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I. G. Breaban and A. I. Breaban
anisms, which lead to further depletion of the oxygen level. When nitrogen and/or
phosphorus-containing pollutants are accumulated in aquatic ecosystems, there is
an over-development of plants and algae, which after the end of their lifetime is
transformed into organic oxygen-consuming matter, the process being known as
eutrophication (Fig. 3.19).
Organic pollutants can be divided into following categories:
(a) Oxygen Demanding Wastes The waste water, regardless of their type (domestic
sewage, industrial: slaughterhouses, food canning, textile, leather, paper and
pulp, etc.), are loaded with varying amounts of biodegradable organic compounds, in various forms: dissolved, suspended, colloidal [10, 32, 67, 75, 114,
163, 161, 174, 188, 190, 191]. These, through microorganisms, are aerobically
biodegraded, degradation and decomposition taking place simultaneously with
the consumption of dissolved oxygen available in water sources. Aquatic ecosystems are adversely affected if the amount of dissolved oxygen decreases below
4 mg/L, dissolved oxygen lowering the outlines of an indicator of pollution in
waters.
(b) Synthetic Organic Compounds As a result of various anthropogenic activities,
synthetic organic compounds are likely to enter aquatic ecosystems, such as
their production processes, discharges during transport, and their use in various applications. These compounds include synthesis products such as volatile
organic compounds (VOCs), pesticides, insecticides, detergents, food additives,
pharmaceuticals, paints, synthetic fibers, plastics, solvents, which even in low
concentrations are not suitable for various uses, most resistant to microbial
degradation (detergents form foams and volatile substances that can cause explosion in sewers). Persistent organic pollutants (POPs) are compounds organic,
non-polar, and hydrophobic, with extremely low solubility in water, lipophilic,
which causes accumulation in the fatty tissues of the organisms. In aquatic
ecosystems, these compounds are adsorbed on sediment particles or particles
suspended in the mass of water, particularly on organic particles, and accumulate
in the tissues of end-of-trophic chain (fish, mammal, bird and human species)
and may be much higher than the concentration in the environment [70, 66, 111,
147].
(c) Oil is a natural product, a complex mixture of hydrocarbons, degradable under
bacterial action [143, 175, 176]. It enters in aquatic ecosystems through leaks
from oil wells, transport pipelines and wastewater from production and refining, oil tanker spills. Having lower densities than water, they have the ability
to dissipate at the surface of the water, thus blocking water contact with air,
implicitly decreasing the amount of dissolved oxygen, as well as reducing the
photosynthetic activity by obstructing light transmission. For different oils the
biodegradation yield is distinct, the tars being some of the slowest.
I. G. Breaban and A. I. Breaban
anisms, which lead to further depletion of the oxygen level. When nitrogen and/or
phosphorus-containing pollutants are accumulated in aquatic ecosystems, there is
an over-development of plants and algae, which after the end of their lifetime is
transformed into organic oxygen-consuming matter, the process being known as
eutrophication (Fig. 3.19).
Organic pollutants can be divided into following categories:
(a) Oxygen Demanding Wastes The waste water, regardless of their type (domestic
sewage, industrial: slaughterhouses, food canning, textile, leather, paper and
pulp, etc.), are loaded with varying amounts of biodegradable organic compounds, in various forms: dissolved, suspended, colloidal [10, 32, 67, 75, 114,
163, 161, 174, 188, 190, 191]. These, through microorganisms, are aerobically
biodegraded, degradation and decomposition taking place simultaneously with
the consumption of dissolved oxygen available in water sources. Aquatic ecosystems are adversely affected if the amount of dissolved oxygen decreases below
4 mg/L, dissolved oxygen lowering the outlines of an indicator of pollution in
waters.
(b) Synthetic Organic Compounds As a result of various anthropogenic activities,
synthetic organic compounds are likely to enter aquatic ecosystems, such as
their production processes, discharges during transport, and their use in various applications. These compounds include synthesis products such as volatile
organic compounds (VOCs), pesticides, insecticides, detergents, food additives,
pharmaceuticals, paints, synthetic fibers, plastics, solvents, which even in low
concentrations are not suitable for various uses, most resistant to microbial
degradation (detergents form foams and volatile substances that can cause explosion in sewers). Persistent organic pollutants (POPs) are compounds organic,
non-polar, and hydrophobic, with extremely low solubility in water, lipophilic,
which causes accumulation in the fatty tissues of the organisms. In aquatic
ecosystems, these compounds are adsorbed on sediment particles or particles
suspended in the mass of water, particularly on organic particles, and accumulate
in the tissues of end-of-trophic chain (fish, mammal, bird and human species)
and may be much higher than the concentration in the environment [70, 66, 111,
147].
(c) Oil is a natural product, a complex mixture of hydrocarbons, degradable under
bacterial action [143, 175, 176]. It enters in aquatic ecosystems through leaks
from oil wells, transport pipelines and wastewater from production and refining, oil tanker spills. Having lower densities than water, they have the ability
to dissipate at the surface of the water, thus blocking water contact with air,
implicitly decreasing the amount of dissolved oxygen, as well as reducing the
photosynthetic activity by obstructing light transmission. For different oils the
biodegradation yield is distinct, the tars being some of the slowest.