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Tannery Effluent Treatment

Despite all preventive measures, a sizeable portion of pollutants can only be removed by the end-of-pipe methods, i.e. treating effluents discharged in the course of leather processing. One of the most successful areas of interventions implemented or facilitated by UNIDO was designing and managing the construction of cost effective [Common] Effluent Treatment Plants ([C]ETP). More than 250 such plants have been designed, established or upgraded through various technical assistance projects. Achievements and experiences were documented in technical papers, reports and manuals which are available in this section. A special Animated Visual Training Tool was also developed by UNIDO and is available in the section “e-Learning".

Introduction to Treatment of Tannery Effluents

In view of ever increasing legal and social pressures, no tanner can afford to be unfamiliar with the main issues and principles of environmental protection pertaining to tannery operations. Among these, preventing pollution and promoting cleaner leather processing, which ultimately leads to lower treatment costs, clearly remain a priority. Through the application of industrially proven low-waste advanced methods - such as using salt-free preserved raw hides and skins, hair-save liming, low-ammonia or ammonia-free deliming and bating, advanced chrome management system, etcetera - it is possible to decrease the pollution load expressed as COD and BOD5 by more than 30%, sulphides by about 60 to 70 %, ammonia nitrogen by 80%, total (Kjeldahl) nitrogen by 50%, chlorides by 70%, sulphates by 65 % and chromium by 90%. Yet, despite all preventive measures, there is still a considerable amount of pollution load to be dealt with by the end-of-pipe methods. The purpose of this booklet is to help a tanner or a tannery manager (possibly a well-trained leather technologist) to get familiarized with basic principles and methods of treatment of tannery effluents. This knowledge should make him better equipped for communications with the factory’s environmental unit, environmental authorities and NGOs. To keep the manual short and concise, there are many simplifications and omissions of details; for in-depth understanding of the complexities of treatment of effluents and solid wastes (sludge) we recommend you to consult extensive literature on this subject. Finally, and contrary to the widespread misperception that vegetable tanning is environmentally harmless (in reality its effluents have very high, difficult-to-treat COD), the manual basically refers to the combined chrome tanning (i.e. chrome tanning supplemented by vegetable and synthetic tanning agents) because it is by far the most prevailing leather tanning method.

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PDF icon introduction_to_treatment_of_tannery_effluents.pdf

Tannery Effluent Treatment Plants, India

In Chennai and Tamil Nadu/India, which was the basis for demonstration of UNIDO regional projects, circumstances at the time of project (mid 90's) commencement were such that the tanning Industry was under considerable pressure vis-à-vis effluent treatment. As a result several tanneries or clusters had already undertaken investments in primary or secondary effluent treatment. Rather than create a possible redundant model plant, the project strategy was oriented towards demonstration of four full scale model effluent treatment plants representing different aspects of tannery effluent treatment plant in terms of influent, treatment process and size. Thus, the Ranitec CETP with treatment capacity of 4,000 m3/d receiving effluent from 76 tanneries processing from raw to finished and using amongst others an anaerobic treatment system (lagoon) was upgraded to serve as a model for similar treatment plants in the region. The Vishtec CETP with a capacity of 3,400 m3/d of effluent using two stage aerobic treatment system was upgraded (mainly process control) to be a second model site. The President Kid Leather Company ETP, 120 m3/d receiving effluent from semi-finished to finished tanning processes from an isolated was upgraded as a model site (automatic dosing, laboratory). The MHT Company ETP, capacity 100 m3/d, receiving effluent from a traditional isolated vegetable tannery, a low cost anaerobic treatment system, was upgraded and serves as a model for similar units.

Detailed reports describing assisted tannery effluent treatment plants:

i) Common Effluent Treatment Plant, Amburtec, Ambur, India

ii) Common Effluent Treatment Plant, Kolkota, Leather Complex Kolkota, India

iii) Effluent Treatment Plant,  Meera Hussain Tannery, Melvsiharam, India

iv) Common Effluent Treatment Plant, Pallavaram, Chennai, India

v) Common Effluent Treatment Plant, Ranitec, Ranipet, India

vi) Common Effluent Treatment Plant, SIDCO, Ranipet, India

vii) Common Effluent Treatment Plant, VISHTEC, Melvisharam, India

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PDF icon Common Effluent Treatment Plant, Amburtec, Ambur, India
PDF icon Common Effluent Treatment Plant, Kolkota, Leather Complex Kolkota, India
PDF icon Effluent Treatment Plant, Meera Hussain Tannery, Melvsiharam, India
PDF icon Common Effluent Treatment Plant, Pallavaram, Chennai, India
PDF icon Common Effluent Treatment Plant, Ranitec, Ranipet, India
PDF icon Common Effluent Treatment Plant, SIDCO, Ranipet, India
PDF icon Common Effluent Treatment Plant, VISHTEC, Melvisharam, India

Costs of Tannery Waste Treatment

Towards the end of the 20th century the tanning industry has made a considerable progress in controlling the environmental pollution caused by its activities, yet the situation varies from country to country and even from region to region within some large countries. Some tanners in industrialized countries hold the view that lax environmental regulations and poor enforcement account for lower production costs, higher competitiveness and hence further expansion of the tanning industry in developing countries.

This study compares the costs of treatment of tannery effluents, including indicative investments costs in selected industrialized and developing countries. While the figures concerning the investment and operational costs by now are quite obsolete and technologies change, the comparisons of the cost structures are still quite elightening.

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PDF icon Costs of Tannery Waste Treatment, J. Buljan

Benchmarking in the Tanning Industry

This paper attempts to discuss the main, predominantly technical, issues with regard to benchmarking; it is intended to assist those who are willing to admit to the fact that despite all explanations and definitions available, they are not quite sure what it is all about and whether and how it could be applied in the tanning industry. The paper outlines "cock-pit" check lists for ten areas - components: 1. Tannery location, infrastructure 2. Production parameters 3. Cleaner technologies 4. Energy management and consumption 5. Quality assurance, reprocessing, delivery time, failures 6. Product development, strategies 7. Occupational safety and health at work, maintenance 8. Effluent treatment, solid waste, air emissions 9. Financial indicators 10. Human resources and staff welfare, CSR. Some typical production parameters are also provided.

 

 

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PDF icon Benchmarking in the Tanning Industry

Life Cycle Assessment, Carbon Footprint in Leather Processing (Review of methodologies and recommendations for harmonization)

Th report provides an overview of publications, standards and references for the calculation of the Product Carbon Footprint (PCF) of the product Finished Leather together with recommendations for harmonization and the main elements needed to define system boundaries. The inherent complexity and inadequate exactness of carbon footprint analyses contrasts with the need to communicate the results in a simple, clear and unambiguous way. The report was prepared for and presented by Mr. F. Brugnoli  in the 18th  UNIDO Leather Panel in Shanghai/China September/2012

International concern has increased over the years on Climate Change. The ten hottest years on record have all occurred since 1998. Out of the last 21 years 18 are among the 20 warmest years since 1880. Data and findings add weight to the common conclusion that the clear long-term trend is one of global warming. Most of the observed increase in global average temperature since the mid - 20th century is very likely due to the observed rise in anthropogenic greenhouse gas concentrations. Among these, particular attention is paid on CO2 (carbon dioxide). Latest estimates show that global CO2 emissions increased to 30,600 million tonnes in 2010. Industry and manufacturing contribute for 19% of all Greenhouse Gas Emissions. Interest has been developed in estimating the total amount of GHG produced during the various stages in the life cycle of products. The outcome of these calculations, are referred to as Product Carbon Footprints (PCFs). Currently, there is no single methodology and no agreement has been reached internationally on Leather PCF calculation methods.

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PDF icon Life Cycle Assessment, Carbon Footprint in Leather Processing (Review of methodologies and recommendations for harmonization)

Reed Beds for the Treatment of Tannery Effluent

Conventional technologies for treatment of tannery effluent are generally energy & chemical intensive and continuous process monitoring and control are required to achieve optimum results. In search for alternatives, robust, easy to operate and low maintenance technologies, constructed wetland system, also known as root zone treatment system, using reeds for treatment of effluent, has been considered a possible option. This system is widely used in Europe and elsewhere to treat municipal sewerage. However, there was no practical experience, at least at semi-industrial scale, about its applicability in purification of tannery effluents. Accordingly, in cooperation with willing tanneries and management of common effluent treatment plants (CETP)  in Tamilnadu, India, UNIDO, under its Regional Programme, established four pilot and demonstration reed beds, each with different features, to deal with effluent of different characteristics. Practical experience and results are reported in this paper.

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PDF icon Reed Beds for the Treatment of Tannery Effluent

Application of Ultrafiltration in Treatment of Tannery Waste Water

Under the Regional Programme for pollution control in the tanning industry in South-East Asia UNIDO has been actively looking for methods to improve conventional treatment processes which simultaneously reduce the nitrogen content and give the possibility of dealing with TDS/chlorides present in the effluent. The following technologies relating to the issues mentioned were implemented in pilot demonstration units:

  •  Mechanical/manual removal of excess salt from wet salted hides and skins
  • Reverse osmosis (RO) of treated tannery effluent
  • Improved solar evaporation
  • Carbon dioxide (CO2) deliming in a small scale tannery to reduce ammonical nitrogen
  • Constructed wet land treatment system (reed beds) possibly resulting in nitrification/denitrification
  • Ultrafiltration

A study with preliminary estimates of costs of multistage evaporation system to recover salt from reject generated by RO has also been prepared.

In another study, the scope of replacement of secondary clarifier in the biological treatment stage by ultrafiltration has been assessed. (Mladen Bosnic, December, 1997).

This report deals specifically with ultrafiltration.

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PDF icon ultrafiltration_application_in_tannery_waste_water_treatment.pdf

Multiple Stage Evaporation System to Recover Salt from Tannery Effluent

UNIDO through its Regional Programme for Pollution Control in the Tanning Industry in South-East Asia has been actively looking for solutions to tackle saline tannery effluent. The following technologies have been tested at pilot scale demonstration units (PDUs):

  • Mechanical / manual removal of excess salt from wet salted hides and skins
  • Reverse osmosis (RO) of treated tannery effluent
  • Improved (accelerated) solar evaporation
  • Recycling of floats in the beamhouse
  • Use of ultrafiltration in tannery effluent.

This report provides preliminary estimates of costs of setting up a multistage evaporation system for recovery of salt from the concentrate (reject) resulting from the Reverse Osmosis (RO) of treated effluents..

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PDF icon multiple_stage_evaporation_for_salt_recovery_from_effluent_rv_2.pdf

Accelerated Evaporation of Saline Streams in Solar Pans

Total dissolved solids (TDS), specifically chlorides, in effluent are a major concern for its discharge into surface waters and its use for irrigation. Conventional treatment systems do not help reduce TDS in the industrial effluent. Taking advantage of the sunshine available for most part of the year, tanneries in Tamil Nadu, India, were required by the regulatory authority to segregate highly saline effluent (soak and pickle streams)  and evaporate it in solar pans. Due to very dissapointing results of evaporation in solar pans attempts have been made to accelerate the evaporation by simple means like combination of improved warming of the effluent and use of sprinklers. This paper reports on results of these pilot scale tests carried out under UNIDO Regional Programme in India during late 90's.

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PDF icon accelerated_evaporation_of_saline_streams_in_solar_pans.pdf

Prospects and Problems of Establishing an International ECO-label for the Leather and Leather Products Industries

Presented publications documents UNIDO's involvement in promoting Eco-Labelling in the leather industry. Life-cycle assessments or the evaluation of the potential environmental impact of a product system from cradle to grave are fundamental features of some ecolabelling schemes and environmental management systems. Nowadays rhe environmental auditing protocol and reporting mechanism developed and maintained by the Leather Working Group aims to tackle important topical issues, and reflect improvements or changes of technology within the sector.

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PDF icon eco_labelling_in_the_leather_based_industries.pdf
PDF icon prospects_and_problems_of_establishing_an_international_eco-label_for_the_leather_and_leather_products_industries.pdf
PDF icon ecolabelling_in_the_leather_industry.pdf
PDF icon eco_labelling_wf_1995_lju_workshop.pdf
PDF icon Ecolabelling, Environmental Management and Related Activities - April 2001 including all annexes

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