Glass Industry Water Standards

Ultra-pure water equipment used in the glass industry is also called continuous electro-deionization (EDI) systems. It is a pure water preparation technology that combines technologies of ion exchange, ion exchange membrane, and ion migration. Ultra-pure water equipment used in the glass industry belongs to high-tech green environmental protection technology.

Advantages of Ultra-Pure Water Equipment Used in the Glass Industry

1. The effluent water quality has excellent stability.
2. It can continuously produce ultra-pure water that meets customers’ requirements.
3. Modular production allows for automated control.
4. No acid-base regeneration is required, and there is no pollution discharge.
5. There is no downtime due to regeneration.
6. No regeneration equipment or chemical transportation and storage are needed.
7. The equipment has a compact structure and a small footprint.
8. Operating and maintenance costs are low.
9. The operation is simple and the labor intensity is low.

Water Quality Standards for EDI Ultrapure Water Equipment in the Glass Industry

The water quality of the effluent from ultrapure water equipment used in the glass industry fully complies with the American ASTM pure water quality standards, the water quality technical standards of the Ministry of Electronic Industry of China (five levels of standards of 18MΩ.cm, 15MΩ.cm, 10MΩ.cm, 2MΩ.cm, and 0.5MΩ.cm), the trial standards for ultrapure water quality of the Ministry of Electronic Industry of China, the pure water indicators used in the American semiconductor industry, the water quality standards for integrated circuits in Japan, and large-scale integrated circuit water quality standards both domestically and internationally.

The use of ultrapure water equipment in the glass industry greatly saves labor costs and maintenance costs, with a high water utilization rate, reliable operation, and economical rationality. Compared with other similar products, the equipment has higher cost performance and equipment reliability.

1. Water Quality Requirements for Printing and Dyeing

Throughout the printing and dyeing process, the amount of steam water used by the printing and dyeing plant is relatively large compared to the amount of water used in the pre-treatment process. According to statistics, the water consumption for producing 1 km of cotton printing and dyeing fabric in a printing and dyeing plant is nearly 20 tons, and the water used in pretreatment accounts for about 50% of the total water consumption. The water quality not only affects the quality of pre-treatment and its products but also affects the consumption of dyeing and finishing materials and auxiliaries. 

Although various measures can be taken to improve water quality, any improvement will occupy equipment and space, consume energy and chemicals, and thus increase the cost of the printing and dyeing plant. Therefore, the printing and dyeing plant should establish sufficient water sources, ensure good water quality, and have suitable conditions for wastewater discharge.

Water quality requirements for printing and dyeing plants: Transparency > 30, chroma ≤ 10 (platinum-cobalt scale), pH value between 6.5 and 8.5, iron content ≤ 0.1mg/L, manganese content ≤ 0.1mg/L, total hardness: dyeing solution and soap washing water < 0.36mg/L, general washing water 3.6mg/L.

2. Hard Water and its Softening

Water containing calcium and magnesium salts is called hard water (the content of calcium and magnesium salts is expressed in terms of hardness), while water with low calcium and magnesium salt content is called soft water. The standards for soft water and hard water areas are as follows: soft water 0-57 ppm, slightly hard water 57-100 ppm, hard water 100-280 ppm, and very hard water > 280 ppm.

Calcium and magnesium salts in hard water can hinder the action of soap, causing difficulty in dissolving and forming calcium and magnesium soap deposits on fabrics during the dyeing and finishing process. In addition, the alkaline solution is difficult to dissolve and forms scale deposits on the pre-treatment equipment (such as tank walls, valves, and guide rollers), which hinders the production process. 

If the iron and manganese salt content in the water exceeds the specified limit, it can cause rust spots during the boiling and bleaching process, and the iron and manganese salts can catalyze the oxidation of cotton fibers, making them brittle. For boilers, hard water can lead to scale deposits that tightly adhere to the boiler tube wall, reducing the thermal conductivity of the boiler and increasing fuel consumption. Scale deposits can also cause boiler explosions.

Water softening refers to the removal of calcium and magnesium salts from hard water. Different softening methods can be used for pre-treatment, dyeing, printing, and washing water according to the requirements of water quality. Generally, soft water with a hardness of around 3.6mg/L (180 ppm) is required. River water and tap water in cities usually meet the requirements. When preparing chemical solutions for pre-treatment, water with a hardness of 0.36mg/L should be used. Soft water is used for equipment such as dryers, radiators, and steam water, and it can also be used to supply sufficient amounts of chemical solutions. Softening agents are added to the water before adding dyeing and finishing chemicals.