Comparison of electrocoagulation and chemical coagulation with fiber filters for water treatment

A combined electrocoagulation(EC)-fiber filter system has been presented as a new technology for water treatment. The objective of this study was to evaluate the feasibility of applying an aluminum EC-fiber filter for water treatment. We compared the water treatment efficiency of the chemical coagulation (CC)-fiber filter and EC-fiber filter. A comparison of the EC and CC processes reveals that EC significantly outperformed CC when the water to be filtered using fiber filters was pretreated with aluminum. For particle size less than 6 μm, the removal efficiency was 66%, 43% for EC and CC, respectively, and the average removal efficiency of the total organic carbon (TOC) was 50%, 65% for CC and EC. Therefore, EC reduced the amount of aluminum utilized by 25%, and the effluent turbidity improved by approximately 0.11 NTU to 0.19 NTU. Also, the average log removal value (LRV) for heterotrophic plate count (HPC) was 2.5 and 1.9 for EC and CC. respectively. Therefore, the aluminum used for EC proved to be excellent for pretreating the water to be filtered by a fiber filter.     

Treatment of potato chips manufacturing wastewater by electrocoagulation

Treatment of wastewater from potato chips manufacturing by electrocoagulation (EC) was investigated. Experiments were conducted to determine the optimum operating conditions such as electrode type, pH, current density and retention time. Aluminium and iron electrodes were used, and aluminium electrodes were found to be more suitable since it had a higher removal rate of COD, turbidity and suspended solids than the iron electrode. The removal efficiencies of COD and turbidity were high, being 60% and 98%, respectively, with retention time < 40 min. 0.05–1.75 kg (per kg COD removed) of dried sludge was removed. COD removal kinetics during EC process was described by a macro-kinetics model. Results from the kinetic studies showed that the kinetic data fit the second-order kinetic model well. The operating costs investigated in the present study were the energy cost of EC and the material cost due to the consumption of aluminium electrode. Operating costs were varied in the range of 0.48 to 5.42 $/m³ and 0.62 to 6.32 $/m³ wastewater treated at 20–300 A/m² and 5–40 min, respectively. The energy consumption was 4 kWh/m³ for wastewater treated less than 8 min under typical operating conditions.     

泥渣回流强化混凝工艺处理城市污水二级生化出水

采用城市污水处理厂二沉池出水为回用水源,对常规化学混凝和泥渣回流强化混凝工艺处理效果进行比较,试验结果表明:泥渣回流强化混凝工艺对COD的去除率比常规混凝处理工艺提高4%～6%,浊度去除率平均提高约7%,TP去除率提高8%～31%。泥渣回流强化混凝工艺处理二沉池出水的效果优于常规混凝处理工艺。并通过优化泥渣回流量和速度梯度G值,探索出泥渣回流强化混凝工艺处理回用水的最佳运行条件:泥渣回流量为2.91L/h,G为22～52.6s-1。     

Treatment of dairy wastewater by electrocoagulation process: Advantages of combined iron/aluminum electrodes

ABSTRACT

The objective was to assess the efficiency of electrode material in an electrocoagulation (EC) process for wastewater treatment by comparing the efficiency of aluminum (Al–Al), iron (Fe–Fe) and combined Fe–Al electrodes. The treatment of synthetic dairy wastewater, characterized by high levels of 5-day biological oxygen demand (BOD₅) and chemical oxygen demand (COD), was used to compare electrode materials. Experimental results showed that all electrodes materials achieved the same final removal yield in the range of current studied (55% COD, 60% total organic carbon, 90% total nitrogen, and nearly 100% turbidity) when equilibrium was achieved. But at fixed current density and initial concentration of dairy waste, the Al–Al assembly exhibited the fastest elimination, whereas the slowest removal rate was observed with the Fe–Fe electrodes, even though adsorption was always the main removal mechanism. Finally, an Fe–Al system using an Fe anode with an Al cathode emerged as a techno-economic trade-off because of the low price of iron: both metals contributed to the removal of dairy waste, and the treatment time to achieve equilibrium values was closer to the Al–Al assembly at fixed current density. Moreover, experimental results proved the additivity of the mechanisms reported for Al–Al and Fe–Fe systems with Fe–Al.     

Removal of arsenic from drinking water by the electrocoagulation using Fe and Al electrodes

A novel technique of electrocoagulation (EC) was attempted in the present investigation to remove arsenic from drinking waters. Experiments were carried out in a batch electrochemical reactor using Al and Fe electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as pH (4–9), current density (2.5–7.5 A m⁻²), initial concentration (75–500 μg L⁻¹) and operating time (0–15 min) were examined. Optimum operating conditions were determined as an operating time of 12.5 min and pH 6.5 for Fe electrode (93.5%) and 15 min and pH 7 for Al electrode (95.7%) at 2.5 A m⁻², respectively. Arsenic removal obtained was highest with Al electrodes. Operating costs at the optimum conditions were calculated as 0.020 € m⁻³ for Fe and 0.017 € m⁻³ for Al electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10 μg L⁻¹ with Fe and Al electrodes. The adsorption of arsenic over electrochemically produced hydroxides and metal oxide complexes was found to follow pseudo second-order adsorption model. Scanning electron microscopy was also used to analyze surface topography of the solid particles at Fe/Al electrodes during the EC process.     

Treatment of industrial liquid wastes by electrocoagulation: Experimental investigations and an overall interpretation model

The paper presents the results of experimental investigations of treatment of concentrated wastes by electrocoagulation using sacrificial aluminium (Al) anodes. Tests were carried out batchwise in an electrochemical cell with recirculation for various wastes of industrial significance: the technique was shown to allow efficient abatement of the suspensions with concentrations of dissolved Al ranging from 150 to . Hydrogen evolution and Al dissolution occurred with current yields over unity. Besides, the time variation of the COD largely depended on the nature of the waste treated: whereas the treatment proceeds regularly for latex suspensions, the COD abatement with oil and silica suspensions starts only after sufficient accumulation of Al (III) species in the media. We proposed a phenomenological model for prediction of the waste abatement in term of COD by complexation of the matter suspended by Al (III), and taking into account the “latency” period observed experimentally. The values of the parameters involved are discussed in relation to the suspension treated.     

氯乙酸生产工艺及成本分析

介绍了国内外氯乙酸的主要生产工艺,比较了不同工艺的生产成本及特点。指出我国传统的硫磺法氯乙酸生产工艺要进一步节能降耗、提高产品质量及治理环境,以提高竞争力。     

混凝沉淀法处理含铅矿坑涌水

实验采用常见的聚合氯化铝(PAC)、聚合硫酸铁(PFS)、聚丙烯酰胺(PAM)通过烧杯混凝实验进行除铅, 比较了3种絮凝剂对矿坑涌水中铅的去除效果;进而比较了3种絮凝剂分别组合之后对铅的去除效果, 筛选出既高效又经济的混凝剂组合, 并最终确定混凝剂组合为PFS和PAM。并且考察了投加顺序和pH值对组合混凝剂除铅效果的影响。结果表明:分别在最佳PAC、PFS投药条件下与PAM混用, 对含铅矿坑涌水的处理效果要比单独使用PAC、PFS任何一种絮凝剂效果好, PAM有利于提高PAC、PFS对铅的去除率。PFS与PAM组合除铅最佳工艺条件为:pH值为9.5, PFS投加量200mg/L, PAM投加量1mg/L, 投加顺序为快速搅拌时投加PFS, 慢速搅拌时投加PAM, 混凝反应时间14min, 静沉15min, 含铅矿坑涌水经该工艺处理后, 铅去除率可达99.05%, 出水铅浓度降至0.238mg/L, 达到国家污水综合排放标准(GB8978—1996)。     

Use of native species and biodegradable chelating agents in the phytoremediation of abandoned mining areas

BACKGROUND: The application of phytostabilization and assisted phytoextraction to the remediation of abandoned mining areas can be a valuable method to reclaim these areas without modifying soil and landscape characteristics. An in situ application of a continuous phytoextraction technique was carried out in the area of Campo Pisano (Sardinia, Italy), followed by a laboratory assisted phytoextraction test using the biodegradable chelating agents methylglycine diacetic acid (MGDA) and iminodissuccinic acid (IDSA). The plants used were Scrophularia canina subsp. bicolor, Cistus salviifolius and Teucrium flavum subsp. glaucum. RESULTS: The plant that accumulated more Pb was T. glaucum (353 mg kg^?1) while C. salviifolius demonstrated better ability to accumulate Zn (1560 mg kg^?1). S. bicolor showed a better tolerance to metals but accumulated 119 mg kg^?1 of Pb. Accumulation of metals immediately after chelant application was up to 300 mg kg^?1 of Pb and 3000 mg kg^?1 of Zn which did not further increase during the assisted phytoextraction experiment. CONCLUSION: The plant that demonstrated to be most suitable for phytoremediation application was S. bicolor due to its higher biomass production and tolerance to metals. The low cation exchange capacity and the high concentration of Ca and Mg in soil determined a low chelant effectiveness. Copyright © 2009 Society of Chemical Industry     

微絮凝连续砂滤技术在矿区生活污水回用中的应用

采用微絮凝连续过滤技术深度处理矿区生活污水,当滤料粒径采用0．8～1．0mm,滤床厚度1．2m,滤速6～8m／h,砂循环速率在4mm／min,PAC投加量20mg／L,PAM投加量0.3mg／L时,出水SS小于5mg／L,去除率达到94．7％以上,其它各项指标达到并优于建设部《生活杂用水水质标准》（CJ25．1—89）要求,可以实现中水回用。     

原地钻孔浸铜技术开采难采、选氧化矿之设想

提出采用原地钻孔浸铜技术开采大冶铜山口难采、选氧化铜矿的设想。设计了两种原地钻孔浸铜方案,通过“钻孔布液、钻孔收液”及“钻孔布液、巷道收液”两种溶浸开拓方案的采场投资经济比较,认为前者更有经济优势。根据矿岩地质特征、水文条件及矿石特性分析了IV矿体铜原地钻孔浸出的有利条件和不利因素．认为对其施实原地钻孔浸铜技术具有可行性。     

尼龙废水深度处理中水补充循环水存在问题及对策

河南神马尼龙化工公司是国内最大的尼龙化工产业基地,生产用原水量大,废水排放量多,公司决定对生产废水进行深度处理为中水用于循环水补水。按照中水水质国标的要求,制定中水回用方案。实施表明,中水回用可大幅降低企业生产成本,具有开源节流减少污染的双重功效。     

电石法生产PVC树脂的成本分析与控制

介绍了石河子中发公司采用电石法生产PVC树脂的成本分析及采取的措施：（1）加强电石采购管理,次品电石使用量降至20%以下,使电石单耗降低;（2）氯化氢纯度控制应大于93%;（3）适当扩大生产能力（由8kgt/a增至2.5万t/a）。改进后生产成本由5419元/t下降至3955元/t。     

Treatment of compost leachate by the combination of coagulation and membrane process☆

This study describes the treatment of composting leachate by the combination of coagulation and nanofiltration process.Poly ferric sulfate(PSF) was used as coagulant,and the effect of p H value and PSF dosage on the coagulation performance was investigated.The results indicated that the chemical oxidation demand(COD)and turbidity removal efficiency could reach to 62.8% and 75.3%,respectively at an optimum dosage of1200 mg·L~(-1)at p H 6.0.During the nanofiltration process,the operation conditions such as temperature and pressure were optimized,89.7% of COD,78.2% of TOC,72.5% of TN,83.2% of TP,and 78.6% of NH3-N were retained when tested at 0.6 MPa at 25 °C.The final leachate effluent concentration of COD,BOD5,NH3-N,TOC,SS was92 mg·L~(-1),31 mg·L~(-1),21 mg·L~(-1),73 mg·L~(-1)and 23 mg·L~(-1),respectively,which reached the local discharge standard.The combination of coagulation-filtration is useful for composting leachate treatment.     

MVR+A~2/O+MBR法处理毒死蜱环化废水

以三维丰海公司毒死蜱环化废水的深度处理工程为实例,介绍了该工艺的特点、设计参数、处理效果及运行成本。处理后最终出水水质良好,COD、BOD5、NH3-N、SS的去除率分别高达99.7%、99.7%、99.3%、99.0%,总盐分也由30 000 mg/L降至357 mg/L,出水指标优于国家《污水综合排放标准》(GB 8978—1996)一级标准,可直接回用于循环冷却水的补充用水。     

高陡山区房柱法开采岩体移动分析

在实测资料统计分析基础上,建立了高陡山区房柱法地下开采岩体移动变形预测分析模型,并给出了岩体变形破坏的极限值。通过工程实例分析,理论预计结果与现场实测结果吻合。     

间歇用水系统中废水回用与集中再生处理的调度优化设计方法

针对间歇用水系统建立了废水回用与废水集中再生处理协调运行和调度优化的数学规划设计模型。在多周期运行条件下,以保证循环周期中水系统最优运行为目标,提出了消除不同操作周期下储罐中水量和浓度波动的多周期反算求解策略,并确定了多周期操作下优化的用水网络。通过单杂质间歇用水系统实例阐明了所提出方法的有效性,为具有废水集中再生处理的间歇用水系统从启动到稳定的多周期操作和设计提供依据。     

合流污水处理系统中水回用改建工程的效果分析

介绍了实现中水回用的合流污水深度处理改建过程.结合上海合流污水管理所彭越浦分所内原中水回用设施改造的实际案例,对比了新老工艺并分析了新工艺的实际效果.结果表明污水经改建后的合流污水处理可达到中水回用标准,同时可以满足周边停车场车辆清洗和附近绿化的用水需求.     

Hybrid CV-CC operation of capacitive deionization in comparison with constant current and constant voltage

Capacitive deionization (CDI) is a technique used to desalinate saline water by means of electrical potential applied to the electrode along both sides of a spacer channel through which water flows. CDI operates either at constant voltage (CV) or at constant current (CC) operation to desalinate saline water. The purity of the water is the main requirement at the outlet of the cell. The lowest effluent concentration is achieved within a very short time by operating the CDI cell at CV, but after that the effluent concentration continues to increase. On the other hand, in CC, the lowest concentration is achieved later as compared with CV, but once it is achieved it continues to remain constant until the target voltage is reached. In this paper, we combine both CV and CC operation to get the lowest concentration for maximum time during the adsorption process so that more desalinated water is produced. We compare hybrid CV-CC and constant voltage and constant current in terms of effluent concentration, energy consumption per ion removal, water recovery, and water quality by varying operational parameters like cell potential. It was observed that ultrapure water can be produced with hybrid CV-CC operation by systematically varying different process parameters like flow rate and cell potential to get better results.     

混凝-水解酸化/接触氧化-臭氧曝气生物滤池处理制革废水

采用混凝沉淀-水解酸化/接触氧化-臭氧曝气生物滤池工艺处理某制革厂废水,给出了工艺流程,并对处理前后的水质指标进行了分析。结果表明,最终出水COD、氨氮分别可以稳定在50 mg/L和7 mg/L以下,达到了回用标准,约67%的最终出水得到回用,减少了95.56%的COD和97.78%的氨氮排放量。在不考虑人工费及折旧的情况下,运行成本约为3.41元/t。