LIFE project for Tunisian tanneries3 September 2007
Thanks to their previous experience with Spanish leather industries, INESCOP carried out several Initial Environmental Reviews in Tunisian tanneries as a starting point of the environmental analysis. A questionnaire was then prepared to gather information on the most important environmental problems and CNCC technicians visited 17 Tunisian tanneries in order to assist them in filling in the questionnaire.
At the same time the wastewater from ten tanneries was collected and analysed over five consecutive days in order to assess the efficiency of wastewater treatment systems in the tanneries. The most important environmental problems are listed below: 1. Generation of wastewater For the preparation of tanning baths, most tanning operations require the use of water as well as chemicals, which will be absorbed by skins. The characteristics of process effluents depend on their fluctuation, in terms of flow and frequency of discharge. Furthermore, the type and concentration of the polluting load depends on the use of different types of chemicals in the diverse operations. This makes the characterisation and treatment of wastewater difficult. 2. Generation of solid waste The amount of solid waste produced from raw skins depends on the type and process they undergo. However, the processing of 1,000kg of animal skins produces about 450kg of solid waste. 3. Emissions into the atmosphere Atmospheric pollution is caused by extraction of Volatile Organic Compounds through extractor hoods. These compounds are present in organic solvent based chemicals that are frequently used for leather finishing. In addition, boiler combustion gases have to be also considered. OVERVIEW The Tunisian leather industry has been traditionally considered as one of the most important sectors in this country. More than 12% of interviewed tanneries have been operating for more than 45 years. At present, the Tunisian leather and footwear sectors are comprised of 440 industries distributed all over the country, 225 of which are exclusively export companies. In 2000 production amounted to €600 million, rising 6% to €760 million in 2004. Exports during this period rose 7% from €270 million to €360 million. 56% of interviewed companies trade their products in the domestic market. Those companies involved in exports export up to 50% of their production, with Europe being their main destination market. Italy is the most important client (40%), followed by France (38%) and Germany (10%). The dimensions of the interviewed tanneries are quite different, employing from 4-430 workers. Annual production reaches 15,000,000 sq ft. 59% of Tunisian tanneries participating in this survey carry out the whole tanning process. Figure 1 shows the distribution of interviewed tanneries with regard to the type of tanning operations they perform. Another important aspect is the type of skin processed in the tanneries, because the pollution generated will depend highly on this. Figure 2 shows the different types of skins processed in Tunisian tanneries, goatskin, sheepskin and bovine being the most important types. Wastewater Water supply In the interviewed tanneries, water is supplied from the public network and own wells. 65% of tanneries participating in the survey are supplied by both sources, 17.5% of tanneries get their water from the public network and 17.5% from own wells. Some of the interviewed tanneries use 200,000m3/year, the cost of water supply being 0.05/m3. The maximum volume of water flow in a tannery is 1,600m3/day, while average volume is 170m3/day. 82% of interviewed companies claim to carry out some kind of water treatment before leather processing, in order to avoid damage in subsequent equipment. 35% of companies perform filtration, 18% filtration and ionic exchange and 12% only ionic exchange. Wastewater treatment 76% of tanneries have a purification system available, although 18% of them affirm that these systems present problems in their functioning and wastewater is finally discharged without undergoing any previous treatment. From the survey results, it can be concluded that the most common purification systems in Tunisian tanneries may be classified into two main groups: physical-chemical treatment of wastewater (45% of purification systems) and physical-chemical followed by a biological treatment (55%). Figure 3 shows the distribution of the wastewater treatment stages carried out in the different tanneries. Table 1 shows the chemicals that are most frequently used for the physical-chemical treatment of waste water: 73% of tanneries that have a purification system available often carry out analysis on their wastewater. These analyses are performed in external laboratories such as those of the National Leather and Footwear Centre (CNCC), National Sanitation Utility (ONAS) and the Tunis International Centre for Environmental Technologies (CITET), amongst others. In addition, 38% of tanneries perform analysis in their own facilities. The most frequently analysed parameters are: pH, COD, BOD5, chlorides, sulfurs, chromium, nitrogen, colour and suspended solid matter (SSM). The most remarkable features of wastewater after being purified are shown in Figure 4. In 75% of the tanneries that purify their waste water, purified water is muddy and has an unpleasant smell. Surveyed tanneries attribute a cost of about 0.77-0.83€/m3 for the purification of waste water. Purification sludge produced can amount to 20 tons/day (with 25% of dry matter), which implies a management cost of 10.62 €/sludge ton. The main techniques used for dehydrating sludge are drying beds and filter-presses. The final destination of tannery sludge is the dumping site. 55% of tanneries analyse their sludge. Wastewater discharge Finally, after treatment or not the effluents from the diverse tanneries are discharged into the environment, directly into rivers, ravines or the sea, or to the town sewer. 53% of surveyed tanneries pour their wastewater into the town sewer, and the rest into a public waterway. In order to discharge its wastewater, a tannery requires a license. However, 59% of tanneries claim not to have the necessary permission for wastewater discharge. In general terms, the surveyed tanneries do not monitor their wastewater flow. Only two have a meter installed by SONEDE (National Water Distribution Utility of Tunisia) to enable them to conduct a survey. 100% of tanneries confirm that they have been inspected by ONAS (National Sanitation Utility) or ANPE (National Agency of Environment Protection) for the control of their wastewater. The fact that all the surveyed companies have received a tour of inspection is significant and proves that the Administration is trying to monitor the tannery wastewater problem. But the real situation is even more significant: only 6% of surveyed tanneries meet the legal limits as regards wastewater discharge and 75% have been fined as they had no control on their wastewater discharge. In 40% of surveyed tanneries, where chemical analyses were made, wastewater is poured into the public sewer system and 60% a public waterway. Tables 2 and 3 show the values obtained for the chemical parameters analysed in the wastewater. The tables show the degree of compliance with the legal limits. Tannery wastewater was shown to have a significant polluting load. Furthermore, it is worth mentioning that an important variation between the results of the different tanneries can be observed, as well as a considerable variation in values recorded for the same parameter in the same tannery during the five consecutive days of sampling. This variation can be explained by the following considerations: * In spite of the fact that 91% of surveyed tanneries report having a homogenisation tank, such equipment did not exist in ten of the selected tanneries or it existed but its dimensions were not sufficient to suitably carry out homogenisation of effluents, which affects the success of subsequent treatments. * Sampling was carried out randomly. In future, sampling should be carried out integrally, throughout the working day. * Due to the methodology of Tunisian tanneries, the whole tanning process is not carried out every day. This causes the production of wastewater effluents with very different characteristics, hindering subsequent treatment, unless there is a homogenisation tank available with suitable retention time so as to properly carry out the homogenisation of effluents. Furthermore, it is worth mentioning that many limits in the Tunisian legislation are stricter than the corresponding European limits. This makes it even more difficult for the Tunisian tanneries to meet the legislation. For instance, as regards discharge into the sewer system, those parameters that are stricter than the corresponding European parameters are the following: SSM, BOD5, pH, sulfates, chlorides and oils/fats, meanwhile, in terms of the discharge to a public waterway, these stricter parameters are pH, SSM, COD, chlorides, sulfates, sulfurs and oils/fats. Analysis of purification systems In order to assess the performance of the different purification systems currently available in Tunisian tanneries, several parameters were analysed before and after the purification system. Only two out of the ten selected tanneries had a wastewater purification system in use, one based on the physical-chemical treatment and the other based on the physical-chemical treatment followed by a biological treatment. In both companies water samples were taken before and after the treatment for five consecutive days in order to assess the efficiency of the treatment. In the case of the company with the physical-chemical + biological treatment, sampling was carried out after the physical-chemical and after the biological treatments, in order to assess both stages separately. In both tanneries all the tanning operations are carried out on bovine, goat and sheepskins. One tannery discharged wastewater into the sewer system and the other into a public waterway. The results of analysis carried out in the tannery with the physical-chemical treatment are shown in Table 4 (the values that do not exceed the legal limits are shown in bold type). The most important results obtained after the physical-chemical treatment are the following: * Reduction of oils/fats by 90% * Reduction of SSM by 67% * Reduction of COD, BOD5 and nitrites by 50% * Reduction of conductivity, chlorides, sulfates and sulfurs by less than 50% In view of the obtained results, it was verified that the physical-chemical treatment was not enough to reduce the polluting load of the tannery wastewater, so as to meet the established limits for discharge into the sewer system. Table 6 shows the results of the analysis carried out on wastewater from the tannery with the physical-chemical + biological treatment (the values that do not exceed the legal limits are shown in bold type). The most important results obtained through the combination of both treatments are as follows: * Reduction of SSM and nitrites by 90% * Reduction of chromium, sulfurs and ammonium by 70-80% * Reduction of nitrites, COD and BOD5 by 45-60% * Reduction of conductivity by 10% In accordance with the analysis of this tannery, the physical-chemical + biological treatment currently in use in the company is not efficient enough to reduce the polluting load of wastewater below the limits established for discharge into public waterways. Only the pH parameter meets the current legislation. It is worth mentioning that reduction percentages attained for the analysed parameters are better when both treatments are combined, although still to be improved. The above-mentioned results show that despite the reduction of polluting load obtained thanks to the use of the purification systems implemented in the tanneries, these systems are not enough and the situation should be improved. In order to achieve this aim, first of all, tanneries should implement measures for the prevention of pollution during the manufacturing process. These measures are the implementation of cleaner production systems, the detection of possible causes of environmental inefficiency and the assumption that added financial advantages could be achieved by reducing the polluting load. Apart from these preventative measures, the efficiency of end-of-pipe measures should be improved, such as the improvement of the performance of physical-chemical and biological treatments available in the tanneries. For this the two new pilot plants that CNCC has available thanks to the LIFE-EAUCUIR project, could be useful. Other environmental aspects Chemicals consumption Tanneries normally use a large variety of chemicals in all the operations of the manufacturing process. Many of these chemicals may be harmful to the environment as well as the workers' health or the population in general if they are not adequately stored or handled. For this reason it is essential to know which are the products most frequently used by these industries and revise the way they are stored in the tanneries. 59% of surveyed tanneries reported having a store area for chemicals, physically separated from the work area. Although only in 20% of cases is this area duly indicated. In the remaining 41%, chemicals are stored within the work area and they are duly indicated only in 57% of tanneries. As regards the labelling of chemical products in terms of content and hazardousness in order to avoid possible accidents, it is correctly done in 53% of tanneries. Furthermore, only 35% of the tanneries have the safety sheets of the chemicals they use. It addition, it must be noted that these safety sheets are not available to the workers that deal with these chemical products in any of the tanneries that confirm having these safety sheets. Energy consumption Energy saving means an obvious environmental advantage as it involves a reduction in the consumption of non renewable natural resources (such as petroleum and coal). It would also reduce the emission of pollutants into the atmosphere, such as CO2 that is produced through combustion of fossil fuel in thermal stations. Therefore, the improvement and reduction of energy consumption should be an environmental goal for tanneries and it also involves a reduction in financial expenses. Tanneries use different energy sources, such as electricity, gas oil, fuel and natural gas. Annual energy consumption is very different in the diverse tanneries participating in this survey due to the different manufacturing processes and production volume. 30% of tanneries confirm that they use measures to save energy, such as the installation of transparent ceilings in order to save in electric lighting. Waste production The production of solid waste is an important aspect in tanneries due to the volume and financial cost of its annual management. Solid waste production involves different obligations/requirements for the tanneries, such as their correct storage, handling and management. 47% of the interviewed tanneries have storage areas for waste. But only 25% of these tanneries separate non-hazardous from hazardous waste and only 13% of these tanneries have their storage areas set apart for hazardous and non-hazardous waste. In 56% of cases, the storage areas for hazardous waste have, as their main safety measure, a leak-proof floor. The storage period of waste in tanneries depends on the quantity that is being produced by every company and how often it is removed. In fact, in some tanneries, waste is removed every day while in others it is removed on a monthly basis. In 43% of interviewed tanneries, waste finally ends up in an authorised institution for the treatment or elimination of waste. Furthermore, it is worth mentioning that in 71% of tanneries the management of non-hazardous waste consists of dumping at a designated site. Finally, none of the studied tanneries has achieved any special technique in order to reduce the waste, except for the optimisation of raw materials for economic reasons. Emissions into the atmosphere The most important pollutants usually sent into the atmosphere by tanneries are certain volatile substances mainly derived from the use of finishing products during tannage. Noise pollution is also considered here. Emissions into the atmosphere have been measured in only 14% of surveyed tanneries but these tanneries do not report whether or not they meet the limits established by the Tunisian Standard NT 106-004. This highlights the lack of knowledge of the polluting potential of emissions into the atmosphere. Furthermore, 50% of companies participating in the survey reported unpleasant smells could be detected in the area surrounding their facilities. As regards noise emissions, no tannery taking part in the survey reported that environmental noise had been measured in their companies. Other aspects As it has been already mentioned, 100% of tanneries have been inspected as regards wastewater discharge. Furthermore, 50% of tanneries have also been inspected concerning industrial waste. 18% of tanneries have been inspected in order to verify if they have all the necessary permissions and only 6% as regards environmental noise measurement. As a result of the above-mentioned inspections, 82% of tanneries have been fined, 59% of which by ANPE. Otherwise, only in 18% of cases, neighbouring properties have complained due to unpleasant smell and noise. There is a designated person responsible for environmental issues in 65% of tanneries and in 66% of cases they have a University degree. 47% of tanneries confirm that their workers have been trained in environmental issues, mainly as regards wastewater. One of the tools allowing the company to know their environmental situation is the carrying out of an Initial Environmental Review (IER). This review allows the identification of the most significant environmental aspects and impact of processes, activities and products in the tannery. 47% of tanneries have been subjected to an IER. Furthermore, it is worth mentioning that one of the tanneries has implemented an environmental management system. In addition, emergency plans to face possible environmental problems are only available in 12% of tanneries. Conclusions The main conclusions taken from the environmental study of the Tunisian tanning sector are listed below: * Tunisian tanneries are not usually aware of the current environmental legislation and, even less, of the requirements that its application involves * Tanneries perform an inappropriate management of their waste: only 25% separate waste by category (hazardous and non-hazardous) and 13% have differentiated storage areas * Most tanneries do not know if their emissions into the atmosphere meet the established limits * Only 30% of tanneries have implemented an energy saving measure * 59% of tanneries admit not having the required permission for the discharge of their wastewater * Most tanneries are not aware of the flow of their wastewater discharge * 76% of tanneries reported having a purification system for their wastewater. However, after the CNCC visit to the ten tanneries chosen for the study of their wastewater, only two of them had a purification system running * Although 91% of the tanneries reported having a homogenisation tank, the visits made, together with the tests carried out, prove that the current tanks do not allow the appropriate homogenisation of the effluents produced * None of the participating tanneries that discharge wastewater to the sewerage system or public waterways meets the legal discharge limits * All tanneries were inspected for control of their wastewater discharge and 82% of them were sanctioned * All the tanneries are willing to train their workers on environmental issues, with wastewater being a priority issue for training Although there is clearly scope for improvement in most environmental aspects researched, Inescop would like to highlight the concern and interest shown by Tunisian tanneries on environmental issues.