CHAPTER 18 • Management of Tokyo Bay
333
Another notable trend is that the majority of cargo in the bay is being handled at
private piers, such as piers built on individual factory sites for handling cars for export. Private piers include highly efficient offshore sea-berths at which crude oil and
oil products are handled, both of which are major items transported in Tokyo Bay. On
the other hand, public piers handle less and less of the total cargo moved, e.g., in 1986
only 26.5% in Tokyo Port, 10.3% in Yokohama, 8.7% in Chiba.
The fact that some piers are not used efficiently in terms of cargo handled per unit
length of pier, plus the trend of increasing containerization of cargoes and the increasing proportion of private piers, suggest that less mooring length will be needed in the
future, even if total demand for marine transport in the six ports continues to grow.
Therefore, it seems logical to transform the inefficiently used piers and wharves to other
uses, sU,ch as civic, business, and recreational. The criterion used to identify efficiency
in pier utilization in the study was 1000 t m- I of pier.
Total length of piers where the efficiency was less than 1000 t m- I in 1980 was about
21 km, or 14% of the total length of piers in the six ports of Tokyo Bay. However, the
total tonnage of cargo handled at these piers was only 3% of the total tonnage in the
six ports. Based on this analysis, shifting the use of piers from marine transport to
water-based recreation was a logical option for consideration.
18.2.5
Liquid Waste Disposal and Water Quality
The analysis relating to water quality focused on Chemical Oxygen Demand (COD)
and Dissolved Inorganic Nitrogen (DIN). COD is an indicator of organic pollution
which is directly linked to such problems as low oxygen levels in water (thereby threatening survival of finfish, shellfish, and other marine species), offensive odour, poor
transparency, and blackish colours. COD is used as the criterion for some of the governmental pollution reduction programs in Japan.
Among nutrients, nitrogen and phosphorus are particularly important as substances
of concern in metabolism of algae, and should therefore be considered as limiting factors to primary production. In comparing these two, nitrogen is less abundant than
phosphorus in Tokyo Bay in light of the amount needed for algal growth. This means
that additional inputs of nitrogen would combine with already available phosphorus
to stimulate algal growth. Thus, nitrogen is selected as the focus of the analysis.
In order to analyze the loads of COD and DIN to Tokyo Bay, the classification of
residential and commercial activities according to the methods of handling liquid
wastes is essential. Currently there are four methods of handling nightwaste in the Tokyo
Bay area, as indicated in Fig. 18.3. These are:
1. Discharge into municipal sewerage systems and hence into municipal sewage treatment plants;
2. Store nightwaste in a tank, for subsequent removal to nightwaste treatment plants,
with other wastewaters being discharged directly to adjacent gutters or rivers;
3. Treat nightwaste with digestion chamber ("independent" septic tank) on-site, and
discharge other wastewaters directly;
4. Treat both nightwaste and other wastewaters with digestion chamber ("combined"
septic tank, or community plant).
333
Another notable trend is that the majority of cargo in the bay is being handled at
private piers, such as piers built on individual factory sites for handling cars for export. Private piers include highly efficient offshore sea-berths at which crude oil and
oil products are handled, both of which are major items transported in Tokyo Bay. On
the other hand, public piers handle less and less of the total cargo moved, e.g., in 1986
only 26.5% in Tokyo Port, 10.3% in Yokohama, 8.7% in Chiba.
The fact that some piers are not used efficiently in terms of cargo handled per unit
length of pier, plus the trend of increasing containerization of cargoes and the increasing proportion of private piers, suggest that less mooring length will be needed in the
future, even if total demand for marine transport in the six ports continues to grow.
Therefore, it seems logical to transform the inefficiently used piers and wharves to other
uses, sU,ch as civic, business, and recreational. The criterion used to identify efficiency
in pier utilization in the study was 1000 t m- I of pier.
Total length of piers where the efficiency was less than 1000 t m- I in 1980 was about
21 km, or 14% of the total length of piers in the six ports of Tokyo Bay. However, the
total tonnage of cargo handled at these piers was only 3% of the total tonnage in the
six ports. Based on this analysis, shifting the use of piers from marine transport to
water-based recreation was a logical option for consideration.
18.2.5
Liquid Waste Disposal and Water Quality
The analysis relating to water quality focused on Chemical Oxygen Demand (COD)
and Dissolved Inorganic Nitrogen (DIN). COD is an indicator of organic pollution
which is directly linked to such problems as low oxygen levels in water (thereby threatening survival of finfish, shellfish, and other marine species), offensive odour, poor
transparency, and blackish colours. COD is used as the criterion for some of the governmental pollution reduction programs in Japan.
Among nutrients, nitrogen and phosphorus are particularly important as substances
of concern in metabolism of algae, and should therefore be considered as limiting factors to primary production. In comparing these two, nitrogen is less abundant than
phosphorus in Tokyo Bay in light of the amount needed for algal growth. This means
that additional inputs of nitrogen would combine with already available phosphorus
to stimulate algal growth. Thus, nitrogen is selected as the focus of the analysis.
In order to analyze the loads of COD and DIN to Tokyo Bay, the classification of
residential and commercial activities according to the methods of handling liquid
wastes is essential. Currently there are four methods of handling nightwaste in the Tokyo
Bay area, as indicated in Fig. 18.3. These are:
1. Discharge into municipal sewerage systems and hence into municipal sewage treatment plants;
2. Store nightwaste in a tank, for subsequent removal to nightwaste treatment plants,
with other wastewaters being discharged directly to adjacent gutters or rivers;
3. Treat nightwaste with digestion chamber ("independent" septic tank) on-site, and
discharge other wastewaters directly;
4. Treat both nightwaste and other wastewaters with digestion chamber ("combined"
septic tank, or community plant).