DELISTING OF HAZARDOUS WASTE PRODUCED IN A TANNERY

DELISTING OF HAZARDOUS WASTE PRODUCED IN A TANNERY

by

CAROL HOOGHIEMSTRA

MINI- DISSERTATION

Submitted in partial fulfillment of the requirements for the Degree

MAGISTER SCIENTIAE

in

ENVIRONMENTAL MANAGEMENT

in the

FACULTY OF SCIENCE

at the

UNIVERSITY OF JOHANNESBURG

Supervisor: Dr J Meeuwis

November 2005

Delisting of hazardous waste produced in a tannery

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ABSTRACT Waste generation and waste disposal forms part of our everyday lives, even more so for a tanning facility. This mini dissertation discusses the delisting of waste generated at a tanning facility. This facility produces crust leather from partially tanned hides received from other tanneries in the Mpumalanga province. Crust leather is the product in the penultimate process before it attains its desired leather like properties. The crust leather is sent to a finishing plant for the final process of painting before it is supplied to the automotive industry for upholstery purposes. Large volumes of raw materials including chemicals, water and hides are used in the retanning process to produce crust leather. During the production of this leather various waste streams are generated including effluent, solid waste and tanning sludge. The tanning sludge is classified in terms of the Department of Water Affairs and Forestry’s Minimum Requirements for Handling, Classification and Disposal of Hazardous waste as a possible or potentially hazardous waste. Hazardous waste must be disposed of to a permitted hazardous waste landfill site which has a significant cost implication for the tanning facility. This mini-dissertation focuses on the attempt to delist the tanning sludge. This mini-dissertation highlights the problems associated with hazardous waste disposal in the form of sludge from the tannery. This disposal is expensive because there is only one permitted hazardous waste landfill site in the Gauteng and Mpumalanga provinces. This site is called Holfontein and is situated approximately 200 km from the tanning facility. The high disposal cost encountered is owing to the specialist management required because of the environmental risks involved in operating this waste disposal site. However, an option to delist the hazardous tanning sludge waste is available to the tanning facility, which could mean that the hazard rating is reduced from extremely hazardous to a lower rating or even to general waste. Delisting the tanning sludge will allow it to be disposed of to a general landfill site. Previous attempts to delist the tanning sludge were not successful as the presence of hexavalent chromium (Cr (VI)) and cyanide (CN) in the tanning sludge caused it to remain classified as extremely hazardous waste. Due to the increasing waste disposal cost the tanning facility once again engaged in the processes to delist the tanning sludge. The personnel of the tanning facility is of the opinion that hexavalent chromium (Cr(VI)) and cyanide (CN) should not be present in the tanning sludge as these substances are not used generally in the tanning industry. Therefore, the main aim of this mini-dissertation is to delist the tanning sludge to general waste thus allowing it to be disposed of to a general landfill site, which in turn will result in a reduction in the waste disposal costs.


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In order to achieve the main aim, the study entailed a literature review of the retanning process explaining the generation of the various waste streams, the possible presence of chromium (Cr) and hexavalent chromium (Cr(VI) in the process, and a review of the environmental legislation that will determine the waste disposal options. To delist the tanning sludge the tanning facility followed a defined procedure as determined by the Department of Water Affairs and Forestry. The tanning sludge was assessed using analytical procedures as specified. The objective was to characterise the leachability of the tanning sludge, as well as to verify the presence of any hazardous substances which prevent the tanning sludge from being delisted. Leachability is the potential mobilisation of substances from the sludge under circumstances similar than that of the waste disposal sites. This includes the presence of hexavalent chromium (Cr(VI)) and cyanide (CN) in the tanning sludge. In an approach to verify the presence of hexavalent chromium (Cr(VI)) and cyanide (CN) in the tanning sludge the composition of the raw materials (chemicals and hides) were evaluated and samples were taken from the various effluent streams. The tanning sludge was sampled separately to determine the leachability characteristics. No hexavalent chromium (Cr(VI)) and cyanide (CN) were found to be present in the raw materials or in any of the waste effluent streams. However, small quantities of cyanide (CN) and hexavalent chromium (Cr(VI)) were found to be present in the tanning sludge. The reason for the presence of these constituents could not be determined as it was proved that hexavalent chromium (Cr(VI)) and cyanide (CN) do not enter the process through the raw materials. It was further proved that the process does not support circumstances to oxidise trivalent chromium to hexavalent chromium (Cr(VI)). Further, the presence of cyanide (CN) cannot be explained since it is not a substance that is generally used in the tanning industry. Part of the study included determining treatment options for the tanning sludge. It was found that treating the tanning sludge with lime reduced the concentration of heavy metals such as hexavalent chromium (Cr(VI)). However, after analysis and classification of the tanning sludge it was found that it was not the hexavalent chromium (Cr(VI)) and cyanide (CN) that prevented the tanning sludge from being delisted to a lower hazard rating but rather the presence of small quantities of cadmium (Cd). Cadmium (Cd) is classified as extremely hazardous and therefore it is this substance that is responsible for the high hazard rating classification of the sludge. Although the objective to delist the tanning sludge was not achieved, it was determined that the waste can be disposed of to a general waste landfill site permitted to accept a certain amount of waste containing heavy metals (such as chromium and manganese). The reduction in the waste disposal cost will therefore be achieved and the tanning facility will dispose of their waste in a


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sound and environmentally responsible method ensuring it will not have a significant impact on the environment.


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OPSOMMING Afval bestuur en die weg doen van afval vorm deel van die mens en industrie se alle daagse bestaan. Hierdie mini tesis ondersoek die afval wat tydens ‘n leer looiery genereer word en die verskillende opsies wat beskikbaar is vir die wegdoen daarvan. Die looiery wat bespreek word, produseer ‘n leer produk wat aan ‘n ander maatskappy gelewer word vir die die finale afronding waartydens die leer geverf word. Groot hoeveelhede rou materiale, chemikaliee, water en huide word gebruik vir die produsering van die leer produk vir die motor industrie. Tydens die proses word groot volumes afval geproduseer wat op ‘n veranwoordelike manier weg gedoen moet word. Hierdie afval sluit onder andere in proses water, slik and vaste afval. Die slik wat gegenereer word, is volgens die “Minimum Requirements for Handling, Classification and Disposal of Hazardous waste” as uiters gevaarlik geklassifiseer en hierdie het ‘n koste implikasies vir die looiery. Die afval wat as uiters gevaarlik geklassifiseer word moet op ‘n gevaarlike afval terrain weggedoen word en dit het verskeie koste implikasies vir die looiery. Die kostes wat hiermee gepaard gaan is baie hoër as wat dit sou gewees het, indien dit na ‘n gepermiteerde algemene afval terrein gestuur sou word. Daar is verskeie redes wat aanleiding gee tot die hoër kostes. Die ontwerp en algemene bedryf van ‘n gevaarlike afval stortings terrein sluit in gespesialiseerde risiko bestuur om die omgewings risko’s en impakte te verminder. Verder is hierdie terrreine ook skaars. Die looiery maak gebruik van die enigste terein, Holfontein, wat vir die Gauteng en Mpumalanga provinsies beskikbaar is. Die terrein is omtrent 200 km, in Mpumalanga, van die looiery wat aanleiding gee tot verhoogde vervoer kostes. ‘n Ander opsie behalwe om die slik na hierdie gevaarlike afvalstortings terreine te stuur, is beskikbaar. Dit behels ‘n proses waartydens die klassifikasie van die slik verander word na ‘n minder gevaarlike afval of selfs as algemene afval, wat sal veroorsaak dat dit na ‘n algemene stortings terrain gestuur kan word. Hierdie proses word duidelik uit een gesit in die Department van Waterwese en Bosbou se riglyne vir die weg doen van gevaarlike afval. Die looiery het voorheen deur die proses gegaan om die slik se klassifikasie te verander sodat dit na ‘n algemene stortings terrein gestuur kan word. Dit was egter nie suksesvol nie as gevolg van die teenwoordigheid van klein hoeveelhede heksavalente chroom en sianied. Dus was die proses gestaak en die slik se klassifikasie is nie verander nie. Die toenemende verhoging in kostes om die afval op ‘n verantwoordelike manier weg te doen het aanleiding daartoe gegee dat die proses weer heroorweeg is. Die redes waarom heksavalente chroom (Cr(VI)) en sianied (CN) in die slik teemwoordig is, is nie bekend nie en is in hierdie


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studie ondersoek. Die doel van hierdie studie was dus om die klassifikasie van die slik te verander sodat dit na ‘n algemene stortings terein toe gestuur kan word. Die klassifikanse proses wat deur die Departement van Waterwese en Bosbou (DWAF) uiteengsit word is gevolg. Omdat die sianied and heksavalente chroom die oorsaak was dat die slik se klasifikasie die vorige keer nie verander het nie, is daarop gekonsentreer om die moontlike bronne te identifiseer. Die samestellings van die rou materiale is ondersoek, monsters is geneem van al die afval water in die proses en monsters van die slik wat geproduseer is. Die rou materiale is ondersoek om te bepaal of dit dalk nie die heksavalente chroom en sianied in die proses inbring en sodoende versoorsaak dat dit in die slik teenwoordig is. Die verskillende afval water is ook getoets om te bepaal of die chroom (Cr) en sianied (CN) tydens die proses gemaak kan word, en laaste is die slik se loog potensiaal bepaal. Loog potensiaal is die moontlikheid dat seker metale en ander veranderlikes gemobiliseer kan word in die stortings terrein. ‘n Literatuur studie was ook gedoen om die redes vir die teenwoordigheid van die heksavalente chroom (Cr(VI) en die sianied (CN) te bepaal. Volgens die literatuur studie word heksavalente chroom (Cr(VI) nie in die leer looiery gebruik nie en sianied (CN) is nie ‘n bestandeel wat algemeen gebruik word nie. Analises van die rou materiale en die afval water strome het geen sianied (CN) of heksavalente chroom (Cr(VI) opgelwer nie. Van die slik monsters wat geanaliseer is het weer positief getoets vir klein hoeveelhede heksavalente chroom (Cr(VI)) en sianied (CN). Die redes hiervoor is onbekend omdat die proses wat gevolg is het bewys dat daar geen sianied (CN) of heksavalente chroom (Cr(VI)) in die rou materiale is of dat dit nie deur die prose gemaak word nie. Tyderns die klassifikasie van die slik het dit egter aan die lig gekom dat dit nie die heksavalente chroom (Cr(VI)) of sianied (CN) was wat verhoed het dat klassifikasie nie kon verander het nie. Dit was die teenwoordigheid van cadmium (Cd). Cadmium (Cd) is ‘n uiters gevaarlike veranderlike wat in klein hoeveelhede toksies kan wees vir die omgewing. Dus was die proses om die klassifikasie van die slik te verander nie suksesvol nie as gevolg van die teenwoordigheid van cadmium (Cd). Die proses het wel aan die lig gebring dat die slik na ‘n ander gepermitteerde algemene stortingsterrein weggedoen kan word. Hierdie stortingsterrein is gepermitteer om slik wat klein hoeveelhede swaar metale soos chroom (Cr) en cadmium (Cd) bevat te aanvaar. Dus kan ‘n besparing in die kostes wat aangegaan word om die slik weg te doen geimplimenteer word. Dit word voorgestel dat die metodes wat gebruik word om vir heksavalente chroom (Cr(VI)) en sianied (CN) te toeds ondersoek word asook die moontlikheid van kontaminasie van die slik op een of ander manier.


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ACKNOWLEDGEMENTS I would like to take the time to mention a few people without whose help I would not have completed this dissertation: • To my God and saviour, thank you Lord for giving me the faith, perseverance and patience to

hang in there to complete this dissertation • To my best friend and husband, Herman, thank you for the endless encouragement, patience

and support when everything seemed so dark and the ensurance that the sun will shine again the next day. Thank you for always cheering me up and the endless cups of coffee that you made with so much love and understanding

• To my father Glen, my mother Santjie, my sister Nadine and brother-in-law Hein, thank you

for always being my reality check, the numerous phone calls to encourage me with a vote of confidence and humour. Without your support I would not have done it either.

• To John MacDonnell who made it possible for me to use this study for my mini-dissertation • To Jenny Ward, thank you for the time to proof read each page to ensure that all the gremlins

in the language were addressed • To my friends Cecelia and Christa, thank you for your understanding and support for the past

two years when I was not available to do things with you. Thank you for always being there for a quick cup of coffee and cheering up

• To Dr. Meeuwis, thank you for your time and perseverance especially during the last few

weeks to ensure that I completed this mini-dissertation • To Dr Dave Baldwin, thank you for your encouragement to choose this title for my mini-

dissertation


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TABLE OF CONTENTS

ABSTRACT ....................................................................................................................................I

OPSOMMING ............................................................................................................................. IV

ACKNOWLEDGEMENTS ........................................................................................................VI

TABLE OF CONTENTS .......................................................................................................... VII

LIST OF FIGURES..................................................................................................................... IX

LIST OF TABLES....................................................................................................................... IX

APPENDICES................................................................................................................................X

1. INTRODUCTION .......................................................................................................... 1

1.1 BACKGROUND TO STUDY .......................................................................................................................1

1.2 MAIN AIM...................................................................................................................................................3

1.3 RELEVANCE OF THE STUDY ...................................................................................................................3

2. PROBLEM STATEMENT............................................................................................ 9

3. PRODUCTION OF CRUST LEATHER ................................................................... 11

3.1 THE BEAMHOUSE OPERATIONS ...........................................................................................................11

3.2 THE TANNING PROCESS.........................................................................................................................11

3.3 THE FINISHING PROCESS .......................................................................................................................12

3.4 THE RETAN PROCESS FOLLOWED AT THE TANNING FACILITY .....................................................13

3.4.1 Splitting and shaving ...................................................................................................... 15 3.4. Wetting back ................................................................................................................... 15 3.4.3 Retanning........................................................................................................................ 16 3.4.4 Dyeing............................................................................................................................. 16 3.4.5 Fatliquoring.................................................................................................................... 16 3.4.6. Setting out and drying .................................................................................................... 16

4 WASTE STREAMS PRODUCED DURING THE RETAN PROCESS................. 18

4.1 DEFINITION OF WASTE ..........................................................................................................................18

4.2 DEFINITION OF HAZARDOUS WASTE ..................................................................................................19

4.3 WASTE STREAMS GENERATED IN THE RETAN PROCESS ................................................................20

4.3.1 Atmospheric waste causing air pollution ....................................................................... 22 4.3.2 Liquid waste.................................................................................................................... 22


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4.3.3 Solid waste...................................................................................................................... 24

5. THE PRESENCE OF HEXAVALENT CHROMIUM (CR(VI) AND CYANIDE(CN) IN THE RETAN PROCESS............................................................ 29

5.1 CHROMIUM AND HEXAVALENT CHROMIUM (CR(VI)) ..................................................................29

5.2. CYANIDE (CN)........................................................................................................................................33

6 ENVIRONMENTAL LEGISLATION GOVERNING WASTE MANAGEMENT.. ........................................................................................................................................ 35

6.1 CLASSIFICATION OF WASTE .................................................................................................................39

6.2 REVISION OF THE MINIMUM REQUIREMENTS .................................................................................44

7. DATA COLLECTION AND METHODOLOGY..................................................... 46

7.1 VERIFICATION OF RAW MATERIALS ...................................................................................................48

7.1.1 Reasons for evaluating the raw materials include the following:................................. 48 7.1.2 Analysis of the data ........................................................................................................ 50 7.1.3 Difficulties encountered during this phase..................................................................... 51 7.2 SAMPLING OF EFFLUENT WASTE STREAMS CONNECTED TO THE RETAN PROCESS .................51

7.2.1 Reasons for the sampling of the effluent waste streams connected to the retan process 52 7.2.2 Analysing the data .......................................................................................................... 53 7.2.3 Difficulties encountered during the process................................................................... 53 7.3 ANALYSIS OF THE TANNING SLUDGE.................................................................................................53

7.3.1 Reasons for sampling the tanning sludge....................................................................... 54 7.3.2 The method used for tanning sludge sampling and analysis .......................................... 57 7.3.3 Analysing the tanning sludge results .............................................................................. 60 7.3.4 Difficulties encountered during the analysis of the tanning sludge. .............................. 61

8. DISCUSSION OF RESULTS...................................................................................... 63

8.1 VERIFICATION OF RAW MATERIALS ...................................................................................................63

8.2 RESULTS OBTAINED FROM THE WET WASTE STREAMS INCLUDING THE WETTING BACK, RETAN EFFLUENT AND FINAL DISSOLVED AIR FLOTATION EFFLUENT DISCHARGED.............64

8.3 RESULTS OBTAINED FROM THE TANNING SLUDGE WASTE STREAMS.........................................71

8.4 PRESENCE OF CYANIDE (CN) ..............................................................................................................78

9. CONCLUSIONS........................................................................................................... 81

10. RECOMMENDATIONS ............................................................................................. 83

11. REFERENCES ............................................................................................................. 84

APPENDIX I................................................................................................................................ 88


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APPENDIX II .............................................................................................................................. 91

APPENDIX III............................................................................................................................. 93

LIST OF FIGURES Figure 1: Actual cost for the removal of tanning sludge to a hazardous landfill site ................... 5 Figure 2: Comparison of disposal costs to a hazardous landfill and a general waste landfill ...... 6 Figure 3 Process description of the Retan process..................................................................... 14 Figure 4: Waste streams produced during the Retan process ..................................................... 21 Figure 5: The dissolved air flotation plant that is used for partially treating the Retan effluent 25 Figure 6 : Comparison of the tonne tanning sludge produced vs. the square meters of hides

processed ..................................................................................................................... 26 Figure 7: The filter press was installed to reduce the moisture content of the tanning sludge ... 27 Figure 8: The process of classifying the tanning sludge ............................................................. 40 Figure 9: The manufacturing process described as a system ...................................................... 48 Figure 10: The tanning sludge waste bins into which the dried tanning sludge from the filter press

was disposed of for removal by Wastec ...................................................................... 58 Figure 11: The size of tanning sludge that was sampled from the various bins varied significantly

..................................................................................................................................... 77

LIST OF TABLES Table 1: Comparison of disposal cost to a hazardous landfill and general landfill site. ............. 6 Table 2: Composition of the effluent originating from the retan process before treatment ...... 23 Table 3: Identification of Hazardous waste (DWAF(a), 1998)................................................... 41 Table 4 SABS Code 0228 classify hazardous substances into nine classes ............................. 42 Table 5: Constituents analysed for in the wetting back and retan effluent samples.................. 53 Table 6: Analysis conducted on the first tanning sludge sample to verify the presence of

hexavalent chromium (Cr(VI)).................................................................................... 55 Table 7: Analysis conducted on the second tanning sludge sample .......................................... 56 Table 8 Analysis conducted on the third tanning sludge sample ............................................. 57 Table 9: Information received in response to letters sent to the suppliers regarding restricted

substances in their products......................................................................................... 63 Table 10 Results of the analysis of the Wetting back samples................................................... 65 Table 11: Results of the ad hoc of the Retan samples ................................................................. 67


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Table 12: Results of routine monitoring of the retan and Dissolved Air Flotation effluent results..................................................................................................................................... 69

Table 13: Results of the first tanning sludge sample taken to determine whether there is cyanide (CN) and hexavalent chromium (Cr(VI)) present in the tanning sludge..................... 71

Table 14: Results of the analysis conducted on the tanning sludge samples............................... 74

APPENDICES

Appendix I Black list of restricted and prohibited substances Appendix II Letter to suppliers Appendix III Dangerous goods register


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1. INTRODUCTION

1.1 Background to study

Leather tanning is one of the oldest professions in the world and involves the processing of hides and skins of animals for use in numerous products such as upper leather for shoes, clothing, furniture and automotive leather for upholstery in motor vehicles (Iqbal et al, 1998). Tanneries produce the different types of leather products depending on customer needs. The tanning facility used in this study manufactures crust leather for the automotive industry. Crust leather is the product produced before the leather undergoes the finishing process i.e. painting and embossing the leather to produce finished leather (Anonymous, 2005). Automotive leather is manufactured using a tanning and retanning process. Retanning is a second tanning process to produce crust leather and the actual process used by the tanning facility will be described in Section 3. The processing of hides for automotive leather inevitably leads to the production of waste. During the retanning of hides a number of wastes are generated which include water effluent, general waste and tanning sludge. The production of tanning waste will be discussed in Section 4 of this mini-dissertation. Tanning waste produced during the retanning process is considered hazardous. In terms of the Department of Water Affairs and Forestry’s Minimum Requirements for the Handling, Classification and Disposal of Hazardous Waste (referred to as the Minimum Requirements in the rest of the document), all waste generated in the leather or associated industries is classified as potentially or possibly hazardous (DWAF(a), 1998). Waste is considered hazardous when it has the potential, even in low concentrations, to have a significant adverse effect on the public health and the environment because of its inherent toxicological, chemical and physical characteristics (DWAF(a), 1998). Waste classified as hazardous must be disposed of to a permitted hazardous landfill site in terms of the Minimum Requirements (DWAF(a), 1998). This disposal to a permitted hazardous landfill site has significant cost implications for the company involved in this study, since it produces waste at a rate of approximately 50 tonnes per month. These costs are attributed to disposal cost per tonne of waste disposed and the transportation costs. Hazardous waste landfill sites are limited in the Gauteng and Mpumalanga provinces. The nearest hazardous landfill to the tanning facility is Holfontein, which is close to Delmas, in the Mpumalanga province. Costs to dispose of waste to a hazardous landfill site such as Holfontein is in the order of R 324.12 per tonne of waste with additional transportation costs of R 3960.60 per load of waste removed from the tanning facility. The high costs for disposal is attributed to the specialist management required


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by the site due to the associated environmental risks. Holfontein is also the only hazardous waste landfill site in the Gauteng and Mpumalanga province. Alternatively, instead of disposing the tanning sludge to a hazardous landfill, the tanning sludge could be delisted. This means that the hazard rating of the tanning sludge can be down graded in terms of its classification to a less hazardous waste, and thus disposed of in a general landfill site, permitted to accept such waste. This entails following a well-defined procedure specified in the Minimum Requirements (DWAF(a), 1998). The classification and delisting of waste will be discussed in Section 6 of this mini – dissertation when the legislation pertaining to the disposal of waste will be discussed. If the tanning facility succeeds in delisting the tanning sludge to a lower hazard rating, the tanning sludge could be disposed of to a general landfill site such as Rosslyn. The cost would be R 252.82.00 per m3 and the transportation to the site an additional R 2574.00. Therefore, the disposal to a general landfill site instead of a hazardous waste landfill would amount to a saving of approximately R 1457.98 for each load, depending on the volume (in m3) or the weight (in tonne). The tanning facility in the study under consideration, started with the process to classify and delist the tanning sludge but this was stopped due to the presence of cyanide (CN) and hexavalent chromium (Cr(VI)) in the tanning sludge. The facility’s tanning sludge was analysed by various waste management companies in order to determine the approach for disposal of the waste sludge. In 2002, The Waste Group determined that the tanning sludge at the tanning facility had a high moisture content of 80%, and that this tanning sludge leached hexavalent chromium (Cr(VI)) and other heavy metals, such as manganese and lead when it was subjected to the leachability tests (Waste Group, 2002). The waste produced in the tanning process was then classified as extremely hazardous and therefore had to be disposed of to a hazardous landfill facility. Waste specialists, Golder and Associates (Golder & Associates, 2004), classified the tanning sludge as a Class 6 waste (toxic or infectious substance) due to the presence of small amounts of cyanide (CN) and hexavalent chromium (Cr(VI)). Based on the organic and inorganic constituents found in the waste, it was assigned a Hazard Rating 1 (Extreme Risk), still requiring that it be disposed of to a permitted hazardous landfill site. Notwithstanding the abovementioned attempts to classify and delist the tanning sludge according to the Minimum Requirements (DWAF 1998) the company was still required to dispose of the waste to a permitted hazardous landfill site. On evaluating the results of the waste management companies, the tanning facility decided to re-evaluate the leaching characteristics of the tanning sludge and to determine the origin of the hexavalent chromium (Cr(VI)) reported by The Waste Group (2002) and the cyanide (CN) identified by Golder and Associates (2004). Staff of the tanning facility are of the opinion that these two components (hexavalent chromium (Cr(VI)) and


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cyanide (CN)) should not be generated during the tanning process. Therefore if these were found not to be present, it is likely that the waste could be delisted for disposal to a permitted general waste landfill such as Rosslyn a general landfill site situated north of Pretoria approximately 100 km from the tanning facility. This would considerably reduce the total cost of waste disposal per annum with approximately R 32 000.

1.2 Main aim

The main aim of this study is to delist the tanning sludge, produced during the tanning process, to a lower hazard rating. This is driven by the need to reduce the waste disposal costs. As mentioned previously the waste could not be delisted on two separate occasions due the presence of hexavalent chromium (Cr(VI)) and cyanide (CN). Therefore, should it be proved that these constituents are absent in the tanning sludge this will allow the company to attempt to delist the tanning sludge and dispose of it to a permitted general waste landfill site at Rosslyn. This process of classifying the waste will involve determining the source of hexavalent chromium (Cr(VI)) and cyanide (CN), and whether it is present in the raw materials or produced during the process. Part of achieving the main aim will involve analysing all the incoming raw materials and composition of the various effluent waste streams produced during the process for the presence of hexavalent chromium Cr(VI) and cyanide (CN). The raw materials include the chemicals used in the process and the hides provided by various tanneries. The classification and delisting of the tanning sludge to a lower hazard rating forms the main subject of this mini-dissertation.

1.3 Relevance of the study

Waste generation and the disposal of waste forms part of our everyday lives, even more so for industries such as tanneries. No tannery has the ability to produce or manufacture leather without generating a waste product; it may be minimised to a smaller volume but it will never be totally prevented. In terms of the relevant legislation (discussed in Section 6) waste generated at the tannery is classified as hazardous waste and must be disposed of to a permitted hazardous waste landfill site (DWAF(a), 1998). However, appropriate permitted and designed hazardous landfill sites are becoming increasingly scarce and very expensive to plan, develop, construct and manage due to the environmental risks associated with them, increasing pressure groups and resistance from community groups (Miller, 2004). Therefore the existing sites should be managed optimally to ensure that waste and specifically hazardous waste, be disposed of responsibly. This


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includes the prevention of disposal of non- or less hazardous wastes to the permitted hazardous waste sites. Preventing the disposal of non- or less hazardous waste to the hazardous waste landfill sites will ease the burden on sites such as Holfontein. Holfontein is the only hazardous waste landfill site in the Gauteng and Mpumalanga area where the tanning sludge can be disposed of. It is situated approximately 250 km from the tanning facility. Miller (2004) describes the attempts to manage wastes in ways to reduce environmental harm by burying, burning or shipping it off to another state or country as just transferring the waste from one part of the environment to another. Therefore other sustainable options should be investigated and these include reduction, reusing and recycling of waste. As well as the environmental implications that hazardous waste disposal has on available land, there are major cost implications for industries needing to dispose of waste to permitted hazardous waste landfill sites such as Holfontein (Miller, 2004). In Figure 1, the actual cost incurred by the company to dispose of hazardous waste to Holfontein is shown. Only 11 months of data was readily available for analysis. Figure 1 is used to portray the history of waste disposal at the tanning facility for 11 months. The tonnes of waste removed from the premises depicted in Figure 1 for this period are directly dependant on the production of the product, in this case crust leather. The production of crust leather is directly depended on customer demand. Therefore the variances from month to month are directly dependent on the month to month variance in customer demand. The reason for variance in customer demand has no relevance to this study. Figure 1 indicates variability in terms of cost encountered and waste removed. Month 2 had the highest amount of waste removed and therefore also the highest cost, while month 8 had the lowest figures. The general trend is one of decreasing waste removed but variable cost and this could be attributed to the cost of the additional transportation of waste from the site and will be discussed in detail below. The actual cost incurred takes into account the disposal of the waste to Holfontein, which is R324 per tonne of waste disposed with an additional cost of R3960 for transportation. The bar graph indicates the cost encountered for each specific month for the tonnes removed, while the line graph shows the tonnes of waste removed for the same period. No waste was removed for month 11. This does not imply that no waste was generated for period 11, but that the waste generated did not necessitate removal from the premises. In order to reduce waste disposal costs an arrangement was implemented whereby the waste is only to be removed once three six cubic meter skips have been filled to prevent unnecessary trips to the tanning facility to remove waste containers that were not full. The production of waste during month 11 did not reach 18 cubic meters and was therefore not removed.


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Cost 55499.05 77698.67 55499.05 40898.44 33299.43 22199.62 23792.40 20803.06 31723.20 20803.06 0.00

Tons 64.95 90.75 52.95 40.40 36.35 16.75 37.32 29.04 45.61 29.02 0.00

Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 Month 7 Month 8 Month 9 Month 10 Month 11

Figure 1: Actual cost for the removal of tanning sludge to a hazardous landfill site

Figure 2 and Table 1 compare the disposal cost, for the same volume of waste produced, to a permitted hazardous landfill site (Holfontein) and to a permitted general landfill site (Rosslyn). Rosslyn is a general landfill site which is allowed to accept a certain amount of hazardous waste as long it falls within its permit conditions. Figure 2 shows the difference in costs between disposal to Holfontein and what it could have been if disposed to a permitted general landfill site- for each month. The larger the volume of tanning sludge that needs to be disposed of, the more significant the difference in cost between the two sites as seen for month 2. Table 1 also includes the actual costs encountered by the company. The cost to the landfill site indicated only takes into consideration the tonnes of waste removed and excludes the transportation costs. The cost saving that could be achieved should the general landfill site be used is conservatively calculated at approximately R32 000 (excluding the transportation costs) for the 10 month period portrayed in the graphs. Thus, by delisting the waste to a lower hazard rating the company could save conservatively at least R32 000 per annum.


6

0.00

5000.00

10000.00

15000.00

20000.00

25000.00

30000.00

Was

te re

mov

al c

osts

in S

outh

Afr

ican

Ran

ds

Cost to Holfontein 21051.59 29413.89 17162.15 13094.45 11781.76 5429.01 12096.16 9412.44 14783.11 9405.96 0.00

Cost to Roslyn 16420.66 22943.42 13386.82 10213.93 9190.01 4234.74 9435.24 7341.89 11531.12 7336.84 0.00


Figure 2: Comparison of disposal costs to a hazardous landfill and a general waste landfill

Table 1: Comparison of disposal cost to a hazardous landfill and general landfill site

Period Tonnes of

tanning sludge

removed from site

Actual cost encountered

including transport cost

Disposal cost to hazardous landfill –

Holfontein per tonne

Disposal cost to general landfill -

Rosslyn

Difference between

disposal to hazardous and general landfill

Month 1 64.95 55499.05 21051.59 16420.66 4630.94

Month 2 90.75 77698.67 29413.89 22943.42 6470.48

Month 3 52.95 55499.05 17162.15 13386.82 3775.34

Month 4 40.40 40898.44 13094.45 10213.93 2880.52

Month 5 36.35 33299.43 11781.76 9190.01 2591.76

Month 6 16.75 22199.62 5429.01 4234.74 1194.28

Month 7 37.32 23792.40 12096.16 9435.24 2660.92

Month 8 29.04 20803.06 9412.44 7341.89 2070.55

Month 9 45.61 31723.20 14783.11 11531.12 3251.99

Month 10 29.02 20803.06 9405.96 7336.84 2069.13

Cost Saving 32 000


7

As part of sound environmental management practices the company has implemented an environmental management system. This system is based on international ISO 14001 standards. These standards are developed by the International Standards Organisation. Compliance is voluntary and not a legal requirement. However, ISO 14001 is based on continuous improvement of the environmental management system and compliance with all the relevant environmental legislation and includes principles as stipulated in various Acts. In classifying and attempting to delist the waste, the tanning facility’s commitment to sound and responsible waste management is validated. Therefore, this study is further needed to prove the company is fulfilling its duty of care as defined in the National Environmental Management Act 1998, (Act 107 of 1998). The duty of care principle means that the tanning facility is responsible for the fate of all waste that it generates at all times thus implementing its duty to society. Implementation of the duty of care and waste minimisation principles are considered essential for waste management. It ensures the implementation of a successful environmental management system that is entrenched in daily operations. It also takes into account the disposal options that are available for potential hazardous waste. The objective of implementation of the duty of care principle is twofold as it prevents the illegal disposal of potential hazardous waste into the environment and eliminates the disposal of non-hazardous waste into already limited hazardous waste landfill sites. Waste management at the tanning facility forms part of environmental management and good housekeeping. Good housekeeping is the management of the waste management area where the tanning sludge and other waste is disposed to: everything has its place and should be in its place. Future legislation may force an industry to demonstrate its commitment to waste minimisation by going through the process of classifying and delisting the waste sludge. The classification and delisting of the waste is necessary to: • Reduce waste disposal costs, • Form part of sound environmental practices • Ensure compliance with the necessary environmental legislation. In the next section the scope of this dissertation will be set out and discussed. In order to understand the scope of work for this study an overview will be provided of the tanning process to produce crust leather in the tanning facility (Section 3), the types of waste generated during the process (Section 4), and the reasons why chromium (Cr) is used in the process will be provided (DWAF(a), 1998). In order to understand the reasons for the disposal of waste to a hazardous landfill the legislation determining the disposal route and treatment options will be considered.


8

In this mini -dissertation, a brief outline of the legal issues pertaining to the disposal of waste, the waste minimisation strategy of the Government and the classification of waste in terms of the Minimum Requirements is presented in Section 6.


9

2. PROBLEM STATEMENT The tanning facility, used in this study, produces crust leather for the automotive industry during the retanning of wet whites and wet blues. Wet blues are hides and skins that have been tanned with chrome sulphate (CrSO4) (Tanners Council of America, 1969). Wet whites are skins and hides that are tanned using vegetable tanning material such as aldehydes. During the retanning process various types of waste are generated including tanning sludge, effluent, wet white and blue shavings and general waste. The generation of tanning sludge results in waste disposal problems for the tanning facility due to significant cost implications and disposal to the applicable landfill site as already explained in Section 1. The disposal to a landfill site is determined by the Minimum Requirements published by Department of Water Affairs and Forestry (DWAF(a), 1998). The Minimum Requirements (DWAF(a), 1998) provides the necessary guidelines for disposal and treatment of the waste generated by a tanning facility. According to these guidelines, waste produced by a tannery is considered possibly or potentially hazardous. Therefore, the tanning sludge needs to be disposed of to a permitted hazardous waste landfill site. However it, does allow for the delisting of waste to a lower hazard rating enabling it to be disposed of to a permitted general landfill site. Due to the presence of cyanide (CN) and hexavalent chromium Cr(VI) in the tanning sludge, it could not be delisted in the past. However, due to the ever-increasing costs of waste management, including waste disposal, the company was left with no other option but to restart the process of classifying and delisting the tanning sludge. According to staff of the facility, hexavalent chromium (Cr(VI)) and cyanide (CN) should not be present in the raw materials, or be generated during the retanning process. Therefore, if it could be proved that these constituents ((hexavalent chromium (Cr(VI)) and cyanide (CN)) are absent it is likely that the waste can be delisted for disposal to a permitted general landfill site such as Rosslyn, resulting in the reduction of the total cost of waste disposal. The main aim of this dissertation will thus be to classify and delist the tanning sludge for disposal to a general landfill site. The following objectives will ensure that the main aim is achieved: • Describe and discuss the production of crust leather • Identify the various waste streams produced during the retan process • Determine whether hexavalent chromium (Cr(VI)) and cyanide (CN) could be formed in

the process, through determining what is available in the literature. In determining whether these components could be produced during the process the literature study can be compared with the existing conditions in the tanning facility


10

• Identify the relevant legislation pertaining to waste management including the disposal of tannery waste i.e. tanning sludge

• Determine the presence of hexavalent chromium (Cr(VI) and cyanide (CN) in the raw materials (incoming materials) used in the production of crust leather

• Determine the presence of hexavalent chromium (Cr(VI) and cyanide (CN) in the effluents as this will provide an indication whether it is produced in the process

• Determine the presence of hexavalent chromium (Cr(VI) and cyanide (CN) in the tanning sludge. Determine the leachate character of the existing tanning sludge to determine the presence of hexavalent chromium (Cr(VI) and cyanide (CN). The tanning sludge will be analysed following the analytical procedure described in the Minimum Requirements (DWAF(a), 1998)

• Classify the tanning sludge according to the Minimum Requirements (DWAF(a), 1998) • Make recommendations for the tanning sludge disposal In the next section the production of crust leather will be discussed to provide an overview of the process and to explain the circumstances in which the hexavalent chromium (Cr(VI)) and cyanide (CN) could be found.


11

3. PRODUCTION OF CRUST LEATHER In the leather industry a variety of finished leather is produced depending on the customers’ needs (Ford Motor Company, 2003). Leather tanning is the process of converting raw hides into leather and the tanning can be divided into three different processes: • The beamhouse operations • The tanning itself • The finishing activities These different processes are described briefly as follows:

3.1 The beamhouse operations

In the beamhouse hides are prepared for tanning. During the beam house processing the raw hides are soaked and limed. The hides are converted from their preserved state through a number of process steps, to a pickled state in preparation for the tanning step (ISTT, 2004). Hides are soaked in water to rehydrate them, to remove the preserving salts, dirt and blood and unstructured proteins and to attack the epidermal structure in preparation for the tanning process. This process is necessary for optimum preparation of the hides for the subsequent tanning process. The purpose of the liming process is to open up the fibre structure of the hide and to remove the hair and epidermis (Reeder(a),1999). The deliming process follows which neutralises the effects of the liming process, causing the skin to become flaccid by releasing the bound water from the swollen protein fibre. The bating process follows the deliming process and removes the scud i.e. hair roots, pigment and other protein substances left from the liming thus avoiding the precipitation of this matter onto the grain during subsequent pickling and tanning operations (Reeder(b) 1999). The hides are then ready to be tanned.

3.2 The tanning process

The hides are tanned to prevent them from being damaged by bacteria. Hides can be tanned in a number of different ways by using chrome tanning agents added as a powder or a liquid to produce wet blues, or by adding vegetable tannins to produce wet whites (ISTT, 2004). Wet blues are not leather, but hides that have been tanned with chromium sulphate (CrSO4) (Tanners Council of America, 1969). They are merely a stable form of the hide. The chrome gives the leather an initial blue grey colour. The tanned hides can be stored for long periods and are also more easily transported without fear of being damaged by bacteria (ISTT, 2004;


12

www.tanschool.co.za). Wet blues are recognized as an internationally traded commodity. The chrome tanning method is widely applied for the preparation of finished leather (Iqbal et al, 1998). Wet whites on the other hand are skins and hides that are tanned using vegetable tanning material such as aldehydes. Leather that is tanned using vegetable tannins has different properties and is usually much firmer. These hides will go through the dye house operations to convert the wet blue and wet whites into a product that has leather-like properties. The process in the dye house can be compared to the retan process used, in this mini dissertation, to produce crust leather (ISTT, 2004).

3.3 The finishing process

Leather finishing is the final process that is carried out in a tannery to make the leather look better and stay looking good for longer while withstanding weather and wear. Leather finishing in very simple terms is the application of paint to the leather surface. The paint that is applied usually consists of the following (ISTT, 2004): • Water or solvent (to dilute the pigments/dyes and resins) • Pigment and/or dyestuff (to give the colour to the finish) • Resins (to bind to the leather surface and give toughness and stretch and flexibility to the

finish) The paint or finish mixture can be applied to the leather in a number of different ways: • Spraying- the hides enter through a spray booth where they are sprayed with high pressure

sprayers • Roller coating- the hides move through a large roller which would have a pattern on it • Padding by hand – workers apply the paint by hand using a spatula like object

During the finishing process, it is common to put the leather through a press. These presses have either a flat plate or cylinder which is heated up. This hot metal surface is pressed against the leather, finishing and smoothing the surface of the leather. It also helps the finish to stick to the leather surface (ISTT, 2004). Different leathers need different amounts of finish applied to them. Some leathers are very lightly finished while others may need a lot of finishing. Some of these press plates or cylinders


13

have a pattern on them. If these patterns are pressed against the leather surface, the pattern becomes imprinted onto the leather. This process is called embossing (ISTT, 2004).

3.4 The retan process followed at the tanning facility

In this case the tanning facility being investigated produces crust leather for the automotive industry from wet blues and wet whites. These tanned hides (the wet blues and whites) are bought from other tanneries to be retanned in order to produce the crust leather. The crust leather in turn is supplied to another facility for finishing and cutting. Therefore this tanning facility is known as a retan facility only. Leather produced for the automotive market is of the highest quality. Hides are retanned to level out the structure of a hide, by filling the loose and empty parts in the bellies and necks, to improve the cutting yield. Wachsman (1999) considers this is where retanning agents with real tanning properties are necessary and where either chrome salts, syntans, glururaldehyde, vegetable extract, polymers, resins aldehydes and metals provide these properties to the wet blues and wet whites used (ISTT, 2004). The objectives for retanning hides can be described as follow (Wachsman, 1999): • To improve the handle and feel of the leather, to make it softer or firmer; • To change the colour of the chrome tanned leather to black, pastel or any other shades

required by the customer; • To improve the buffing properties for corrected grain leathers; • To improve the embossing properties especially for very pronounced grain patterns; • To adjust dyeing properties for drum dyeing; • To produce crust leather with the right properties for fast and level spray dyeing or other

dyeing methods like printing; • To support water resistance/ water proofing (as mentioned before, the leather produced

for the automotive market is of the highest and finest qualities); and • To improve certain specific properties like perspiration resistance, fastness to washing,

thermal conductivity, flammability etc. Figure 3 indicates the process that is followed in the tanning facility to produce crust leather and shows that the process can be divided into the next steps: • Wetting back before the hides are entered into the retan process the hides must be

hydrated • The hides are then dried through wringing to remove the excess water


14

WET WHITE/ BLUE HIDES

CRUST LEATHER

Figure 3 Process description of the Retan process

WETTING BACK

WRING

MEASURING

SPLITTING

SHAVING

RETAN

SET OUT

DYEING

FATLIQUORING

TOGGLE DRYING


15

• The hides are then measured by placing them on the measuring bridge to determine the hides to be processed in squire meters

• Splitting and shaving involves the cutting of the hides into the correct thickness • The hides enter the retanning process • Dyestuff is added to colour the dyes • Fatliquor is added to prevent it from drying out • Now the leather is allowed to dry Wet whites and wet blues are not leather and therefore they do not have leather like properties. They are also a blue-grey colour and are usually as thick as the original thickness of the animal hide. In order to convert these hides into a product that has leather like properties, it has to go through a number of process stages in the dye house as described in Figure 3. The process is very complex and producing leather, especially automotive leather, is a very fine art. The steps in the retan process as identified in Figure 3 on the next page will be described below in order to facilitate the understanding of the process.

3.4.1 Splitting and shaving If the wet blue or wet white hides, bought from other tanneries, are close to the required thickness they are put through a shaving machine to give it a uniform or even thickness. If the thickness is too great, the hide is put through a splitting machine which has a band knife running along a bed. The splitting machine can be adjusted to split the leather to any required thickness. The thickness will be determined by the customer’s requirements. In the process of splitting, two pieces of splits (the grain split and the lower flesh split (dropsplit)) can be obtained from one hide. After splitting the hide it may still be necessary to shave the grain split to the required thickness (ISTT, 2004) The grain split is the most valuable and is further used in the process. The flesh split (or also known as the drop split) can be used for industrial gloves, suede leather, or it could be finished to look like a grain split. The tanning facility sells these off to other companies to be reused.

3.4.2 Wetting back During this process the hides are added into the retanning drums with water and surfactant or degreaser. The purpose of this step is to allow the hides to regain their moisture and to become soft again. The surfactant or degreaser helps to wash off any grease or dirt on the wet white or the wet blue. Just before retanning the hides are neutralised by adding chemicals such as sodium formate, sodium bicarbonate, ammonia and neutralising syntans. Neutralising the wet blue is important in


16

order to allow the chemicals, which will be added later in the process, to penetrate the leather (ISTT, 2004).

3.4.3 Retanning As the hides have already been tanned in the process to make wet whites or blues, the second tannage is known as a retannage (Wachsman, 1999). Retanning converts the wet blues and wet whites into leather products. These leather products have the following properties: • Softness • Fullness • Roundness • A pleasant feel. The retanning chemicals, such as syntans, polymers, resins, aldehydes and metals provide these properties to the wet blues and whites (ISTT, 2004).

3.4.4 Dyeing The dyeing process can no longer be regarded as just another step in leather making. It is a very important tool in adding value and differentiation to the final product. Dyeing is used to turn ordinary blue, chrome or beige–brown, or even white leather into a myriad of fashionable hues with all the correct performance and aesthetic properties at a price the consumer can afford (Tremlett, 1999). Therefore to obtain the desired colour of the final crust leather after retanning, the hides must be dyed. Numerous dyes are used by the tanner to get the final colour of the leather. Some of these are conveniently premixed by a chemical supplier to the desired end colour. Others are mixed by the tanner to achieve the required colour. Formic acid is then used to fix the dye (ISTT, 2004).

3.4.5 Fatliquoring During the process oils or fats are added to the leather to prevent it from drying out and becoming hard and useless when the grain cracks. Fatliquors provide lubrication of the leather fibres and this is done by drumming the leather with various types of fats and oils. This is carried out by mixing fats and oils that can easily mix with warm water. Formic acid is used to lower the pH which ensures that all chemicals are firmly fixed to the leather (ISTT, 2004).

3.4.6. Setting out and drying The wet leather is passed through a setting out machine which squeezes the water out of the leather, and allows it to dry more quickly. The setting out machine also has a spreading action to


17

increase the area of the leather and this helps to remove creases and wrinkles. To dry the leather the tanning facility makes use of the toggle drying method. This drying method is used to give certain properties to the leather in order for it to be used in the automotive industry. The crust leather is ready to be provided to other facilities for the final finishing which is basically applying the paint to the leather. The finishing chemicals consist of water based pigments/dyes and resins, pigment and/or dyestuff to give colour to the finished hides, resins to bind to the leather surface and to give toughness and stretch and flexibility to the leather.

In this section the process for producing crust leather in the tanning facility under investigation was discussed. In the next section the various waste streams produced during the tanning process will be identified and discussed. In order to understand what is waste, waste must be defined. Section 4 starts with the definition of waste and explains when waste is considered as general waste or hazardous waste.


18

4 WASTE STREAMS PRODUCED DURING THE RETAN PROCESS

In Section 3 of the mini-dissertation the process of making automotive leather was discussed. In this section the origin of the various waste streams will be covered. Before the various waste streams are identified, it is important to define waste and determine when waste is considered as general and possibly and/or potentially hazardous waste. This will be discussed in the section below.

4.1 Definition of waste

Fuggle & Rabie (2002) refer to the numerous nouns in the legislation to describe waste. Among them are the following: ‘by-product’, ‘carcass’, ‘cuttings’, ‘debris’, ‘dung’; ’excrement’, ‘filth’, garbage’, ‘litter’, ‘manure’ ‘trimmings’, ‘waste’ and ‘waste products’. The Environment Conservation Act of 1989 (ECA) defines the concepts of waste in terms of the legal definition, and as updated in the Government Gazette, as: “an undesirable or superfluous by-product, emission, residue or remainder of any process or activity, any matter, gaseous, liquid or solid or combination thereof, which: • is discarded by any person or • is accumulated and sorted by any person with the purpose of eventually discarding it with

or without prior treatment connected with the discarding thereof; or • is stored by any person with the purpose of recycling, re-using or extracting a usable

product from such matter

However, the abovementioned nouns and definitions only take into account the so-called general waste. Internationally hazardous wastes on the other hand have various legal definitions. Miller, (2004), describes the legal definition of hazardous waste as it is used in the United States as: “Any discarded solid or liquid material that: • contains one or more of 39 toxic, carcinogenic, mutagenic or teratogenic compounds at

levels that exceed established limit • catches fire easily (gasoline, paints and solvents) • is reactive or unstable enough to explode or release toxic fumes (acids, bases, ammonia

chlorine bleach), or • is capable of corroding metal containers such as tanks, drums and barrels (industrial

cleaning agents and oven and drain cleaners)


19

In most cases definitions of hazardous waste are relatively vague and mostly refer to a list of compounds and/or types of wastes concerned. Some of the main identification criteria include: • Type of hazard involved (flammability, corrosivity, toxicity, reactivity) • The generic category of the products involved (e.g. pesticides, solvents and medicines) • Technological origins (e.g. oil refining, electroplating) and • Presence of a specific substance or group of substances (e.g. PCB, dioxin, lead

compounds). The South African definition of hazardous waste is based upon the UNEP definition: “Waste, other than radioactive waste, which is legally defined as hazardous waste in the state in which it is generated, transported or disposed of”. The definition is based on chemical reactivity or toxic, explosive, corrosive or other characteristics which cause, or are likely to cause, danger to health or to the environment, whether alone or in contact with other waste (DWAF(a), 1998). South Africa has decided that the most practical method of identifying and classifying hazardous substances includes the following (DWAF(a), 1998): • Inclusion of lists of substances • Incorporation of a degree of hazard approach, not only to designate a waste as hazardous

or not, but also to differentiate between degree of hazard regarding disposal methods and sites

• Use of concentration levels and total loading or the assimilation capacity of sites, to guard man and the environment against future detrimental effects and

• The use of “acceptably low risk” levels to allow for the delisting or re-classification of a hazardous waste as a general waste for waste disposal, if it can be shown that the risk posed to the environment is acceptably low.

Taking the abovementioned into account, hazardous waste will be defined in text below. In the next section the concept of hazardous waste will be explained.

4.2 Definition of hazardous waste

Hazardous waste is defined in the Minimum Requirements (DWAF(a), 1998) as waste that has the potential, even in low concentrations, to have a significant adverse effect on public health and the environment because of its inherent toxicological, chemical and physical characteristics. It is generated during a wide range of commercial, industrial, agricultural and domestic activities and may take the form of tanning sludge, as is the case in this mini-dissertation. These characteristics


20

contribute not only to degree of hazard, but are also of great importance in the ultimate choice of a safe and environmentally acceptable method of disposal. The definition of hazardous waste is very broad as wastes can vary substantially in nature, composition, size, volume, appearance and degree of harmfulness. Hazardous wastes are classified into various classes and then further grouped into four hazard ratings. The classification of hazardous waste will be discussed in the legal section of this mini-dissertation. These hazard ratings differentiate between a hazardous waste that is fairly or moderately hazardous and one that is extremely hazardous. The hazard ratings will also determine the class of hazardous waste landfill to which the tanning facility may be dispose of its waste. In South Africa the following hazard ratings apply:

• Hazard Rating 1 Extreme risk H:H (such as Holfontein) • Hazard Rating 2 High risk H:H • Hazard Rating 3 Moderate risks H:H or H:h • Hazard Rating 4 Low risk H:H or H:h landfill

(An H:H landfill is more stringently designed, operated and monitored than an H:h landfill) The definition of waste and hazardous waste is clarified therefore the waste streams generated in the retan process are identified and discussed in the following section.

4.3 Waste streams generated in the retan process

During the retan process large volumes of raw materials are used in the manufacturing of crust leather. Raw materials used are chemicals, which include dyes, retanning materials, formic acids, water and the wet white or blue hides. Most of the chemicals used to prepare the hides for retanning find their way back into the environment in the form of wastes including (Iqbal et al, 1998): • Atmospheric waste causing air pollution • Liquid waste • Solid waste Figure 4 explains the process and identifies the type of waste streams generated in the retan process at the tanning facility as well as the disposal options currently adopted. Waste streams produced during the tanning process include effluent and solid waste:


21

PROCESS WASTE STREAMS DISPOSAL OF WASTE

Figure 4: Waste streams produced during the Retan process

Wetting back

Wring

Measuring

Splitting

Shaving

Retan

Set out

Dyeing

Fatliquoring

Toggle drying

Effluent

Effluent

Drop splits

Solid waste shavings

Effluent

Eff

luen

t pla

nt E

fflu

ent

Slud

ge

Dis

pose

d to

the

sew

er n

etw

ork

Filter press

Disposed to

hazardous waste site

WET WHITE/BLUE HIDES

CRUST LEATHER


22

The effluent water originates from all the areas where water is used in the tanning process, which includes the wetting back water, water from the wringer and the water dropped during the retanning process. The effluent water is diverted to a partially treatment plant which will be described later in Section 4.3.3. The partial treatment of the water results in the production of the tanning sludge and effluent that is disposed to the Municipal sewer network. Solid waste streams originate from the splitting of the hides and as a result of the effluent treatment plant. The drop splits are sold to another company for reuse, the shavings from the shaver are disposed of as general waste and the tanning sludge are disposed of to a hazardous landfill site. Although a brief description is provided for each of the wastes produced, the main focus of this dissertation is on the tanning sludge produced during the treatment of the effluent.

4.3.1 Atmospheric waste causing air pollution A potential source of air pollution (atmospheric waste) may originate from the boiler. The boiler is used to produce hot water for the retan process. Possible contaminants include the release of gases. However, due to the size of the boiler used, this is not a scheduled process in terms of the Atmospheric Pollution Prevention Act, Act 45 of 1965 (APPA). The boiler uses less than 10 tonnes of sabufuel (a sort of paraffin) per hour and it does not use coal as an energy source. Therefore, it is expected not to have a significant impact on the environment.

4.3.2 Liquid waste Tanneries are major consumers of water. The water in the wet processes and operations is used as a chemical carrier to facilitate all chemical reactions involved in leather processing. After completion of the process and operation, the water leaves the system as waste water in the same quantity as it is added to the system (Iqbal et al, 1998). Liquid waste or waste water includes all process water produced throughout the retan process as described in Figure 4. The waste water originates from the various stages including the wetting back, wringing and retan processes. The water volume requirements depend on each of the specific retanning processes and the specific product that needs to be manufactured at that specific time (Stephen Roberts & Kirsten (SRK), 1989). In the tanning facility under investigation process water is disposed of to the effluent plant for partial treatment. The specific water intake (SWI), for a particular period divided by the number of hides produced, is estimated, by SRK, to be an average of 389l per hide (SRK, 1989). This will equal the volume of water disposed of to the effluent plant for partial treatment.


23

Effluent originating during the various stages of the process is disposed to an effluent treatment plant for partial treatment, before it is disposed of into the municipality’s sewer network for further treatment. The effluent disposed of must be treated in order to comply with the local authorities’ standards for disposal of industrial effluent. The water is treated through the addition of treatment chemicals (polymers, flocculants coagulants and lime), followed by dissolved air floatation of the solids. The Dissolved Air Flotation (DAF) provides successful removal of the suspended solids (SS), oil and greases, as well as any heavy metals such as chromium (Cr), Manganese (Mn), Aluminium (Al) and Iron (Fe). Table 2 shows the typical composition of the effluent before it is treated. Tannery effluent is characterized by a high chemical oxygen demand (COD) and high salt content measured as total dissolved solids/salts (TDS). High chloride (Cl), Sodium (Na), Sulphate (SO4) concentrations are also present in the waste stream due to their presence in the raw materials and this contributes to the high salinity levels of the effluent stream. It also contains a high level of suspended solids and chrome. According to Iqbal et al, (1998) this is characteristic of tannery waste water. The chrome (Cr) will only be present when wet blues are processed and chrome tanning salts are used.

Table 2: Composition of the effluent originating from the retan process before treatment

Variable pH Ec

(mS/m)

NH4

mg/l Cl

mg/l SO4 mg/l

Na mg/l

TDS mg/l

SS mg/l

COD mg/l

Range in mg/l

3.8-5.4 900 - 1800

120- 400

600-2000

1500-5000

1100-2300

6300-12000

200-1500

300-1000

The chemical oxygen demand (COD) indicated in Table 2 represents the oxygen consumption for chemical oxidation of organic material under strongly acid conditions. It only provides an indication of the potential oxygen depletion that may occur from discharging organic material into surface waters (Verheijen et al, 1996). The suspended solids (SS) in Table 2 are insoluble organic and inorganic particles present in the waste water that originates from the hides and chemicals used. Suspended solids (SS) are mainly material that are too small to be collected as solid waste. Discharge of high concentrations of SS increases the turbidity of water and causes a long term demand for oxygen because of the slow hydrolysis rate of the organic fraction of the material. It has been estimated that using traditional tanning methods chromium salts which are not fixed to the collagen during the tanning process, are discharged as salinity Total Dissolved Salts (TDS).


24

The chromium complex is relatively stable and slightly biologically available and therefore the chromium should not be oxidised to hexavalent chromium (Cr(VI)) during the retan process. The characteristics of chromium and hexavalent chromium (Cr(VI)) will be discussed in Section 5. The Chemical Oxygen Demand (COD) and Suspended Solids (SS) are the only constituents that are removed from the effluent through the partial treatment process, as this treatment does not remove any salts in the effluent. The operation of the effluent plant will be discussed in the next section since the tanning sludge is generated here as a result of the removal of heavy metals, Chemical Oxygen Demand (COD) and suspended solids.

4.3.3 Solid waste Figure 4 shows an additional waste stream, the solid waste. The solid waste produced includes the tanning sludge produced at the effluent plant, shaving buffings, raw material packaging (especially plastics) and general office waste. The majority of general solid waste is separated at source and recycled where possible. Empty drums, containers, plastics, white papers and carton boxes are recycled by outside contractors. All the effluent produced in the tanning facility reports to the effluent plant for partial treatment, to ensure that the water complies with the standards set by the Local Authority. The effluent plant in Figure 5 on the next page is a dissolved air flotation plant. The Dissolved Air Flotation (DAF) is designed to partially remove the Chemical Oxygen Demand (COD) and the Suspended Solids (SS). Flocculants and coagulants used to remove SS and Chemical Oxygen Demand (COD) generate the tanning sludge in this process. The Dissolved Air Flotation (DAF) plant functions on the principle of flotation. Flotation is used for the removing of suspended solids from mixed effluent. Air is dissolved into the incoming effluent under pressure. When this pressure is subsequently lowered in the treatment vessel, small air bubbles are released, carrying the suspended solids to the surface. Lime, ferrous sulphate and polyelectrolyte are usually used in order to thicken tanning sludge for easier handling (Mozes, 1995). In order to reduce the tanning sludge volumes for disposal, a filter press was introduced to dewater the tanning sludge. Prior to the implementation of the filter press the tanning facility made use of filter beds. Although these required low capital they were labour intensive. The drying beds were filled and emptied manually once the tanning sludge from the Dissolved Air Flotation (DAF) was dry. Mozes (1995) determined that the tanning sludge may be shovelled when the solids content is around 25-30%, at which point the cake may be removed for disposal. The tanning sludge and slurries produced by the tanning facility must be separated and dewatered prior to disposal as this influences the disposal options. The disposal of the final dried tanning sludge (considered as possibly and/or potential hazardous waste (DWAF(a), 1998)) poses


25

problems due to a lack of proper permitted disposal sites. Currently the tanning sludge is disposed of to Holfontein permitted as a hazardous landfill site allowed to accept any kind of hazardous waste.

Figure 5: The dissolved air flotation plant that is used for partially treating the Retan effluent


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Figure 6 shows a general trend in the volume of tanning sludge produced per month. This trend follows the amount of hides (indicated in square meters) processed per month to produce crust leather. As soon as the production increases more effluent is produced due to the increased demand of water in the process. The increase in water use results in more tanning sludge produced due to the effluent disposed of to the dissolved air flotation for partial treatment. Therefore Figure 6 shows a trend when the production increases the tanning sludge increases. The opposite is also true. The bar graph in Figure 6 shows an increase in the production of hides for months 6 and 7 and just after this a significant decrease in hides from 200 000 to 100 000 square meters processed. This variance is dependent on the customers. The increase in production is attributed to an increase in customer demand and once this was satisfied the production rate decreased again until the next demand increase. Due to the variances it is not possible to quantify the relationship between the waste and the amount of hides processed except to point out the trend that when the production increase the waste increases. However it shows that no tanning sludge was produced for month 11, although there were 70 480m2 hides processed. An explanation for this is the agreement that exists between the tanning facility and the waste removal company whereby in order to combat waste disposal costs the tanning sludge will only be removed from site once it reaches a certain volume (in this case it is three 6m3 waste skips). This reduces the transportation cost as the waste contractor will only remove the waste once they are notified that there are sufficient volumes to be removed in one load. Therefore, during month 11 the production decreased to such an extent that the tanning sludge production did not reach the agreed volume to be removed.

0

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Figure 6 : Comparison of the tonne tanning sludge produced vs. the square meters of hides processed


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The disposal of the tanning sludge forms the essence of this mini-dissertation. The disposal is of concern to the tanning facility due to the financial implications of disposing the tanning sludge to Holfontein, the only available permitted hazardous landfill site in close proximity to the facility. Mozes (1995) states that the problems experienced with tanning sludge disposal originating from tanneries will influence the choice of treatment process. For example, the lack of landfill facilities may encourage agricultural re-use of the tanning sludge. However, due to the location of Holfontein/ Rosslyn and the lack of farming land, the disposal of the tanning sludge to a permitted landfill site is still seen as the most cost effective disposal method. Moses (1995) further goes on to mention that tanning sludge handling and disposal forms part of best practice control technology available from the economic point of view. With this theory in mind the filter press, in Figure 7, was installed to reduce the moisture content before the tanning sludge is disposed of to Holfontein. This resulted in the reduction of the moisture content in the tanning sludge from more than 40% to less than 16.5% which addressed a concern raised in the Waste Group report in 2002. The fact that the tanning sludge contained more than 40% of moisture was raised as a concern because this will also influence the options to dispose of the sludge to a general landfill site.

Figure 7: The filter press was installed to reduce the moisture content of the tanning sludge

The tanning sludge is pumped into the filter press as slurry until the filter press reaches its capacity. The filter press takes about 10 000 l before it is filled to capacity. Once the filter press is filled, pressure is applied which forces the water from the tanning sludge. The effluent from


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the filter press is returned to the effluent plant. The tanning sludge is then dry containing only approximately 16% moisture content and is dropped from the filter press onto a conveyor which removes the tanning sludge to a skip for disposal. The partial treated effluent will determine the composition of the tanning sludge. The tanning sludge is the result of the Chemical Oxygen Demand (COD), Suspended Solids (SS) and heavy metals removed from the effluent through the use of precipitation by adding flocculants and coagulants. It could therefore contain various constituents such as chromium (Cr), manganese (Mn) and aluminium (Al). Previously it was mentioned the focus of this study is on the presence of hexavalent chromium (Cr(VI)) and cyanide (CN) in the tanning sludge. Taking the water quality results mentioned in Section 4.3.2 of this mini- dissertation into consideration hexavalent chromium (Cr(VI)) and cyanide (CN) is not characteristic of the tannery effluent. The presence of these constituents cannot be explained since they are not used in the process and are not produced during the process, and as it was mentioned chromium is a stable complex. In the next section the writer will attempt to discuss chromium (Cr) and hexavalent chromium (Cr(VI)) and possible reasons why they may or may not be present in the tanning sludge generated. The personnel at the tanning facility is of the opinion that it is impossible for hexavalent chromium (Cr(VI)) and/or cyanide (CN) to be present in this process as they are not general constituents used or produced during the process.


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5. THE PRESENCE OF HEXAVALENT CHROMIUM (CR(VI) AND CYANIDE(CN) IN THE RETAN PROCESS

The purpose of this section is to determine whether there is any literature available to describe chromium and the reasons why hexavalent chromium (Cr(VI)) and cyanide (CN) would be present in the tanning sludge.

5.1 Chromium and hexavalent chromium (Cr(VI))

In order to understand what chrome is and why hexavalent chromium (Cr(VI)) would be present in the retan process, it is important to understand where chromium comes from and why it is used in tannery operations. Chromium is abundant in the earth’s crust. Chromium (Cr) occurs in the environment primarily in two valence states, trivalent chromium(Cr(III) and hexavalent chromium(Cr(VI). These two valence states differ significantly in environmental compatibility. Vegetable tanning materials have been used for hundreds, possibly thousands of years to produce leather. The use of vegetable tannins, was the way most leather was made before chrome tanning was discovered in the 1880s. Currently trivalent chromium (Cr(III) is widely used in tanneries and it is the predominant leather tanning agent in use today so most tannery wastes contain significant amounts of chromium, which is exclusively present as trivalent chromium (Cr(III) (Rutland, 1991; International Union of Environment: Leather Technologists and Chemist Society (IUE) , 2001). Bivalent chromium (Cr(II)) and trivalent chromium (Cr(III)) are the reduced forms of chromium (Cr) and are less soluble than hexavalent chromium (Cr(VI)) and do not constitute a serious health hazard. However, chromium (Cr) also functions as an essential element, being a component of hormones and vitamins. It functions as a co-factor with insulin, required for normal glucose utilization and growth. The primary storage site is in the liver, while excretion if absorbed is largely via the kidneys (DWAF, 1996). Hexavalent chromium (Cr(VI)) compounds, on the other hand, are in general primarily of anthropogenic origin. Hexavalent chromium (Cr(VI)) is a highly oxidized state of metal chromium. It is the toxic dermatic and carcinogenic form of chromium (Cr). It is highly water soluble at all pH values especially physiological and environmental pH levels. Therefore, it is very mobile in the environment and readily moves through the soil profile contaminating groundwater supplies. Trivalent chromium (Cr(III)) can be reoxidised to hexavalent chromium (Cr(VI)) under oxidizing conditions (Rutland 1991; DWAF, 1996, Verheijen et al, 1996)


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Chromium salts are widely used in the tanning process to convert raw pelt to leather as they yield the most stable tannage (Van den Bosshe et al, 1997; Dewhurst (1999). The use of chromium salts have various advantages over vegetable tanning and are the preferred tanning agent for the following reasons: • The method is rapid, simple and easy to reproduce; • A wide range of leather types can be made which include a wide range of colours and rich

or pastel shades are possible; • Good hydrothermal stability can be achieved; • Wet blue is a convenient holding stage since this is used to convey hides throughout the

world; • Chromium (Cr) could be recycled from the effluent should it be necessary; and • Wet blue waste water is also more easily treated in the dissolved air flotation effluent

plant than wet white waste water. A powder form of chromium (Cr) is used in the tanning process and consists of chromium sulphate (which is exclusively trivalent chromium (Cr(III)). In solution it has a strong attraction of the hydroxyl ions (OH-) which associate with the molecule by replacing one or more of the sulphate ions (SO42-). As more hydroxyl ions (OH-) are made available (i.e. the pH rises) they enter the chromium sulphate molecule and increase the molecule’s reactivity towards the collagen in the hide. During the process chromium hydroxide can be formed should the pH rise above 4.3. This is insoluble and would therefore possibly form part of the chromium that is precipitated in the tanning sludge should it be present in the wet blue hides that are washed out during the wetting back process (Dewhurst, 1999). This forms the basis of any of the chrome tanning processes. Rutland (1991) describes the tanning process as depended on the unique ability of trivalent chromium (Cr(III) to form stable, kinetectically inert co-ordination complexes which can bind and crosslink to the hide protein fibres (collagen). Such biochemical stabilisation provides the necessary protection from putrefaction and gives improved hydrothermal stability (which corresponds with the reasons Dewhurst explained for using Cr as a tanning agent). Further hexavalent chromium (Cr(VI)) compounds are not tanning substances as they do no have the ability to form such co-ordination complexes (Rutland, 1991). The reducing characteristics of tanning sludge, owing to organic matter and sulphide compounds, stabilise trivalent chromium Cr(III) therefore it is not possible to oxidise trivalent chromium Cr(III) to hexavalent chromium (Cr(VI)) (IUE, 2001), so the possibility for hexavalent chromium (Cr(VI)) to be present in the tanning sludge is very slim. The International Union of Leather Technologists and Chemists


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Society updated report in 2001 confirmed that hexavalent chromium (Cr(VI) is not used in the tanning process due to its toxic and chronic nature (IUE, 2001,). This has also previously been stated by the International Chromium Development Association (Van den Bosshe et al, 1997). Taking the abovementioned into consideration the production of waste containing chrome is a major challenge. Chrome waste (waste containing trivalent chromium (Cr(III)) from leather processes poses a significant disposal problem due to the perception that exists with the Authorities, dealing with the environment, that chromium is dangerous and poses a health issue. Trivalent chromium (Cr(III)) is also present in all three waste forms i.e. liquid waste, solid tanned waste and tanning sludge. The environmental impact of chrome waste from tanneries has been a subject of extensive scientific and technical dispute in the past (Ludvik, 2000) due to perception, and positive analysis for hexavalent chromium (Cr(VI)). Therefore significant research has been done on this issue and a few examples will be discussed in the section below. Commercial trivalent chrome (Cr(III) tanning products are prepared by reduction of sodium dichromate. The trivalent chrome tanning products are carefully formulated with excess reducing agents to ensure the absence of hexavalent chromium (Cr(VI)). In addition, typical tanning recipes contain masking agents (organic acid radicals such as formate or acetate) which help to control the tanning reaction and further ensure the chromium is exclusively trivalent. They also ensure that the tanning waste produced in the tanning process is exclusively in the trivalent chromium form. Due to the high organic content of these waste materials it is highly unlikely that soluble hexavalent chromium (Cr(VI)) compound could persist in such a waste environment (Rutland, 1991). Hauber (2000) provided an overview of articles that were published describing the main findings of investigations that were carried out at the leather institute in Germany (LGR) in 2000. The findings of the articles on the possible formation and avoidance of chromate in leather were as follows: • The use of wetting auxiliary agents with reducing abilities prior to the dyeing process could

not avoid the formation of hexavalent chromium (Cr(VI)), in cases under drastic conditions such as heating the leather at 80°C. This was also confirmed by the Leather Institute of Germany that higher concentrations of hexavalent chromium (Cr(VI)) was detected after heating at 80°C which resulted in a 6% water content that could be detected after Ultra Violet lightening.

• Vegetable tanning agents like wattle, quebracho, chestnut and tara play an important role in avoiding chromate formation in leather. Tara was especially effective even used in very low concentrations prevented the formation of hexavalent chromium (Cr(VI).


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• Polymers or synthetic retanning agents had neither a negative nor a positive effect on hexavalent chromium (Cr(VI)) formation in leather and are heavily influenced by fatliquors, especially natural products such as fish oils.

• Mechanical processes like vacuum drying or buffing of the leather seem not to contribute to the formation of hexavalent chromium (Cr(VI)).

• The relative humidity of air during the storage of chrome tanned leather also plays a role in the formation of chromate. Graf (2000) states that hexavalent chromium (Cr(VI) can only be formed if the leather is in contact with atmospheric oxygen

• Combusting leather at temperatures between 500° and 800°C increased the levels of hexavalent chromium (Cr(VI)) although the original sample when analysed showed no traces of hexavalent chromium (Cr(VI)) (Ferreira et al, 1999)

Hauber (2000) mentions that results of investigations in Italy do not show any evidence of hexavalent chromium (Cr(VI)) after the conventional chrome tanning processes were performed. Each process performed was analysed. However, after thermal treatment and UV radiations, high amounts of hexavalent chromium (Cr(VI)) were found in the crust leathers. Experiments using single chemical substances showed that fatliquoring with sulphited fish oils resulted in high hexavalent chromium (Cr(VI)) values. Retannage with natural tannins did not support hexavalent chromium (Cr(VI)) formation. The research done does not provide a safe recipe to avoid the formation of hexavalent chromium (Cr(VI)) in leather. Hauber (2000) suggests the following recommendations to prevent the formation of hexavalent chromium (Cr(VI)): • Do not use natural products such as fish oils • Employ vegetable retanning agents • Adjust the pH values in the neutralization • Avoid ammonia as a wetting agent before dyeing, rather use agents with reducing

possibilities and • A higher moisture content during storage of the leather is positive for lowering or

preventing hexavalent chromium (Cr(VI)). In evaluating the abovementioned findings from the comprehensive research, it can be assumed that hexavalent chromium (Cr(VI)) will be present once oxidation circumstances occur. However, in comparing the abovementioned reasons why hexavalent chromium (Cr(VI)) could be present in the process, none of these conditions apply in the retan facility. No oxidation circumstances are provided during the retanning process to oxidise the trivalent chromium (Cr(III) to hexavalent chromium (Cr(VI)), thus there should be no hexavalent chromium (Cr(VI)) present in the tanning sludge generated in the dissolved air flotation effluent plant.


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Taking all the abovementioned into consideration, chromium is considered one of the most potentially hazardous waste materials originating from the tanneries. Sometimes chromium concentrations are abnormally high in an effluent discharged and could be disposed of as part of the solid waste. Basic chromium sulphate used in tanneries is not always optimally absorbed by the hides. Raju & Tandon (1999) estimated that 55 -70% of it is taken up by the hides and the rest is discharged as part of either the effluent or the solid waste. Once again it must be emphasised that the Cr is present as trivalent chromium (Cr(III) and not hexavalent chromium (Cr(VI)) due to the high organic content of the various wastes.. Taking into account that the literature states and mentions that trivalent chromium (Cr(III) is extensively used and that there is no reason why hexavalent chromium (Cr(VI)) should be present, the following questions arise: • What could the possible reasons be for the positive results for hexavalent chromium

(Cr(VI)) in the tanning sludge? • Is there a possibility that it could be formed in the process? • Could it be a result of the test method that is used to test for hexavalent chromium

(Cr(VI))? However, the evaluation of test methods in order to explain the hexavalent chromium (CR(VI)) does not form part of this study and should maybe be considered as additional work that should be investigated at a later stage.

5.2. Cyanide (CN)

As some light is shed on the presence of hexavalent (Cr(VI)) in the tanning sludge the presence of cyanide (CN) remains a mystery and should still be explained. The presence of cyanide (CN) in previous tanning sludge samples (Golder & Associates, 2000) cannot be explained, since cyanide (CN) is not normally used in the process nor is it present in tannery waste. However, the fact that cyanide (CN) is detected in the waste could be due to the following reasons (Baldwin, 2005):

• It could be brought into the process as an impurity in one or more of the materials and reagents used;

• It is generated by a reaction between two or more materials and reagents used; and/or • There is an interference in the analytical determination and other constituents are being

detected and measured as cyanide (CN) Answers to these questions will be discussed in Section 8.


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The retan process has been explained together with the various waste streams that are generated. An explanation was provided for the presence or absence of hexavalent chromium (Cr(VI)) in the tanning sludge. However, the last section that still needs to be taken into account before the approach to the study is discussed, is the applicable legislation to dispose of waste and potentially hazardous waste. The environmental legislation is the determining factor in this study, and where the tanning sludge can be disposed of and whether the tanning sludge will be allowed to delist. In the next section the applicable legislation will be reviewed and discussed in general terms.


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6 ENVIRONMENTAL LEGISLATION GOVERNING WASTE MANAGEMENT

The retan process was discussed in Section 3 and the various waste streams formed during the retan process were identified in Section 4. The disposal of the tanning sludge still needs to be addressed as disposal is determined by environmental legislation in South Africa. The purpose of this section will be to highlight the applicable legislation to be considered for the process of disposing the tanning sludge to an appropriate permitted landfill and the process that needs to be followed to classify and delist the tanning sludge. It is becoming more and more difficult to produce leather and leather products due to the increasing stringent environmental legislation, the disposal cost of waste produced during the process and the environmental impacts associated with the waste disposed (Miller, 2004). The applicable legislation will be discussed below. Section 24 of the Constitution of South Africa of 1996, (Act 108 of 1996) (Government of South Africa, 1996) guarantees all South Africans the right to an environment that is not harmful to their health or wellbeing. Existing legislation, and especially new proposed legislation in the form of the White Paper on Integrated Pollution Control and Waste Management, is working towards implementing a healthier community and an environment free from hazardous waste. The State of Environment Report of 2001 highlights the challenges that the Government faces in implementing responsible waste management. South Africa produces 539 million tonnes of waste per annum, of which 2 million tonnes are defined as toxic. Half of the 2 million tonnes originates from the industrial sector and the other half from the mining sector. The report further explains that landfill site management has created significant problems for local government (Clark, 2002). Waste minimisation and waste disposal is increasingly becoming the focus points of the legislators owing to the impacts associated with the disposal facilities. This is demonstrated in the speech by the Deputy Minister of Environmental Affairs and Tourism (Mabudafhasi, 2005). “Steps were taken during the past year towards entrenching the commitment to a waste management system based on the principles of reduce, re-use and recycle. Substantial progress was made in addressing issues related to the management of hazardous waste streams”. In 2002 in an announcement on the White Paper on Integrated Pollution Control and Waste Management the Minister of Environmental Affairs said: “It puts pollution and waste management issues at the top of our Government’s agenda” (Clark, 2002)


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However, control and regulation of waste management is difficult. Environmental legislation, used to govern industry, to prevent and/ or minimise impacts on the environment and ensure that these impacts are acceptable are fragmented. A number of Acts and regulations deal with certain aspects of solid waste and hazardous waste (Fuggle & Rabie, 2000). The first and most important part to consider in this mini-dissertation is the determination of the legal requirements that the company needs to comply with to dispose of the tanning sludge. The bylaws of the municipality will not to be considered for the purpose of the dissertation, as the disposal of the tanning sludge is governed by national legislation. Section 20 of the Environment Conservation Act 1989, (Act 73 of 1989) (ECA) requires that waste be disposed to an appropriate permitted facility (DEAT, 1989). This implies that the responsibility lies with the company to ensure that their waste is disposed of to an appropriate permitted landfill, therefore ensuring that the receiving facility has the appropriate permits issued by the Department of Water Affairs and Forestry (DWAF). The National Environmental Management Act 1998, (Act 107 of 1998) (NEMA) also regulates waste management but in much broader principles. It is not as prescriptive as the Environment Conservation Act 1989, (Act 73 of 1989) but requires the implementation of governing principles such as duty of care, and the precautionary principle. Waste management must therefore apply to these governing principles, which are also set out in the Minimum Requirements (DWAF(a), 1998), before any disposal options can be considered. The following principles must therefore be considered: • Duty of care The individual or organization that generates wastes incurs a duty of care that is owed to

society. This means that the tanning facility is responsible for the fate of the waste at all times and in all circumstances. The tanning facility is therefore responsible for disposal of their waste in a responsible manner, which includes the disposal to a permitted waste site depending on the classification of the waste. The waste contractor removing the waste must therefore provide the company with a safe disposal certificate, proving that the tanning facility has handled, stored, transported and disposed of the waste according to legislation and in an environmentally sound and responsible manner.

• Precautionary principle The precautionary principle assumes that a waste or an identified contaminant of a waste is

both highly hazardous and toxic until proven otherwise. The Waste Management Series produced by the Department of Water Affairs and Forestry in 1998 are currently used to provide guidance on the classification and disposal of general and


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hazardous waste. These requirements represent the lowest acceptable standards and are therefore termed Minimum Requirements (DWAF(a), 1998). The newest contribution to the regulation of waste is the White Paper on Integrated Pollution and Waste Management for South Africa. The Department of Environmental Affairs published the White Paper in May 2000. This document is to ensure that visible actions are taken in establishing waste management infrastructure in townships, and deals with medical and other hazardous waste that contribute to the increased poverty and degradation of the environment, (Mabudafhasi, 2000). The implementation programme on waste and pollution has prioritised the following: • The minimisation of waste and pollution in the industrial sector • Hazardous waste management. The White Paper focuses on the importance of preventing pollution and waste as well as avoiding environmental degradation. Effective mechanisms to deal with unavoidable waste will remain necessary, but greater attention must be directed to the introduction of preventative strategies aimed at waste minimisation (DEAT, 2000). The White Paper’s aim would be to implement co-operative governance as envisaged in the constitution and to do away with the fragmented and uncoordinated way in which waste is currently being dealt with. The management of waste will be implemented in a holistic and integrated manner and will extend over the entire waste cycle, from cradle to grave. This includes the generation, storage, collection, transportation, treatment and final disposal of waste (DEAT, 2000). This dissertation focuses on the last part of the waste cycle, namely the disposal of the hazardous waste and the delisting of the waste. The White paper has adopted three principles specific to pollution and hazardous waste management which correspond with the National Environmental Management Act (NEMA) (DEAT, 2002): • Trans-boundary movement: potential trans-boundary effects on human health and the

environment will be taken into account • Duty of care principle: Any institution which generates waste is always accountable for

the management and disposal of its waste and will be penalised appropriately for any and every transgression committed

• Universal applicability of regulatory instruments: All industrial, agricultural, domestic/household and governmental operations in South Africa will be subjected to the same integrated pollution and waste management regulatory system.


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The National Waste Management Strategy presents a long term plan (up to the year 2010) for addressing key issues, needs and problems experienced with waste management in South Africa. The strategy gives effect to the Bill of Rights, Constitution of South Africa of 1996, (Act 108 of 1996). This also translates into action the Government’s policy on waste as set out in the Draft White Paper on Integrated Pollution and Waste Management in South Africa (published in 1998 by DEAT and Department of Water Affairs and Forestry) (DEAT & DWAF, 1999). The primary objective of introducing an integrated waste management planning system is to integrate and optimise waste management so that the efficiency of the waste management system is maximised and the impacts and financial costs associated with waste management are minimised (DEAT & DWAF, 1999) Government is considering the phasing out of co-disposal of hazardous waste with general waste, therefore it becomes increasingly important to classify the tanning facility’s waste so that it can be in line with the new legislation to be implemented in the near future. According to the National Waste Management Strategy and Action plans it will attempt to phase out co-disposal in hazardous landfill sites. Thus it is of utmost importance to ensure that non hazardous waste is not disposed of to hazardous waste sites (DEAT & DWAF, 1999). As well as the legalities involved with the management of waste, tanning sludge generation and the disposal of the tanning sludge, and major cost implications for the tanning facility are being investigated. Tanning sludge is produced as a by-product which needs to be disposed of by the tanning facility because it cannot be reused or recycled and is directly dependent on the production of hides. The Department of Water Affairs and Forestry (DWAF) regulates hazardous waste management in South Africa. Until recently it was responsible for the permitting of all landfill sites but this has been changed. The responsibility of permitting general landfill sites now lies with the provincial government. However, the management of the hazardous waste sites still remains a function of the Department of Water Affairs and Forestry. In order to upgrade the standard of waste management in South Africa and to provide a system whereby waste disposal can be regulated, the Department of Water Affairs and Forestry started to develop the Waste Management Series in 1994. These requirements represent the lowest acceptable standards and are therefore termed Minimum Requirements (DWAF(a), 1998).


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The series comprises three documents namely:

• Document 1: Minimum requirements for the handling, classification and disposal of hazardous waste sets out the classification system. The Minimum Requirements in this mini-dissertation refer mostly to this document (DWAF(a), 1998.

• Document 2: Minimum requirement for waste disposal by landfill, addresses landfill classification and the siting, investigation, design, operation and monitoring of landfill sites (DWAF(b), 1998.

• Document 3: Minimum requirements for the monitoring of water quality at waste management facilities: addresses the monitoring of water quality at and around waste disposal facilities (DWAF(c), 1998.

The Minimum Requirements for the Handling, Classification and Disposal of Hazardous Waste sets out a systematic framework for identifying and classifying the hazardous waste in accordance with the degree of risk that it poses. This document addresses important aspects of the hazardous waste disposal process so that the cradle to grave principle is implemented. The documents are intended to improve waste management in South Africa and to facilitate conformance with the international standards required by future trading partners and the Basel Convention. Thus these documents were extensively used in this mini-dissertation to describe the process involved to classify and delist the tanning sludge. In terms of the Minimum Requirements (DWAF(a), 1998) all industrial waste is classified as possibly or potentially hazardous. If the definition of waste is further considered, the tanning sludge produced during the process falls within this definition.

6.1 Classification of waste

The disposal of hazardous or potentially hazardous waste has major implications for the tanning facility. It requires stringent control and management to prevent harm or damage to the environment to reduce the tanning facility’s liabilities. In order to determine the risk associated with the disposal of the tanning sludge, the facility needs to go through a process of classifying the waste. The classification of hazardous waste is set out in Figure 8 as described in the Minimum Requirements (DWAF(a), 1998). Figure 8 illustrates the steps to be followed when waste is to be classified. The first step in the process is to identify the waste or waste stream and determine whether the waste is hazardous or not. Industries and processes, which are likely to generate hazardous waste, can be identified by determining whether the processes or industry is listed in the Minimum Requirements (DWAF(a), 1998). Tanneries and associated industries form part of the listed waste streams as described in


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Table 3. Once a process is listed in Table 3 it is assumed that waste generated in this process is potentially or possibly of a hazardous nature and needs to be controlled. Step 2 in Figure 8 confirms that when the waste is hazardous, it must be analysed for its properties and its substances according to the analytical methods provided in the Minimum Requirements(DWAF(a), 1998). These are then compared to the list of characteristics, properties and substances in SABS Code 0228, the Basel Convention and waste classification tables as set out in the Minimum requirements (DWAF(a), 1998; Fuggle & Rabie, 2000).

Figure 8: The process of classifying the tanning sludge

Step 1: Identify the waste or waste streams as probably hazardous

Step 2: Test and analyse the waste to determine the hazardous properties,

characteristics and components

Step 3: Classification and treatment in accordance of SABS Code 0228

Step 4: Analysis and hazard rating of the waste or its residue, in order to determine the hazard rating and the minimum requirements for

disposal


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Table 3: Identification of Hazardous waste (DWAF(a), 1998) Select Industrial group Identify process Key Identify waste stream A Agriculture, forestry and food products A – Agriculture, forest management, fisheries

- Animal and vegetable products from the food sector - Drink industry - Manufacture of animal feed

A1 A2 A3 A4

A Inorganic wastes • acids and alkalis • cyanide wastes • heavy metal sludge and solutions • Asbestos wastes • Other solid residues

B Mineral extraction and upgrading (excluding hydrocarbons)

B - Mining and quarrying of non metallic minerals - Mining and quarrying of metallic minerals

B1 B2

B Oily wastes • Primarily from processing, storage and use of

mineral oils C Energy C – Coal industry including gas works and coking

- Petroleum and gas industry including extraction of refined pre-cuts - Production of electricity

C1 C2 C3

C Organic wastes • Halogenated solvents residues • Non- halogenated solvent residues • PCB wastes • Paint and resin wastes

D Metal Manufacture D – Ferrous metallurgy - foundry and metal working operations

D1 D2 D3

D Putrecible organic wastes • Production of edible oils, slaughter houses, tanneries

and other animal based products E Manufacture of non metal mineral products E- Construction materials, ceramics and glass

- Salt recovery and refining - Asbestos goods - Abrasive products

E1 E2 E3 E4

E High volume/ Low hazard wastes • Those wastes which, based on their intrinsic

properties, represent relatively low hazards, but may pose problems because of their high volumes (e.g. drilling mud, fly ash from power plants, mine tailings, etc)

F Chemical and related industries F- Petrochemicals - Production of primary chemicals and feedstock - Production of fine chemicals - Production of inks, varnish, paint and glue - Fabrication of photographic products - Production of pharmaceuticals - Rubber and plastic materials - Production of explosives - Production of biocides - Waste and water treatment

F1 F2 F3 F4 F5 F6 F7 F8 F9 F10

F Miscellaneous wastes • Infectious waste from diseased human/ animal tissue • Redundant chemicals • Laboratory wastes • Explosive wastes from manufacturing operations or

redundant chemicals

G Metal goods, engineering, and vehicle industries

G- Mechanical engineering - Electronic and electrical engineering Manufacture of motor vehicle parts

G1 G2

H Textile, leather, timber and wood industries H – Textile, clothing and footwear industry - Hide and leather industry - Timber, wood and furniture industry

H1 H2 H3

J Manufacture of paper and products, printing and publishing

J- Paper and cardboard industry - printing, publishing and photographic laboratories

J1 J2

K Medical Sanitary an other Health Services K – Health, hospitals, medical centres and laboratories - veterinary services

K1 K2

L Commercial and personal services L – Laundries, dyers and dry cleaners - domestic services - Cosmetic institutions

L1 L2 L3


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Step 3 in Figure 8 involves the classification and treatment in accordance of the SABS Code 0228: “The identification and classification of dangerous goods and substances” is a system which is used to classify hazardous substances for transport purposes (SABS, 2000). In this Code hazardous substances are given an identification number and divided into nine classes as described in Table 4. The waste must, therefore, be tested against these classes to determine into which class it can be divided, and to determine the minimum requirements that must be met when the waste is disposed of (DWAF 1998; Fuggle & Rabie, 2000). The SABS Code is used as an inclusive hazardous waste list, and explicitly identifies hazardous substances. The presence of a substance on the list automatically brings the waste into the regulatory control system. However, the absence of a substance from this list does not necessarily imply that the substance is not hazardous (DWAF(a), 1998).

Table 4 SABS Code 0228 classify hazardous substances into nine classes

Class Description

Class 1 Explosives

Class 2 Gases

Class 3 Flammable liquids

Class 4 Flammable solids

Class 5 Oxidising substances and organic peroxides

Class 6 Toxic and infectious

Class 7 Radioactive substances

Class 8 Corrosive

Class 9 Other miscellaneous substances

The Minimum Requirements can also be used to determine whether waste can be treated to reduce its hazardousness (DWAF(a), 1998). To understand the classification, the hazard rating must be considered. The hazard rating of waste is the toxicity of the waste after treatment. This is determined for waste that falls within Class 6 of the SABS Code 0228 (SABS, 2000). Hazardous substances in this Class 6 are given danger ratings for transport and divided into two danger groups: • Toxic • Infectious These danger groups relate mainly to the risk the substance poses to man during transport, whereas the hazard rating for disposal takes into account the risk to the environment, therefore


43

the acute ecotoxicity of a substance is used in addition to the acute mammalian toxicity (LD50) (DWAF(a), 1998). Hazard Rating is a system for classifying and ranking hazardous waste according to the degree of hazard they present (DWAF(a), 1998). Acute ecotoxicity is the potential to harm animals and plants, but more specifically ecosystems (DWAF(a), 1998) whereas acute mammalian toxicity (LD50) indicates the statistical dosage that will kill 50% of the test organisms concerned, and values are expressed per kg body mass (DWAF(a), 1998). The hazard rating for disposal is complex and takes into account the LC50, which is the concentration at which a substance will kill 50 per cent of organisms if it were disposed of directly into a water body. Should the concentration of the hazardous substance be only ten per cent of the LC50, it should have very little effect on the aquatic organisms. This represents the Acceptable Risk Level (ARL) (DWAF(a), 1998). The Acceptable Risk Level (ARL) is the concentration of a substance that will have a minimal effect on the environment. This is represented by the acute ecotoxicity multiplied by a chosed safety factor of 10% (0.1 x LC50) (DWAF(a), 1998) The Estimated Environmental Concentration (EEC) is used to provide an exposure level and assimilation capacity approach. In this approach, chemical compounds are regarded as being hazardous above a threshold concentration. In order to determine the hazard rating the estimated environmental concentration of the substance is calculated in grams disposed of per hectare per month multiplied by a factor of 0.66. The Estimated Environmental Concentration is compared to the Acceptable Risk Level (ARL). If the estimated environmental concentration is higher than the Acceptable Risk Level (ARL), then the waste remains in the originally classified Hazard Rating. If the estimated environmental concentration is lower than the Acceptable Risk Level (ARL), the waste may delist to a lower hazard rating (DWAF(a), 1998). The Estimated Environmental Concentration is therefore used to determine the amount of a substance that can safely be disposed of per hectare per month at a landfill site. It is also used to determine the total amount of a hazardous substance that may be accepted at a certain landfill site, before it be must closed for that substance (DWAF(a), 1998). The fate of the waste stream is regulated by the most hazardous contaminant of which the estimated environmental concentration exceeds the Acceptable Risk Level (ARL) (worse case scenario). Hazardousness can be reduced by treatment. The idea of treatment is to treat the contaminant from one specie to another in order to prevent or minimise its leachability and hence it mobility into the environment. Legislation is stricter for highly hazardous and toxic wastes and the costs associated with the treatment and disposal are consequently higher than waste of lower hazards. It is therefore of the utmost importance that the tanning facility obtain the necessary proof that the tanning sludge


44

produced during the production of the crust is not hazardous and could probably be disposed of to a general waste landfill site. The burden of the proof shall always be on the tanning facility which is responsible for the generation of the waste. The main reason for this study is to provide the necessary proof that the waste that is generated is not hazardous or toxic, therefore the retanning process will now be evaluated in the next section in an attempt to understand the characteristics and properties of the tanning sludge

6.2 Revision of the Minimum Requirements

DWAF is required in terms of the National Waste Management Strategy, which was completed in 1999, to revise the Minimum Requirements every five years and, therefore the Department in collaboration with the DEAT, has embarked on a process which is expected to lead to a third edition of the documents (Baldwin, 2005). The principles governing the revision are that they must provide solutions for South African conditions, be of the highest technical standard, be cost effective and include social issues such as waste salvaging. The major changes are expected in the hazardous waste document, where the classification system will be modified to include human toxicology not just ecotoxicity (toxicity to fish). The total load principle will be revised, guidelines will be included for evaluation of waste utilization options and a sectorial approach to the metallurgical and other industries will be included. The current hazardous waste document gives a very conservative approach to waste classification, and although this is expected to be modified, it will in the future form the primary or “tier one” assessment of the environmental risks posed by waste. The third edition may be expanded considerably to include guidelines for second and third tier risk assessment that will be site specific and include study factors such as site design, site location, hydrology, geology, meteorology, leachability and human and ecotoxicology (Baldwin, 2005). Site specific issues that are expected to be included in the revised hazardous waste document are: • Attenuation in the landfill, • The saturated zone beneath the landfill • A specific pathway may not be present, when assessing the risks associated with a

particular action.


45

The applicability of the Toxicity Characteristic and Leaching Procedure (TCLP) and Acid Rain Leaching Procedure (ARLP) tests are under discussion. Both of these tests leach wastes under conditions that are not observed in a permitted landfill and operated in terms of its permit requirements. Therefore these tests tend to over estimate the environment risks. The possibility exist that additional leaching tests are being considered. These tests could include those that leaches wastes at a higher pH (pH 7) than the Toxicity Characteristic Leaching Procedure (TCLP) and/or at the resting pH of metallurgical wastes. The high pH of some monolithic materials such as slags and cement based pre-cuts can result in an increase in leaching of anionic species such as Arsenic (As) and hexavalent chromium (Cr(VI)). Compared to the levels observed at low pH (pH 4) values such as the Toxicity Characteristic Leaching Procedure (TCLP) and ARLP. The impact of the above changes will allow one to more realistically assess the potential impact on the environment of any wastes generated and an approach to evaluation of wastes as alternative material is expected to be developed. The methodology and approach that was followed to verify the presence of hexavalent chromium (Cr(VI)) and cyanide (CN), and determining the characteristics of the tanning sludge will be discussed in detail in the next section.


46

7. DATA COLLECTION AND METHODOLOGY In the following section the approach and methodology used to the collect the data on the various waste streams produced during the retan process is discussed. In order to achieve the main aim to classify and delist the tanning sludge from the retan process, the objectives set out in Section 2 must be achieved. These objectives include the following: • Describe and discuss the production of crust leather • Identify the various waste streams produced during the retan process • Determine whether hexavalent chromium (Cr (VI)) and cyanide (CN) could be formed in

the process, by determining what is available in the literature. In determining whether hexavalent chromium (Cr (VI))and or cyanide (CN) could be produced during the process the existing conditions in the tanning facility must be compared to the literature

• Identify the relevant legislation pertaining to waste management including the safe disposal of tanning sludge

• Determine the presence of hexavalent chromium (Cr (VI)) and cyanide (CN) in the raw materials (incoming materials) used in the production of crust leather

• Determine the presence of hexavalent chromium (Cr (VI)) and cyanide (CN) in the effluents as this will provide an indication whether it is produced in the process or not

• Determine the presence of hexavalent chromium (Cr (VI)) and cyanide (CN) in the tanning sludge. Determine the leachate character of the existing tanning sludge to determine the presence of Cr (VI) and cyanide (CN). The tanning sludge will be analysed following the analytical procedure described in the Minimum Requirements (DWAF(a), 1998)

• Classify the tanning sludge according to the Minimum Requirements (DWAF(a), 1998) • Make a recommendation on where the tanning sludge could be disposed of. In the previous section an overview was provided of the legislation pertaining to the waste management including the disposal of the tanning sludge. In the following section the methodology used to achieve the objectives to classify and delist the tanning sludge will be discussed. This will include: • A list of the data required • The type of data needed • The reasons for this data • A brief discussion on the problems encountered.


47

Before the data is identified, it must be determined what baseline information is needed to determine whether the tanning sludge is hazardous. The Minimum Requirements provides the following list of properties and sources that would result in the tanning sludge being hazardous: (DWAF(a), 1998): • The raw materials utilized in the manufacturing process, or the intermediates and products

in a manufacturing process should be evaluated and classified as hazardous in terms of the SABS Code 0228, The Basel Convention, or the Waste Classification Tables as published in the Minimum Requirements. As discussed in Section 6, Table 4 on page 37 determines that any waste originating from leather industries is considered to be hazardous.

• Products used in service industries that are classified as hazardous substances, e.g. solvents, grease and oil

• The nature and properties of the waste, e.g., oily residues, sludge from heavy metal processing, water treatment, or organic chemicals processing; or waste with flammable, toxic, reactive, corrosive or explosive properties.

• Putrecible organic waste, e.g. waste arising from the production of edible oils, skins and other animal based products

• Poisonous or toxic chemicals utilized in agriculture, forestry and related industries; • Packaging materials contaminated with hazardous substances; • Waste arising from hospitals, medical clinics, veterinary services and similar services; • Pharmaceutical wastes; • Residues such as ash, slag and leachate; and • Waste designated as hazardous by authorities. The tanning facility produces a putrecible organic waste i.e. waste arising from the production of hides and therefore it is also listed in the waste classification tables as set out in Table 3. As described in the Minimum Requirements, the onus and responsibility is on the Generator to determine whether the waste is hazardous or not. In order to determine whether the tanning sludge produced during the manufacturing of automotive leather is hazardous, it is necessary to engage in a process to determine the characteristics of the tanning sludge. In this section the process that was followed to determine the data needed to achieve the objectives as set out in Section 2 and above will be discussed. The following data was required to achieve the objectives. Each of these requirements will be discussed in detail below in terms of the reasons for the data, how it was obtained etc: • The first step was to ensure that no restricted substances such as cyanide (CN)) and

hexavalent chromium (Cr(VI)) enters the process through the raw materials and thus


48

ending up in the tanning sludge. This entailed the review of the composition of substances found in the raw materials.

• In addition to the verification of the raw materials, it must be determined whether hexavalent chromium (Cr(VI)) or cyanide (CN) is present in the effluent waste streams. This includes the wetting back water, the retan effluent discharged to the dissolved air flotation plant and the effluent discharged to the sewer network.

• The third step was characterising the tanning sludge in order to determine what constituents are present in the tanning sludge and to verify the presence/and or absence of specifically the hexavalent chromium (Cr(VI)) and cyanide (CN).

Each of these will be discussed in more detail below. It must be noted that the collection of data ran in parallel with each other.

7.1 Verification of raw materials

In the abovementioned list obtained from the Minimum Requirements (DWAF(a), 1998) to determine whether waste is hazardous it is important to note that that it starts off with evaluating the raw materials used in the manufacturing process. The raw materials include all the chemicals that are used in the process as well as the wet whites and wet blues. For obvious reasons it is important to determine whether any of the raw materials, including the hides and chemicals, contain any substance that will result in the tanning sludge not being delisted.

7.1.1 Reasons for evaluating the raw materials include the following: • In Figure 9 the tanning facility is illustrated as an open system as described. The raw

materials enter the retan process and products and waste are produced. The raw materials enter the retan process and are changed to form the products that leave the process. It can be assumed, that should the raw materials be classified as hazardous or contain hazardous substances such as cyanide (CN) or hexavalent chromium (Cr(VI)) and are used in significant quantities, the product and waste will contain the hazardous substance.

Figure 9: The manufacturing process described as a system

Raw Materials

(Chemicals, water, hides)

RETAN

PROCESS

Products (Crust leather)

+ Waste

(Effluent, solid waste)


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• The process determining whether the tanning sludge is hazardous started with the evaluation of the raw materials that are used so that it could be eliminated as a source of hexavalent chromium (Cr(VI)) and cyanide (CN). The incoming raw materials were evaluated specifically for the presence of hexavalent chromium (Cr(VI)) or cyanide (CN) since these were the two substances found previously in the tanning sludge which caused it to be classified as extremely dangerous/ or hazardous and resulted in the tanning sludge not being delisted. Refer to Appendix III for a list of the raw materials that is used.

• Another important reason for gathering this data is the requirements of the environmental management system. The environmental management system requires that necessary proof must be provided on the control that the tanning facility has or is expected to have over its products, services and activities, which include the control over the substances in the raw materials and therefore also in the waste (SABS, 2004).

Customers of the tanning facility have strict requirements on what chemical substances are allowed to be in and/or on the final product. Some of these chemical substances might be present in very low concentrations where as others are not allowed to be present under any circumstances. The tanning facility has compiled a list of substances that the majority of customers will not tolerate in the product supplied to them. This was compiled to form the so-called Black List as seen in Appendix I. Two of these restricted substances include hexavalent chromium (Cr(VI)) and cyanide (CN). It is also possible that some of the other substances on the Black List may cause the tanning sludge not to delist if found to be present in high concentrations, for example arsenic.

A conservative approach was followed in obtaining information on the compositions of the raw materials. This means that no assumptions were made regarding the necessary information but that as much information as possible was requested from the suppliers of the hides and chemicals. A letter was drafted and sent to all the suppliers of raw materials used in the process, requesting information on the presence of any of the restricted substances listed in the Black List. A copy of the letter is included in Appendix II. In addition to the letters sent to the suppliers of raw materials, the Material Safety Data Sheets (MSDS) of the chemicals used in the Retan process were evaluated by reading through the Material Safety Data Sheets (MSDS). A Material Safety Data Sheet (MSDS) is a document used in transferring essential information on the hazards of handling a chemical substance during transport, storage and processing from the supplier to the handler. In terms of regulations promulgated under the Occupational Health and Safety Act (Act No. 85 of 1993) (R1449 of 6 September 1996; Government Notice No. 17403), it is compulsory for the supplier of any hazardous chemical substance to provide a material safety data sheet to any party which receives such a substance (Department of Labour 1993; Chief Health and Safety Inspector 2002). The


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Material Safety Data Sheets (MSDS) contain the following information and are therefore considered as an option to evaluate the raw materials: Material Safety Data Sheets (MSDS) comprise the following 16 sections: • Section 1 : Chemical product and company identification • Section 2 : Composition/information on ingredients • Section 3 : Hazardous identification • Section 4 : First aid measures • Section 5 : Fire-fighting measure • Section 6 : Accidental release measures • Section 7 : Handling and storage • Section 8 : Exposure controls/personal protection • Section 9 : Physical and chemical properties • Section 10 : Stability and reactivity • Section 11 : Toxicological information • Section 12 : Ecological information • Section 13 : Disposal considerations • Section 14 : Transport information • Section 15 : Regulatory information • Section 16: Other information, e.g. Label requirements, NFPA classification, references,

etc. A dangerous goods register was compiled to summarise the available information. This is included in Appendix III.

7.1.2 Analysis of the data The letters of the various suppliers were evaluated and checked against the customers’ requirements such as the Black List and other requirements specified (Ford Company, 2003). The feedback from customers will be discussed in Section 8.1. The seconds step was to determine whether any hazardous substance could be identified through evaluating the Material Safety Data Sheets of each of the chemical substances. This was not a very successful exercise as the information in the Material Safety Data Sheets was not sufficient.


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7.1.3 Difficulties encountered during this phase The following difficulties were encountered during this phase: • The information on the Material Safety Data Sheets (MSDS) does not contain any

specific information on the composition of the chemicals, or sufficient information on the possible impacts of the chemicals on the environment

• The suppliers are not willing to provide specific information on the composition of their products, due to the intense competitiveness between the various companies.

In order to overcome this problem the next step was to sample and determine whether any of the effluent waste streams of the retan process could probably contain cyanide (CN) and hexavalent chromium (Cr(VI)).

7.2 Sampling of effluent waste streams connected to the retan process

Once the raw materials were being evaluated it was necessary to determine whether the hexavalent chromium (Cr(VI)) and cyanide (CN) were present at any time during the process in any of the effluent waste streams. The reasons for sampling the different effluent waste streams was to determine whether hexavalent chromium (Cr(VI)) could be generated in the various phases of the retan process resulting in hexavalent chromium (Cr(VI)) being present in the tanning sludge. Hexavalent chromium (Cr(VI)) is a highly oxidized state of metallic chromium and occurs as a yellow coloured dichromate salt under neutral (pH 6.5 – 9) or alkaline (pH > 9) conditions and as the orange – coloured chromate salt under acidic conditions (pH< 6.5). Hexavalent chromium (Cr(VI)) is highly water soluble at a wide range of pH values and thus testing for it is relatively easy (DWAF, 1996). Various ad hoc samples were taken from the following effluent waste streams: • The wetting back water • The retan effluent just before it enters the dissolved air flotation plant • The final effluent The results of the analyses will be discussed in Section 8.2


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7.2.1 Reasons for the sampling of the effluent waste streams connected to the retan process The Wetting back water was tested for the following reasons: As discussed earlier in the description of the process in Section 3, the wetting back phase is used only to restore the moisture in the hides. During this process no additional chemicals, but water, a surfactant and degreaser are added and milled for approximately 30 minutes. The wetting back effluent would therefore be the first effluent to be tested for hexavalent chromium (Cr(VI)) as this would be an indication whether hexavalent chromium (Cr(VI)) is entering the process from outside the tanning facility as part of the wet blues. Furthermore hexavalent chromium (Cr(VI)) physical properties and characteristics allow for it to be tested as it is highly soluble under these pH conditions. Similar reasons to that of the wetting back water apply for analysing the retan effluent: • In testing the retan effluent it can be determined whether any of the raw materials used in

the retanning process contain hexavalent chromium (Cr(VI)) as this will test positive should it be present under these conditions

• To determine whether there are any circumstances, during the process, which could result in the oxidation of the trivalent chromium (Cr(III) to hexavalent chromium (Cr(VI)) (as discussed in the literature overview in Section 5).

Samples of the wetting back, retan water and the dissolved air flotation effluent were taken according to the principles described in Minimum Requirements for Water Monitoring at Waste Management Facilities. These principles for sampling were used to ensure that all samples are taken in the same way so that these results could be reproducible in the future should it be necessary (DWAF(c), 1998): • Three 500 ml samples were taken from the water discharged to the drains at various times

and dates from various suppliers to ensure that a representative sample is taken from the process.

• The samples were submitted to an approved laboratory specialising in water analysis, the Waterlab, within 2-3 hours after taking the samples. The analysis was conducted for the constituents listed in Table 5 on the next page. These constituents form part of the monthly effluent monitoring programme that is conducted on the effluent produced in the tanning facility. These constituents were chosen as they are representative of the tanning effluent. Heavy metals are analysed to determine whether this are present in the wetting back water.


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• Samples were analysed according to the Standard Methods for the examination of water and waste water for each of these elements (Clescerl et al, 1998 ).

Table 5: Constituents analysed for in the wetting back and retan effluent samples

Constituents Constituents

pH Chromium as Cr

Conductivity in mS/m at 25 ° C Hexavalent chromium as Cr(VI)

Alkalinity as CaCO3 Copper as Cu

Calcium as Ca Iron as Fe

Magnesium as Mg Manganese as Mn

Chloride as Cl Vanadium as V

Sulphate as SO4 Total dissolved solids at 180 ° C

Sodium as Na Chemical oxygen demand as O2

7.2.2 Analysing the data Once the results were obtained from the Waterlab these were scrutinised to determine whether cyanide (CN) and hexavalent chromium (Cr(VI)) were present and further compared to the Municipality’s Effluent Standards and the SABS drinking water qualities.

7.2.3 Difficulties encountered during the process A shortcoming identified during this phase was, that the analysis did not include cyanide (CN) as a constituent to be analysed for in the initial sampling run of the wetting back and retan effluents. The reason for this was that cyanide (CN) is not a substance that is normally used in the tanning industry. Therefore it was never included as part of the constituents analysed for. The fact that cyanide (CN) was detected in the tanning sludge on the previous occasions that testing was undertaken was contributed to the use of iso-cyanates as cross linkers in the tanning process. Therefore cyanide (CN) was not included into the initial sampling analysis since no reason could be determined as to why the cyanide (CN) should be present in the effluents. Wetting back and retan effluent were tested for the presence of cyanide (CN) much later in the project, following the same principles as set out above for taking samples. If this testing was carried out in the original exercise, considerable time could have been saved.

7.3 Analysis of the tanning sludge

It is fair to say that all the bases have been covered to determine the possible sources from where hexavalent chromium (Cr(VI)) and cyanide (CN) could enter into the retan process and therefore


54

explain their presence in the tanning sludge. Therefore the next phase that must be discussed is the determination of the characteristics of the tanning sludge and to determine whether hexavalent chromium (Cr(VI)) and cyanide (CN) are present in the tanning sludge. Once again, the reader is reminded that although the project is divided into three phases, all these phases run concurrently. The reasons for analysing the tanning sludge were to: • Determine the properties of the sludge • Correctly identify any other possible hazardous substances in the waste, • Provide the information needed for classification and hazard rating. In following these steps the tanning facility will be able to determine whether a hazardous or potential hazardous waste is being produced.

7.3.1 Reasons for sampling the tanning sludge Three dry tanning sludge samples, were taken from the tanning sludge waste bins as these are representative of the condition of the tanning sludge that will be disposed of to Holfontein. These samples originate from the filter press which removes 80% of the water from the tanning sludge. The method for taking tanning sludge samples will be discussed in detail later in this section. Three different sets of tanning sludge samples taken from the waste skips were submitted to the same laboratory used for the effluent sample analysis. Three samples were taken for the following reasons: • The first tanning sludge sample was used for screening purposes to determine what the

potential substances are that could pose a problem resulting in the tanning sludge not being delisted. This sample focused mainly on the presence of the hexavalent chromium (Cr(VI)). Table 6 provides the list of constituents that were tested for in order to characterise the tanning sludge. These constituents were chosen in consultation with a specialist on the classification of waste. The results are discussed in Section 8.


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Table 6: Analysis conducted on the first tanning sludge sample to verify the presence of hexavalent chromium (Cr(VI))

Constituents Constituents

TCLP solution II Aluminium as Al

Mass (g) Boron as B

Volume (ml) Chromium as Cr

Moisture Chromium as Cr(Umgeni)

Conductivity in mS/m at 25 ° C Copper as Cu

Total dissolved solids at 180 ° C Hexavalent chromium as Cr6+

Alkalinity as CaCO3 Hexavalent chromium as Cr6+ (Umgeni)

Ammonia as N Iron as Fe

Chloride as Cl Manganese as Mn

Sulphate as SO4 Vanadium as V

Ortho phosphate as P Zinc as Zn

Sodium as Na Free cyanide as CN

Calcium as Ca Magnesium as Mg

• Once the presence of hexavalent chromium (Cr(VI) was determined, a second tanning

sludge sample was taken for full analyses of all the applicable constituents required in terms of the Minimum Requirements as set out in Table 7 (DWAF(a), 1998). The tanning sludge was further treated with lime to determine the physical treatment options before the waste is disposed of to a landfill site. Lime is used as a precipitating agent to remove heavy metals from the solution (DWAF(a), 1998). Both the extractions from the tanning sludge sample and the treated tanning sludge were analysed strictly according to the Minimum Requirements (DWAF(a), 1998). Part of the toxicity characteristic leaching procedure analysis makes use of a Toxicity Characteristic Leaching Procedure (TCLP) solution II which is a more conservative method compared using Toxicity Characteristic Leaching Procedure (TCLP) solution I. This analysis will be discussed in more detail later in the section.

The Minimum Requirements can also be used to determine whether the waste can be

treated to reduce its hazardousness (DWAF(a), 1998). To understand the classification the hazard rating must be considered. The hazard rating of waste is based on the toxicity of the waste after treatment. Therefore the tanning sludge was treated with lime in order to determine what the hazard rating would be after treatment.


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Table 7: Analysis conducted on the second tanning sludge sample

Constituents Constituents Constituents

TCLP II Magnesium as Mg Selenium as Se

MASS (g) Aluminium as Al Titanium as Ti

VOLUME (ml) Arsenic as As Vanadium as V

10% pH Barium as Ba Zinc as Zn

pH Boron as B Free cyanide as CN

Conductivity in mS/m at 25 ° C Cadmium as Cd Silver as Ag

Chloride as Cl Chromium as Cr Beryllium as Be

Sulphate as SO4 Chromium as Cr [Umgeni] Bismuth as Bi

Ortho-phosphate as P Cobalt as Co Lithium as Li

Silica as Si Copper as Cu Molybdenum as Mo

Fluoride as F Hexavalent chromium as Cr6+ Antimony as Sb

Sodium as Na Hexavalent chromium as Cr6+ [Umgeni] Tin as Sn

Potassium as K Iron as Fe Strontium as Sr

Calcium as Ca Lead as Pb Zirconium as Zr

Mercury as Hg Manganese as Mn Nickel as Ni

• The first two sets of samples were subjected to a toxicity characteristic leaching procedure

with very low pH (as required by the Minimum Requirements). However, this is not deemed to be representative of the environment that exists or may exist in landfill sites, therefore a less conservative approach was followed for the analysis of the third tanning sludge sample extractions. A full analysis was conducted for all the constituents as listed in Table 8. The Toxicity Characteristic Leaching Procedure (TCLP) were conducted at a higher pH (5.5) to model a more representative environment in the landfill site at which hazardous substances such as heavy metals will be mobilised or leached. The results will be discussed in Section 9.


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Table 8 Analysis conducted on the third tanning sludge sample

Constituents Constituents Constituents

TCLP I Aluminium as Al Selenium as Se

MASS (g) Arsenic as As Titanium as Ti

VOLUME (ml) Barium as Ba Vanadium as V

10% pH Boron as B Zinc as Zn

pH Cadmium as Cd Free cyanide as (CN)

Chloride as Cl Chromium as Cr Silver as Ag

Sulphate as SO4 Chromium as Cr [Umgeni] Beryllium as Be

Ortho-phosphate as P Cobalt as Co Bismuth as Bi

Silica as Si Copper as Cu Lithium as Li

Fluoride as F Hexavalent chromium as Cr6+ Molybdenum as Mo

Sodium as Na Hexavalent chromium as Cr6+ [Umgeni] Antimony as Sb

Potassium as K Iron as Fe Tin as Sn

Calcium as Ca Lead as Pb Strontium as Sr

Magnesium as Mg Manganese as Mn Zirconium as Zr

Mercury as Hg Nickel as Ni

7.3.2 The method used for tanning sludge sampling and analysis The following approach was adopted to sample the tanning sludge and to determine the leachate character of the tanning sludge: • Three samples were collected on different days at different times from the tanning sludge

removed from the filter press. In Figure 10 on the next page the waste bins are shown that are used to dispose of the tanning sludge from the filter press before it is removed by an approved waste management company. Each sample comprised of ten 500 ml glass jars filled randomly from the different waste bins in order to obtain composite samples that would be representative of the tanning sludge produced during the process.

• The samples were submitted to the Waterlab for processing and analysis • All three samples were prepared for analysis by using the toxicity characteristic leaching

procedure as set out in the Minimum Requirements for handling, classification and disposal of hazardous waste (DWAF(a), 1998)

• The second and third samples were also treated with lime to determine the possible treatment options required for disposal.


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Figure 10: The tanning sludge waste bins into which the dried tanning sludge from the filter press was disposed of for removal by Wastec

• The tanning sludge was dried, and sieved through a 9.5 mm sieve Tanning sludge samples were prepared as follows: 100 g of dried sieved tanning sludge was extracted for 20 hours with Toxicity

Characteristic Leaching Procedure (TCLP) extract no II or no I and filtered through a glass fibre filter

The tanning sludge & lime samples were prepared as follows: 91 g of dried sieved tanning sludge was mixed with 9 g lime - this mixture was

extracted for 20 hours with Toxicity Characteristic Leaching Procedure (TCLP) extract no II or no I and filtered through a glass fibre filter

This Toxicity Characteristic Leaching Procedure (TCLP) testing procedure was developed

in the United States of America by the Environmental Protection Agency (EPA) to measure the leachability of wastes and hence the risk it posed to groundwater. The method used in South Africa to do this is called the Estimated Environmental Concentration (DWAF(a), 1998). This is a method whereby the exposure of fauna to compounds of concern in the waste is estimated and quantified. The two approaches to waste classification, Estimated Environmental Concentration and the Concentration Based Exemption Criteria have a number of important fundamental differences. However in general they lead to comparable values for the hazardousness of various wastes and waste streams. The Toxicity Characteristic Leaching Procedure (TCLP) can therefore be used to support or affirm the Estimated Environmental Concentration (DWAF(a), 1998).


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• The toxicity characteristic leaching procedure is used when a waste is to be disposed of in

a landfill site that receives a variety of organic and inorganic wastes. The process stimulates the dissolving action of the organic acid leachate formed in a landfill where hazardous waste has been co-disposed with general waste. The results can be used to determine the mobility of organics and inorganics in liquid, solid and multiple wastes (Toxicity Characteristic Leaching Procedure Federal Register and Toxicity Characteristic Rule, ibid 1990). The extract obtained during this Toxicity Characteristic Leaching Procedure, simulate the potential leachate that may form once the waste is co-disposed of to a hazardous landfill site. This leachate is then analysed for the constituents of concern since this will be mobilised during low pH (4.5) conditions (DWAF(a), 1998). The Waterlab conducted the analysis according to the Standard Methods for the examination of water and waste water for each of these elements (Clescerl et al, 1998).

The toxicity characteristic leaching procedure (TCLP) is based on the fact that different

hazardous constituents exhibit different solubilities under landfill conditions. For example, a waste containing mercuric sulphide, which is extremely insoluble under normal conditions, might be mobilised during the prevailing conditions in a landfill site. It is important to note that the mobility of particular identified hazardous elements or compounds will depend on their nature and composition. The procedure is also useful for evaluating the residues or products of wastes after solidification or other waste treatment technologies.

In order to verify the analysis of the hexavalent chromium (Cr(VI)) it was decided to make use of an additional laboratory to the Waterlab. Extraction from the tanning sludge samples were submitted to Umgeni Water for chromium (Cr) and hexavalent chromium (Cr(VI)) analysis. Umgeni Water uses a different analysis method than the Waterlab. Umgeni makes use of the Ion Chromatography method which allows for a lower detection limit of 0.004 mg/l, compared to the standard colorimetric method used by the Waterlab which gives a detection limit of 0.025 mg/l. The analysis conducted on the extractions by the Waterlab was conducted according to the Standard Methods for the Examination of Water and Waste Water for each of these elements (Clescerl et al, 1998). Thiocynate analysis was conducted on the third sample in order to determine the presence of the free cyanide (CN) or whether the thiocynate may interfere with the cyanide (CN) analysis. The tanning sludge samples were not analysed for any organic compounds as previous studies had demonstrated that the sludge does not leach volatile and semi-volatile organic compounds at


60

significant concentrations that would have an impact on the environment and/or promote the leachability of heavy metals (Golder and Associates, 2002).

7.3.3 Analysing the tanning sludge results The aim of analysing the tanning sludge for the constituents is to characterise the tanning sludge. Once this is done it can be classified in terms of its hazard ratings. Once the hazard ratings are determined and found to be lower than the previous hazard ratings the tanning sludge can be delisted and therefore disposed of to a general landfill site. The aim of disposing hazardous waste is to implement reasonable controls to make disposal of the waste acceptable and therefore conform to an acceptable risk to man and/or the environment. Various pathways of exposure exist for the hazardous substances, which may effect the environment or health of people and animals. The end point of effect could therefore be any kind of living matter, whether man, plant or animal. In the case of hazardous waste disposal, the environment that is most likely to be affected is groundwater. This in turn is a potential pathway ultimately reaching man, animals or plants. However the aquatic environment is the first to suffer therefore the aquatic environment is considered as the end point to be affected. In order to determine whether the risk is acceptable the Estimated Environmental Concentration (EEC) must be determined for each of the variables that were analysed. It would involve the calculation of the total amount of a contaminant in a waste stream which would be disposed on a specific unit area of the site (one hectare). The results of the tanning sludge were compared to the Acceptable Risk Limit (ARL). In the Minimum Requirements the delisting concentrations are defined as (Baldwin, 2005): • HG 1 ? HG3/4 when the EEC is < ARL This means that the waste can delist from an extreme high hazard rating to a moderate or

low hazard rating provided that the estimated environmental concentration is less than the Acceptable Risk Level (ARL) for the aquatic environment.

• HG1 ? General when the EEC is < ARL/10 Waste can delist from an extreme high hazard rating to a general waste rating provided

that the estimated environmental concentration is ten times less than that of the estimated environmental concentration.

• HG2/3/4 ? General when the EEC is < ARL Waste can be delisted from a high, moderate and low hazard rating to general waste

provided that the estimated environmental concentration is less than the Acceptable Risk Level (ARL) for the aquatic environment


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• Also total load in g/ha/m = ARL in ppb/0.66 The disposal of a total load in grams/hectare/month of the hazardous substance to a

landfill site should be less than 0.66 times of the Acceptable Risk Level (ARL).

7.3.4 Difficulties encountered during the analysis of the tanning sludge. Various problems were encountered during the collection of the data in order to classify the tanning sludge in an attempt to delist it, and to allow it to be disposed to a general landfill site. The problems resulted due to a lack of understanding or rather underestimating the composition and characteristics of the tanning sludge. Various assumptions were made when the original sampling of the tanning sludge commenced during 2004, which in hindsight were incorrect. The following problems were encountered during the process to characterise the tanning sludge: • Due to the characteristics of the process and the tanning sludge, the results obtained from

the analysis varied significantly. The tanning sludge was in the form of large cakes when it was obtained from the filter press resulting in various differences in characteristics such as the size of the filter cakes. Sometimes the material was softer, and other times it was found to be more irregular and granular. Discussions with the personnel at the Waterlab explained that this could significantly influence the results. The processes used in the actual plant did not change.

• The variance in results obtained from the various laboratories especially in the hexavalent chromium (Cr(VI)) and total chromium (Crtotal ). This was attributed to the different testing methods used by the different laboratories

• Limited laboratories could be found to do specialised analysis, i.e. cyanide (CN), hexavalent chromium (Cr(VI)) and thiocyante. The detection limits at which these constituents were analysed also posed to be a problem. The detection limits for the constituents were in some cases not low enough to determine whether the specific substance found, were in concentrations that were acceptable compared to the acceptable risk limit.

• The detection limits of the thiocyante were too high (5 mg/l) at the only specialised laboratory known to do these analysis.

In the section above the reasons were discussed for the various samples and the methodology used to take samples of the various waste streams in order to determine whether hexavalent chromium (Cr(VI)) and cyanide (CN) were either introduced into the retan process or produced in the retan process. In the next section the results which were obtained during this phase of collecting data will be discussed:


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• The first section will discuss the feedback from the suppliers to the request for information on the presence of the restricted substances listed in the Black list (Appendix A)

• The second section will discuss the results obtained from the analysis on the effluent streams to determine whether the hexavalent chromium (Cr(VI)) and cyanide (CN) were found in these effluent waste streams

• Thirdly, the analysis of the tanning sludge and the characterisation of the tanning sludge will be discussed and whether the results indicate that the tanning sludge could be delisted to a lower hazard rating.


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8. DISCUSSION OF RESULTS In this section the data that was collected in Section 7 will be discussed in the following sequence: • Firstly it will be determined whether any of the raw materials contain hexavalent

chromium (Cr(VI)) and cyanide (CN). • Secondly it will be determined whether hexavalent chromium (Cr(VI)) and cyanide (CN)

was found in any of the effluent waste streams which will indicate the source of hexavalent chromium (Cr(VI)) and cyanide (CN)

• And then the analysis of the tanning sludge results will be discussed in order to determine whether hexavalent chromium (Cr(VI)) and cyanide (CN) is still present in the tanning sludge.

8.1 Verification of raw materials

Table 9 provides the response to the letters from the suppliers regarding any chemicals containing restricted or prohibited substances on the Black List. Table 9 also shows that the suppliers responded and indicated that none of their products contain cyanide or hexavalent chromium (Cr(VI)). However, some of the suppliers did indicate that their products contained restricted substance for example products supplied by Buckman contained nonyl-phenolethoxylate which is used as a biocide.

Table 9: Information received in response to letters sent to the suppliers regarding restricted substances in their products

Supplier Response

Bohme Africa Confirmed that no products supplied by Bohme Africa to the tanning facility contain chemicals from the Black List. In terms of their environmental policy they are committed to responsible practices and the principle of sustainable development.

Buckman Laboratories

The products do not contain any of the substances listed in the Black List except for nonyl-phenolethoxylate used by the tanners as a degreaser and surface active ingredient. Buckman laboratories currently has a consignment of surface active ingredients that is nonyl-phenolethoxylate free that will be evaluated to determine its impact on the water resources. Consequently this will be replaced with a suitable alternative.

C&S Marketing Supply Aluminium Sulphate to the company and therefore does not contain any of the listed substances.

Clarient Provides two products which contain biocides and the other is nonyl-phenolethoxylate. Neither of these products contains cyanide (CN) or hexavalent chromium (Cr(VI)).


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Supplier Response

JPA United Chemicals

None of the chemicals supplied to the tanning facility contain any of the restricted substances as set out in the Black List.

MIMOSA Central Co-operative Ltd.

None of the chemicals supplied to the tanning facility contain any of the chemicals listed in the Black List provided.

Schill & Scheilacher

A certificate of confirmation was sent to the tanning facility indicating that the production recipes of the leather auxiliaries do not contain any prohibited or restricted substances.

Stahl Forwarded a list of substances that are present in their product. However these are present in less than 1%. These substances are all organic compounds and none of them included hexavalent chromium (Cr(VI) and cyanide (CN).

Tannin Corporation

The corporation supplies tara powder to the tanning facility. This is manufactured by grinding pods of the tree. While none of the substances listed were tested for, based on their knowledge there is no reason to expect to find any of the items listed in the product.

TFL Received a statement of compliance from TFL Leather Technology Ltd. confirming that TFL products supplied and sold from the central TFL warehouse in Europe pose no toxicological or ecological risks

North West Tanning (Pty) Ltd.

The tannery specifically states that no cationic chrome VI is used in its tanning process and only contains chrome III which is not a carcinogen. Other chemicals used do not contain any of the Black Listed substances. Letters from their suppliers were also forwarded indicating the status of their products. The majority of their suppliers also supply the tanning facility with chemicals and therefore have already been covered. The only Back Listed compound present is once again Nonyl-Phenolethoxylate which is an organic compound used. North West Tanning are also running trials on TMBTC free fungicide.

Brits Leathers Indicated that none of the listed substances were present in the products that they are using (mostly TFL products)

From Table 9 the conclusion can now be made that the information from the various suppliers indicated that cyanide or hexavalent chromium (Cr(VI)) cannot enter the retan process through the raw materials.

8.2 Results obtained from the wet waste streams including the wetting back, retan effluent and final dissolved air flotation effluent discharged.

As indicated in the overview of the tannery process and the section on waste, chromium (Cr) is an issue and was researched in detail. The Institute for Leather in Germany is still conducting research on the impacts on the environment associated with the tanning industry. Rutland (1991) has investigated the leachability of chromium (Cr) from tannery waste in order to determine what the possible impacts could be on the environment. He has found that the typical chrome-tanned waste materials contain 1.5 – 5.6% chromium (Cr). The majority of this chromium is tightly


65

bound to hide protein fibre and, even in wet blue leather, less than 5% is leached using the Toxicity Characteristic Leaching Procedure (TCLP) test procedures. Trivalent chromium (Cr(III)) compounds are highly insoluble in the common environmental pH range of 6-9. Thus the limited amount of chromium extracted from the leather wastes in these tests would not be leached under normal aquatic environmental conditions. The results of the analysis conducted on the effluent waste streams, wetting back and retan effluent, confirmed previous mentioned analysis in section 3 of typical effluents discharged from a tannery. Results obtained from the analysis on the wetting back effluent are presented in Table 10. During the wetting back only water is added to wash the hides before they are processed and to introduce the correct moisture balance again to ensure the optimum uptake of the chemicals in the retan process. The only chemicals that are added during this process are a degreaser and surfactant (soap).

Table 10 Results of the analysis of the Wetting back samples

Sample name

Analyses in mg/l

Municipality standards for

effluent discharged to

sewer networks

Wetting back 27/07/2004


10:00


11:00

pH 6-10 4,0 3,9 4,3 Conductivity in mS/m at 25 ° C

500 2150 5070 1899

Alkalinity as CaCO3 < 5 < 5 < 5

Calcium as Ca 273 497 417

Magnesium as Mg 430 923 379

Chloride as Cl 3180 4715 2233

Sulphate as SO4 1800 5048 13012 5671

Sodium as Na 3391 5686 2433

Chromium as Cr 10 170 211 81 Hexavalent chromium as Cr < 0,025 < 0,025 < 0,025

Copper as Cu 0,026 < 0,025 < 0,025

Iron as Fe 2,00 3,36 1,57

Manganese as Mn 2,74 7,59 3,81

Vanadium as V 0,03 < 0,03 < 0,03

Total dissolved solids at 180 ° C

3500 13580 27088 11482


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Sample name

Analyses in mg/l

Municipality standards for

effluent discharged to

sewer networks



10:00


11:00

at 180 ° C Chemical oxygen demand as O2

5000 1847 1458 1823

Table 10 indicates that the results vary significantly from batch to batch of hides that are processed. The explanation can be attributed to the different suppliers that are used to supply hides. Although the tanneries supply wet whites or wet blues they do not necessarily follow the same recipes during the production of these hides. One of the major differences could be that they do not implement the same amount of washes during their processes. The tanning process comprises various stages when chemicals are added or when the hides are washed to remove the excess chemicals. From Table 10 the following results from the analysis of the wetting back effluent are noted: • The wetting back effluent represents the chemicals that will be introduced into the

effluent waste water for example: the salinity load, chromium and then also the hexavalent chromium (Cr(VI)). This effluent waste water will be treated in the Dissolved Air Flotation effluent plant and therefore have an impact on the effluent discharged to the sewage works and on the tanning sludge that will be removed from the system, contributing to the salinity and heavy metals such as trivalent chrome (Cr(III)) that is present.

• The wetting back effluent is high in salinity and exceeds the Municipal Standards for effluent allowed to be discharged to the sewage works. The reason for the high salinity load is due to the process that is used to produce the wet white or wet blue hides and the type of chemicals used

• High concentrations of chromium (Cr) (170 mg/l and 211 mg/l) are present which indicate a low adsorbsion of the chromium to the hides or an overdose of chemicals that are used to ensure that the maximum chrome is adsorbed to make a good quality wet blue. In addition it could indicate that a proper wash of the hides were not implemented in the final stages of the process before supplying the hides to the tanning facility

• No hexavalent chromium (Cr(VI)) was found in the effluent. Therefore it confirms that no hexavalent chromium (Cr(VI)) is introduced through the hides from the tanneries into the tanning facility’s retan process. On the other hand, the detection limit is 0.025 mg/l and this indicates that no hexavalent chromium (Cr(VI)) up to a detection limit of 0.025 mg/l is detected.


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• High values of manganese (Mn) were noticed in two of the three samples taken from the wetting back effluent. This could impact on the amount of manganese (Mn) present in the tanning sludge as it will be precipitated by the lime used in the Dissolved Air Flotation plant.

The results of the analysis conducted on the Retan effluent waste stream are presented in Table 11. These samples taken do not represent the actual effluent discharged from the total Retan process but were taken as ad hoc samples during various stages of the process. The Retan process was described in section 3 in detail explaining the different chemicals that are introduced in order to have a product that meets the customer’s requirements. The retan process continues over 12 to 18hrs depending on the customers’ requirements and the product in the process. During the actual retan process, water and chemicals are discharged at various stages in the process. Therefore if a sample is taken from the retan effluent before it enters into the Dissolved Air Flotation plant, it will be representative of the stage in the process during which effluent is discharged.

Table 11: Results of the ad hoc of the Retan samples

Sample name

Analyses in mg/l Retan 05/08/04

13:00

Retan 05/08/04

15:00 pH 4,6 4,2

Conductivity in mS/m at 25 ° C 937 1073

Alkalinity as CaCO3 40 < 5

Calcium as Ca 144 160

Magnesium as Mg 146 146

Chloride as Cl 720 769

Sulphate as SO4 1855 2098

Sodium as Na 1200 1312

Chromium as Cr 35 51

Hexavalent chromium as Cr < 0,025 < 0,025

Copper as Cu < 0,025 < 0,025

Iron as Fe 1,55 2,01

Manganese as Mn 1,22 1,31

Vanadium as V < 0,03 < 0,03

Total dissolved solids at 180 ° C 6296 7640

Chemical oxygen demand as O2 3726 5832


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The following can be noted from the results of the analysis on the retan effluent as portrayed in Table 11: • The salinity (conductivity and total dissolved solids) exceeds the municipal standards

(937 and 1073 mS/m opposed to the limit of 500 mS/m) due to the amount of chemicals such as formic acid, sodium formate, sodium bicarbonate and dye stuff chemicals used in the process. Sulphate is the main anion, which contribute to the salinity load. Once again this confirms the findings of the literature study in Section 4.3.2 that effluent from a tannery is high in salts, Chromium (Cr), and Chemical Oxygen Demand (COD).

• Chromium (Cr) concentrations are high (35 and 55 mg/l) in the retan effluent compared to the allowed concentration of 10 mg/l that is allowed to be discharged to the sewer network. These concentrations are high due to the retan chemicals and dyestuffs used in the process. All the Cr it is not taken up by the leather and therefore it will remain in the effluent to be discharged

• Hexavalent chromium (Cr(VI)) concentrations are less than the detection limit of 0.025 mg/l. Therefore the assumption is made that it is not present in the retan effluent. This confirms the information provided by the suppliers that the products supplied to the tanning facility do not contain any hexavalent chromium (Cr(VI))

• The manganese (Mn) concentrations are significantly lower than that of the wetting back sample, indicating that the manganese enters the retan process through the hides received

• Chemical Oxygen Demand (COD) concentrations are significantly higher than that of the wetting back due to the addition of organic substances such as formic acid. Chemical Oxygen Demand (COD) are an indication of the total organics present in the samples

As mentioned in the section above, the samples taken from the Retan effluent might not be representative of the actual Retan effluent. Therefore it was decided to include additional results of analysis done on a routine monthly monitoring programme. These results include both the analysis conducted on the Retan effluent as well as the effluent discharged from the Dissolved Air Flotation plant to the sewer networks. This is done in order to compare these results with the abovementioned retan results specifically for the presence of hexavalent chromium (Cr(VI)). The results in Table 12 are from analysis done on composite samples. Composite samples are taken at a monthly frequency as part of the effluent monitoring programme over a period of 12 hours. Table 12 portrays the results of the retan and Dissolved Air Flotation plant effluent. As discussed in Section 4 the Dissolved Air Flotation plant only partially treats the effluent. The plant was designed to remove the suspended solids, Chemical Oxygen Demand (COD) and oils and greases. Due to the high pH (pH 9) at which the plant is operated heavy metals such as


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manganese (Mn), chromium (Cr), aluminium (Al) and iron (Fe) will be precipitated in the tanning sludge that is removed from the plant. From Table 12 the following differences are noted between the Retan effluent before it is treated and the Dissolved Air Flotation effluent after partially treated: • The pH was increased from 4 to 7.4 in order to comply with the set standards by the

Municipality by adding lime to the holding tank • Conductivity increases to the effluent plant due to the addition of lime and calcium

sulphate (CaSO4) to remove the suspended solids and heavy metals through precipitation • Ammonia levels are high (233 mg/l) due to the addition of ammonia (NH4) to the process

and the Dissolved Air Flotation plant cannot remove the ammonia (NH4)

Table 12: Results of routine monitoring of the retan and Dissolved Air Flotation effluent results

Sample name

Analyses in mg/l

Municipality Standards for

effluent discharged to sewer networks

Retan effluent 08/07/2004

Dissolved air flotation effluent

08/07/2004 pH 6-9 4,1 7,5 Conductivity in mS/m at 25°C

500 1175 1585

Alkalinity as CaCO3 < 5 720

Ammonia as N 233 254


Sulphate as SO4 1800 2157 2501

Sulphide as S2- 50 4,5 9,6

Ortho-phosphate as P 1,7 0,2

Sodium as Na 1759 2061 Hexavalent chromium as Cr (VI) < 0,025 < 0,025

Total dissolved solids at 180 ° C

3500 8916 10652

Oil and grease 233 70

Suspended solids at 1050C 2000 402 409 Chemical oxygen demand as O2

5000 6199 5672


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• Sulphide tests were done on both of the retan and final effluent samples and these comply with the standards set by the Municipality

• Once again the hexavalent chromium (Cr(VI)) was below the detection limit of 0.025 mg/l in both the Retan and Dissolved Air Flotation effluent plant. This again confirms that the information obtained from the suppliers and the other analysis in Table 11 that cyanide and hexavalent chromium (Cr(VI)) are not present in the effluents and therefore it is not processed in the retan process

• The Dissolved Air Flotation (DAF) plant removes the oils and grease from the retan effluent

• Suspended solids are removed from the Retan effluent therefore ensuring that the effluent complies with the standards set by the Municipality

The removal of the Chemical Oxygen Demand (COD) was not sufficient to comply with the standards as it exceeded the level of 5000 mg/l. It appears as if the Dissolved Air Flotation (DAF) plant was not functional and this could result in the high Chemical Oxygen Demand (COD) concentrations being released to the Municipal sewer. The overall quality of the effluent does not comply with the standards set by the Municipality which could result in fines. Constituents for conductivity (EC), sulphate (SO4), the total dissolved solids (TDS) and the Chemical Oxygen Demand (Chemical Oxygen Demand (COD)) does not comply with the standards set out in Table 12. Although the Chemical Oxygen Demand (COD) and other substances may be discharged to the Municipality’s water care works, the high salinity will impact on the quality of the Municipality’s effluent discharged. This poses as general background information and does not form part of the scope for this mini-dissertation and will therefore not be discussed further. Once the issue regarding the hexavalent chromium (Cr(VI)) was cleared additional samples were taken of the wetting back effluent and the various stages of the retanning process for cyanide (CN). These samples were submitted to a specialised laboratory in Modderfontein for analysis. The results came back indicating no cyanide (CN) was present. Up to now the necessary proof was provided in the Table 11 to 13 that there is no hexavalent chromium (Cr(VI)) present in any of the waste effluent streams. These streams were sampled and analysed as hexavalent chromium (Cr(VI)) is highly soluble at these pH values (pH 4 -9). Additional samples taken for cyanide (CN) showed no indication of cyanide (CN) in the effluent waste streams.


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In the following section the results obtained from the analysis conducted on the tanning sludge will be discussed. Once again it is emphasised that there were no positive results for hexavalent chromium (Cr(VI)) and cyanide (CN) in any of the effluent waste streams.

8.3 Results obtained from the tanning sludge waste streams

As discussed in section 8, the first tanning sludge sample taken to be analysed was specifically to verify the previous findings of cyanide (CN) and hexavalent chromium (Cr(VI)) in the tanning sludge. Table 13 provides a summary of the results that were obtained during the first analysis. From Table 13 the following was observed:

• The sample leached high concentrations of salinity (TDS = 12 106 mg/l) and manganese (Mn) at concentrations of 86 mg/l

• The amounts of chromium that was leached from the tanning sludge compared to the amount present in the wet streams, indicated that the chromium forms insoluble compounds as indicated in the literature study in section 5 and therefore it will not be leached from the tanning sludge under the natural environmental conditions in a landfill site

• No hexavalent chromium (Cr(VI)) was detected at a limit of 0.025 mg/l and it was decided to have the tanning sludge analysed for hexavalent chromium (Cr(VI)) at Umgeni water in order to obtain a lower detection limit of 0.004 mg/l. The hexavalent chromium (Cr(VI)) was analysed by using Ion Chromatography as opposed to the standard colorimetric method used as discussed in the Standard Methods for the examination of water and waste water for each of these elements (Clescerl et al, 1998)

• Cyanide (CN) was detected in small quantities compared to the SABS drinking water quality standards

Table 13: Results of the first tanning sludge sample taken to determine whether there is cyanide (CN) and hexavalent chromium (Cr(VI)) present in the tanning sludge

Sample name Analyses Tanning sludge

16/09/2004 Units mg/l mg/kg

TCLP / ACID RAIN SOLUTION / DIST WATER TCLP

Mass (g) 100

Volume (ml) 2000


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Sample name Analyses Tanning sludge

16/09/2004 Moisture 10%

pH 6,1

Conductivity in mS/m at 25 ° C 1130

Total dissolved solids at 180 ° C 12106 242120

Alkalinity as CaCO3 2960 59200

Ammonia as N 9,6 192


Sulphate as SO4 1158 23160

Ortho phosphate as P < 0,2 < 4

Sodium as Na 778 15560

Calcium as Ca 1700 34000

Magnesium as Mg 515 10300

Aluminium as Al 3,16 63

Boron as B 0,81 16

Chromium as Cr 2,71 54

Chromium as Cr(Umgeni) 3,62 72

Copper as Cu 0,047 0,94

Hexavalent chromium as Cr6+ < 0,025 < 0,5

Hexavalent chromium as Cr6+ (Umgeni) < 0,004 < 0,08

Iron as Fe 0,913 18

Manganese as Mn 86 1720

Vanadium as V < 0,03 < 0,6

Zinc as Zn 0,189 3,78

Free cyanide as (CN) 0,29 5,8

In the first sample that was analysed no hexavalent chromium (Cr(VI)) was present. The presence of cyanide (CN) still remains a problem and it cannot be explained. Therefore additional samples (16/11/04 and 27/01/2005) were taken to analyse for a wider variety of constituents as summarised in Table 14. The constituents were added to ensure that all the possible elements are tested which could pose to be a problem for delisting the tanning sludge. In order to determine the treatment possibilities of the tanning sludge, it was also treated with lime to determine what the effect would be on the heavy metals. In Table 14 the results of the tanning sludge extractions are compared to the acceptable risk limits (ARL) is described in the Minimum Requirements. The Acceptable Risk Level (ARL) is defined


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as the concentration of that substance that will have a minimal effect on the environment based on the aquatic environment. This is represented by the LC50 multiplied by a safety factor of 10%. From Table 14 the following results are obtained • The results from the tanning sludge samples vary significantly from each other. After

discussions with the personnel from the Waterlab this could be attributed to the variance in the physical properties of the tanning sludge which include the size of the filter cakes (dry tanning sludge) sampled as shown in Figure 11 on page 67. The larger the filter cakes or samples are, the smaller the actual area that is exposed to the chemicals. The opposite is true for smaller pieces of the tanning sludge. The area exposed to the Toxicity Characteristic Leaching Procedure (TCLP) solution is much greater and therefore the maximum substances will be leached.


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Table 14: Results of the analysis conducted on the tanning sludge samples

Sample Name Standards

Analyses Sludge 16/11/2004

Tanning sludge & lime

16/11/2004

Tanning sludge 27/01/2005


27/01/2005

Hazard group

Acceptable Risk limit (mg/l

Units mg/l mg/kg mg/l mg/kg mg/l mg/kg mg/l mg/kg - - TCLP / ACID RAIN SOLUTION / DIST WATER TCLP II TCLP II TCLP 1 TCLP 1 - -

Mass (g) 100 100 (9% LIME) 100 100 (5% LIME) - -

Volume (ml) 2000 2000 2000 2000 - -

10% pH 7,0 - 7,9 - - -

pH 4,8 8,3 5,5 8,9 - -

Conductivity in mS/m at 25 ° C 574 954 - -

Chloride as Cl 89 1780 87 1740 99 1980 89 1780 NT -

Sulphate as SO4 433 8660 519 10380 567 11340 620 12400 NT -

Ortho-phosphate as P < 0,2 < 4 < 0,2 < 4 < 0,2 < 4 < 0,2 < 4 4 10

Silica as Si 8,3 166 7,7 154 7,7 154 1,4 28 NT -

Fluoride as F < 0,2 < 4 0,3 6 < 0,2 < 4 < 0,2 < 4 3 1

Sodium as Na 291 5820 314 6280 184 3680 231 4620 NT -

Potassium as K 30 600 30 600 27 540 28 560 4 43.2

Calcium as Ca 1003 20060 2117 42340 481 9620 866 17320 NT -

Magnesium as Mg 194 3880 87 1740 156 3120 68 1360 NT -

Aluminium as Al 30 600 1,02 20 0,551 11 1,71 34 3/4 10

Arsenic as As 0,005 0,1 < 0,002 < 0,04 0,003 0,06 <

0,002 < 0,04 2 0.43

Barium as Ba 0,32 6,4 0,34 6,8 0,12 2,4 0,17 3,4 3 7.8

Boron as B 0,54 10,8 0,17 3,4 0,17 3,4 0,06 1,2 4 10


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16/11/2004



27/01/2005

Hazard group


Cadmium as Cd 0,012 0,24 0,045 0,90 0,012 0,24 0,024 0,48 1 0.031

Chromium as Cr 5,44 109 0,192 3,84 0,812 16 0,057 1,14 3 4.7

Chromium as Cr [UMGENI] 6,97 139 0,216 4,32 0,918 18 0,025 0,50 3 4.7

Cobalt as Co 0,172 3,44 0,151 3,02 0,048 0,96 0,064 1,28 2 6.9

Copper as Cu < 0,025 < 0,5 0,032 0,64 <

0,025 < 0,5 < 0,025 < 0,5 2 0.1

Hexavalent chromium as Cr6+ < 0,025 < 0,5 <

0,025 < 0,5 < 0,025 < 0,5 <

0,025 < 0,5 1 0.02

Hexavalent chromium as Cr6+ [UMGENI] 0,027 0,54 <0,00

4 0,08 <0,004 < 0,08 <0,00

4 < 0,08 1 0.02

Iron as Fe 9,21 184 0,117 2,34 6,89 138 0,142 2,84 3 9

Lead as Pb < 0,050 < 1 <

0,050 < 1 < 0,050 < 1 <

0,050 < 1 2 0.10

Manganese as Mn 32 640 0,349 6,98 18 360 1,14 23 2 0.30

Mercury as Hg < 0,002 < 0,04 0,014 0,28 <

0,002 < 0,04 < 0,002 < 0,04 1 0.022

Nickel as Ni 0,164 3,28 0,222 4,44 0,062 1,24 0,077 1,54 3 1.2

Selenium as Se 0,006 0,12 < 0,003 < 0,06 <

0,003 < 0,06 < 0,003 < 0,06 2 0.26

Titanium as Ti < 0,08 < 1,6 < 0,08 < 1,6 < 0,08 < 1,6 < 0,08 < 1,6 2 0.73

Vanadium as V < 0,04 < 0,8 < 0,04 < 0,8 < 0,04 < 0,8 < 0,04 < 0,8 3 1.3

Zinc as Zn 1,40 28 0,152 3,04 0,230 4,60 0,089 1,78 2 0.70

Free cyanide as cyanide (CN) 0,19 3,8 0,33 6,6 < 0,05 < 1,0 0,12 2,4 1 0.0053

Silver as Ag < 0,02 < 0,4 < 0,02 < 0,4 < 0,02 < 0,4 < 0,02 < 0,4 3 2

Beryllium as Be < 0,025 < 0,5 <

0,025 < 0,5 < 0,025 < 0,5 <

0,025 < 0,5 3 1.2


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16/11/2004



27/01/2005

Hazard group


Bismuth as Bi < 0,010 < 0,2 <

0,010 < 0,2 < 0,010 < 0,2 <

0,010 < 0,2 - -

Lithium as Li 0,11 2,2 0,07 1,4 < 0,025 < 0,5 <

0,025 < 0,5 3 1.7

Molybdenum as Mo < 0,02 < 0,4 < 0,02 < 0,4 < 0,02 < 0,4 < 0,02 < 0,4 4 3.7

Antimony as Sb 0,36 7,2 0,09 1,8 0,28 5,6 0,07 1,4 3 1

Tin as Sn 0,098 1,96 0,086 1,72 0,060 1,20 0,089 1,78 3 2.9

Strontium as Sr 0,32 6,4 7,4 148 0,13 2,6 2,1 42 NT 180

Zirconium as Zr < 0,07 < 1,4 < 0,07 < 1,4 < 0,07 < 1,4 < 0,07 < 1,4 3 2

NT – non toxic: na - not analysed


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Figure 11: The size of tanning sludge that was sampled from the various bins varied significantly

• All the untreated tanning sludge samples leached manganese (Mn) at concentrations

above the acceptable risk limit of 0.30 mg/l. Other elements leaching above their acceptable risk limits in one or more samples were aluminium (Al), chromium (Cr), and Iron (Fe). Note that hexavalent chromium (Cr(VI)) was not detected down to a detection limit of 0.004 mg/l in the samples collected on the 16 September 2004 and 27 January 2005 but was apparently leached at a concentration of 0.027 mg/l from the sample collected on 16 November 2004. The reason why this would be present cannot be explained as it has been proved that there were no hexavalent chromium (Cr(VI)) in the raw materials or in any of the other effluent streams.

• The concentration of extreme hazard cation cadmium leached from two samples was measured at 0.012 mg/l and 0.045 mg/l respectively. For an extreme hazard species, such as cadmium, the limit of the waste to be classified as non-toxic is one tenth of its acceptable risk limit, i.e. 0.0031 mg/l. Values between 0.0031 mg/l and 0.031 mg/l classify as a high hazard.

• The sample taken on the 16 September 2004 contains small amounts of cyanide (CN). As explained previously the presence of cyanide (CN) is highly unlikely, although an anion such as thiocyanate may interferes in the cyanide (CN) determination. This is discussed later in detail in the report.

• The pH of the samples was reasonable at 7.0 and 7.9 but they have little buffer capacity, as the final pH of the Toxicity Characteristic Leaching Procedure (TCLP) leach solution,


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which is acidic waste was 4.8 and 5.5 respectively. The lower pH observed in the sample taken on 16 November 2004 compared to that taken on the 27 January 2005, results in a significantly higher leachable concentration of most species due to the more acidic conditions. This suggests that the environmental risk posed by the tanning sludge can be reduced by increasing the 10% pH, preferably above 8.5.

• The moisture content of the tanning sludge is 16.5% which means that it is unlikely to contribute to the leachate generated at a landfill site. Normally if the moisture content is below 40%, the waste is assumed not to contribute to the amount of leachate generated in the landfill.

• Leaching of heavy metals from the tanning sludge was significantly reduced with the addition of the lime. Elements such as manganese (Mn), aluminium (Al), trivalent chromium (Cr(III)) and copper (Cu) are leached at lower concentrations at a high pH. Some amphoteric species such as aluminium (Al) and sink (Zn) can leach in moderate amounts at high pH (pH9).

• Both the leachability of manganese (Mn) and cadmium (Cd) decreased with the addition of lime. The amount of hexavalent chromium (Cr(VI)) leached from the sample taken on 16 November 2004 also decreased with the addition of lime. The leachable concentrations in the lime treated sample fell below the detection limit.

The 5% lime treated waste classifies as a high hazard waste due to the presence of manganese (Mn) above its acceptable risk limit and cadmium (Cd) at between its acceptable risk limit and one tenth of this value. From these results it can now be seen that it was not only hexavalent chromium (Cr(VI) and cyanide (CN) that posed a problem as a potential constituent that could prevent the tanning sludge from delisting to a lower hazard rating. Various substances leached at concentrations that are above the Acceptable Risk Level (ARL) resulting in classification of the tanning sludge as a waste with a high hazard rating, therefore it must still be disposed of to a hazardous waste landfill. However, after treatment with lime the leachability of these substances is significantly reduced except for the presence of cyanide (CN). The presence of cyanide (CN) is still an issue and, should it be present, the waste will be classified as a waste with an extreme hazard. In the next section an attempt will be made to explain the presence of cyanide (CN) in the retan process and thus in the tanning sludge.

8.4 Presence of cyanide (CN)

Baldwin (2005) states in his report that the determination of cyanide (CN) as a potential constituent in some of the tanning sludge samples may mean that the waste would have to be


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disposed to a hazardous waste landfill site. He explains the detection of the cyanide (CN) in waste as follows: • It could be present as an impurity in one or more of the materials and reagents used in the

process. • It is being generated by reaction between two or more of the materials and reagents used. • Or there is interference in the analytical determination of cyanide (CN) in the laboratories

and some other species are being detected and measured as being cyanide (CN). The types of material used were evaluated to determine if it is possible that cyanide (CN) is being introduced inadvertently into the process. One type of substance used in relative quantities that has been suggested as being a possible source are cyanate and possibly thiocyanate, which are anions that can interfere with the cyanide (CN) analysis are the isocyanates. Isocyanates contain the chemical group, - N=C=O bound to an alkyl or aryl group. The isocyanate is highly reactive particularly with water and alcohols and the di- isocyanates are used as cross linking agents in the production of polymer such as the polyurethanes (Baldwin, 2005). Isocyanates are potentially a source of cyanate, NCO-, and in the presence of sulphur present itself as thiocyante, although when an isocyanate reacts with water, carbon dioxide is normally given off and the reaction is highly exothermic: Isocyanate + water ? Ammonia + Carbon Dioxide

R-N=C=O + H2O ? R- NH2 + CO2

If present, the cyanate and thiocyanate, could interfere with the analysis by the standard method used to analyse for cyanide (CN). Cyanide is classified as an extreme hazard, whereas thiocyanate and cyanate are classified as moderate hazards. The leachate of the tanning sludge were analysed for thiocyanate. However the detection limit is 5mg/l and it was not detected at these concentrations (Baldwin, 2005) Taking into account the results that were obtained during this data collection exercise, it is important to note that although the raw materials and the effluent streams contained no hexavalent chromium (Cr(VI)) or cyanide (CN), it was still present in some of the tanning sludge samples resulting in the waste not being delisted to a lower hazard rating. Once the analysis was done it was also found that it was not hexavalent chromium (Cr(VI)) or cyanide (CN) that determined the load or dose that can be disposed to the landfill but cadmium. However once the tanning sludge was treated with lime the leachability of the substances (including manganese and cadmium) was significantly reduced. Although a logical explanation is provided for the presence of cyanide (CN) it does influence the hazard rating.


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Therefore taking into account the discussion presented in Section 8, the disposal of the waste to the Rosslyn landfill site is still recommended. This landfill is permitted as a general waste landfill site which allows for the disposal of waste containing heavy metals. The element that will determine the load or dose that can be disposed to landfill is that with the highest concentration relative to its acceptable risk limit. From the lime treated waste, which classifies as a high hazard, cadmium (Cd) is the element that determines the load, because it is classified as an extreme hazard and is present at concentration above one tenth of its acceptable risk limit. The load or dose of the 5% lime treated tanning sludge that can be disposed is given by the following equation (Baldwin, 2005) Amount = Acceptable Risk Limit of Cadmium (Cd) (in ppb) 0.66 x 10 x (pollutant in mg/l) For example, in the 5% lime treated tanning sludge sampled on the 27 January 2005, the leachable cadmium concentration is 0.024 mg/l and, therefore, the load or dose is given by: = 31 tonnes per hectare per month

0.066 x 10 x 0.024 = 196 tonnes per hectare per month.

As only 50 tonnes of tanning sludge are produced per month, the treated waste can be disposed to the Rosslyn landfill site. The site has an area of 31 ha and therefore, theoretically, up to 6076 tonnes could be disposed of per month. Because of its large area, the Rosslyn Landfill could accept 207 tonnes per month of the 5% treated tanning sludge, even if cyanide (CN) is taken into account the sludge will still be allowed to be disposed of to Rosslyn (Baldwin, 2005).


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9. CONCLUSIONS The main objective of this study was to classify and delist the tanning sludge that is produced during the retanning of hides to produce automotive leather. The purpose for delisting the waste was to dispose of it to a general landfill site at Rosslyn as opposed to the current arrangements to dispose of it to the hazardous landfill site at Holfontein. The motivation for changing the disposal from a hazardous to a general landfill site was based on the waste disposal costs that would be reduced by R10 000 per month without taking into account the transport costs. In conclusion the following were achieved during this study in an attempt to achieve the various objectives that were set: • The relevant legislation pertaining to waste management and including disposal of

tannery waste i.e. tanning sludge was identified and discussed in detail in section 7. • It was proved without a doubt that hexavalent chromium Cr(VI) and cyanide (CN) are not

present in the raw materials used in the retan process. This was done by obtaining letters of confirmation that the raw materials do not contain any hexavalent chromium (Cr(VI)) and cyanide (CN) from all the suppliers used by the company. This was further confirmed with the analysis conducted on the effluent waste streams.

• During the analysis of the effluent waste streams no hexavalent chromium (Cr(VI)) and cyanide (CN) were found in any of the results. This was confirmed by using different laboratories for the analysis of the hexavalent chromium (Cr(VI)) and cyanide (CN). Therefore it can now be concluded that there is no way that the hexavalent chromium (Cr(VI)) or cyanide (CN) can enter the process through the raw materials, or that it can be produced during the process as the samples were taken from the various processes.

• During the literature research (Section 5) it was mentioned that hexavalent chromium (Cr(VI)) can be produced during the tanning process. However, taking into account the conditions under which this occurred, and comparing it to the tanning facility’s existing processes, it is not possible to produce hexavalent chromium (Cr(VI)) in the tanning facility’s retan process.

• The reason for the presence of cyanide (CN) in the tanning sludge is unknown, as the facility in South Africa is the only tanning facility of the Holding Group with cyanide (CN) in its tanning sludge. Cyanide is not used as part of the processes. The wetting back water and the final wash water from the Retan were sampled and tested to determine whether the biocides used in the process could contribute to the positive cyanide (CN) results. These results were once again negative.

• The tanning sludge samples analysed according to the Minimum Requirements (DWAF(a), 1998) leached significant concentrations of various substances that were above their


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Acceptable Risk Levels. Substances that leached significantly included manganese (Mn), cadmium (Cd), iron (Fe), aluminium (Al) and chrome (Cr). Hexavalent chromium (Cr(VI)) was also leached from one of the samples. The concentrations of Cadmium leached at 0.012mg/l and 0.045mg/l classifying the waste as extremely hazardous.

• The treatment of tanning sludge with lime reduced the leachability of the abovementioned constituents significantly.

• However, the presence of the cyanide (CN) remains an issue as the hazard rating of the tanning sludge is affected.

• The treatment of the tanning sludge with 5% lime reduced the leachability of the tanning sludge so that the waste can be classified as high hazard instead of extreme hazard due to the presence of the cadmium. The cadmium therefore determines the load of disposal.

• Although the tanning waste could not be classified as a waste with a moderate risk, it could still be disposed of to Rosslyn as it is permitted as a General Landfill site that is allowed to accept a waste containing a certain amount of heavy metals in the tanning sludge. Therefore, although the waste was not delisted to a lower hazard rating, the tanning facility has still benefited from this project. The tanning facility will be allowed to dispose of the tanning waste to Rosslyn.

The final conclusions therefore are: • The tanning sludge could not be delisted to a lower hazard rating or to general waste • The tanning sludge can be disposed of to Rosslyn which will lower the waste disposal

costs


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10. RECOMMENDATIONS The tanning facility has benefited by the process as it was still proved that it can dispose of the waste to Rosslyn. However, if the tanning facility wants to consider the possibility of disposing its waste to a general landfill site other than Rosslyn it will have to review the existing process. The main objective of delisting the tanning sludge to a lower hazard rating has not been achieved. Various situations or circumstances should be investigated in order to determine the source of the cadmium (Cd), cyanide (CN), manganese (Mn) and hexavalent chromium (Cr(VI)) and it is suggested that the following recommendations be considered if there is to be any other gain from delisting the tanning sludge even further: • The high concentrations of manganese should be investigated since this not only

influences the delisting possibility but could also have an impact on the quality of the crust leather being produced. Manganese (Mn) can be present in the raw water or the incoming hides from other tanneries.

• An investigation should be launched into the different analysis techniques that is used to

determine, for example, the hexavalent chromium (Cr(VI)). Under extreme circumstances such as the use of a very strong acid, like nitric acid, trivalent chromium (Cr(III)) could be oxidised to hexavalent chromium (Cr(VI)).

• The purity of chemicals, specifically the aluminium sulphate (AlSO4) and polymers, used

at the effluent plant should be investigated since these chemicals are used to partially treat the effluent. The possibility does exist that the lime could contain impurities that will influence the quality of the tanning sludge and once again result in the tanning sludge not being delisted.

• The possibility that the biocides used contain cyanide (CN) should be considered.

However, the possibility should be slim as the suppliers indicated that their products do not contain any cyanide (CN).

• Other options that could be considered are the possibility of cross contamination in the

tanning sludge waste bins. However, it must be emphasised that should the abovementioned recommendations not add significant value to the process or waste management including the disposal of waste, it is not necessary to implement them as the tanning sludge may now be disposed of to Rosslyn so the savings incentive has been reached.


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11. REFERENCES Anonymous 2005: Dictionary of leather terms www.tanschool.co.za Baldwin, D. 2005: Classification and Evaluation of effluent tannery and sludge. Environmental and Chemical Consultants. Cresta Chief Directorate of Occupational Health and Safety 2002: Guide Completing Material Safety Data Sheets. Government Printer. Pretoria Clark, J. 2002: Coming back to earth South Africa’s changing environment. Jacana (Pty) Ltd. Houghton Clescerl L.S, A.E Greenberg and A.D. Eaton 1998: Standard Methods for the examination of water and waste water 20th edition. American Public Health Association, American Water Works Association and Water environment Federation. Washington Department of Environment and Tourism (DEAT) 1965: Atmospheric Pollution Prevention Act, Act 45 of 1965. Government printer. Pretoria Department of Environment and Tourism (DEAT) 1989: Environment Conservation Act, 1989, Act 73 of 1989. Government printer. Pretoria Department of Environment and Tourism (DEAT) 1998: National Environmental Management Act, Act 107 of 1998. Government printer. Pretoria Department of Environmental Affairs and Tourism (DEAT) 2000: White Paper on integrated pollution and waste management for South Africa. A policy on pollution prevention, waste minimization, impact management and remediation. Government notice No 227. Government Printer. Pretoria Department of Environmental Affairs and Tourism (DEAT) and Department of Water Affairs and Forestry (DWAF) 1999: National Waste Management Strategy: National Waste Management Strategies and action plans South Africa: Strategy formulation phase. Version D. Department of Environmental Affairs and Tourism. Pretoria (www.environment.gov.za) Department of Labour 1993: Occupational Health and Safety Act (Act No. 85 of 1993) (R1449 of 6 September 1996; Government Notice No. 17403. Government printer. Pretoria


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Department of Water Affairs and Forestry (DWAF) 1996: South African Water Quality Guidelines: Volume 1: Domestic Water use, Second edition. Department of Water Affairs and Forestry. Pretoria Department of Water Affairs and Forestry (DWAF(a)) 1998: Minimum Requirements for the handling, classification and disposal of hazardous waste. Department of Water Affairs and Forestry. Pretoria Department of Water Affairs and Forestry(b) (DWAF) 1998: Minimum Requirements for Waste Disposal by Landfill, Second edition. Department of Water Affairs and Forestry. Pretoria Department of Water Affairs and Forestryc) (DWAF) 1998: Minimum Requirements for Water Monitoring at Waste Management Facilities, Second edition. Department of Water Affairs and Forestry. Pretoria Dewhurst, J. 1999: Leather technologists pocket book - Chapter 4 – A tanner’s view - Chrome tanning. Society of leather technologists and chemists. East Yorkshire Ferreira , M.H., M.F. Almeida and T. Pinto 1999: Influence of temperature and holding time on hexavalent chromium formation during leather combustion. JSLTC 83 (1999) p 135 Ford Motor Company 2003: Engineering Material Specification WSS – M99P9999 – A1 Ford Global Technologies Fuggle R.F & M.A. Rabie 2000: Environmental Management in South Africa Rustica Press. Western Cape Golder Associates 2004: Classification of effluent treatment sludge. Golder Associates Africa (Pty) Ltd. Halfway house Government of South Africa, 1996: The Constitution of South Africa of 1996, (Act 108 of 1996) Government Printer. Pretoria Graf, D. 2000: The influence of the relative humidity of air during storage on the formation lowering of hexavalent chromium (Cr(VI)) in chrome tanned leathers. World Leathers 13 (2000) 5 p 38


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Hauber, C. 2000: Formation, prevention and determination of hexavalent chromium (Cr(VI)) in leather. A short overview of recent publications. United Nations Industrial Development Organisation. International School of Tanning Technology, 2004: Executive leather course. International School of Tanning Technology. Grahamstown International Union of the Environment 2001: Assessment for Chromium containing waste from the leather industry – Updated report IUE Commission Cape Town (www.iultcs.org/IUE ) Iqbal, M., I ul Haque, J.A.S. Berns 1998: The Leather Sector: Environmental Report The Federation of Pakistan Chambers of Commerce & Industry. Pakistan Ludvik, J. 2000: Chrome balance in leather processing US/RAS/92/120/11-51 Regional programme for pollution control in the tanning industry in South East Asia. United Nations Industrial Development Organisation report Mabudafhasi, R. 2000: Speech at the release of the White Paper on Integrated pollution and waste management for South Africa www.environment.gov.za Mabudafhasi, R. 2005: Speech by Deputy Minister of Environmental Affairs and Tourism, during the National Assembly Debate Budget Vote 2005 www.deat.gov.za Miller, G.T. 2004: Living in the environment 13th edition. Copyright c 2004 United States of America Mozes, T 1995: Treatment and disposal options for tanning waste and effluents Phase I. Report done on behalf of Wastetec (Pty) Ltd. Raju, M. & S.N. Tandon 1999: Operationally determined speciation of chromium in tannery sludges. Chemical Speciation and Bioavailability 11 (2) Reeder(a), R 1999: Leather technologists pocket book – Chapter2 – Modern beamhouse procedure: soaking and liming. Society of leather technologists and chemists. East Yorkshire Reeder(b) , R 1999: Leather technologists pocket book – Chapter3 – Modern beamhouse procedure: deliming and bating. Society of leather technologists and chemists. East Yorkshire


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Rutland F.H. 1991: Environmental compatibility of chromium containing tannery and other leather product wastes at land disposal sites. Leather Industries Research Laboratory. Cincinnati South African Bureau of Standards Code 0228. 2000: The Identification and classification of dangerous substances and goods. South African Bureau of Standards. Pretoria South African Bureau of Standards ISO 14001 2004: Environmental management systems – requirements with guidance for use. South African Bureau of Standards. Pretoria Steffen, Robertson and Kirsten, 1989: Water and waste water management in the tanning and leather finishing industry, WRC project No 145. Water Research Commission. Pretoria Tanners Council of America 1969: Inc Dictionary of leather terminology. 6th Ed. New York Tanners Council of America. Toxicity Characteristic leaching procedure Federal Register and Toxicity Characteristic Rule, ibid 1990 Tremlett, R.J. 1999: Leather technologists pocket book – Chapter7 – Dyes and dyeing. Society of leather technologists and chemists. East Yorkshire Van den Bossche, V, G. Gavend and M. Brun 1997: The Chromium Files. The international Chromium Development Association Lyon France (www.chromium-asoc.com) Verheijen L.A.H.M., D Weiersema, L.W. Hulshoff Pol, and J. de Wit 1996: Management of waste from animal product processing. International Agriculture Centre Wageningen. The Netherlands (www.fao.org ) Wachsman, H.M. 1999: Leather technologists pocket book – Chapter 6 – Retannage. Society of leather technologists and chemists. East Yorkshire Waste Group, 2002: Waste management plan for the tanning facility. Bon Accord


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APPENDIX I Black List of substances or groups of substances which must not be used. New products containing listed substances must not be put into use. Phase out plans with final date of use are required for substances which were not fully phased out when introduced.


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90


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APPENDIX II A copy of the letter that was sent to the suppliers of all raw materials


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01/09/2004 Supplier PO Box XXX CCCC XXXX To Whom It May Concern: Company : Manufacturing of environmentally responsible products Environmental awareness amongst customers and the public is ever increasing. Stringent environmental standards and continued increasing awareness requires the company to evaluate all raw materials that are used in the process and to follow the golden thread through to the quality of the waste products that are produced as a result of the manufacturing processes. The aim is to ensure that we comply with all the necessary environmental legislation. Company manufactures leather for the automotive industry. Part of the process is using a vast majority of different chemicals to manufacture a product that complies with the client’s specifications. Your company is responsible for supplying some of the chemicals, which are used in the process and therefore becomes part of the process that needs to be evaluated. Thus, in order to provide the necessary proof that the Company is producing a responsible product in terms of the environment and health and safety standards you are required to provide the company with the following information: 1. Do the chemicals, that are provided by your company, contain any of the

chemicals attached in the lists known as the black list as provided by our customers.

In evaluating all the various chemicals that are used as raw materials in the process the company wishes to show the implementation of responsible cradle to grave principles. It would be appreciated if you could forward the necessary information before 30 September 2004. Should you have any further queries please do not hesitate to contact Ms Carol Hooghiemstra, our Environmental Manager. Yours faithfully PURCHASING EXECUTIVE MANAGER


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APPENDIX III

The dangerous goods register for the raw materials used in the retan process

Documents

DELISTING OF HAZARDOUS WASTE PRODUCED IN A TANNERY