3
1 Eutrophication: Challenges and Solutions
between input and output is that the net P storage in soil and
fresh water ecosystems of the world is estimated to be about
75 % higher than during preindustrial times. A large portion
of this P accumulation is in agricultural soils, as might be
expected. A major problem associated with this increased P
content of soils is that any factors that increase soil erosion
will also increase runoff of P with soil to streams, rivers,
lakes, and coastal regions.
Nutrients entering waterways come from a variety of
sources and originate from two main categories, direct and
indirect sources.
1.3 Drivers of Eutrophication
Drivers of the ecosystem often interact with one another in
synergistic ways in causing increased occurrence of eutrophication. Direct drivers of eutrophication include higher
energy consumption, increased fertilizer consumption, landuse change etc. Population growth, economic growth, structural change, and globalization are the most commonly identified indirect drivers that impact consumer consumption and
the growth of intensive agriculture.
1.3.1 Direct Drivers of Eutrophication
Direct drivers are usually associated with intensive agriculture and discharges at a particular point. These include piggeries, sheep holding yards, dairies and horticulture, meat
processing plants, vegetable processing plants, fertilizer factories, and other industries. Intensive animal industries often
produce large quantities of wastewater and nutrients. Nutrient concentrations in these wastes are often much higher
than those leaving indirect sources. Many of these industries
currently combine ponding, irrigation, and diversion to waterways to dispose of nutrient-rich wastewater. Humans discharge the equivalent of 1 kg of phosphorus annually as a result of domestic activities. Detergents make up approximately 50 %. Disposal in septic tanks or improperly constructed
or sited sewerage works can lead to nutrient contamination
of both ground and surface waters.
1.3.1.1 Wastewater Flow
Municipal wastewater treatment plants and industrial wastewater discharges, nitrogen leaching from below-ground septic tanks, and storm water runoff are some of the urban and
industrial sources of nutrient losses. They are typically the
most controllable sources of nutrients and are often regulated
in developed countries. The most prevalent urban source of
nutrient pollution is human sewage, although its importance
varies by region and country. Sewage is estimated to contribute 12 % of riverine nitrogen input in the USA, 25 % in
Western Europe, 33 % in China, and 68 % in the Republic
of Korea (MA 2005). Urban wastes are processed in sewage
treatment plants that work on the principle of bacterial oxidation of organic matter. In this way, all the major elements
from the wastes are oxidized. These elements therefore become soluble and drain in high concentration in the effluent
from the treatment plant. Such effluents are point sources of
nitrogen and phosphorus.
Storm water runoff is another significant source of nutrients from urban areas. Rainfall events flush nutrients from
residential lawns and impervious surfaces into nearby rivers and streams. In some cities, combined sewer overflow
(CSO) systems worsen storm water runoff problems. CSOs
are designed to collect rainwater, domestic wastewater, and
industrial wastewater in the same pipe. During heavy rain
or snowmelt, wastewater volume can exceed the capacity of
the CSO system, as well as that of the wastewater treatment
plant receiving the flow. As a result, the excess wastewater,
including raw sewage, is discharged directly into nearby
streams and rivers.
For industrial sources of nutrient pollution, certain industries are larger sources than others. Pulp and paper
mills, food and meat processing, agroindustries, and direct
discharge of sewage are some of the larger sources of industrial nutrient pollution. Industrial wastes and domestic sewage together are the major urban sources of nutrient overload, responsible for 50 % of the total amount of
phosphorus unloaded into lakes from human settlements
(Smith et al. 2006). Approximately 15 % of the US population contributes phosphorus-containing wastewater effluents to lakes, resulting in eutrophication (Hammer 1986).
By 1970, nearly 10,000 public lakes had been affected by
excessive human-influenced nutrient enrichment (KnudHansen 1994).
1.3.1.2 Livestock Intensification
The rapidly changing nature of raising livestock has also
contributed to a sharp increase in nutrient fluxes over the last
century. Animal production is intensifying with increasingly
more production occurring further away from feedstock supplies. The large quantity of manure produced by these operations is applied to land as fertilizer, stacked in the feedlot,
or stored in lagoons. The consequence is that livestock units
become point sources of nutrients runoff rather than diffuse
sources, and under improper management practices they
may pose serious problems. They may contribute to organic
pollution of the receiving body of water as well as nutrient
enrichment. Frequently, the rate and timing of land application of manure is dictated by the volume and availability of
manure and not by crop needs. This leads to ill-timed application or overapplication of manure, further exacerbating
nutrient runoff and leaching.
1 Eutrophication: Challenges and Solutions
between input and output is that the net P storage in soil and
fresh water ecosystems of the world is estimated to be about
75 % higher than during preindustrial times. A large portion
of this P accumulation is in agricultural soils, as might be
expected. A major problem associated with this increased P
content of soils is that any factors that increase soil erosion
will also increase runoff of P with soil to streams, rivers,
lakes, and coastal regions.
Nutrients entering waterways come from a variety of
sources and originate from two main categories, direct and
indirect sources.
1.3 Drivers of Eutrophication
Drivers of the ecosystem often interact with one another in
synergistic ways in causing increased occurrence of eutrophication. Direct drivers of eutrophication include higher
energy consumption, increased fertilizer consumption, landuse change etc. Population growth, economic growth, structural change, and globalization are the most commonly identified indirect drivers that impact consumer consumption and
the growth of intensive agriculture.
1.3.1 Direct Drivers of Eutrophication
Direct drivers are usually associated with intensive agriculture and discharges at a particular point. These include piggeries, sheep holding yards, dairies and horticulture, meat
processing plants, vegetable processing plants, fertilizer factories, and other industries. Intensive animal industries often
produce large quantities of wastewater and nutrients. Nutrient concentrations in these wastes are often much higher
than those leaving indirect sources. Many of these industries
currently combine ponding, irrigation, and diversion to waterways to dispose of nutrient-rich wastewater. Humans discharge the equivalent of 1 kg of phosphorus annually as a result of domestic activities. Detergents make up approximately 50 %. Disposal in septic tanks or improperly constructed
or sited sewerage works can lead to nutrient contamination
of both ground and surface waters.
1.3.1.1 Wastewater Flow
Municipal wastewater treatment plants and industrial wastewater discharges, nitrogen leaching from below-ground septic tanks, and storm water runoff are some of the urban and
industrial sources of nutrient losses. They are typically the
most controllable sources of nutrients and are often regulated
in developed countries. The most prevalent urban source of
nutrient pollution is human sewage, although its importance
varies by region and country. Sewage is estimated to contribute 12 % of riverine nitrogen input in the USA, 25 % in
Western Europe, 33 % in China, and 68 % in the Republic
of Korea (MA 2005). Urban wastes are processed in sewage
treatment plants that work on the principle of bacterial oxidation of organic matter. In this way, all the major elements
from the wastes are oxidized. These elements therefore become soluble and drain in high concentration in the effluent
from the treatment plant. Such effluents are point sources of
nitrogen and phosphorus.
Storm water runoff is another significant source of nutrients from urban areas. Rainfall events flush nutrients from
residential lawns and impervious surfaces into nearby rivers and streams. In some cities, combined sewer overflow
(CSO) systems worsen storm water runoff problems. CSOs
are designed to collect rainwater, domestic wastewater, and
industrial wastewater in the same pipe. During heavy rain
or snowmelt, wastewater volume can exceed the capacity of
the CSO system, as well as that of the wastewater treatment
plant receiving the flow. As a result, the excess wastewater,
including raw sewage, is discharged directly into nearby
streams and rivers.
For industrial sources of nutrient pollution, certain industries are larger sources than others. Pulp and paper
mills, food and meat processing, agroindustries, and direct
discharge of sewage are some of the larger sources of industrial nutrient pollution. Industrial wastes and domestic sewage together are the major urban sources of nutrient overload, responsible for 50 % of the total amount of
phosphorus unloaded into lakes from human settlements
(Smith et al. 2006). Approximately 15 % of the US population contributes phosphorus-containing wastewater effluents to lakes, resulting in eutrophication (Hammer 1986).
By 1970, nearly 10,000 public lakes had been affected by
excessive human-influenced nutrient enrichment (KnudHansen 1994).
1.3.1.2 Livestock Intensification
The rapidly changing nature of raising livestock has also
contributed to a sharp increase in nutrient fluxes over the last
century. Animal production is intensifying with increasingly
more production occurring further away from feedstock supplies. The large quantity of manure produced by these operations is applied to land as fertilizer, stacked in the feedlot,
or stored in lagoons. The consequence is that livestock units
become point sources of nutrients runoff rather than diffuse
sources, and under improper management practices they
may pose serious problems. They may contribute to organic
pollution of the receiving body of water as well as nutrient
enrichment. Frequently, the rate and timing of land application of manure is dictated by the volume and availability of
manure and not by crop needs. This leads to ill-timed application or overapplication of manure, further exacerbating
nutrient runoff and leaching.