The dual role of microalgae in wastewater treatment

The dual role of microalgae in wastewater treatment
The wastewater that is being generated every day from the industries has to be treated before being discharged into waterbodies because of the presence of harmful metals, carbon, nitrogen and phosphorus in it. As per the latest estimate, out of 22900 millions of litres of wastewater generated every day in India, only 5900 millions of litres is treated and the rest is disposed of as untreated. The wastewaters that are being treated only undergo primary and secondary treatment processes; whereas, tertiary and quarternary treatment processes are yet to be implemented in most of the cities in India. The so-called treatment processes cannot remove inorganic nitrogen and phosphorus which results in the eutrophication of waterbodies.

Disadvantages of already existing processes
  • The primary and secondary treatment methods already being followed are not so effective in removing the nutrients because of the difference in the efficiency of treatment of different nutrients.
  • The high cost of the process (chemical) makes the treatment an unfeasible one in many cities and the secondary pollution caused as a result of usage of chemicals makes it undesirable.
  • A valuable source of nitrogen and phosphorus which can be utilised as a potential nutrient is lost in the treatment process.

  • There is a demand for a cost-effective treatment process that would utilise the nutrients as an effective source for the production of a useful product thereby reducing their concentration in the wastewater.

    Microalgae - an effective means to treat wastewater
  • Microalgae serve as a better solution to treat the wastewater further (tertiary and quarternary) as a result of their ability to use inorganic nitrogen and phosphorus for their growth and metabolism.
  • Microalgae also have the capacity to remove heavy metals and some toxic organic compounds.
  • The increase in pH during oxygen-evolving photosynthesis creates a disinfecting environment that removes coliform bacteria.

  • Before treating the wastewater with microalgae, primary treatment has to be carried out. The centrate which results in the treatment of wastewater using activated sludge process is rich in nutrients that can be used as an alternative media for the cultivation of microalgae.

    When the centrate is used as a cultivation media for the growth of microalgae, the growth is very high because of the presence of essential nutrients, such as carbon, nitrogen and phosphorus in high concentrations. The presence of cofactors, such as K, Ca, Mg, Fe, Cu and Mn plays a major role in the metabolism of the algae.

    The use of centrate (partially treated wastewater) for microalgae cultivation could serve the dual role of waste reduction and biomass production which in turn can be used for the production of methane, biofuel. The biomass can also be used in composting and as a feed for animals or in aquaculture.
    How to cite this article:
    Chris Gabriella Rachel A. The dual role of microalgae in wastewater treatment. BioLim O-Media. 07 September, 2016. 4(9).
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