Recouping the wastewater: a way forward for cleaner leather processing

Leather processing employs copious amounts of water. This leads to the generation of enormous amounts of liquid effluent. The high effluent volume requires huge investments for effluent treatment plants in order to meet the required specification for the discharge of liquid effluents to various water bodies. Increasingly therefore, water use minimization in leather processing assumes greater significance due to increased treatment costs. End-of-pipe treatment methods alone do not meet the requirements and hence, in-plant control measures are gaining importance. The new era of cleaner technology has begun in leather processing. Pre-tanning and tanning operations contribute about 57% of the water consumption in leather processing and the washings about 35%. The proper adoption of integrated cleaner technologies provides a viable solution to the conservation of water in leather processing. This paper presents an integrated approach for water use minimization through recycling and optimization in leather processing. The integrated approach provides considerable reduction in the use of process water.     

清洁生产技术在制革工业生产中的应用

分析了我国制革工业的污染现状 ,提出了制革工业推行清洁生产的必要性及实现清洁生产的途径。通过生产性试验研究出羊皮制革工业的清洁生产技术 ,详细分析了羊皮制革工业在生产过程中采用清洁生产技术的污染物削减情况。     

Ecological utilization of leather tannery waste with circular economy model

Circular economy (CE) focuses on resource-productivity and eco-efficiency improvement in a comprehensive way, especially on the industrial structure optimization of new technology development and application, equipment renewal and management renovation. The leather industry on the one side boosts the local economic development, on the other side however leads to the tremendous environment pollution and biological chains destruction. The CE model has been implemented as a new way of raw materials, water and energy consumption reduction in the leather industry. Reduce, Reuse, Recycle and Recover of the tannery effluents have been discussed in detail according to the different operation processes. The successful treatment approaches with analysis in the aspects such as wastewater, solid waste, sulfide, Chemical Oxygen Demand (COD), ammonium salt, chloride and chrome of the leather tannery with CE model provide guidance for the sustainable development of leather industry in the future.     

Cleaner tanning practices for tannery pollution abatement: Role of enzymes in eco-friendly vegetable tanning

Concern about pollution related problems in the global scenario are persuading all the processing industries to adopt cleaner manufacturing practices. Thus, the leather industry is also under pressure to look for effective alternative tanning materials for chromium. Natural products like vegetable tannins are regaining importance. However, there are limitations in the use of vegetable tanning materials because of its high organic load in the effluent, which are difficult to degrade leading to high chemical oxygen demand (COD). Moreover, conventional vegetable tanning process requires partial pickling that involves the use of sodium chloride, to suppress osmotic swelling. This results in very high amount of total dissolved solid (TDS) content in wastewaters. In this investigation, an attempt has been made to design an eco-friendly vegetable tanning process combining pickle-free tanning and application of proteolytic enzymes to improve the exhaustion of vegetable tannins. Such an approach has resulted in more than 95% tannin exhaustion in the case of the experimental process, an increase of 10% compared with the conventional vegetable tanning process. The tanned leathers showed slight improvement in hydrothermal stability. Physical and tactile evaluation of experimental leathers has been better than conventionally tanned leathers. Surface colour values illustrated negligible variation in colour and shade between control and experimental leathers. The resultant leather showed opened up, split compact fibre structure that has been well coated, indicating that the enzyme assisted tanning process did not bring about any major change or destruction on the fibre structure of the leathers. The optimized system has been field tested in a commercial tannery. The results showed that the enzyme assisted tanning process is efficient in terms of improved quality of leather and also led to reduction in total solids (TS), chlorides and COD loads. The enzyme assisted tanning system presented appears to be a viable option for combating pollution arising from the conventional vegetable tanning system.     

An improved product-process for cleaner chrome tanning in leather processing

Severe restrictions imposed by the pollution control authorities on the disposal of chromium, total dissolved solids and chlorides in tannery effluents have forced the tanners to look for low-waste, high exhaust chrome tanning salts. An improved chrome syntan with more than 90% uptake of chrome has been developed. The new product serves both as tanning and retanning agent and can be applied directly to delimed pelts thus eliminating the conventional pickling stage in the leather processing. This modified process helps to reduce the chemical oxygen demand (COD), total dissolved solids (TDS) and chlorides in the spent tan liquor by 51, 81 and 99%, respectively. The product offers full, soft leathers having shrinkage temperature comparable to conventional chrome tanned skins. Since the developed product is highly reactive, it saves time and reduces the water requirement when compared to the conventional chrome tanning method. Thus the novel product/process developed not only has advantages in reducing pollution loads but also seems to be techno-economically viable.     

热电行业利用软件管理实现节能降耗

热电行业是我国经济体系中的能耗大户、污染大户,如何在热电行业中做到节能减排、清洁生产,关系到我国的可持续发展。利用软件技术在热电行业中实施清洁生产的管理,实践中证明能实现节能降耗,为同行业开展清洁生产工作提供了新思路。     

A cleaner production method for the synthesis of bronopol – A bactericide that is useful in leather making

In leather industry environmental concern has been growing since 1980s. Increasing levels of pollutant emissions have reached saturation point in spite of the conventional technology that highly industrial countries have adopted to keep them under control. This has started a technology revolution in several industries. These critical levels of pollution may have been caused by high industrial density, by high population density or by the use of old polluting technology. This situation has boosted emerging green technology which has begun to take up a larger portion of research work in the supply and raw materials in industries. Together with consumers growing awareness of the environment, this new technology has ended up affecting the consumer good industry. In leather industry due to the sector's bad public image regarding pollution more emphasis has been given to clean technologies and waste reduction. At this time nearly every part of the tanning process has several cleaner or environmentally friendlier alternatives. In leather industry to prevent damage to the hide and skin, bactericide is added during soaking process to kill the growth of microorganism. Bronopol is used as a bactericide. The active ingredient of bronopol is 2-bromo-2-nitropropane-1,3-diol. Here we have reported simple and cleaner technology of the bronopol by using nontoxic and non-hazardous raw materials and belongs to the modern concept of environmentally friendly low waste or nonwaste technology. Bronopol was characterized by IR and Mass spectral data.     

Cleaner beam house processes trial on cattle sofa leather

Leather processing has been an important light industry in China, which has contributed a lot to economy. The recent environmental challenges caused tremendous pressure to leather manufacture. The conventional beam house processes employ a wide range of chemicals which result in more than 60% of the total pollution in leather processing (mainly based on COD, BOD, TS, SS, NH₃–N). In this study, cleaner beam house processes were tested on cattle sofa leather to provide a clean environment. A control experiment was run parallel using conventional beam house processes. The results show that the de-hairing is complete through pelt histological microstructure, the extent of opening up of fibre bundles is very good, which is substantiated through chrome distribution analysis, scanning electron microscopic pictures of wet blue leathers and the analysis of contents of total proteins, polysaccharide and hydroxyproline in composite liquor, and the performance of the leathers is shown to be satisfied with the quality standard of sofa leather. The results from composite water analysis show that the cleaner processes enjoy in the reduction of emission water, chemical oxygen demand, total solids and ammonia-nitrogen loads by 46%, 93%, 58% and 54%, respectively, compared to the conventional processes. The total dry sludge from the clean processes is almost eliminated, and the composite cost is decreased by 10%.     

Convenient synthesis of methylene bisthiocyanate as microbiocide

Methylene bisthiocyanate (MBT) is used as a biocide in the leather making industry. Commercial biocidal formulations containing a blend of 10% MBT (Methylene bisthiocyanate) and 10% TCMTB (2-Thiocyanomethylthio)-benzothiazole are available. This blend of active ingredients combine the rapid antimicrobial action of MBT with the fungicidal properties of TCMTB. Such biocides are suitable for use over a wide range of tannery applications including the soaking and pickling stages. This paper reports on a simple and cleaner technology of the synthesis of MBT by using non toxic and non hazardous raw materials and belongs to the modern concept of environmentally friendly low wastes or non wastes technology (LWNWT). From the workers health and safety point of view raw materials such as sodium thiocyanate, water, phase transfer catalyst (Benzyl trithylammonium chloride) and halogenating agent (Bromochloromethane, ethylene bromide, methylene chloride) are used which are non hazardous and non toxic. MBT is characterized by conventional methods, IR ¹HNMR and mass spectral data.     

New findings on the generation of waste and emissions, and a modified cleaner production assessment approach-illustrated by leather production

New findings on the causes of waste and emissions, which were obtained from analysing numerous material streams in various sectors of industry, are presented in this article. It describes the implications of these findings for the vision of clean production, for formulating environmental policy concerning cleaner production targets, for the opportunities to assess to what extent the cleaner production targets have been met, and for the cleaner production assessment. A modified cleaner production assessment approach is presented, and illustrated using leather production as an example. The consequent implications for the diffusion of cleaner production are discussed.     

Recovery and reuse of chromium from chrome tanning waste water aiming towards zero discharge of pollution

The leather industry faces very challenging task because of the regulations enforced by the various pollution control bodies to maintain the discharged norms of the chemical in the treated water. The pollution due to the use of chromium and other chemicals in the leather industry is critically analyzed for the harmful effects. Many studies have been undertaken to optimize the amount of chemicals used in leather processing. The pollution due to chromium is one of the major constraints in the leather processing operation. Chrome recovery and reuse methods have become the compulsory recovery methods in the leather industry to recover and reuse the chromium present in the effluent. Several precipitation methods are emerging but still they are not feasible. In this paper, an attempt has been made to recover the chromium present in spent tan liquor using neutralized wattle extract. The wattle extract at different pH conditions (pH 7, 8, and 9) was used for recovery of chromium. The neutralized wattle extract was made to react with chromium in the spent liquor and allowed to settle for a period of 6 h. Major amount of chromium settles at the bottom leaving minimal amount in the supernatant. The chrome was recovered and reused for tanning the pelt. The wattle extract that was left in the tanning bath was reused for post-tanning process as a retanning agent. Therefore, complete utilization of the chromium and wattle extract has been achieved in this work. It has also been noticed that increased level of chrome exhaustion of 85% and 87% (precipitate and supernatant) in experimental leather could be obtained in comparison with the exhaustion of 74% in control sample. The physical strength and color properties of the experimental leather were comparable to the control leather. The overall results show that the recovered chromium can be well used for tanning purpose to obtain the leather of comparable properties.     

Power ultrasound in fatliquor preparation based on vegetable oil for leather application

In recent years, power ultrasound has taken a significant place in chemical and physical activities of the process industries as an effective and non-polluting method of activation. Oil in water emulsions known as fatliquors are used for the lubrication of tanned leather fibres to get softness and also to improve the strength properties. In the present study, ultrasound has been used as a tool for the preparation of fatliquor emulsion for application in leather fatliquoring process. An emulsion is a fine dispersion of one liquid in another liquid. Sulphation is one of the common methods followed to prepare fatliquor emulsion where sulphuric acid is used. In the conventional process, emulsifying agent is also added to increase the stability of oil in water emulsions. The emulsifying agents generally used are chemicals or metal soaps. The potential use of ultrasound in the preparation of stable oil in water emulsions dispensing with sulphation process and with the minimum use of emulsifying agent has been studied and reported in this paper. This process enjoys the benefit of less pollution load in the form of chemical entities. The studies included the effect of process parameters such as ultrasonic output power and amount of oil used. Fatliquor emulsion prepared using ultrasound has been applied in leather fatliquoring process and the strength properties of the leathers were assessed. Emulsion particle size, which is another important parameter for diffusion through leather, has been measured using Laser Diffraction Technique. The stability of the ultrasonically prepared fatliquor emulsion has been found to be good. The results indicate that ultrasound could be effectively utilized in the preparation of non-ionic fatliquor emulsion eliminating sulphuric acid and impart required properties in leather.     

An approach to cleaner production: from hair burning to hair saving using a lime-free unhairing system

One of the methods to decrease the pollution of tanneries' wastewater is hair saving unhairing of hides. An investigation of proteolytic activity of enzymatic preparation (EP) has shown that some EPs have high stability in strong alkaline solutions and can be used for the hair saving process.Based on this investigation, a new hair saving unhairing method using a system containing EP, sodium hydroxide, sodium sulphide, and disodium hydrophosphate was developed. The method results in a high quality pelt suitable for leather manufacturing, decreases the pollution caused by sodium sulphide and the other products of hair degradation and avoids the pollution caused by calcium compounds.     

火电行业清洁生产水平分析与评价——以M火电企业为例

火电行业在能源消耗中占有重要的地位,如果在火电行业中有效地实施清洁生产,将改变目前采取＂末端治理＂为主的被动污染控制模式。以M电力企业为例,分析了其典型的清洁生产措施,并与火电行业清洁生产主要指标进行对比,评价该企业在火电行业的清洁生产水平,其成功的清洁生产措施可以为行业开展清洁生产工作提供经验。     

凉果行业水污染特征及全过程控制技术

针对我国南方特色的蜜饯制品凉果加工过程中产生的水污染问题,解析其废水来源与特征,系统研究凉果行业节水、废料利用和废水处理的技术路线、途径和工艺。按照“源头节水、中间减污、末端治污”的水污染全过程控制技术路线,从清洁生产角度提出基于“超声波节水清洗+工序水分质回用”的果蔬清洗与果坯脱盐漂洗节水技术;从循环经济角度提出腌渍液经真空浓缩+离子交换脱盐后制成低盐饮料及结晶盐回用,废糖液经过滤+澄清+脱色后再生回用及生产副产品的废料综合利用技术;针对凉果废水含盐量和COD高、水质变幅大等特征,从达标减排角度提出生化处理+脱盐处理组合工艺;并提出推动凉果企业清洁化改造,倡导行业集约化发展的对策建议。     

两种柠檬酸生产工艺的清洁生产评价

以江苏某柠檬酸厂的实际生产为基础,对传统钙盐法和连续色谱法两种柠檬酸生产工艺进行了系统的清洁生产评价。结果表明:色谱法比钙盐法消耗的原材料少,排放的污染物也少。以此为基础,为柠檬酸行业的清洁生产提出了建议。     

油气长输管道施工企业清洁生产研究

清洁生产在油气长输管道施工领域涉及较少,观念和方法还未完全推广。油气长输管道施工企业与传统生产型企业有许多不同之处,以某企业清洁生产审核为例,就如何通过清洁生产审核挖掘清洁生产潜力来做探索性、建议性的研究。实践证明,该企业清洁生产机会的突破口为柴油消耗,通过柴油消耗平衡图的建立和重点耗油设备运行状况的调查,找到了降低柴油消耗的清洁生产方案,使企业达到了“节能、降耗、减污、增效”的目的。     

康洁生产——高技术污染下清洁生产的新视点

清洁生产自80年代末在美国等发达国家提出以后。得到国际社会的普遍响应，成为一种环保潮流，被认为是环境战略由被动反应转向主动行动的一个转折点，当今高技术污染呈现许多新的特点。对清洁生产理念提出挑战。文章从清洁生产的起源和发展出发。通过反思高技术污染对清洁生产的挑战，指出了“清洁生产”需要理论完善，提出了“康洁生产”这一环境战略的新观念。     

A chemo-enzymatic pathway leads towards zero discharge tanning

Leather processing has been an important industrial activity, which has gained significant economic relevance in India. The recent practices of leather manufacture cause difficulties with regard to environmental challenges. The conventional method for making the skins ready for tanning and the tanning by itself employs a wide variety of chemicals which result in an increase in chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, sulfates and chromium in the tannery effluent. In this study, an integrated chemo-enzymatic methodology has been explored which would minimize or to some extent eradicate the unsafe chemicals involved in the process to provide a clean environment. The sequence involves an enzymatic dehairing, NaOH based fibre opening and a pickle-less chrome tanning. The modified process results in decrease in COD and TS (total solids) loads by 67 and 78%, respectively, as compared with control process. The process explored appears to be economically viable.     

印制电路板清洁生产最佳可行技术以及污染减排研究

印制电路板行业属于高能耗及高污染行业,是我国实施清洁生产污染防治的重要领域。通过对印制电路板行业清洁生产污染防治技术现状进行分析,构建了清洁生产污染防治最佳可行技术(BAT)体系框架。对38家完成清洁生产污染防治技术改造的印制电路板企业进行调研,确定了印制电路板业清洁生产污染防治备选技术,利用层次分析法确定各评价指标权重,综合评价印制电路板行业清洁生产污染防治技术。通过评价提出印制电路板行业污染物减排建议。