Waste Minimisation In Synthetic Textile Processing

Chittaranjan Desai Paradise Prints Desai Street, Sagrampura Surat 395002, GUJARAT, INDIA Ph. :- 0261-631965

0

Waste Minimization in Synthetic Textiles Process Houses by Chittaranjan Desai Introduction :- After Rio De Janeiro's epic meet on environment, ecology & environment have become quite sensitive issues. Surat being the largest synthetic fabrics center, with more than 200 process houses, can cause considerable pollution problems as wet processing consumes sizeable amount of water & materials, but the Gujarat Pollution Control Board has actually gone overboard by coming up with norms which are even more stringent norms than many of the highly developed European countries & USA. Besides the limits of pollutants are the same for effluent disposal to inland surface waters as well as public sewers, which is not the case in any other country as seen in Table 1 [1]. DISCHARGE LIMIT

SURFACE WATERS

TO COUNTRY GUJARAT State SACHIN (G.I.D.C.) BELGIUM DENMARK

DISCHARGE LIMIT

PUBLIC SEWERS

TO BOD

COD 30 15 30 1

0-20

BOD 100 30 400 70

COD 30

100

300

750

---

---

-100

FRANCE

40

---

500

---

/100 GERMANY

25

160

* *

ITALY SPAIN U.K.

40 40 3 0-70

N. CAROLINA, USA

160 160

250 300

500 500

--*

NA

NA * Charges are levied on polluters according to the concentration of pollutants.

* 250 *

60 0*

Under these stringent regulations, two fundamental approaches to pollution control are available. a) Waste treatment & b) Source Reduction of pollutants. Many waste treatments simply remove an undesirable process waste from one media to another. e.g. Dyes & chemicals in the effluent are converted to sludge, which has to be disposed either by landfilling or incineration. This may contaminate the ground water. An important alternative to treatment is waste minimization. This concept looks to textile processes itself to determine what changes can be made to reduce pollution at source. Waste minimization becomes critical to centers like Surat, where most of the process houses & for that matter even municipal sewerage treatment plants have only primary effluent treatment plants. Besides it requires little or no capital investment & often results in substantial cost savings in the processes.

Various techniques employed to reduce pollution at source are :1) Quality control of dyes & chemicals. 2) Inventory management. 3) Chemical / dye substitutions. 4) Conservation / optimization of Dyes & Chemicals. 5) Water conservation. 6) Process modifications. 7) Equipment modifications. 8) Reuse & recovery.

1) Quality control of Dyes / Chemicals :- A Laboratory, which is still absent in many of the Surat process houses, becomes the first step towards pollution reduction. Strict control on the quality can be maintained by testing supplies of Dyes & chemicals. This would result in lower reprocessing & improved product consistency. This would naturally increase profits as well as reduce wastes associated with reprocessing.

2) Inventory management :- A process house dyes chemicals store generates three kind of major wastes : excess, out of date & no longer used raw materials. These obsolete items are more often than not, directly dumped into the drain. To avoid this situation, inventory control techniques like ABC analysis, FSN analysis, etc. can be employed effectively. Excess inventory often results from "getting a good bargain" by purchasing a tanker load where only a drum is required. This is where Economic order quantity (EOQ) & order levels system would be of immense value. At times surplus stocks of dyes do accumulate due to the changing fashion trends. Under these circumstances Colour computer matching system can be a used to formulate new recipes using these non moving dyes or they can be sold back to a willing supplier or another process house using those dyes.

3) Waste Audit:- From Sep '93, complete environmental waste audit statement has been made mandatory by the Pollution Control Board. A complete waste audit of all the processes & machines in terms of water consumption, COD, BOD, Suspended solids & pH should be carried out to get a complete picture of major trouble spots. All the above parameters except BOD, can be easily tested in the process house laboratory. BOD values can be obtained from an environmental lab. Besides COD, BOD values of all the auxiliaries & dyes used can also be obtained, which can be than be used for substitution. This database can be further enhanced by adding data like Biodegradability, Fish toxicity, Metal content, from Safety Data Sheets supplied by environmentally aware companies like Sandoz. The process wise effluent analysis is shown in the table no. 2.

The auxiliaries consumption / month, their respective COD, BOD loads & other environmental data are as shown in the Table 3. As seen, many gaps exist for information like bioelimination, fish & oral toxicity as they are not readily available with the manufacturers. Environmental Properties of Chemicals & their Consumption & Pollutant Loads. Fabric Quality & their Process wise Effluent Analysis :-

Table 2

No. Quality & Process 1 Poonam Scouring 2 Poonam Scouring Oxalic Wash 3 Hot Rinse 4 Poonam Dyeing (White) 5 Poonam Dyeing (P.Green) 6 Printing 7 Prtg. Washing (Composite)

Machine

Meter Weigh Water s t Vol. 2,400 127.2 450 2,400 127.2 450

Devrekha Jet Devrekha Jet

Devrekha Jet 2400 Devrekha Jet 2,400 Devrekha Jet 2,400 Flat Bed Prtg. M/c. 7,000 Washing Tanks 42,000

127.2 127.2 127.2 371 2058

COD in ppm 1,818 843

450 450 450 24,000 45,500

300 1,276 3,410 72 824

SS in pH ppm 574 >10.5 165 4 53 15 245 33 259

6 5-6 5-6 7.5 7.3

Table 3:NO. AUXILIARY

ORAL TOXICITY BIO EL. % FISH TOXICITY

1 Indrez AG 2 Acetic Acid 3 Ethyl Acetate 4 Non Ionic Detergent 5 Oxalic Acid 6 Hicoklarin KD 7 Sandopur PCI 8 Formic Acid 9 Silicone Defoamer 10 Lyogen DFT 11 Sodium Hydrosulfite 12 Urea 13 Ginasol 6836 (Godrej) 14 Shidofix N 15 Sandacid PBI 16 Sudirol K 17 Diosyn HF 18 Sequacel HD 19 Catalyst DD 20 U.D.A. Powder 21 HicoleveIer BJD

>2000

50-100

50-500

>5000

4800 380

0.97 1.04

COD/MON. BOD/MON % COD % BOD . 0.22 4636.8 1041.6 66.9% 51.9% 0.85 395.2 321.1 5.7% 16.0%

200 125

1.54 1.76

0.29 0.47

308 220

58 58.4

4.4% 3.2%

2.9% 2.9%

1100 165 80 270

0.18 0.95 1.28 0.35

0.14 0.2 0.18 0.15

195.8 156.1 102.4 94.5

154 32.2 14.2 40.5

2.8% 2.3% 1.5% 1.36%

7.7% 1.6% 0.7% 2.02%

250

0.37

0.03

91.5

7.3

1.3%

0.4%

>500 NA

45 250

1.95 0.33

0.54 0.22

87.6 83.3

24.2 55

1.3% 1.2%

1.2% 2.7%

LD0 = 16000, LD100=30000

850

0.09

0.09

76.5

76.5

1.1%

3.8%

150

0.5

0.15

75.6

22.7

1.1%

1.1%

80 40 60 200 90 200 35 45

0.91 1.57 0.9 0.21 0.4 0.15 0.77 0.59

0.25 0.22 0.2 0.15 0.1 0 0.23 0.09

72.5 62.7 53.8 41.6 35.6 29 27 26.5

19.8 8.7 12 30 9 0.8 8.1 3.9

1.0% 0.9% 0.8% 0.6% 0.5% 0.4% 0.4% 0.4%

1.0% 0.4% 0.6% 1.5% 0.4% 0.0% 0.4% 0.2%

LD0 = 100, LD100=200 NA 12 Ld0 = 20 NA >500 LD0 = 100, LD100=200 NA

50-100

>2000

65 50-100

13 >100

>5000

50-100

>100-500

QTY./MON COD

BOD

22 23 24 25 26 27 28 29 30

Mercerine PES Lyogen PA 66 Citric W Diaton PR (Hico) Ammonium 58 Sulfate Caustic Soda Soda Ash Hydrochloric Acid Citric Acid

31 Diethylene Glycol 32 Phenol 33 Sarcol DBN 105

NA

TLm = 1290 (96 hrs) 100-330 LD0 = 625, LD100=894 >5000 5-10

G.TOTAL

80 35 800 35 1100

0.32 0.51 0.02 0.07 0

0.06 0.02 0.01 0.02 0

25.8 17.9 16 2.6 0

4.7 0.8 4 0.7 0

0.4% 0.3% 0.2% 0.04% 0.0%

0.2% 0.0% 0.2% 0.03% 0.0%

1100 400 275 0

0 0 0 0.69

0 0 0 0.4

0 0 0 0

0 0 0 0

0.0% 0.0% 0.0% 0.0%

0.0% 0.0% 0.0% 0.0%

0 0 0

1.49 2.28 0.28

0.12 1.4 0.09

0 0 0

0 0 0

0.0% 0.0% 0.0%

0.0% 0.0% 0.0%

6934.3

2008.2

100%

100%

13,240

Chemical Substitutions :- Several chemical alternatives exist for various wet processing processes. The following factors should be considered to select environmentally friendly chemicals :1) Biodegradability / Bioeliminability, 2) Aquatic Toxicity, 3) COD, BOD values, 4)& Metal concentration. Some substitutions possible in various processing stages, are listed below.

Scouring :- 1) Majority of the scouring pollutant load comes from the sizes, coning oils, fillers & impurities, which many times are added by the weaver just to improve the profitability in these hard times ! A processor cannot do much about it, but a composite mill can definitely select sizes & coning oils having lower COD, BOD value. 2) More than 600 tonnes / Year of non-ionic detergent based on Nonyl phenol ethoxylate is currently being used in Surat. This product on biodegradation gives toxic metabolites, which are highly poisonous to the fishes. Hence German manufacturers had voluntarily stopped it's manufacture from 1988. Now it can be substituted even in India, by Alfa Olefin Sulfonate, marketed by Gujarat Godrej as Ginasol 6836. It is easily biodegradable, non toxic & cheaper as well. Besides fatty alcohol ethoxylates, which are also biodegradable, are also available. 3) Many stain removers contain solvents like Carbon tetrachloride. The harmful effect of CFC's like Freon on Ozone layer is causing lot of concern, what is less known is, that Carbon tetrachloride has ten % more Ozone depletion capacity than CFC! Thus CCl4 based products should also be eliminated immediately. 4) Oxalic acid used for removing of rust stains is also quite toxic to aquatic organisms & besides has a considerable COD, BOD. It can be replaced by Catalyst D (Dharamsee Morarjee). 5) Hydro causes huge depletion of dissolved oxygen in the water. Considerable reduction in COD can be achieved by replacing Hydro which has a COD of 333 mg/g by 1/5th qty. of Thiourea Dioxide (Diosyn-HF) having COD of 208 mg/g, thus effectively reducing COD by 87.5% & Hydro costs by 43%.

Dyeing :- 1) Acetic acid alone can contributes to more than 20% of a Synthetics process house COD, BOD load. It can be substituted by Formic acid resulting in 83% & 91% COD & BOD reductions respectively. COD, BOD can be further reduced by 93% & 99% respectively if Catalyst D (Dharamsee mORARJEe) is used instead. Similarly S-acid PBI has much higher COD, BOD values & hence should be used only when it is absolutely essential. 2) Carriers based on chlorobenzenes are highly toxic & even carcinogenic & hence should be eliminated from dyeing process. Thus a few manufacturers like Sandoz (India) have voluntarily renunciated their chlorobenzene based carriers. Many -PJD type leveling agents contain chlorobenzene as well as perchloroethylene or trichloroethylene, which are again potential carcinogens. 3) The leveling agents also contribute heavily to the process house's effluent load. The conventional leveling agent for polyester based on castor oil ethoxylate has COD, BOD values of 1947 mg/g & 537 mg/g, it can be replaced by Hicoleveller BJD (Hico) having COD, BOD values of 588 & 150 mg/g only. Again this turns out to be the more economical alternative. 4) High quantities of Sequestering agents are required in Surat due to the very hard water. Poly phosphates like TSPP & Sodium Hexa meta phosphate, which have been banned in Europe since long, are still being used as water softeners & even in household detergents. They are not easily biodegradable & hence large amounts end up in the river & ocean. Here they are hydrolyzed to orthophosphates, which promote the growth of algae. Since algae are known for their high oxygen demand, which they withdraw from the water, & hence most of the algae will begin to rot. This will cause the river to die off. The whole process is known as "Eutrophication". Thus these products should be voluntarily banned by the processors. Other popular sequesterants are EDTA & NTA based products are also non biodegradable but unlike polyphosphates, have a strong affinity for Heavy metals & thus could release them later on in the river. Recently phosphonates (Sequacel HD - Excel) have been introduced in the market. They are more effective than EDTA & their complexes are even more stable than EDTA & thus again could remobilise heavy metals in the environment later on. The brighter side is that very small quantity is sufficient & they do not promote algae growth. 5) Hydro in reduction clearing, can be replaced by Diosyn HF as stated earlier.

Printing :- 1) Major environmental problem caused by printing emanates from Pentachlorophenol, used as a preservative in the Printing gum. It has a TLV value of 0.5 mg/meter of Skin & causes dermatitis, it's chronic exposure can lead to liver & kidney damage & it's also carcinogenic. PCP has been banned from January 1993 in India but the Gum manufacturers, barring IGI, are still blatantly using it. 2) Considerable Phenol is used for nylon printing, which can be substituted by Diethylene glycol. This substitution would take care of GPCB's phenol limits. 3) Citric acid contributes quite a bit to the plant COD, BOD levels (686 & 400 mg/g respectively). Substantial reduction in these levels can be obtained (more than 97%) by using Citric - W (Riddhi Rasayan). 4) Ginasol 6836 can also be used for washing of prints instead of non-ionic detergent, as discussed earlier. 5) Zinc sulfoxylate formaldehyde (Safolin) & tin chloride used for discharge printing, increases the metal content of the effluent. Many innovative processors have substituted these products with Sodium sulfoxylate formaldehyde(Rongalite -C) under alkaline conditions to eliminate these metals as well as reduce costs.

Finishing :- 1) The biggest environmental threat comes from Formaldehyde, which has been found to be carcinogenic in some studies. Hence European countries have set quite stringent standard for free formaldehyde of less than 75 ppm for clothes close to skin & 20 ppm for baby clothing [2]. Recently

Sandoz has come up with low formaldehyde & formaldehyde free products. 2) Cationic softeners based on quaternary ammonium compounds & silicone polyquats have less biodegradability & are also toxic to aquatic organisms. The following table shows reduction in COD, BOD levels & costs achieved by some chemical substitutions. A list of chemicals banned, due to their harmful effect on the environment is given in the Appendix. Table 4 No. Chemical Used Acetic Acid Citric Acid N.I. Detergent Castor oil Ethoxylate 5 Phenol 6 Hydro

Qty. COD BOD Substituted COD BOD COD BOD Cost Cost Kgs/Mon Kgs/Mon by Redn. Redn. Redn. % Redn. % Redn. Redn. . . Kgs/Mon. Kgs/Mon % . 1250 1300 1056 Catalyst DD 1209 1054 93% 99% Rs33,750 71% 900 617 360 Citric W 599 356 97% 99% Rs32,850 43% 300 528 140 Ginasol 6836 377 95 71% 68% Rs12,900 54% 250 487 134 Hicoleveller 340 112 70% 84% Rs11,750 42% BJD 100 228 140 Eliminated 228 140 100% 100% Rs5,500 100% 1000 333 220 Diosyn HF 324 192 97% 86% Rs26,00 40%

7 EDTA Na4 G.Total

150 3950

1 2 3 4

0 240 3733

52.5 HEDP 2102.5

226.1 3303.1

45.5 1994.5

94% 88.5%

87% 95.1%

Rs5767 Rs1,2851

77%

7 Dyes :- The following dyes used in Surat are known to be carcinogenic & hence should be voluntarily discontinued by processors, if not the dyestuff manufacturers [3]. Table 5 No. C.I. Generic Name C.I. Number Chemical Class 1 Direct Blue 6 22610 Azo 2 Direct Blue 14 23850 Azo 3 Direct Blue 15 24400 Azo 4 Direct Blue 53 23860 Azo 5 Direct Orange 1 Azo 6 Direct Brown 2 Azo 7 Direct Black 38 30235 Azo 8 Acid Red 26 16150 Azo 9 Acid Red 85 22245 Azo 10 Acid Red 114 23635 Azo 11 Acid Violet 49 42640 Triphenyl Methane 12 Basic Yellow 2 41000 Ketonimin 13 Basic Orange 14 46005 Acridine Many other toxic & dyes allergic to skin have been listed in the earlier paper

Diazo Component Benzidine Tolidine Dianisidine Tolidine Benzidine Benzidine Benzidine Xylidine Benzidine Tolidine ------[3].

Optimization of chemicals & dyes :- Very often, we processors are used to working with unnecessarily high quantities of auxiliaries & chemicals. They needlessly increase costs as well as effluent load. e.g. Leveling agents above 0.5 g/l can reduce 10% - 15% colour yield of dyes like Brown 3REL [4]. Many dyes having good leveling property can be dyed without the addition of leveling agents. Similarly a lot can be done on the dyestuff front. High dyestuff percentages, without any consideration for the optimal concentration are a norm in Surat. A colour computer can do wonders for predicting optimum & economical dyeing recipes. Besides saturation values of dyes can also be computed from it as follows :- A particular dye should be dyed at different concentra-

tions from 0.1% to 5%. Then their K/S values are computed & plotted versus their concentrations . The slope tends to be almost linear till it reaches a certain concentration, after which the curve flattens out. This particular concentration is known as saturation value, above which no appreciable increase in visual depth is perceived. Colourtex & Sandoz have prepared special saturation curves shade cards for their products which can be used to greatly reduce dyestuff consumption. Hence all the process recipes should be optimized & standardized on the basis of " Three E's" viz. Environment, Efficiency & Economy.

Water Conservation :- The following table shows the average water consumed per day in a medium sized process house. Table 5 NO. 1 2 3 4 5 6 7 8 9 10 11 12 13

MACHINE 6 PRINTING MACHINES WASHING TANKS SCREEN WASHING DOMESTIC & SANITATION BOILER 3 DEV. JETS PROCESS WATER

NORM 28 TO 35 lts/min, 16 hrs / day

50 lts / Screen 100 lts / Worker 1000 lts / hr 3450 lts/Batch of Scouring & Dyeing 3 DEV. JETS COOLING WATER 2300 lts/Batch of Scouring & Dyeing DALAL BEAM 1800 lts/Batch of Nylon Dyeing 2 STENTERS 7 JIGGERS 1 BACKGREY Washing WINCH 2 Printing Gum COOKING PANS Printing Colour Kitchen Total Water CONSUMED / DAY

LTS / DAY 190,080 45,500 37,800 35,000 24,000 51,750

% 43.1% 10.3% 8.6% 7.9% 5.4% 11.7%

31,500

7.1%

5,400 7,800 2,640 4,000 4,000

1.2% 1.8% 0.6% 0.9% 0.9%

1,750 441,220

0.4% 100.0%

WATER USED LTS / Meter 9 FABRIC WATER USED LTS / KG 184 FABRIC The water requirement has gone down in the Industry, as most of the process houses have replaced the conventional Jet Dyeing machines with the new more economical low liqour ratio machines(M:L=1:3). They require less than 1/3 rd of water & energy of the conventional machines. The condensate, which goes down the drain in many process houses, should be collected & reused as boiler feed water. Besides as seen in the table, lots of water is required for cooling of Jets & vacuum hydroextractors on stenters. This water can be collected in tanks & reused effectively. As seen in the table, printing machines consume 43% of the total water. Lot of water is wasted on printing machines as the water flow remains on, even when the machine is stopped. This can be curtailed by attaching solenoid valves to the water valve & automating the flow only when the machine starts. One innovative unit is reusing treated effluent for printing machine blanket washing operations. Hence, lot of scope exists in reducing the water requirements of a process house.

Reuse / Recycling :- Some basic areas of reuse are :-

1) Proper removal & reuse of print paste from the screens & squeegees, before washing can go a long way in reducing the costs as well as effluent load, yet this aspect some how remains neglected. 2) Reuse of left over finishing liquors. 3) Dyebath Reuse :- Generally almost 95% of dye exhaustion takes place in Polyester dyeing. Hence an alternative to the discharge of this exhausted bath is to collect it in an over head tank, analyze it for remaining dyes/chemicals quantities & then reconstitute the bath for further use. In this manner, a single bath is currently being reused for more than twelve times for Optical Whitening & three times for light shades, in our unit & yielding significant savings in water, energy, chemicals & effluent treatment are achieved by this relatively simple technique.

Role of Dyes / Chemicals Manufacturers in Waste Minimization :- Manufacturers will play a very vital function in environmental protection. They can make a start by supplying Safety Data Sheets containing data on environmental & toxicological information like Biodegradability, Heavy metal content, Fish toxicity, carcinogenicity, COD, BOD values. Currently, only ETAD members like Sandoz pass on the SDS to the actual users. We processors can then select eco friendly products from this information (after verification). By this environmental oriented product selection (rejection !), we can start a new trend in our industry & forcefully influence manufacturers to develop more "Green" products. Besides voluntary renunciation of many carcinogenic & toxic dyes & chemicals banned in Europe ( As listed in Apppendix) & now even in India, should be another priority. Many times toxic pollutants observed in the process house effluent, are impurities occurring in the dyes & chemicals itself. e.g. Mercury comes as an impurity from Caustic Soda manufactured by Mercury cell method, as very few Chloralkali manufacturers have shifted to the cleaner membrane technology. Cadmium occurs as an impurity from the detergents. Thus clean technology should evolve right from the raw materials manufacturing end. They should come up with new eco friendly products, which can then also be effectively utilized as a "Green Marketing " tool by them.

Formation Of Waste Minimization Group of Surat :- Waste Minimization Group has been formed by the local process houses, dyestuff manufacturers & academicians, voluntarily to propogate Cleaner technologies & Waste Minimization in our Industry. The main objectives of WMG are :1) To create awareness about Environmental issues of our Industry & how Cleaner technologies can be implemented; 2) To share experience regarding the cost benefits of Environmentally friendly Processing; Activities to be started on priority are :1) Inform Industry about the Cost benefits achieved from Environmental Audits & Waste Minimization in the form of a Newsletter. 2) Check 200 Chemicals & Dyes commonly used in Surat, for Environmental & Toxicological properties like Biodegradability, Heavy Metal content, BOD, COD, Carcinogenicity, Fish Toxicity by the Environmental Engineering Department & BioSciences Department. (Safety Data Sheets). 3) Prepare lists of Environmentally friendly & Harmful items from the above study. 4) Organize Seminars on Environmental issues of our Industry. 5) Study on Environmental Impact of our Industry to be jointly undertaken by Environ. Engg. Dept. & our process house. 6) Manuals on Waste Minimization, Energy Conservation & Water Conservation to be prepared.

Conclusion :- The final block in keeping our environment clean would be the "Who cares a damn?", an attitude which has more or less existed during all these years. Environmental aspects of wet processing will gain more importance in the coming years. The standards to which the industry will have to work ,will become more stringent & clearly effluent treatment costs will increase substantially. Under these circumstances, Waste Minimization can reduce the enviironmental impact of wet processing as well as be a productive & cost reduction tool for the management.

Appendix List of Environmentally Harmful Chemicals (Prohibited on textiles in Europe) -[2] A) Innorganic & Organometallic Compounds :1) Arsenic compounds. 2) Cadmium compounds. * 3) Chromium compounds. 4) Copper compounds. 5) Lead compounds. 6) Mercury compounds.

*

7) Silver compounds. 8) Tin (Trimethyl, Tributyl) compounds.

*

9) Flourides. B .1) Organic compounds likely to be used in Fabric manufacture & Processing . 1) Carbon Tetrachloride.

*

2) Chlorinated paraffins. 3) CFC - Chloroflouro Carbons.

*

4) Dibutylphthalate. 5) 1,2,Dichloroethane (Ethlene dichloride).

*

6) Hexachlorobutadiene.

*

7) Halon - Hexafluroethane.

*

8) Nonyl Phenol Ethoxylates. 9) Octachlorostyrene. 10) Pentachlorophenol. 11) Pentachlorobiphenyl.

*

12) Polychlorinated Biphenyls (PCB's). 13) Tributyl phosphate. 14) Trichlorobenzene. 15) Triphenyl phosphates. 16) Trichloroethane.

*

17) Tetrachlorodibenzo -p-dioxin. c) Organic Dye intermediates :1) Benzidine. 2) Benzopyrine. 3) Hexa Chloropentadiene. 4) Chloroaniline. 5) Dichloroaniline. D) Miscellaneous :Xanthates - Ethl, isopropyl, isobutyl. * - Already banned, others to be phased out in the future. References :- 1) "Europäische Abwasserregelungen im Vergleich" - Hartmut Reetz, Mellliand textilberichte 11/1991 pg 632. 2) "Eco standards as a new challenge for industries inn developing countires, The case for India - T. Bunning et al. German Development Institute report. 3) "The ecological & toxicological properties of dyestuffs" - Chittaranjan Desai, Colourage Dec 1992 pg. 51. 4) "Application of Disperse Dyes" - Edited by R.M. Mittal, ATIRA publication pg. 15.