As long as polychlorinated biphenyls (PCB's, see Chap. 9) were widely used in industry, paints, and lubrificants, waste water from cities contained traces of PCB's, and
because PCB's are rather persistent, they still contaminate the environment and will
be found in waste water for a reasonable period of time. In the treatment of waste
water, PCB's in the main get into sludge; the treated effluents therefore are not at
fault. The sludge from New York waste water treatment plants, in 1975, contained
an average of 3.4 mg/kg PCB's calculated for dry matter in the sludge. As a consequence, PCB concentrations in the sediment of the dumping area for sludge in New
York Bight are above 1 mg/kg (dry weight) in the upper 5 cm sediment layer, compared with 1-100 pg/kg in the area farther away (West and Hatcher 1980). One has
to assume that such PCB concentrations originating from the dumping of sewage
sludge accumulate in marine organisms and fish (Lawrence and Tosine 1977), and
PCB's will enter the land vegetation if sludge is disposed on land and used for agricultural purposes.
PCB's range under "organic substances difficult to degrade", like many others, phenolic substances for example. However, they make up only a small fraction of the
total organic matter in sewage sludge. When sewage sludge is anaerobically digested,
for example in Hamburg treatment plant it contains organic substances equivalent to
a Chemical Oxygen Demand (COD) of 37-51 gil. The COD is determined by wet
oxidation of the sludge with dichromate, therefore it includes the large quantities of
organic substances which are not readily degradable and cannot be measured as oxygen demand during microbial degradation (Biochemical Oxygen Demand, BOD,
during a 5-day period, see Chap. 2.1). BOD of Hamburg waste water treatment plant
digested sludge is only 3.5-10 gil, or roughly 10% of COD. There is not enough
knowledge available regarding the nature and fate of the substances in nature which
contribute to the bulk of COD. Certainly they are nontoxic, have properties like
cellulosis, and resemble the material which composes the organic fraction of marine
sediments. The degradation of this material within the sediment, by action of the
sediment bacteria and fungi, is slow, and to a large extent anaerobic in the deeper
sediment layers. Effluents from paper mills, which contain wood fibers and other
cellulosis and lignine material, are in many respects similar to sludge.
4.4 Toxic Substances in Antifouling Paints
Shipping adds to the heavy metal pollution of some coastal areas which are used as
harbors and for yacht clubs, because the ship's bottom is painted with toxic paint to
prevent algae and sessile marine animals like barnacles and mussels from fouling the
hull. Some years ago, mercury was used extensively in antifouling paint, and, for
example in 1969, 12% of the mercury used in the U.S.A. went into such paints (see
Chap. 8.4). Toxic organic substances like DDT and PCB's have been used also. In the
meantime, even if there is no regulation for the do-it-yourself yachtsman, shipyards
in the Federal Republic of Germany have to obey regulations regarding dangerous
materials, and no antifouling paint is allowed which contains compounds of mercury,
arsenic, DDT, HCH, PCB's and PCT (for explanation, see Chap. 9.1), except when
a special permit is granted by the authorities.
68
because PCB's are rather persistent, they still contaminate the environment and will
be found in waste water for a reasonable period of time. In the treatment of waste
water, PCB's in the main get into sludge; the treated effluents therefore are not at
fault. The sludge from New York waste water treatment plants, in 1975, contained
an average of 3.4 mg/kg PCB's calculated for dry matter in the sludge. As a consequence, PCB concentrations in the sediment of the dumping area for sludge in New
York Bight are above 1 mg/kg (dry weight) in the upper 5 cm sediment layer, compared with 1-100 pg/kg in the area farther away (West and Hatcher 1980). One has
to assume that such PCB concentrations originating from the dumping of sewage
sludge accumulate in marine organisms and fish (Lawrence and Tosine 1977), and
PCB's will enter the land vegetation if sludge is disposed on land and used for agricultural purposes.
PCB's range under "organic substances difficult to degrade", like many others, phenolic substances for example. However, they make up only a small fraction of the
total organic matter in sewage sludge. When sewage sludge is anaerobically digested,
for example in Hamburg treatment plant it contains organic substances equivalent to
a Chemical Oxygen Demand (COD) of 37-51 gil. The COD is determined by wet
oxidation of the sludge with dichromate, therefore it includes the large quantities of
organic substances which are not readily degradable and cannot be measured as oxygen demand during microbial degradation (Biochemical Oxygen Demand, BOD,
during a 5-day period, see Chap. 2.1). BOD of Hamburg waste water treatment plant
digested sludge is only 3.5-10 gil, or roughly 10% of COD. There is not enough
knowledge available regarding the nature and fate of the substances in nature which
contribute to the bulk of COD. Certainly they are nontoxic, have properties like
cellulosis, and resemble the material which composes the organic fraction of marine
sediments. The degradation of this material within the sediment, by action of the
sediment bacteria and fungi, is slow, and to a large extent anaerobic in the deeper
sediment layers. Effluents from paper mills, which contain wood fibers and other
cellulosis and lignine material, are in many respects similar to sludge.
4.4 Toxic Substances in Antifouling Paints
Shipping adds to the heavy metal pollution of some coastal areas which are used as
harbors and for yacht clubs, because the ship's bottom is painted with toxic paint to
prevent algae and sessile marine animals like barnacles and mussels from fouling the
hull. Some years ago, mercury was used extensively in antifouling paint, and, for
example in 1969, 12% of the mercury used in the U.S.A. went into such paints (see
Chap. 8.4). Toxic organic substances like DDT and PCB's have been used also. In the
meantime, even if there is no regulation for the do-it-yourself yachtsman, shipyards
in the Federal Republic of Germany have to obey regulations regarding dangerous
materials, and no antifouling paint is allowed which contains compounds of mercury,
arsenic, DDT, HCH, PCB's and PCT (for explanation, see Chap. 9.1), except when
a special permit is granted by the authorities.
68