Significant indicators of water quality 



The chemical composition of the water is im- 

 portant in producing high quaUty leather. For 

 some processes, such as the finishing of leather, 

 distilled or demineralized water is best. The 

 microbiological content of the water is equally 

 important, but this can be controlled by use of 

 disinfectants. The quality requirements at point 

 of use are shown in table V-21. 



tanning industry 

 (SIC 3111) 



Water treatment processes 



Most tanning and leather product industries are 

 located in urban areas and use public water sup- 

 plies or ground water. A few tanneries use surface 

 supplies. Such waters are usually chlorinated. 

 They may also need additional treatment, such as 

 clarification and iron and manganese removal. 



A limited volume of water, whether from the 

 public water supply or company-owned systems, 

 may be softened, distilled, or demineralized. 



Description of industry 



The tanning-leather industry is many industries 

 as each type of leather constitutes a different 

 process. Basically there are only three or four 

 types of tannage (vegetable, mineral, combination 

 of vegetable-mineral, and syntans) but many 

 finishing processes. 



Processes utilizing water 



Water is used in all processes of storage, sorting, 

 trimming, soaking, green fleshing, unhairing, 

 neutralizing, bating, pickling, tanning, retanning, 

 fat-liquoring, drying and finishing of the hides. 

 It is an essential factor in each process. The chemi- 

 cal composition of the water is considered critical 

 in obtaining the desired quality of leather. For this 

 and other reasons there is little reuse of water in 

 the tanning industry. 



The following tabulation gives data on water 

 utilization by the leather tanning and finishing in- 

 dustry as reported in the 1963 census of manu- 

 facturers (7). 



Water use: Water quantity, 

 bgy 



Intake 15. 



Reuse Negligible. 



Consumption do. 



TABLE V-21. Quality Requirements of Water 



at Point of Use by the Leather Tanning and 



Finishing Industry (SIC 3111) 



[Unless otherwise indicated, units are mg/i and values that 



normally should not be exceeded. Quality of water prior to the 



addition of substances used for internal conditioning.] 



Characteristic 



General 

 finishing 

 processes Coloring 



Alkalinity (CaCO^) O 



pH, units 6.0-8.0 



Hardness (CaCO-,) 150 



Calcium (Ca) 60 



Chloride (CI) 250 



Sulfate (SO.) 250 



Iron (Fe) 50 



Manganese (Mn) ('') 



Organics: Carbon 



chloroform extract (°) 



Color, units 5 



Coliform bacteria (°) 



Turbidity (') 



'Accepted as received (if meeting total solids or other 

 limiting values); has never been a problem at concentrations 

 encountered, 



- Lime softened. 



^Zero, not detectable by test. 



^ Demineralized or distilled water. 



= Concentration not known. 



" 1962 U.S. Public Health Service Drinking Water Standards, 

 Pub. 956 (8). 



NOTE. — Above values based on Part 23, ASTIW book of 

 standards (1); APHA standard methods for examination of 

 water and wastewater, (5), 



462-246 0-72-15 



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