How to sequester the CO2 emitted from large scale municipal wastewater treatment plants ?

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Most of the municipal treatment plants employ aerobic treatment as a part of the secondary treatment process.

All the organic impurities which gets oxidized forms CO2 as a product which is emitted to the atmosphere. Even if the CO2 generated might not be in such significant levels as compared to other sources of carbon pollution, why create another problem while we are offering a solution for another ?

Are there any simple feasible alternative to this ?

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5 Answers

  1. The best approach to sequester carbon dioxide as well as other GHG gases has been suggested by Carla. She has hit the nail on the head. In wastewater treatment plants based on MAST Technology (Microbe Algae Sewage Treatment) there is a symbiotic relationship between the microbes and the algae. The algae provides super saturated oxygen to microbes that grow and remediate the wastewater, but in the process some of the microbes die in the process. The microbes that die get converted into water and carbon dioxide. The microalgae will take up the carbon dioxide and grow. 

    MAST Technology systems require 3 inputs to work and carry out remediation. Firstly it requires nutrients, which are naturally found in the wastewater. Secondly they require carbon dioxide, which they get from the microbes and atmosphere. It is an added benefit to have a thermal power plant, a steel plant or a cement plant emitting CO2. This can be directed to the algae in the ponds and the CO2 can be sequestered. The third requirement is sunlight. 

    Microalgae replaces energy guzzling aerators, thus saving energy. Besides this there is no production of sludge but there is production of algal biomass. The transportation of sludge to landfills is another CO2 emitting operation that gets curtailed.

    MAST Technology systems are carbon negative, which means they sequester more carbon dioxide than they generate.

    2 Comments

    1. Microalgae do not die. Lifespan of the microalgae is limitless as long as it is in the wastewater and nutrients are available. You have to be careful of competition of species. The microalgae are constantly being harvested. Microalgae require nutrients, carbon dioxide and sunlight. They will decay only if the nutrients are absent. Also they must be agitated constantly otherwise they will settle to the bottom of the ponds and biofoul. If the ponds are too deep then the sunlight will not reach the algae, which in turn will lead to decay. So there are many factors to be considered.

    2. But what is the life span of a microalgae. Being a living organism microalgae must be having some limitations i suppose. What happens after the microalgae is dead and will there be any reaction once they start decaying ?

  5. Easy solution:  Put up large greenhouses, where the air is laden with CO2 fugitive emission you capture from your process using gas bags over the digesters.  Grow whatever you want that grows fast in the greenhouses, or you could also put in algae culture ponds (even more productive and efficient in removal of CO2).  The algae can be harvested, and pyrolyzed to fuel for transportation or local power generation.