Treatment of tannery wastewater by chemical coagulation

The objective of this study was to develop a treatment system that can effectively reduce the concentration of pollutants in tannery wastewater to environmentally acceptable levels and that can greatly reduce the cost of discharging the effluents. Aluminium sulphate and ferric chloride were used as a coagulant in the process. The influence of pH and coagulant dosages on the coagulation process was studied and conditions were optimised corresponding to the best removal of organic matters, suspended solids as well as chromium. The COD and chromium were removed mainly through coagulation: 38-46% removal of suspended solids, 30-37% removal of total COD from settled tannery wastewaters and 74-99% removal of chromium at an initial concentration of 12 mg/l can be achieved by using the optimum coagulant dosage (800 mg/l) in the optimum pH range (around 7.5). Ferric chloride produced better results than aluminium sulphate. The initial chromium concentrations and pH values of the wastewater had a great effect on chromium removal efficiency. Low chromium concentrations and high pH produced a more effective result on chromium removal than high chromium concentrations and low pH. Higher dosages did not significantly increase pollutant removal and were not economical. Coagulation combined with centrifugation improved the removal efficiency of suspended solids (70%). A high degree of clarification is attained as indicated by an excess of 85-86% colour removal. The results provide useful information for tannery wastewater treatment.     

Membrane application for recovery and reuse of water from treated tannery wastewater

Secondary treated tannery wastewater contains high concentrations of Total Dissolved Solids (TDS) and other residual organic impurities, which cannot be removed by conventional treatment method. A pilot plant membrane system with a designed processing capacity of 1 m³/h, comprising of nano and reverse osmosis (RO) membrane units, accompanied by several pre-treatment operations, was evaluated in order to further treat and reuse the tannery wastewater. The maximum TD S removal efficiency of the polyamide RO membrane was more than 98%. The permeate recovery of about 78% was achieved. The water recovered from the membrane system, which had very low TDS concentration, was reused for wet finishing process in the tanneries. The reject concentrate obtained from the operation was sent to solar evaporation pans. It was evident from the study that the membrane system can successfully be applied for recovery of water from secondary treated tannery effluent, provided a suitable and effective pretreatment system prior to membrane system is employed. Combining nano and RO membranes improved the life of the membranes and permeate recovery rate.     

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。     

Electrochemical pre-treatment of effluents containing chlorinated compounds using an adsorbent

Electrochemical pre-treatment of industrial wastewater to remove refractory and/or toxic organic components, making them more amenable to biological treatment, is likely to be more cost-effective than using a physical or chemical process for complete organic removal. This paper demonstrates the use of a carbon-based adsorbent material that preferentially removes chlorinated organic compounds. Electrochemical regeneration of the adsorbent is shown to be a quick, easy and cheap process, because the adsorbent is both highly electrically conducting and non-porous. High regeneration rates over a number of cycles were obtained by passing a charge of 25 C g⁻¹ through a bed of adsorbent particles, at a current density of 20 mA cm⁻² for 10 min. The energy required to remove a kg of COD from an industrial wastewater was calculated to be 27 kWh.     

Effect of chloride concentration on the electrochemical treatment of a synthetic tannery wastewater

The electrochemical treatment of a synthetic tannery wastewater prepared with 30 compounds used in animal skin processing was studied. Electrolyses were performed in a one-compartment flow cell at a current density of 20 mA cm⁻², using a dimensionally stable anode (DSA^®) of composition Ti/Ir_0.10Sn_0.90O₂ as the working electrode. Effects of chloride concentration and presence of sulfate were evaluated. Variation in the concentration of phenolic compounds as a function of electrolysis time revealed a first-order exponential decay; faster phenol removals were obtained with increasing chloride concentration in the wastewater. Lower phenol removals were obtained in the presence of sulfate. Higher chloride concentrations led to a faster decrease in total organic carbon (TOC), chemical oxygen demand (COD), and absorbance values at 228 nm. Faster wastewater color removal, higher current efficiency and lower energy consumption were also obtained. This electrochemical treatment was also able to reduce the wastewater toxicity for Daphnia similis.     

物化-好氧生物法处理制革废水

采用物化-好氧生物法处理制革废水,取得了较好的效果,对COD、S^2-、SS的去除率分别达到了93．6％、94．8％和96．3％。运行结果表明,该工艺具有工艺设计简单、运行稳定、出水水质好等优点。     

焦化废水深度处理技术综述

焦化废水是煤焦化过程产生的废水,含有高浓度的酚类、苯系物、杂环化合物、多环化合物等有机污染物,并且高盐、高氨氮,是一类难处理的工业废水。随着国家对焦化废水的管理日趋严格,传统的"预处理+生化处理"工艺很难满足排放或回用要求,因此对焦化废水的深度处理势在必行。从物化法和生化法两个方面对目前焦化废水深度处理常用技术的研究和应用情况进行了介绍,并探索性地提出了焦化废水深度处理技术未来的研究和发展方向。     

Catalytic Oxidation of Industrial Wastewater Under Mild Conditions

Cerium?Czirconia-supported ruthenium and activated carbon catalysts were used in catalytic wet air (CWAO) and wet peroxide (CWPO) oxidation of industrial wastewater. Both catalysts were active in the removal of TOC and COD from the wastewater. The degree of biodegradation of organic matter increased during CWAO. Therefore, the CWAO process could be considered as a potential pre-treatment process integrated with subsequent biological treatment to achieve the required level of purification of wastewater.     

Effect of stream segregation on ozonation for the removal of significant COD fractions from textile wastewater

Ozonation was tested on selected streams of cotton finishing textile plant wastewater for optimizing chemical oxygen demand (COD) removal. For this purpose, significant COD fractions in the wastewater were experimentally identified and the effect of ozone on these fractions was investigated. Ozonation experiments were performed with a 1 dm³ sample volume. Ozone treatment of batches of raw wastewater provided, at a rate of 62 mg min^?1 and a gas feeding time of 15 min, achieved complete colour removal but only 21% COD reduction. Increasing the feeding time to 30 min slightly increased the COD removal to 32%. At this feeding time, removal of the readily biodegradable COD was 60%, but soluble inert COD reduction remained at 16%, indicating selective preference of ozone for simpler compounds. At low concentrations, ozone was mainly influential on soluble COD compounds. Longer feeding times also affected particulate compounds, resulting in the solubilization of the COD fractions. Pre‐ozonation of the dye‐house wastewater, as a segregated stream, proved much more effective in the breakdown of refractory organic compounds, rendering the overall plant effluent more amenable to biological treatment. © 2002 Society of Chemical Industry     

某生产甲基磺草酮农药厂废水处理工程实例

针对生产甲基磺草酮过程中会产生多股高浓度难降解有机废水的情况,通过1套先深度预处理,提高可生化性,后续生化处理的工艺来解决该问题。工程设计规模200 m3/d,经该套工艺处理后,出水水质:p H为6~9、色度为30、COD≤100 mg/L、CN-小于0.5 mg/L。废水经处理后达《污水综合排放标准》(GB 8978—1996)表4中一级标准。     

MBR处理电镀前处理废水COD的工程设计

基于电镀前处理废水的性质,选用膜生物反应器(MBR)工艺对处理废水中COD进行了工程设计。对于MBR系统,从系统的角度综合整合了预处理和MBR工艺,并进行整体优化设计。工程运行实践表明该工艺处理电镀前处理废水是可行的,膜组件清洗周期较长,运行费用较低。当进水COD浓度为1000~1500 mg/L时,系统对COD的去除率超过95%,出水COD浓度保持在50 mg/L以下,达到排放标准。     

Fenton oxidation and sequencing batch reactor (SBR) treatments of high-strength semiconductor wastewater

Treatment of a high-strength semiconductor wastewater was experimentally investigated in this study. The wastewater is characterized by a strong dark color, high chemical oxygen demand (COD) concentration, presence of refractory volatile organic compound and low biodegradability. Treatment of this wastewater by traditional activated sludge method is essentially impossible. In the present work, combined physical, chemical and biological methods were synergistically utilized to tackle the wastewater. The combined treatment consisted of air stripping, modified Fenton oxidation and sequencing batch reactor (SBR) method. Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of the combined method. Test results clearly demonstrated the synergistic advantages of the combined treatments. The treatment train was capable of lowering the wastewater COD concentration from as high as 80,000 mg/l to below 100 mg/l and completely eliminating the wastewater color. The overall water quality of the final effluent exceeded the direct discharge standard and better yet, this effluent can even be considered for reuse.     

精细化工废水的污染特性分析及其控制策略

针对精细化工废水处理难以稳定达标的现状,采用国家标准方法、离子色谱、ICP/MS、GC/MS等分析手段研究了浙江省某工业园区精细化工废水的COD、BOD、氨氮、色度等常规指标及主要阴阳离子和有机物组成,从化学与生物水平揭示了精细化工废水的污染特性,并提出了针对精细化工废水污染过程的控制策略。研究结果表明,精细化工废水是一种典型的有毒/难降解工业有机废水,呈现高COD、高氨氮及高色度等特征;精细化工废水中对微生物构成危害的主要成分有COD、氨氮、部分重金属离子、染料及其分解物等,重点是有机污染物;精细化工废水中的有机成分大多属于有毒/难降解有机污染物,对生物系统存在严重的抑制作用,是造成出水不达标的主要原因。因此,对精细化工废水的处理,应着重对有毒/难降解有机物进行优先控制,并综合考虑高效的处理工艺、合理的水质结构及有效的政策性策略。     

Study of Pre-Treatment of Oil Refinery Wastewater by EEF-Enhanced Micro-Electrolysis

Oil refinery wastewater is rich in organic pollutants and cannot be treated easily. This study involves the pre-treatment of oil refinery wastewater by external electric field (EEF)-enhanced micro-electrolysis technology. The anode was titanium net plated with ruthenium, the cathode was barbed wire, and the Fe/C/Al micro-electrolysis filler as particle electrode. The optimum conditions for EEF-enhanced micro-electrolysis were determined to be as initial pH of 3.0, 10 V EEF voltage, and 0.06 mol/L electrolyte concentrations by studying the influence of different experimental parameters. It was also found that EEF-enhanced micro-electrolysis had a higher efficiency than the traditional micro-electrolysis in the degradation of the organic pollutants present in the oil refinery wastewater. Continuous running results showed the removal rate of COD (chemical oxygen demand), ammonia nitrogen and oil of the effluent was stable, and the average value of the effluent B/C (biochemical oxygen demand/chemical oxygen demand) ratio was 0.454 ± 0.013. The values of EC (energy consumption) and ICE (instantaneous current efficiency) were 9.8 kWh/Kg COD and 340.5%, respectively, when the reaction time was 60 min in oil refinery wastewater pre-treatment by EEF-enhanced micro-electrolysis technology. GC/MS was used to analyze the organic compounds present in the wastewater before and after treatment. UV-visible absorption spectroscopy was used to analyze the degradation process of the organic compounds present in the oil refinery wastewater. The results of these analyses confirmed the technical feasibility of EEF-enhanced micro-electrolysis in the pre-treatment of the oil refining wastewater. Finally, the main mechanism involved in the treatment of refinery wastewater by EEF-enhanced micro-electrolysis technology has been discussed.     

Fluidized bed magnetic ion exchange (MIEX®) as pre-treatment process for a submerged membrane reactor in wastewater treatment and reuse

Magnetic ion exchange (MIEX®) resin can effectively remove significant amounts of organic matter from biologically treated sewage effluent. The MIEX® process has mainly been used as a batch process, which requires a large area for accommodating both contact tank and settling tank in the treatment process. In this study, a fluidized bed MIEX® reactor (a semi-continuous process) was used as a pre-treatment for a submerged membrane. When used as a pre-treatment for a submerged membrane, the fluidized bed MIEX® contactor could remove a significant amount of organic matter in the wastewater (80% removal). This pre-treatment helped to reduce membrane fouling and keep transmembrane pressure low during the membrane operation of 8 h (less than 19 kPa). The regeneration of MIEX® resin (number of regeneration, regeneration time, etc.) did not have any adverse effect on the organic removal by MIEX®.     

The possibility and applicability of coagulation-MBR hybrid system in reclamation of dairy wastewater

The significant improvements of membrane technology in reliability and cost effectiveness have increased the reuse probability and recycling extent of dairy wastewater. However, membrane fouling still remains a major bottleneck in wide application. In order to solve the problem, this paper investigated the possibility and applicability of coagulation-membrane bioreactor (MBR) hybrid system in reclaiming dairy wastewater. A comparative experiment based on the removal efficiencies and the membrane performance was designed to achieve the purpose. The results showed that polyaluminium chloride as the appropriate coagulant in coagulation process was effective for turbidity removal. Coagulation process played a very important role in stabilizing the effluent of MBR and the level of transmembrane pressure. MBR was a crucial process in turbidity and aluminum removal. MBR had the capability to resist shock loading and to maintain the high COD removal. Biological flocs in MBR could improve the fouling level of membrane. The hybrid system reduced 98% COD from the original and COD value of the wastewater came down to 8 mg/L. The combination of coagulation with MBR presents the possibility and applicability to reclaim effluent in dairy industries.     

利用生化处理和膜分离技术处理回用化工废水的设计

化工生产废水具有污染程度高、pH变化大、可生化性较差、并且含盐量较高的特点,为了实现废水回用的目的,采用物化预处理、水解酸化 接触氧化 超滤 反渗透相结合的处理工艺.出水回用于循环冷却水补充水,同时达到了节水治污的目标.本技术推动了膜分离技术在化工废水回用中的应用.     

加药气浮-厌氧水解-悬浮生物滤池工艺处理纺织印染助剂生产废水

纺织印染助剂生产废水表面活性剂及乳化剂、氨氮、有机胺和有机物的含量较高,难降解物质多,水质水量波动大。采用调节池-加药气浮池-厌氧水解池-悬浮生物滤池(内分脱碳区、亚硝化区和硝化区)-沉淀池的组合工艺,在进水COD平均为4 284 mg/L,水解酸化后NH3-N质量浓度平均为184 mg/L的情况下,出水COD平均为273 mg/L,去除率达到93.6%,出水NH3-N质量浓度平均为9.6 mg/L,去除率达到94.8%,达到入管排放标准。     

聚硅氯化铝铁絮凝剂的制备及应用研究

以工业固废赤泥、粉煤灰以及盐酸等为原料,采用酸浸的工艺制备聚硅氯化铝铁絮凝剂。初步研究了该絮凝剂的生产工艺条件及产品对皮革废水的絮凝效果。实验结果表明：制备聚硅氯化铝铁絮凝剂的最佳工艺条件为粉煤灰和赤泥的质量比为1∶2,焙烧温度为850 ℃,液固体积质量比为5 mL/g,在此条件下原料中铁的最大浸出率为73.9%。絮凝剂对皮革废水的最佳投放量为250 mg/L,产品对皮革废水COD、SS的去除率可高达73.91%、97.86%,处理过的水透光度高。     

LTBR生物处理工艺处理甲乙酮废水的中试

在高浓度甲乙酮废水的生物处理试验过程中,采用LTBR生物处理工艺,使用特效微生物和营养基质,可以在高COD的不利条件下正常进行有机物降解,探索出了使用生物方法处理甲乙酮废水的合理工艺,为处理甲乙酮废水的工程应用开辟了新思路。