Water treatment processes 



Textile mills require clear process water. Clarifi- 

 cation of surface water is practiced by all textile 

 mills that do not purchase potable water or use 

 ground water. 



The early mills located on soft water supplies. 

 As available soft water sites were filled, mills 

 moved to hard water areas and practiced softening 

 or bought city water. Batch softening or seques- 

 tering with EDTA or polyphosphates is now prac- 

 ticed in the critical processes even when a mill has 

 a soft water supply. Demineralization is used by 

 a few mills where color matching in dyeing opera- 

 tions is critical. 



Chlorination is used to prevent slime on the 

 piping but the concentration must be kept at a 

 minimum since reducing agents are frequently 

 required with sensitive dyes. Adjustment of the 

 pH to a slightly alkaline value for enhancing the 

 effectiveness of chlorine or chlorine dioxide in the 

 removal of manganese creates a problem in meet- 

 ing the pH requirements for some of the mill's 

 processes. 



Control of corrosion is very critical in the water 

 distribution system because the corrosion products 

 can stain cloth. Manganese removal may be nec- 

 essary because loosened deposits of manganese 

 dioxide which accumulate on copper water heat- 

 ing pipes (coils) may create disastrous results in 

 rinsing operations. 



lumber 



and wood products 



(SIC 24) 



Description of industry and processes 

 utilizing water 



In general, the lumber industry collects logs 

 from the forest and prepares them for use by saw- 

 ing the log into various shapes. In the early years 

 in this country, the logs were cut in the winter 

 when the snow was on the ground to lubricate their 

 transfer by dragging them overland to the river. 

 The river transported the log to a millsite. The 

 logs were frequently left in the water if they could 

 be fenced off or driven into a back water to pre- 

 vent them from going further downstream. While 

 the log was floating, the water prevented the log 

 from drying and cracking at the cut end. 



Today, lumber may be transported to a mill 

 which may not be near a river. If the logs accumu- 

 late, it is necessary to keep their ends moist to pre- 

 vent cracking. This can be done by floating them 

 in a pond or by spraying the log pile. The log is 

 frequently debarked by water jets before cutting 

 it into the desired shape. 



Some lumber is treated with chemicals to reduce 

 fire hazards, to retard insect invasion, or prevent 

 "dry rot." These preservation processes use small 

 volumes of water to prepare the solutions of 

 chromates, cupric ions, aluminum ions, silicates, 

 fluorides, arsenates, and pentachlorophenates. 

 Some forest products are processed mechanicaUy 

 or chemicaUy to make a variety of consumer 

 products. 



Significant indicators of water quality 



There are few significant indicators of water 

 quality for the lumber industry. The suspended 

 solids should be less than 3 mm in diameter and 

 the pH should preferably be between 5 and 9 to 

 minimize corrosion of the equipment. Water used 

 for transportation hardly qualifies as process water. 

 Water used for spraying logs or jet debarking 

 should be free of particles that clog the nozzles or 

 jet openings. Such water is frequently recirculated. 

 Water for preparation of solutions for treatment of 

 the lumber should be reasonably free of turbidity 

 and those ions which might react to form precipi- 

 tates. Frequently, because of the highly toxic 

 nature of these solutions, efforts are made to re- 

 cycle as much solution as possible. Thus, makeup 

 water is required to compensate for the portion of 

 the solution forced into the lumber under pressure 

 and then evaporated during seasoning. 



Water treatment processes 



For the lumber production phase only, straining 

 may be required. Clarification may be practiced 

 for water used in lumber preservation but this 

 would be necessary on only a very small volume. 



TABLE V-8. Quality Characteristics of Waters 



That Have Been Used by the Lumber Industry 



(SIC 24) 



Characteristic Value 



Suspended solids <3 mm, diameter. 



pH, units 5 to 9. 



NOTE. — Application of the above values should be based on 

 Part 23, ASTM book of standards (1), or APHA Standard 

 methods for the examination of water and wastewater (5). 



462-246 0-72-14 



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