Compared with water treatment plant, they have a higher load capacity. This means more leather can be processed in each batch, resulting in lower water use. Processing a ton of raw leather to wet blue via the overhead drum yields approximately 35 tons of wastewater, 45 to 60 tons less than what side loaders give out.
Additionally, leather makers in Xinji separate the chrome tanning liquid and lime liquor from the wastewater for recycling. The rest is processed in-house or sent to water-treatment facilities.
Hebei Dongming invested more than $300,000 in equipment for reusing lime liquor. Its engineers filter hair and other organic compounds from the wastewater. The recovered hair is then employed as fertilizer. This process is said to reduce wastewater discharge by 130,000 tons annually. At the same time, more than 30 percent of sodium sulfide, lime and chrome tannins are reused, and the chemical oxygen demand discharge is lowered to below 50 percent.
drinking water treatment machine is adopted in the paper industry as well. Shandong Taishan Paper Co. Ltd has caustic soda recycling equipment with a 100-ton capacity. It also has a 30,000-ton wastewater processing workshop that can keep COD discharge to under 70mg/L.
In-house or community facilities
Putting in place in-house wastewater processing facilities requires spending millions of dollars. In the denim industry, for instance, such equipment alone contributes 30 percent to the total production machinery budget. Although it may take years before they can see any returns on their investment, tier 1 businesses prefer to take this step rather than decrease water usage. One of the reasons for this is that they can charge as much as 40 percent more than competitors without such facilities.
Most companies, however, send their wastewater to community sewage water plants for treatment. Dyeing factories in the Zhejiang province city of Shaoxing, for instance, have sewage pipes leading directly to such plants. Companies pay the facility $0.29 for every ton of wastewater processed.
Guangdong Changrun Garment Co. Ltd has one of the largest washing factories in the province. The company utilizes a treatment plant in the industry park, where wastewater from other factories also goes.
Likewise, ro water treatment plant in Xinji are required to use the common treatment facility in the industry park. There are three such plants in the area, and each charges roughly $1.05 per ton treated.
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