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Algal-sludge Granule for Wastewater Treatment and Bioenergy Feedstock Generation


Background: Water and wastewater treatments consume 3-4% of energy while 60% of energy used at the wastewater treatment plant is dedicated to aeration in the activated sludge process. This novel bio-granule called oxygenic bio-granule proposes to transform wastewater treatment facilities into water resource recovery facilities. The oxygenic bio-granule results from the conversion of activated sludge under photochemical reactions. It is naturally formed and is composed of algae and bacteria within one granular biomass. The bio-granule is a dense spherical aggregate of microorganisms that is a self-immobilized biofilm and forms in the absence of solid substratum. The cohabitation of algae and bacteria within the biogranule allows for an efficient symbiotic wastewater treatment process. The bacteria degrade organic matter utilizing O2 that is produced by the algae. In addition the algae harvest CO2 produced from the organic matter degradation for photosynthesis. The biomass flocculates to be 0.2 to 10mm in size which allows them to be easily separable from water. Technology Description: The oxygenic bio-granule provides O2 by itself due to the symbiotic oxygenation from algal photosynthesis within the granule. It is able to function with or without the addition of external CO2 and consumes more CO2 than it releases thus reducing greenhouse gas emissions and making the system carbon negative. The oxygenic bio-granule can be generated from activated sludge utilizing natural or artificial light without the need of external source of microbes or chemicals. Current aerobic granule sludge (AGS) requires external aeration (energy) for aerobic wastewater treatment whereas the oxygenic bio-granule does not. In addition the AGS releases CO2 into the atmosphere and can only be used in an sequencing batch reactor (SBR) which is impractical for many municipal wastewater treatment systems. The oxygenic bio-granule captures CO2 for algal growth and can be adapted for SBR and any flow-through reactors (e.g. SBR CMFR plug-flow reactor up flow reactor fluidized bed reactor etc.). The oxygenic bio-granule reduces sludge formation and has the potential to bring substantial energy savings for municipal wastewater plants. Applications: 1) Enhanced nitrogen removal 2) Effluent-polishing treatment for wastewater 3) Removal of heavy metals 4) Nutrient treatment and removal at wastewater treatment plants with minimal energy investment 5) Reduction of wastewater treatment carbon footprint 6) Bioenergy feedstock generation e.g. biodiesel fertilizer bioethanol biobutanol and biomass that can be burned to produce heat and electricity


Able to function with or without the addition of external CO2 and consumes more CO2 than it releases thus reducing greenhouse gas emissions.

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