Preventing Water Pollution in the Pulp and Paper Industry

The total organic pollutant load in terms of biochemical oxygen demand (BOD) from domestic sewage was reduced from 750 thousand tons/year in 1970 to 580 thousand tons/year in 1989 (Nakanishi 1994). This reduction was to only threefourths of the original amount. In comparison, the total BOD discharged into public water bodies as wastewater from all Japanese industries was significantly reduced to about one fifteenth of its original value, from 3 million tons/year (in 1970) to 200 thousand tons/year (in the late 1980s) (Fig. 14.4). As the organic pollutant load from the pulp and paper industry was quite large and contributed about half of the total BOD load from all industries, here we will discuss reduction of the wastewater organic pollutant load from the pulp and paper industry in particular.

The organic pollutant load from the pulp and paper industry was about 2.2 million tons/year in terms of chemical oxygen demand (COD) in 1970, and it was reduced to only 200 thousand tons/year in 1989. Assuming no reduction measures had been taken, however, it was estimated that it would have been 4.5 million tons/ year in 1989 based on the amount of pulp and paper production (Nakanishi 1994). The COD reduction was attained mainly by a product shift (58 %) and by black liquor recovery (26 %) (Fig. 14.5). The pulp and paper companies shifted their product from pulp with high unit COD emission load to that of low unit emission load such as Kraft pulp. In addition, waste paper was used as a raw material in place of virgin pulp, which also reduced the emission load.

Black liquor is the spent cooking liquor that is formed when pulpwood is digested into paper pulp by removing lignin, hemicelluloses, and other extractives from wood. This liquor contains a very high concentration of organic pollutants that are hard to remove by biological wastewater treatment processes. Thus, instead of discharging black liquor to treatment plants or directly into water bodies, companies started to concentrate the liquor and burn it to recover heat energy to generate steam

Fig. 14.5 Reduction of COD load in pulp and paper industry (Nakanishi 1994)

and cooking chemicals (sodium hydroxides and sodium sulfide). This process change not only reduced the COD emission but was economically beneficial in terms of energy and chemical use.

The third reduction measure was wastewater treatment, which contributed about 16 % of the total reduction. It should be emphasized, however, that the reduction of waste load by improving the production process was much more effective and economical than end-of-pipe wastewater treatment. In-process reduction also often saved raw materials and energy.

In contrast to industrial wastewater, domestic wastewater load cannot be reduced at the source but is instead reduced by municipal wastewater treatment plants or by small community-based sewage treatment systems. These sewage treatments are usually more expensive and take a longer time to implement than industrial wastewater treatment measures as long sewer pipes have to be installed.

Environmental Standards for Toxic Chemical Substances

As stated in the introduction section, Japan experienced some cases of environmental pollution that caused damage to human health. Because of those experiences, the Japanese government started to regulate a limited number of toxic pollutants that caused problems, such as mercury, cadmium, lead, and PCBs, by setting strict effluent standards (Table 14.1). As a result of these measures, rates of compliance with environmental water quality standards were significantly improved during the 1970s. The number of regulated pollutants in water did not change, however, for about 20 years until the 1990s. In 1993, fifteen new substances including organochlorines and pesticides were added to the items subject to the environmental quality standards. Three more items were added in 1999 and one item was added in 2009. The reason that itemized regulation developed so slowly was that setting an

Table 14.1 Items subject to water quality standards during the 1970s in Japan

Items

Standard (original value)

Year first introduced (revised)

Cadmium Cyanide

0.01 mg/L ND

1970 (2011: 0.01 → 0.003 mg/L)

1970

Lead

Hexavalent chromium

0.1 mg/L

0.05 mg/L

1970 (1993: 0.1 → 0.01 mg/L)

1970

Arsenic

Total mercury

0.05 mg/L 0.0005 mg/L

1970 (1993: 0.05 → 0.01 mg/L)

1970

Alkyl mercury

ND

1970

Organophosphate

ND

1970 (1993: deleted from the list)

PCB

ND

1975

ND Should not be detected

The number of items regulated for protection of human health is currently 27

environmental standard for each item meant extensive and costly monitoring as well as control of emissions in a range of industrial sectors across the nation. It was therefore difficult to get support from all the sectors to add new items. Faced with the difficulty of increasing the number of items subject to standards, in 1993 the Japanese government designated a group of chemicals that should be monitored (currently 26 items) and another group of chemicals that should be under observation (about 300 chemicals). Chemicals in these new groups are not yet regulated by the law but they are being monitored or information is being collected about them. Based on the information collected, new pollutants will be selected for inclusion among the items subject to environmental standards. This type of soft regulation gives warning to industry that, although some of the chemicals they use are not currently regulated, those chemicals should be used with care. Another mechanism that provides companies with an incentive to reduce their pollutant emissions is the pollutant release and transfer register (PRTR) system, whereby companies are requested to report the amounts of listed pollutants they discharge into the environment or transfer to wastewater and solid waste treatment facilities.

 
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