitrile (AN) removal of C₀ = 100 mg/L as fixed input parameter. The variables examined in this study included activated carbon‐granular (AC) dosage, w, temperature, T, and time of contact, t. The significant variables and optimum conditions were identified (w = 4 g/L, T = 30°C, and t = 120 min with AN uptake of 23.97 mg/g of AC) from statistical analysis of the experimental results using response surface methodology (RSM).     

不同絮凝剂的除磷效果研究

在室温条件下,利用常见的三种絮凝剂(PAC、FeCl3、Al2(SO4)3)对人工配置的含磷废水进行混凝处理,寻找对应最佳处理效果的投药量和pH。结果表明,Al2(SO4)3的最佳投药量为60 mg/L,最佳pH为7.0;FeCl3的最佳投药量为40 mg/L,最佳pH为10.05;PAC投药量为120 mg/L,最佳pH为8.0。     

不同混凝剂对马铃薯淀粉废水混凝效果的影响

用混凝剂Fe2(SO4)3、PAC、PFSS、PAFC处理马铃薯淀粉废水,研究了混凝剂的种类、投药量、废水pH值、助凝剂PAM的投加量以及沉降时间等对混凝效果的影响。结果表明,混凝沉淀法预处理马铃薯淀粉废水优选混凝条件为:pH为7,混凝剂PAFC为1 200 mg/L,助凝剂PAM为5 mg/L,沉降25 m in。在此条件下,废水的浊度、COD去除率分别达97.27%及40.55%。投药量明显减少,而沉积物产量较高,为后续生化处理提供了有利条件。     

Effect of coagulation on palm oil mill effluent and subsequent treatment of coagulated sludge by anaerobic digestion

A new effluent treatment scheme is proposed for treating palm oil mill effluent based on coagulation and anaerobic digestion of coagulated sludge. The effectiveness of anionic (N9901) and cationic (N9907) polyelectrolytes manufactured by NALCO (Malaysia) was evaluated both as coagulant and coagulant aid. The results showed that the anionic and cationic polyelectrolytes were best suited as a coagulant aid, and the cationic polyelectrolyte showed better performance than the anionic polyelectrolyte. For an influent chemical oxygen demand (COD) concentration of 59 700 mg L^?1 at an alum dosage of 1700 mg L^?1, the residual COD, suspended solid removal, sludge volume and pH were found to be 39 665 mg L^?1, 87%, 260 mL L^?1 and 6.3, respectively. For the above influent COD and alum dosage with the addition of 2 mg L^?1 of cationic polyelectrolyte as coagulant aid, the results were 30 870 mg L^?1, 90%, 240 mL L^?1 and 6.2, respectively. The sludge resulting from the coagulation process using alum as coagulant and cationic polyelectrolyte as coagulant aid was tested for its digestibility in an anaerobic digester. The quantity of biogas generated per gram of volatile solids (VS) destroyed at a loading rate of 26.7 ± 0.5 and 35.2 ± 0.4 g VS L^?1 d^?1 was found to be 0.68 and 0.72 L g^?1 VS destroyed. The anaerobic biomass when subjected to varying alum dosage in the coagulated palm oil sludge did not exhibit inhibition as the digester performance was in conformity with the regular treatment process Copyright © 2006 Society of Chemical Industry