Treatment of organic polluted wastewater by microalgae method combined with membrane filter

Within the framework of the research project "Treatment of nutrient-rich wastewater by membrane-coupled microalgae method", a team of scientists from the Institute of Environmental Technology led by Dr. Nguyen Tuan Minh has successfully researched nutrient-rich wastewater treatment technology and built a model of nutrient-rich wastewater treatment equipment by using microalgae combined with filters.

Organic matter (compounds of carbon, nitrogen and phosphorus) in livestock wastewater is a usable source of nutrients for microalgae growth. Therefore, when removing pollutants through the process consumed by microalgae, biomass will be created. The resulting microalgae biomass has a high content of polymeric compounds such as fats, proteins, carbohydrates that have the potential for the production of biofuels, animal feed, plant fertilizers, food additives, and bioactive substances that are raw materials for the cosmetic and pharmaceutical industries. The use of wastewater as a source of nutrients for microalgae aquaculture is considered an environmentally sustainable solution to meet the needs of water treatment as well as biomass recovery.

The unicellular green microalgae Chlorella sp. is one of the microalgae widely applied in the world for wastewater treatment due to its fast growth rate, high lipids content, and proven ability to remove carbon, nitrogen and phosphorus. In addition, the application of MBR membrane technology in the microalgae wastewater treatment model allows controlling the flow of the treatment system easily, while maintaining a high biomass content thanks to the ability to separate solid and liquid phases, avoiding algae leaching in the output water.

In this topic, the research team focuses on improving treatment efficiency by combining algae and membranes with wastewater with high concentrations of nutrient pollution. In the experimental system, microalgae growing, developing and existing in suspended form in the laboratory tank will play the role of absorbing and metabolizing nutrients in wastewater to synthesize biomass, while the membrane module will filter and separate biomass from wastewater at the same time to ensure easy maintenance of biomass concentration desire.

Thanks to such a combination of treatment, the system can ensure the ability to thoroughly treat highly polluted wastewater rich in nutrients. In addition, with improved treatment efficiency, this combined technology will reduce energy consumption, construction area, chemicals and greenhouse gas emissions in the field of wastewater treatment in particular, as well as in the field of environmental protection and bioenergy development in general.

Algae Chlorella sp.

On the basis of researching and learning about microalgae and membrane technology in wastewater treatment, the team calculated, designed and manufactured a model of nutrient-rich wastewater treatment equipment by microalgae method combined with membranes with a capacity of 10-20 l / m2 membrane, meeting QCVN 40: 2011 / BTNMT standards for Nitrogen and Phosphorus criteria.

Diagram of livestock wastewater treatment laboratory system using membrane-coupled microalgae

The research team determined the processing efficiency of the membrane-coupled microalgae model system. With a water retention time of 5 days, the use of Chlorella vulgaris microalgae combined with MBR membrane brings relatively large efficiency with NH4+, TP and COD processing efficiency of 96.06%, 70.20% and 86.29%, respectively; these output parameters reach QCVN 40:2011/BTNMT (column B). The research results also show the cause of membrane clogging and optimal operating conditions to minimize membrane clogging with aeration intensity 0.05 l/cm2/min, filtration yield 15 l/m2.h. NaOCl was selected for membrane cleaning by immersing the film in a 1000 mg/l NaOCl solution for 2 hours to restore the membrane's working capacity.

Conventional biological treatment methods such as activated sludge often require strict controls to ensure microbial growth, moreover, the generation of sludge in the treatment system not only causes costs but also creates pressures in the treatment of hazardous waste (sludge). Research combining microalgae and membrane technology to treat wastewater with high nutrient pollutants has thoroughly solved the above-mentioned problem. The use of microalgae is considered an environmentally sustainable development solution to meet the needs of wastewater treatment as well as biomass recovery. When microalgae are applied to wastewater treatment, the retention of biomass content in the system is closely related to treatment efficiency, and membrane technology can be used to address hazardous waste treatment costs and pressures.

The research team has published 01 international article in the journal Water on "Removal of Nutrients and COD in Wastewater from Vietnamese Piggery Farm by the Culture of Chlorella vulgaris in a Pilot-Scaled Membrane Photobioreactor" and published 01 domestic article on "Research on the ability to treat nutrients in livestock wastewater using microalgae" in the Journal of Chemical Analysis, physics and biology.

Translated by Phuong Ha
Link to Vietnamese version

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