A review on algal-bacterial symbiosis system for aquaculture tail water treatment

Microbial-algal symbiotic system drives reconstruction of nitrogen, phosphorus, and methane cycles for purification of pollutants in aquaculture water

Intensive aquaculture's excessive nitrogen, phosphorus, and methane emissions caused environmental degradation. This study explored how algae-bacteria symbiotic systems (ABSS) enhanced water purification by regulating element cycles. We established a Chlorella pyrenoidosa-Bacillus subtilis symbiotic system. At a 1:1 bacteria-to-algae ratio, chlorophyll a and cell dry weight were highest. C. pyrenoidosa supplied organic acids, carbohydrates, and amino acids to B. subtilis, which reciprocated with amino acids, purines, and vitamins. ABSS significantly reduced total nitrogen, ammonia nitrogen (NH4+-N), nitrite (NO2--N), nitrate (NO3--N), phosphate (PO43--P), total phosphorous, dissolved organic carbon, and chemical oxygen demand in aquaculture water. It reshaped microbial communities and enriched key genus (Limnohabitans, Planktophila, Polaromonas, Methylocystis) and upregulating genes linked to organic phosphate mineralization, methane oxidation, and nitrate reduction. These changes strengthened nitrogen-phosphorus-methane cycle coupling, boosting water purification. ABSS offers an eco-engineering solution for aquaculture pollution by optimizing microbial interactions and nutrient cycling.

Microalgae - bacteria based wastewater treatment systems: Granulation, influence factors and pollutants removal

Wastewater treatment based on microalgae and bacteria symbiosis is an environmentally friendly, sustainable technology that has attracted attention recently because of its high efficiency in treating pollutants, saving energy, and short-term biomass recovery. Among them, the granular microalgae and bacteria combination emerges with the advantages of rapid gravity settling, good resistance to adverse environmental conditions, outstanding wastewater treatment performance, and easy biomass recovery. This review aims to clarify the microalgal-bacterial granule (MBG) - based process for wastewater treatment. In particular, MBG characteristics, granulation mechanism, and influence factors on the process are also discussed. The review contributes to the knowledge system related to MBG research in recent years, thereby pointing out research gaps that need to be filled in the future.

Comprehensive assessment of three crayfish culture modes: From production performance to environmental sustainability

Integrated agriculture-aquaculture has emerged as a promising ecological development model. Crayfish, a popular aquaculture species, are traditionally reared either in monoculture ponds (mono-C) or in rice-crayfish polyculture system (poly-RC). In this study, we introduced a novel polyculture system by combining fruit tree with crayfish (poly-FC), aiming to compare these three crayfish culture modes in terms of production performance and ecological sustainability. The results indicated that crayfish reared in the two polyculture modes exhibited significantly higher specific growth rate and condition factor compared to those in mono-C. Crayfish cultured in poly-FC also showed better muscle quality and higher levels of crude fat and flavor or essential amino acids. Isotope mixing model showed that feed and benthic animals were the primary food sources of crayfish in mono-C, whereas aquatic plants, fruit litter or rice contributed more to those in polyculture modes. For greenhouse gas emissions, poly-FC mode emitted almost no CO2 and N2O even favored negative CH4 emission, while poly-RC and mono-C modes showed positive emissions of CH4 and CO2, respectively. Supported by metagenomics, the sink of CH4 in poly-FC was probably due to the lower mcr abundance but the higher pmo abundance in water. The low production and emission of N2O in poly-FC might result from the low-abundant Nitrospirae_bacterium and its coding gene norC in sediment, consistent with the lower denitrification rate but the higher NO3- concentration than mono-C. Overall, our findings reveal the superiority of polyculture of fruit tree with crayfish in terms of production performance and greenhouse gas emissions in the system.

Development and challenges of emerging biological technologies for algal-bacterial symbiosis systems: A review

The algal-bacterial symbiosis system (ABSS) is considered as a sustainable wastewater treatment process. This review provides a comprehensive overview of the mechanisms of ABSS for the removal of common pollutant, heavy metals, and especially for emerging pollutants. For the macroscopical level, this review not only describes in detail the reactor types, influencing factors, and the development of the algal-bacterial process, but also innovatively proposes an emerging process that combines an ABSS with other processes, which enhances the efficiency of removing difficult-to-biodegrade pollutants. Further for the microscopic level, interactions between algae and bacteria, including nutrient exchange, signaling transmission and gene transfer, have been deeply discussed the symbiotic relationship with nutrient removal and biomass production. Finally, recommendations are given for the future development of the ABSS. This review comprehensively examines ABSS principles, development, algal-bacterial interactions, and application in wastewater treatment, aiming to deepen theoretical and practical understanding and advance ABSS technology.

Insights into the removal of antibiotics from livestock and aquaculture wastewater by algae-bacteria symbiosis systems

With the burgeoning growth of the livestock and aquaculture industries, antibiotic residues in treated wastewater have become a serious ecological threat. Traditional biological wastewater treatment technologies-while effective for removing conventional pollutants, such as organic carbon, ammonia and phosphate-struggle to eliminate emerging contaminants, notably antibiotics. Recently, the use of microalgae has emerged as a sustainable and promising approach for the removal of antibiotics due to their non-target status, rapid growth and carbon recovery capabilities. This review aims to analyse the current state of antibiotic removal from wastewater using algae-bacteria symbiosis systems and provide valuable recommendations for the development of livestock/aquaculture wastewater treatment technologies. It (1) summarises the biological removal mechanisms of typical antibiotics, including bioadsorption, bioaccumulation, biodegradation and co-metabolism; (2) discusses the roles of intracellular regulation, involving extracellular polymeric substances, pigments, antioxidant enzyme systems, signalling molecules and metabolic pathways; (3) analyses the role of treatment facilities in facilitating algae-bacteria symbiosis, such as sequencing batch reactors, stabilisation ponds, membrane bioreactors and bioelectrochemical systems; and (4) provides insights into bottlenecks and potential solutions. This review offers valuable information on the mechanisms and strategies involved in the removal of antibiotics from livestock/aquaculture wastewater through the symbiosis of microalgae and bacteria.

Design, construction and application of algae-bacteria synergistic system for treating wastewater

The wastewater treatment technology of algae-bacteria synergistic system (ABSS) is a promising technology which has the advantages of low energy consumption, good treatment effect and recyclable high-value products. In this treatment technology, the construction of an ABSS is a very important factor. At the same time, the emergence of some new technologies (such as microbial fuel cells and bio-carriers, etc.) has further enriched constructing the novel ABSS, which could improve the efficiency of wastewater treatment and the biomass harvesting rate. Thus, this review focuses on the construction of a novel ABSS in wastewater treatment in order to provide useful suggestions for the technology of wastewater treatment.

Metagenomic profiling of antibiotic resistance genes/bacteria removal in urban water: Algal-bacterial consortium treatment system

Antibiotic resistance genes (ARGs) have exhibited significant ecological concerns, especially in the urban water that are closely associated with human health. In this study, with presence of exogenous Chlorella vulgaris-Bacillus licheniformis consortium, most of the typical ARGs and MGEs were removed. Furthermore, the relative abundance of potential ARGs hosts has generally decreased by 1-4 orders of magnitude, revealing the role of algal-bacterial consortium in cutting the spread of ARGs in urban water. While some of ARGs such as macB increased, which may be due to the negative impact of algicidal bacteria and algal viruses in urban water on exogenous C. vulgaris and the suppression of exogenous B. licheniformis by indigenous microorganisms. A new algal-bacterial interaction might form between C. vulgaris and indigenous microorganisms. The interplay between C. vulgaris and bacteria has a significant impact on the fate of ARGs removal in urban water.

Unveiling the hidden risks: Pesticide residues in aquaculture systems

The present study systematically assessed the presence and ecological risks of 79 pesticides in various aquaculture systems, namely pond aquaculture (PA), greenhouse aquaculture (GA), and raceway aquaculture (RA) at different aquaculture stages, along with evaluating the pesticide removal of four tailwater treatment systems. Sixteen herbicides and two fungicides were identified, with the total concentrations ranging from 8.33 ng/L to 3248.45 ng/L. The PA system demonstrated significantly higher concentrations (p < 0.05) and a wider range of pesticide residues compared to the GA and RA systems. Prometryn, simetryn, atrazine, and thifluzamide were found to be the predominant pesticides across all three aquaculture modes, suggesting their significance as pollutants that warrant monitoring. Additionally, the findings indicated that the early aquaculture stage exhibits the highest levels of pesticide concentration, underscoring the importance of heightened monitoring and regulatory interventions during this phase. Furthermore, among the four tailwater treatment systems analyzed, the recirculating tailwater treatment system exhibited the highest efficacy in pesticide removal. A comprehensive risk assessment revealed minimal ecological risks in both the aquaculture and tailwater environments. However, the pesticide mixtures present high risks to algae and low to medium risks to aquatic invertebrates and fish, particularly during the early stages of aquaculture. Simetryn and prometryn were identified as high-risk pesticides. Based on the prioritization index, simetryn, prometryn, diuron, and ametryn are recommended for prioritization in risk assessment. This study offers valuable data for pesticide control and serves as a reference for the establishment of a standardized pesticide monitoring and management system at various stages of aquaculture.

Treatment of agricultural wastewater using microalgae: A review

The rapid development of agriculture has led to a large amount of wastewater, which poses a great threat to environmental safety. Microalgae, with diverse species, nutritional modes and cellular status, can adapt well in agricultural wastewater and absorb nutrients and remove pollutants effectively. Besides, after treatment of agricultural wastewater, the accumulated biomass of microalgae has broad applications, such as fertilizer and animal feed. This paper reviewed the current progresses and further perspectives of microalgae-based agricultural wastewater treatment. The characteristics of agricultural wastewater have been firstly introduced; Then the microalgal strains, cultivation modes, cellular status, contaminant metabolism, cultivation systems and biomass applications of microalgae for wastewater treatment have been summarized; At last, the bottlenecks in the development of the microalgae treatment methods, as well as recommendations for optimizing the adaptability of microalgae to wastewater in terms of wastewater pretreatment, microalgae breeding, and microalgae-bacterial symbiosis systems were discussed. This review would provide references for the future developments of microalgae-based agricultural wastewater treatment.

Role of microalgae-bacterial consortium in wastewater treatment: A review

In the global effort to reduce CO2 emissions, the concurrent enhancement of pollutant degradation and reductions in fossil fuel consumption are pivotal aspects of microalgae-mediated wastewater treatment. Clarifying the degradation mechanisms of bacteria and microalgae during pollutant treatment, as well as regulatory biolipid production, could enhance process sustainability. The synergistic and inhibitory relationships between microalgae and bacteria are introduced in this paper. The different stimulators that can regulate microalgal biolipid accumulation are also reviewed. Wastewater treatment technologies that utilize microalgae and bacteria in laboratories and open ponds are described to outline their application in treating heavy metal-containing wastewater, animal husbandry wastewater, pharmaceutical wastewater, and textile dye wastewater. Finally, the major requirements to scale up the cascade utilization of biomass and energy recovery are summarized to improve the development of biological wastewater treatment.

Role of phosphate in microalgal-bacterial symbiosis system treating wastewater containing heavy metals

Phosphorus is one of the important factors to successfully establish the microalgal-bacterial symbiosis (MABS) system. The migration and transformation of phosphorus can occur in various ways, and the effects of phosphate on the MABS system facing environmental impacts like heavy metal stress are often ignored. This study investigated the roles of phosphate on the response of the MABS system to zinc ion (Zn2+). The results showed that the pollutant removal effect in the MABS system was significantly reduced, and microbial growth and activity were inhibited with the presence of Zn2+. When phosphate and Zn2+ coexisted, the inhibition effects of pollutants removal and microbial growth rate were mitigated compared to that of only with the presence of Zn2+, with the increasing rates of 28.3% for total nitrogen removal, 48.9% for chemical oxygen demand removal, 78.3% for chlorophyll-a concentration, and 13.3% for volatile suspended solids concentration. When phosphate was subsequently supplemented in the MABS system after adding Zn2+, both pollutants removal efficiency and microbial growth and activity were not recovered. Thus, the inhibition effect of Zn2+ on the MABS system was irreversible. Further analysis showed that Zn2+ preferentially combined with phosphate could form chemical precipitate, which reduced the fixation of MABS system for Zn2+ through extracellular adsorption and intracellular uptake. Under Zn2+ stress, the succession of microbial communities occurred, and Parachlorella was more tolerant to Zn2+. This study revealed the comprehensive response mechanism of the co-effects of phosphate and Zn2+ on the MABS system, and provided some insights for the MABS system treating wastewater containing heavy metals, as well as migration and transformation of heavy metals in aquatic ecosystems.

Effect of mariculture wastewater concentrations on high-value production and pollutants removal with bacterial-algal coupling reactor (BACR)

To achieve the goal of cost-effective mariculture wastewater treatment, a novel Bacteria-Algae Coupling Reactor (BACR) integrating acidogenic fermentation with microalgae cultivation was applied for the mariculture wastewater treatment. Currently, there is limited research on the impact of different concentrations of mariculture wastewater on the pollutant removal and the high-value products recovery. In this study, different concentrations (4, 6, 8, and 10 g/L) of mariculture wastewater were treated with BACR. The results showed thatoptimalMW concentrations of 8 g/L improved the growth viability and biochemical components synthetic of Chlorella vulgaris, which increased the potential for high-value products recovery. The BACR exhibited the excellent removal efficiency of chemical oxygen demand, ammonia-nitrogen and total phosphorus with 82.30%, 81.12% and 96.40%, respectively. This study offers an ecological and economic approach to improve the MW treatment through the utilization of a novel bacterial-algal coupling system.

Potential interactive effect on biomass and bio-polymeric substances of microalgal-bacterial aerobic granular sludge as a valuable resource for sustainable development

The algal/bacterial biomass and extracellular polymeric substances (EPSs) existing in microalgal-bacterial aerobic granular sludge (MB-AGS) offer a promising bioresource. The current review-based paper presents a systematic overview of the compositions and interactions (gene transfer, signal transduction, and nutrient exchange) of microalgal and bacteria consortia, the role of cooperative or competitive partnerships of MB-AGS in the treatment of wastewater and recovery of resource, and the environmental/operational factors affecting their interactions and EPS production. Moreover, a brief notes is given on the opportunities and major challenges of utilizing the microalgal-bacterial biomass and EPS for phosphorus and polysaccharides chemical recovery, renewable energy (i.e. biodiesel, hydrogen, electricity) production. Overall, this compact review will pave the way for developing MB-AGS future biotechnology.