Abstract
Eutrophication of water catchments and the greenhouse effect are major challenges in developing the global economy in the near future. Secondary effluents, containing high amounts of nitrogen and phosphorus, need further treatment before being discharged into receiving water bodies. At the same time, new environmentally friendly energy sources need to be developed. Integrating microalgal cultivation for the production of biodiesel feedstock with the treatment of secondary effluent is one way of addressing both issues. This article provides a comprehensive review of the latest progress in microalgal cultivation in secondary effluent to remove pollutants and accumulate lipids. Researchers have discovered that microalgae remove nitrogen and phosphorus effectively from secondary effluent, accumulating biomass and lipids in the process. Immobilization of appropriate microalgae, and establishing a consortium of microalgae and/or bacteria, were both found to be feasible ways to enhance pollutant removal and lipid production. Demonstrations of pilot-scale microalgal cultures in secondary effluent have also taken place. However there is still much work to be done in improving pollutants removal, biomass production, and lipid accumulation in secondary effluent. This includes screening microalgae, constructing the consortium, making use of flue gas and nitrogen, developing technologies related to microalgal harvesting, and using lipid-extracted algal residues (LEA).
Highlights
Wastewater treatment plants (WWTPs) have played a significant role in improving water environments and the efficient use of water resources
In China in particular, many WWTPs are facing pressures to improve effluent quality to meet the Chinese National First A-level Sewage Discharge Standard. This means that secondary effluent should not exceed the threshold of chemical oxygen demand (COD) 50 mg/L, ammonium 5 mg/L, total nitrogen (TN) 15 mg/L, and total phosphorous (TP) 0.5 mg/L
The results indicated that Scenedesmus sp. (LX1) was well adapted to secondary effluent
Summary
Wastewater treatment plants (WWTPs) have played a significant role in improving water environments and the efficient use of water resources. The most effective BNR processes are the Modified Bardenpho and the University of Cape Town (UCT) treatment process, which exhibit excellent nitrogen and phosphorus removal efficiency, as reviewed by Arita et al [11]. Biodiesel derived from oil crops, animal fats and waste oil plays an effective part in addressing the problems caused by the use of fossil fuels [14,15,16,17]. Compared to existing bioresources, microalgae are regarded as an excellent alternative for biodiesel production
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