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4 Nitrogen and Phosphorous Recovery from Municipal Wastewater …
4.7 Environmental Impacts of the Nutrient Recovery
from Municipal Wastewater and Sludge
The environmental impacts of phosphorous recovery from municipal wastewater
and sludge are assessed through cumulative energy demand, global warming potential and acidification potential. Cumulative energy demand is defined as the energy
requirements such as electricity and gas throughout the entire life cycle of a product
or process [54]. Global warming potential is an indicator of greenhouse gas emissions and the acidification potential is defined as the impacts on soil acidity due
to gaseous emissions of SO 2 equivalents in fertilizers. These environmental factors
greatly depend on the technological principles of each recovery method. Generally,
the technologies that recover phosphorous from wastewater are able to reduce the
environmental impacts; however, they have lower potential for phosphorous recovery
due to the low P concentration in wastewater. In contrast, wastewater sludge has
significantly higher phosphorous concentrations relative to the wastewater, more
attention is given to the phosphorous recovery from sludge to increase the process
efficiency. As an example, struvite recovery from sludge dewatering process has
demonstrated to be the most technically and economically viable process for phosphorous removal [53]. Generally, nutrient recovery processes from wastewater sludge
ash have the beneficial effect of reducing the environmental indicators as well as high
potential for phosphorous recovery [54].
Nutrient recovery can also be beneficial for land application. The nutrient management for lands is based on the nutrient sensitivity of each field and is assessed by
Phosphorous Index (P Index). P Index is a mean to evaluate the risk of surface
water contamination from nutrient (specifically phosphorous) application on lands
and depends on conditions of a field such as phosphorous level in the soil, soil
erosion and soil runoff risk, the quantity of nutrients to be applied and the distance
to the nearest surface water [53, 55]. Nutrients in land-applied biosolids can cause
water pollution due to runoff and leaching. The risk is even higher in the plants that
favor PAOs as they typically have much more phosphorous than nitrogen relative
to the crop’s need. Nutrient recovery proportionally reduces the phosphorous from
biosolids and provides a more ergonomically balanced product for the lands that
have limitations for biosolids application [53].
As an example, the Crystal Green fertilizer from the Ostara Pearl’s process is
an inorganic fertilizer product with important characteristics such as purity, density,
hardness and low solubility. The Crystal Green fertilizer has slow nutrient release
rate which helps the plant to take up more of the released nutrients and results in less
running off, thus reduces the non-point source pollution. It also provides performance
benefits such as securing sufficient product sales revenue to cover the operational
costs [53].
For large communities, biological phosphorous removal is a more economical and
environmentally sustainable method compared to the chemical phosphorous removal
process. The increasing chemical prices and decreasing chemical availabilities as
4 Nitrogen and Phosphorous Recovery from Municipal Wastewater …
4.7 Environmental Impacts of the Nutrient Recovery
from Municipal Wastewater and Sludge
The environmental impacts of phosphorous recovery from municipal wastewater
and sludge are assessed through cumulative energy demand, global warming potential and acidification potential. Cumulative energy demand is defined as the energy
requirements such as electricity and gas throughout the entire life cycle of a product
or process [54]. Global warming potential is an indicator of greenhouse gas emissions and the acidification potential is defined as the impacts on soil acidity due
to gaseous emissions of SO 2 equivalents in fertilizers. These environmental factors
greatly depend on the technological principles of each recovery method. Generally,
the technologies that recover phosphorous from wastewater are able to reduce the
environmental impacts; however, they have lower potential for phosphorous recovery
due to the low P concentration in wastewater. In contrast, wastewater sludge has
significantly higher phosphorous concentrations relative to the wastewater, more
attention is given to the phosphorous recovery from sludge to increase the process
efficiency. As an example, struvite recovery from sludge dewatering process has
demonstrated to be the most technically and economically viable process for phosphorous removal [53]. Generally, nutrient recovery processes from wastewater sludge
ash have the beneficial effect of reducing the environmental indicators as well as high
potential for phosphorous recovery [54].
Nutrient recovery can also be beneficial for land application. The nutrient management for lands is based on the nutrient sensitivity of each field and is assessed by
Phosphorous Index (P Index). P Index is a mean to evaluate the risk of surface
water contamination from nutrient (specifically phosphorous) application on lands
and depends on conditions of a field such as phosphorous level in the soil, soil
erosion and soil runoff risk, the quantity of nutrients to be applied and the distance
to the nearest surface water [53, 55]. Nutrients in land-applied biosolids can cause
water pollution due to runoff and leaching. The risk is even higher in the plants that
favor PAOs as they typically have much more phosphorous than nitrogen relative
to the crop’s need. Nutrient recovery proportionally reduces the phosphorous from
biosolids and provides a more ergonomically balanced product for the lands that
have limitations for biosolids application [53].
As an example, the Crystal Green fertilizer from the Ostara Pearl’s process is
an inorganic fertilizer product with important characteristics such as purity, density,
hardness and low solubility. The Crystal Green fertilizer has slow nutrient release
rate which helps the plant to take up more of the released nutrients and results in less
running off, thus reduces the non-point source pollution. It also provides performance
benefits such as securing sufficient product sales revenue to cover the operational
costs [53].
For large communities, biological phosphorous removal is a more economical and
environmentally sustainable method compared to the chemical phosphorous removal
process. The increasing chemical prices and decreasing chemical availabilities as