well in the dark, in aerobic conditions or anaerobically, using fermentative processes for energy production. In this latter case, reduced organic compounds are
produced (e.g., succinate, lactate, acetate, propionate, formate) as well as CO 2
and H 2 [24, 26]. The versatility of PPB is reflected on the high number of
applications that use them for wastewater treatment, and production of high
value-added compounds (e.g., Polyhydroxyalkanoates) has detailed in further
sections.
Finally, microalgae and cyanobacteria are oxygenic primary producers that
generally dominate the top layers of stratified sediments [20]. In general, the
preferred mode of growth of microalgae/cyanobacteria is photoautotrophy, but
some species are also capable of photoheterotrophy, taking up simple organic
molecules like glucose, acetate, glycerol, and ethanol as carbon source [27, 28].
This feature, combined with their oxygen producing ability, capacitates
microalgae for wastewater treatment in bacterial–microalgae consortia [29, 30]
and in particular, for phosphorous recovery in consortium with phosphate
accumulating organisms (PAOs), as recently proposed in the photo-EBPR process [31, 32]. Additionally, microalgae and cyanobacteria have also been thoroughly studied along the years for their use as fertilizers, source of food and
animal feed [29, 33], and capacity to produce biofuels and commercially
attractive molecules, like antioxidants and carotenoids [34].
Overall, the clear distinction between the metabolism of microalgae/
cyanobacteria and APB and their different ecological distributions, strongly
impacts the metabolic capacity of these organisms and from a technical point of
view, also their applications to different environmental situations. The high
diversity of phototrophic organisms offers a multitude of metabolic solutions that
can be assembled in photosynthetic factories for robust responses to each
demanding scenario.
3 Wastewater Treatment and Resource Recovery
The worldwide increase of population and the lifestyle improvement is leading to
an escalating generation of solid wastes and polluted liquid streams, namely
wastewaters. To guarantee sanitation and avoid pollutant discharges in the
environment, it is fundamental to implement wastewater collection and reliable
treatment systems. The technologies used in wastewater treatment can be complex and expensive but along the years, new, low-cost, more environmentally
responsible and suitable wastewater treatment technologies were continuously
proposed to fit the requirements of environmental, economic, and social sustainability [35]. The sustainability of wastewater treatment has to be approached
within the larger frame of water resource management, where water must be
preserved and used more efficiently. Taking into account the current global water
scarcity and the expensive operation and maintenance cost of wastewater
treatment, it is crucial to move wastewater treatment from being primarily a
New Phototrophic Factories for Resource Recovery
419
produced (e.g., succinate, lactate, acetate, propionate, formate) as well as CO 2
and H 2 [24, 26]. The versatility of PPB is reflected on the high number of
applications that use them for wastewater treatment, and production of high
value-added compounds (e.g., Polyhydroxyalkanoates) has detailed in further
sections.
Finally, microalgae and cyanobacteria are oxygenic primary producers that
generally dominate the top layers of stratified sediments [20]. In general, the
preferred mode of growth of microalgae/cyanobacteria is photoautotrophy, but
some species are also capable of photoheterotrophy, taking up simple organic
molecules like glucose, acetate, glycerol, and ethanol as carbon source [27, 28].
This feature, combined with their oxygen producing ability, capacitates
microalgae for wastewater treatment in bacterial–microalgae consortia [29, 30]
and in particular, for phosphorous recovery in consortium with phosphate
accumulating organisms (PAOs), as recently proposed in the photo-EBPR process [31, 32]. Additionally, microalgae and cyanobacteria have also been thoroughly studied along the years for their use as fertilizers, source of food and
animal feed [29, 33], and capacity to produce biofuels and commercially
attractive molecules, like antioxidants and carotenoids [34].
Overall, the clear distinction between the metabolism of microalgae/
cyanobacteria and APB and their different ecological distributions, strongly
impacts the metabolic capacity of these organisms and from a technical point of
view, also their applications to different environmental situations. The high
diversity of phototrophic organisms offers a multitude of metabolic solutions that
can be assembled in photosynthetic factories for robust responses to each
demanding scenario.
3 Wastewater Treatment and Resource Recovery
The worldwide increase of population and the lifestyle improvement is leading to
an escalating generation of solid wastes and polluted liquid streams, namely
wastewaters. To guarantee sanitation and avoid pollutant discharges in the
environment, it is fundamental to implement wastewater collection and reliable
treatment systems. The technologies used in wastewater treatment can be complex and expensive but along the years, new, low-cost, more environmentally
responsible and suitable wastewater treatment technologies were continuously
proposed to fit the requirements of environmental, economic, and social sustainability [35]. The sustainability of wastewater treatment has to be approached
within the larger frame of water resource management, where water must be
preserved and used more efficiently. Taking into account the current global water
scarcity and the expensive operation and maintenance cost of wastewater
treatment, it is crucial to move wastewater treatment from being primarily a
New Phototrophic Factories for Resource Recovery
419