Biological performance and membrane fouling of a microalgal-bacterial membrane photobioreactor for wastewater treatment without external aeration and carbonation

• Published in: Environmental research 2024-04, Vol.247, p.118272-118272, Article 118272
• Main Authors: Wang, Zhaozhao, Liao, Yichen, Yan, Lina, Liao, Baoqiang
• Format: Article
• Language: English
• Subjects: Biological nutrient removal; Biomass characteristics; Membrane fouling; Microalgal-bacterial membrane photobioreactor; Non-aerated wastewater treatment
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2024.118272

Biological nutrient removal processes involving the use of activated sludge (AS) to treat municipal wastewater normally result in high aeration energy consumption and significant greenhouse gas (GHG) emissions. Therefore, developing cost-efficient and environmentally friendly processes for wastewater treatment is vital. In this work, a novel non-aerated microalgal-bacterial membrane photobioreactor (MB-MPBR) was proposed, and its feasibility for organic contaminant and nutrient removals was evaluated, for the first time. The effects of inoculation ratio (microalgae to bacteria (M/B)) on the biological performance and membrane fouling were systematically investigated. The results showed that 95.9% of the chemical oxygen demand (COD), 74.5% of total nitrogen (TN), 98.5% of NH4+-N and 42.0% of total phosphorus (TP) were removed at an inoculation M/B ratio of 3:2 at steady state, representing a significant improvement compared to the M/B inoculation ratio of 1:3. Additionally, the higher inoculation M/B ratio (3:2) significantly promoted the biomass production owing to the favorable mutual exchange of oxygen and carbon dioxide between microalgae and bacteria. Cake layer formation was the primary fouling mechanism owing to the absence of aeration scouring on the membrane surface. The membrane fouling rate was slightly higher at the higher inoculation ratio (M/B = 3:2) owing to the increased biomass and extracellular polymeric substances (EPS) productions, despite the larger particle size. These results demonstrated that the non-aerated MB-MPBR could achieve superior biological performance, of which the inoculation M/B ratio was of critical importance for the initiation and maintenance of microalgal-bacterial symbiotic system, yet possibly caused severer membrane fouling in the absence of external aeration and carbonation. This study provides a new perspective for further optimizing and applying non-aerated MB-MPBR to enhance municipal wastewater treatment. [Display omitted] •The feasibility of using a non-aerated MB-MPBR in wastewater treatment was investigated.•Non-aerated MB-MPBR demonstrated the potential to meet effluent discharge standard in a single step.•The inoculation M/B ratio had a significant impact on the initiation and operation of non-aerated MB-MPBR.•Biomass concentration and EPS level played an important role in controlling membrane fouling.•Cake layer formation was identified as the dominant membrane fouling mechanism in the non-aerated MB-MPB