Membranes and Microalgae in Wastewater Treatment

Membranes and Microalgae in Wastewater Treatment

DOI: 10.4018/978-1-7998-2645-3.ch012
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Abstract

The application of microalgae-based wastewater treatment was first introduced in the 1940s to treat municipal wastewater. Microalgae have been studied for its various potentials such as for nutrients removal, carbon dioxide (CO2) removal, biofuel production from biomass, etc. This chapter focuses on the potential of microalgae membrane bioreactors for wastewater treatment, microalgae cultivation, and harvesting. Furthermore, the selection of microalgae species is covered by comparison of nitrogen, phosphorus, COD, and BOD removal from various studies. Microalgae membrane bioreactors combine the biological treatment of microalgae with the conventional membrane bioreactor. Still, membrane fouling phenomenon is a challenge in microalgae membrane technology. Thus, several other technologies of immobilized microalgae are introduced which can potentially reduce the membrane fouling occurrence and concurrently remove the need for microalgae harvesting process.
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Microalgae For Wastewater Treatment

Many researchers have been exploring the utilization of nutrient removal in wastewater through the cultivation of microalgae in the wastewater generated from municipal, agro-industrial or industrial. This has opened up the opportunity to utilize the available unlimited resources of wastewater in order to cultivate microalgae for the dual purpose of removing nutrients and producing biofuels.

Research in this field was conducted to utilize microalgae nutrient uptake to treat municipal wastewater. The samples were obtained from the effluent of primary settling tank (PS), the effluent from an anaerobic digestion tank (AD) and the conflux of wastewaters rejected from sludge-concentrate tanks and dewatering facilities (CR) in a municipal wastewater treatment plant in Busan, Korea. The study was conducted to investigate the feasibility of utilizing the readily available nutrients in sewage for microalgae cultivation as well to treat the wastewater. From the experiment, it was found that the value of total nitrogen and total phosphorus was able to be totally removed from 250 mg/L and 17 mg/L to respectively in 5 days. However, the Chemical Oxygen Demand (COD) content increased over time caused by the increased biomass within the system (Cho et al., 2013). This shows that a reliable separation technique is important at the end of the treatment to ensure the effluent is well under the specified limit.

A combination of microalgae treatment with membrane bioreactor has been experimented to polish effluent sample from an anaerobic membrane bioreactor (MBR) fed with domestic wastewater. The treatment system consisted of two parts, the MBR system and a subsequent microalgae membrane reactor (mMR). Both of the treatment stages utilized a commercial membrane of pore size 0.45 μm (PES, Millipore). The experiment which lasted for 23 days was able to remove on average 50% of NH4, 75% of NO2, 35% of NO3 and 60% of PO4 consistently from the MBR effluent under the conditions tested.

Key Terms in this Chapter

N:P Ratio: Ratio of nitrogen to phosphorus present in a medium.

Nitrogen and Phosphorus: Two major nutrients needed by microalgae to conduct photosynthesis.

Microalgae Biomass: Microalgae material that has high values as a renewable energy resource.

Microalgae Membrane Bioreactor: Membrane technology that combines the photobioreactor and membrane bioreactor.

Microalgae Harvesting: Process of collecting microalgae that have been grown and cultivated.

Microalgae: Photosynthetic microscopic-sized algae mostly found in freshwater and marine system which requires only a few basic necessities to thrive, including CO 2 supply, light and nutrients.

Microalgae Immobilization: Process by naturally or artificially preventing the microalgae from moving independently from its original location to all parts of an aqueous phase of a system by attachment of the microalgae onto materials to eliminate the need for the harvesting of the microalgae later on.

Microalgae Cultivation: Process of growing microalgae to produce biofuels and bioproducts.

Photobioreactor: Bioreactor technology that is used to cultivate microalgae through photosynthesis using a light source, nutrients, and CO 2 .

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