Comparison of recycled paper and plain paper (2)

The papermaking industry has a large amount of waste water and is widely distributed. It is one of the most polluting industries in China. The production of one ton of pulp requires 100 tons (wood pulp) to 400 tons (grass pulp) of water, and most of this wastewater is discharged. China's papermaking industry emits more than 30% of its total aerobic organic compounds. The black liquor produced by papermaking is the most polluted, with 10 tons of black liquor discharged per ton of pulp produced. Wastewater from papermaking contains large amounts of carbohydrates, proteins, oils, and lignin. These substances are easily decomposed under the action of microorganisms. During the decomposition process, a large amount of oxygen is consumed, which reduces the oxygen content in the water and affects the growth of fish and other aquatic organisms. After the dissolved oxygen is exhausted in the water, the water is in an anaerobic state. Under the action of anaerobic bacteria, organic substances produce unpleasant toxic gases such as hydrogen sulfide, ammonia, and mercaptan, which further deteriorates water quality. Recycled paper can reduce waste water discharge by 50% during the manufacturing process. In particular, several steps in the early stage of papermaking can be saved, and the black liquor with the most serious pollution will not be produced and will be greatly reduced.