Nitrogen and phosphate removal from wastewater with a mixed microalgae and bacteria culture

• Complex biological and non-biological interactions involved in the removal of ammonium and phosphate from domestic sewage.
• A microbial consortium that included microalgae involved.
• The biological removal activity was mainly influenced by the temperature and not light availability.
• The biological removal activity correlated with the culture photosynthetic activity.
• Abiotic factors were involved in both ammonia removal and phosphate precipitation.

Microalgae are able to convert nutrients (nitrogen and phosphorus) from wastewater into biomass and bio-products, thus improving the sustainability of wastewater treatment. In High Rate Algal Ponds (HRAP), biomass productivity and water treatment efficiency are highly dependent on environmental parameters such as temperature, light intensity and photoperiod. The influence of temperature and photoperiod on biomass productivity and the removal of dissolved nitrogen and phosphorus from municipal wastewater by a native microalgae-bacteria consortium was assessed in batch cultures in view of the development of an HRAP at a larger scale. Temperature affected the growth rate and microalgae biomass production as well as ammonium and phosphate removal rates. At the temperatures 15 and 25 °C, the average total nitrogen and phosphorus removal extents ranged from 72 to 83% and 100% respectively. Additionally 33.0 ± 0.1% of the total nitrogen was eliminated by stripping at 25 °C, and 50 ± 2% was assimilated by the microorganisms under all conditions tested.

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