Treatment of tannery wastewater through the combination of a conventional activated sludge process and reverse osmosis with a plane membrane

Tannery wastewater contains high concentrations of organic matter (COD) with a significant percentage of refractory organic compounds, ammonium substances, salts (i.e. chloride and sulphate) as well as sulphur. Contaminants have to be removed in order to avoid significant environmental impacts. This paper presents the results obtained from a pilot scale study developed in the tannery district of Solofra in Southern Italy. It was aimed at evaluating the reuse of wastewater produced in the retanning process. The treatment process consisted of a biological treatment, as a pre-treatment, followed by a physico-chemical process (with a polymer as a coagulant) and reverse osmosis with a plane membrane. The biological pre-treatment was able to remove approx. 67% of COD, while the membrane system completed the purification process with the removal of the refractory organic compounds (chloride and sulphate). In the test carried out, the combination of a biological pre-treatment with a plane membrane system showed satisfactory results in terms of wastewater recovery and reuse in the tannery production cycle.     

Performances of RO and NF processes for wastewater reuse: Tertiary treatment after a conventional activated sludge or a membrane bioreactor

Wastewater reclamation requires processes and technologies having the ability to reduce the presence of micropollutants which are not wholly treated in conventional WWTP. Due to the complexity of membrane-solute interactions and the diversity of secondary treatment effluent (STE) matrices, deeper investigations are required to identify the major foulant species and more specifically their behaviour at high concentration in real waters. This study investigates the rejection and fouling potential of nanofiltration (NF) and low-pressure reverse osmosis (RO) membranes with two STEs sampled from i) a conventional activated sludge process coupled with ultrafiltration (CAS-UF) and from ii) a membrane bioreactor MBR (AquaRM^®, SAUR (France)). Whatever the origin of the effluent, RO seems to be the best solution to prevent pollution of tertiary effluents (expected result) but also to obtain low fouling levels. The different composition and molecular weight distribution of MBR and CAS-UF effluents can explain the different fouling behaviours that were observed.     

印染废水处理与回用技术应用研究

采用气浮、膜生物反应器(MBR)与反渗透(RO)组合工艺,对某印染企业生产废水进行深度处理和回用。通过气浮、MBR去除有机污染物,利用RO系统去除剩余的有机物和盐分。实际运行结果表明,RO淡水水质可满足企业生产工艺用水要求,RO浓水水质达到了《污水综合排放标准》(GB 8978—1996)的三级标准。     

电镀废水处理及回用工程实例

采用混凝沉淀+水解酸化+膜生物反应器(MBR)+过滤+反渗透(RO)组合工艺,对某电镀企业生产废水进行深度处理和回用。首先通过混凝沉淀、生化和过滤去除重金属、有机物和悬浮物,然后利用RO系统去除剩余的有机物和盐分。实际运行结果表明,RO淡水水质可满足企业生产工艺用水水质要求,RO浓水水质达到了《电镀污染物排放标准》(GB 21900—2008)表2中的新建企业水污染物排放限值。     

污水回用中双膜法的保护运行

双膜法在污水回用工程中使用时,常由于各种原因造成膜元件的污堵,使其性能衰减,使用寿命降低.需要针对不同的工况条件及污染形式,采取正确的措施,才能使系统安全平稳地顺利运行.     

炼油厂污水回用于循环冷却水系统的工业试验研究

为了保证污水回用后循环冷却水水质可控,防止换热设备的腐蚀、结垢趋势加剧,选择合理的污水回用工艺技术,重新筛选水稳剂配方.工业放大试验表明,外排污水适度处理回用能够达到节水减排和循环冷却水场水质达标的目的.     

膜分离技术在造纸工业废水回用中的应用

造纸工业是我国水资源消耗大户,造纸废水水量大、有机物含量高、造成的环境污染影响大,对造纸废水治理在全世界范围内都在关注废水回用,提高水循环利用率,减少水资源消耗和废水排放污染。膜分离技术是在一定压力下进行混合液分离的技术,近年来膜分离技术快速发展,在海水淡化、化工、食晶、医药、电子等工业废水处理中应用较多,本文对膜分离技术在国内外造纸工业废水回用中的应用研究进行了介绍,并对膜分离技术在造纸工业废水回用的研究方向进行了论述。     

Nanofiltration of textile wastewater for water reuse

The textile industry produces a large amount of wastewater that is highly coloured with high loading of inorganic salt. Crossflow nanofiltration using thin film composite polysulfone membrane was used to recover the electrolyte solution and reject the colour. Using a synthetic textile effluent of reactive dye and NaCl solution, the study focused on the mechanism controlling flux and rejection by varying four main parameter; crossflow velocity, initial dye concentration, feed pressure, and electrolyte concentration. Results show that flux was dominated by the osmotic pressure created from the presence of NaCl, and that dye concentration did not significantly effect the flux or rejection. Working at low pressures of up to 500 kPa, relatively high fluxes were obtained, with an average dye rejection of 98% and NaCl rejections of less than 14%. Thus, a high quality of reuse water could be recovered. Even after a number of cycles, the membrane did not foul irreversibly, with an overall mean waterflux recovery of 99%.     

稠油废水回用热采锅炉供水工艺与工程实践

总结了稠油废水的来源和特性,针对稠油废水出路,阐述稠油废水回用热采锅炉供水的意义.评介稠油废水进出水水质、工艺流程、回用工艺认识,阐述缓冲调节、混凝沉降、溶气浮选、吸附除硅、粗精过滤、弱酸软化、污泥脱水等各单元处理工艺的应用现状、工艺特点、选择经验、发展趋势,并简述工程实践概况.提出存在的主要技术难题和解决对策,为回用工艺的进一步发展完善提供借鉴.     

Viability study of different reverse osmosis membranes for application in the tertiary treatment of wastes from the tanning industry

The tanning industry uses large quantities of water and produces a correspondingly large amount of wastewater with high levels of salts and organic materials. Before these wastewaters can be eliminated, they must be submitted to a suitable depuration treatment. However, conventional treatments such as those used for urban wastewater are not able to reduce the salt content sufficiently and new methods need to be studied in the light of new technologies. In this aspect, membrane technology is increasingly used as a separation technique in chemical and environmental engineering, including desalination, selective separation and wastewater treatment. In this paper, we describe a comparative study of six different reverse osmosis membranes, which were tested for their ability to reduce the salt content in the tertiary treatment after the elimination of chromium salts and organic matter of an effluent from a pilot plant for treating industrial wastewater from the tanning industry to reach the legal levels established for their safe disposal. The membranes were checked using a 3×10⁻³ m² flat cell, where the concentrated streams were recirculated to the feed reservoir.     

Sand filtration of wastewater for tertiary treatment and water reuse

The performance of rapid sand filters was evaluated in three tertiary wastewater treatment plants in the State of Kuwait. These plants are located at Ardiya, Rikka and Jahra, and receive municipal wastewater flows of 220,000, 95,000 and 42,000 m³ d⁻¹, respectively. The Ardiya plant uses a two-stage activated sludge process for the secondary treatment of wastewater whereas both the Rikka and Jahra plants use the extended aeration process. Daily records were obtained from each plant over a period of 1 year, and the efficiency of the tertiary sand filters was determined based on reductions in SS, VSS, BOD, and COD. Analysis of these records showed that the secondary-treated effluent quality is highly variable. Seasonal variations were observed due to nitrification and denitrification that enhance the production of nitrogen gas and carry over of sludge solids in the effluent during summer, causing more frequent backwashing of the filters. The data were also statistically analyzed using the ANOVA program. The results obtained indicated significant improvements, at 95% and 99% significance levels, in solids (SS, VSS) and organics (BOD, COD) removal by sand filtration. They also showed that, in addition to improving effluent quality, the tertiary filtration played an important role in the stability of effluent quality so as to dampen variations in the quality of secondary-treated effluent. The tertiary effluent consistently satisfied the water quality requirements for irrigation.     

印染废水回用水处理复合药剂的开发与应用

针对印染废水回用率低、回用水水质要求高等特点,采用活性炭、聚合硫酸铁(PFS)、聚合氯化铝(PAC)、膨润土等药剂对印染废水生化出水进行处理,考察单一药剂成分对废水处理效果的影响。结果表明,单一PAC、PFS难以同时有效去除印染废水中的CODCr和色度,活性炭的处理效果较好,但成本较高。基于各药剂成本、处理效果等多种因素,开发了针对漂洗回用水水质标准的复合药剂1和针对染色用水水质标准的复合药剂2。复合药剂1中m(活性炭)∶m(PAC)∶m(PFS)∶m(膨润土)=5∶60∶5∶30;复合药剂2中m(活性炭)∶m(PAC)∶m(PFS)∶m(膨润土)=45∶30∶5∶20。研究结果表明,复合药剂1和复合药剂2处理1#水样的最佳投加量均为500 mg/L,最佳初始p H值分别为6和7,反应时间均为30 min;处理2#水样的最佳投加量分别为400和500 mg/L,初始p H值为6和6~7,反应时间分别为45~60和60 min。2种印染废水经复合药剂处理后水质均能达到相关出水水质的要求。     

炼油污水回用技术的开发与工业应用

在对炼油碱渣分质处理至达标排放的基础上,对其它达标外排污水采用以高效生物处理为核心工艺的炼油污水回用技术进行适度处理回用。结果表明,主要污染物COD、石油类、氨氮去除率可以达到65.5%、80.7%、96.0%,出水达到中国石化循环冷却水补充水标准;2010年回用水量254万吨,比装置投用前提高82.7%,加工吨原油消耗新鲜水量0.478 t/t。     

污水深度回用装置反渗透膜的污染及化学清洗

结合水处理中常见的污染物种类,介绍了污水深度回用装置的反渗透膜污染情况及合理的化学清洗方案。     

Chemical cleaning of reverse osmosis membranes used for treating wastewater from a rolling mill process

An analysis of fouling material and the effects of chemical cleaning were examined for a reverse osmosis (RO) membrane, which was used for the treatment of wastewater from a rolling mill process in the steel industry. The bulk foulant accumulated in the membrane module consisted mainly of CaSO₄·2H₂O, and the organic contaminants were contained at a very low level. The test pieces obtained from the exhausted RO membrane module (spiral-wound type) were used to examine chemical cleaning with the following solutions: acid and alkaline solutions with EDTA added, 50% methanol, and 10% ethyleneglycol monobutyrate (EGMB). Although a major component of the fouling material was calcium salt, the acid or alkaline solution containing EDTA did not promote the effective recovery of the water flux. On the other hand, cleaning with 50% methanol or 10% EGME solution increased the water flux significantly. The atomic force microscopy images of the membrane surface indicated that relatively large particles accumulated at the surface of the fouled membranes, and the large particles remained even after acid or alkaline cleaning. In the case of EGMB cleaning after alkaline cleaning, large particles did not remain, and uniform and fine particles were observed. The results that calcium salt, a major fouling material, was not removed effectively with the acid and alkaline solution may be due to trace organic materials in the fouling layer that act as a binder for inorganic fouling materials.     

净化污水回用于循环水的技术控制

污水场外排净化污水经过过滤、吸附、杀菌等适度处理可回用作循环水补充水。这一回用技术在中石化济南炼油厂经过几年应用取得了初步成果。通过试验及现场应用,确定了最佳工艺路线,着重介绍了工艺条件的选择、回用水质指标的确定及现场处理效果。     

制革废水治理工艺的研究进展

介绍了制革废水的物化处理和生化处理,总结了其优、缺点并展望制革废水处理技术的发展前景。     

钢铁企业综合废水处理及回用工程

根据某钢厂废水水质特点,选择了高效沉淀池-V型滤池-超滤-反渗透的组合处理工艺,并介绍了该工艺流程及其主要构筑物设计参数。工程运行结果表明,出水水质优于GB 50721—2011《钢铁企业给水排水设计规范》中生产新水水质指标,可节约工业新水消耗量340×104 m3/a,同时减少了对环境的污染。     

Simultaneous removal of chromium and organic pollutants in tannery wastewater by electroprecipitation technique

The simultaneous removal of chromium and other organic pollutants from tannery wastewater was investigated in a batch electrochemical membrane reactor. This reactor, having a total capacity of 1 liter, was separated into two compartments (anodic and cathodic compartments) by using an anionic membrane. A stainless steel sheet with the square holes having total surface area of 0.0215 m² and a Ti/RuO₂ grid was used as the cathode and anode, respectively. The results indicated that the optimum condition for removal of chromium from tannery wastewater was found at the current density of 60.5 A/m² at initial pH of 4.5. At this condition, more than 98% of chromium was removed within 60 min. Some organic pollutants contained in wastewater such as oil and grease, color and the level of biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total kjeldahl nitrogen (TKN) were also markedly reduced.     

Nanofiltration and reverse osmosis of model process waters fromthe dairy industry to produce water for reuse

In dairy plants the process waters generated during the starting, equilibrating, interrupting and rinsing steps contribute to the production of effluents. They correspond to milk products (milk, whey, cream) diluted with water without chemicals. The treatment of these dairy process waters by nanofiltration (NF) or reverse osmosis (RO) operations was proposed to concentrate dairy matter and to produce purified water for reuse in the dairy plant. The study reports one-stage and two-stage (NF + RO and RO + RO) spiral-wound membrane treatments with five model process waters representative of the main composition variations observed in dairies. Performances (permeate flux, milk components rejection, purified water characteristics) of the different operations were compared. Discussion was focused on the comparison between quality of produced waters and vapour condensates (from product drying and evaporation processes) reused in dairy plants. Accordingly, both total organic carbon (TOC) and conductivity of water treated by a single RO or NF + RO operations were convenient for reuse as heating, cooling, cleaning and boiler feed water. With the two-stage RO + RO process, a more purified water complying with the TOC drinking water limit was achieved.