This survey of wastewater treatment in the Japanese pulp and paper industry is based on operations of 102 mills in 2002. Data covers 98% of pulp production, except recycled pulp including deinked pulp, DIP, and 89% of the production of paper and board products, and is compared with the last survey’s in 1991.
As the Japanese economy has been sluggish in this 11 years, pulp production in 2002 has decreased by 9% and paper and board production has been confined to 10% increase. One third of the mills each produces annually over 0.3 million tonnes of market products. 72% of the mills produces both pulp and paper products. 31% of the mills has kraft pulping process. Half of the mills discharges effluents into river and 41% into seas. Enclosed coastal seas, Tokyo Bay, Ise Bay and Seto Inland Sea, receives effluents from 30% of the mills.
Enhanced awareness of the environmental preservation in Japan has further strengthened the effluent limitations. Discharge limits of suspended solids (SS) and biological oxygen demand (BOD5) are lowered by an average of 20% and chemical oxygen demand (COD
Mn) by 10%.
As the result of sustained effort of the Japanese pulp and paper industry, the average specific discharge of SS in 2002 has decreased to 2.6 kg per ton of market products, BOD to 2.8 kg⁄t , COD to 7.4 kg⁄t, and the average specific consumption of water has been lowered to 88 m
3⁄t , which correspond to a reduction of 29% on SS, 42% on BOD, 30% on COD and 16% on water consumption.
Though coagulation-sedimentation is still the mainstream of wastewater treatment, the multistage processing including some biological treatments has spread progressively. Many activated sludge plants have shifted their aeration gas from air to oxygen, and then more than 50% of BOD and COD loads in wastewater have been removed by the activated sludge process.
The average number of operational staff of wastewater treatment is 4. 7. has decreased to one third from 1991.
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