Wastewater, Volumes and Composition
1.1.4 Population Equivalent
Sometimes the volume of wastewater is calculated by using the unit Population
Equivalent (PE). For water, 1 PEwater= 0.2 m 3 I d.
The unit PE is independent of the actual volume of wastewater per person, see
Example 1.6. There are other definitions of population equivalent (PEooo PES& PEN
etc.), so attention should be paid to the basis used when stating aPE figure. 1 PEooo
is 60 g BOD I d. 1 PE is also equivalent to 125 g COD I d, 13 g N I d and 2.5 g PI d. The
values vary from country to country.
Example 1.6
A catchment area is inhabited by 1000 people. The water consumption is 150m 3 /d.
The volume of wastewater reaching the treatment plant is 250m 3 /d.
Find the infiltration and the Population Equivalent on the basis of the volume of wastewater.
The infiltration can be approximated by the difference between the volume of wastewater and water consumption:
Q (infiltration)= 250-150 = 100 m 3 /d
Population Equivalent is
PE = Q (wastewater)/0.2 = (250 m 3 /d)/(0.2 m 3 /(d · PE)) = 1,250 PE
1.1.5 Prognoses
When expanding and rebuilding treatment plants, it is necessary to estimate the
volumes of wastewater for the next 10-20 years. In the '50s and '60s, the increases in
the specific wastewater volumes were comparatively steady in many parts of the
world, but since the beginning of the '70s the development has changed so that the
specific volumes of wastewater are either stagnant (households) or actually decrease (industry). Water rates and charges on industry for wastewater service have
significantly reduced the industrial consumption of water as well as pollution (in
areas where payment is made in proportion to polluting load). Renovation of the
sewer system also contributes to reducing the volume of wastewater.
Prognoses can be based on population growth and increased industrial production
in the catchment area. The respective figures can be found in urban area development plans.
Example 1.7 shows the calculation, incl. prognoses, of the volumes of wastewater in
Nyk0bing Falster (Denmark) 1141.
25
1.1.4 Population Equivalent
Sometimes the volume of wastewater is calculated by using the unit Population
Equivalent (PE). For water, 1 PEwater= 0.2 m 3 I d.
The unit PE is independent of the actual volume of wastewater per person, see
Example 1.6. There are other definitions of population equivalent (PEooo PES& PEN
etc.), so attention should be paid to the basis used when stating aPE figure. 1 PEooo
is 60 g BOD I d. 1 PE is also equivalent to 125 g COD I d, 13 g N I d and 2.5 g PI d. The
values vary from country to country.
Example 1.6
A catchment area is inhabited by 1000 people. The water consumption is 150m 3 /d.
The volume of wastewater reaching the treatment plant is 250m 3 /d.
Find the infiltration and the Population Equivalent on the basis of the volume of wastewater.
The infiltration can be approximated by the difference between the volume of wastewater and water consumption:
Q (infiltration)= 250-150 = 100 m 3 /d
Population Equivalent is
PE = Q (wastewater)/0.2 = (250 m 3 /d)/(0.2 m 3 /(d · PE)) = 1,250 PE
1.1.5 Prognoses
When expanding and rebuilding treatment plants, it is necessary to estimate the
volumes of wastewater for the next 10-20 years. In the '50s and '60s, the increases in
the specific wastewater volumes were comparatively steady in many parts of the
world, but since the beginning of the '70s the development has changed so that the
specific volumes of wastewater are either stagnant (households) or actually decrease (industry). Water rates and charges on industry for wastewater service have
significantly reduced the industrial consumption of water as well as pollution (in
areas where payment is made in proportion to polluting load). Renovation of the
sewer system also contributes to reducing the volume of wastewater.
Prognoses can be based on population growth and increased industrial production
in the catchment area. The respective figures can be found in urban area development plans.
Example 1.7 shows the calculation, incl. prognoses, of the volumes of wastewater in
Nyk0bing Falster (Denmark) 1141.
25