Effect of co-culturing bacteria and microalgae and influence of inoculum ratio during the biological treatment of tannery wastewater

Comparison of single and mixed microalgae in microalgae-bacteria MB-MBR:From efficiency of wastewater treatment, bioactivity and membrane fouling

In this study, two microalgae-bacterial moving bed membrane bioreactors (MB-MBRs) were constructed for co-culture of L1 (Scenedesmus obliquus) and L2 (Chlorella pyrenoidosa and Scenedesmus obliquus) with activated sludge. Nutrient removal efficiency, biological activity and membrane fouling of two microalgae-bacterial MB-MBRs were evaluated. Both reactors demonstrated robust performance, with L2 exhibiting superior functionality. near-complete ammonia nitrogen removal (99.33 ± 1.11 %), total organic carbon (TOC) removal of 73.72 ± 4.83 %, chemical oxygen demand (COD) removal of 92.93 ± 3.23 %, and dehydrogenase activity (DHA) peaked at 10 μg TF/(mL·h). L2 sludge flocs displayed a more compact circular morphology compared to those of L1. It was found that proteins in the extracellular polymeric substance (EPS) were the key to initial biofilm attachment, while polysaccharides facilitated biofilm maturation. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy demonstrated that tryptophan and aromatic proteins played critical roles in biofilm formation and membrane fouling. According to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, ΔGAB was the main factor influencing membrane fouling. These results demonstrate that hybrid microalgae-bacterial systems with biofilm carriers synergistically enhance wastewater treatment efficiency, increase biological activity, and alleviate membrane fouling, offering a sustainable strategy for wastewater treatment.

Study on wastewater treatment characteristics and microbial ecosystem of bacteria-algae symbiosis coupling under carbon neutralization background

At present, environmental pollution is becoming more and more serious, the sustainable development of human society is facing severe challenges. As a crucial nexus for pollutant discharge and greenhouse gas emissions, the establishment of carbon-neutral wastewater treatment processes in wastewater treatment plants, aiming to achieve coordinated development of pollution reduction and carbon mitigation, constitutes a pivotal pathway for environmental governance in the new era. The bacteria-algae symbiotic culture system, based on microalgae biological treatment technology, integrates wastewater treatment, carbon fixation, and biomass energy recovery. It represents a green, low-carbon, economical, and sustainable integrated sewage treatment technology, aligning with the requirements of carbon neutrality. This study constructed an algae-assisted sequencing batch photobioreactor (A-SBPBR) and individual microalgal systems to compare the degradation efficiencies of soluble chemical oxygen demand (sCOD), ammonia nitrogen (AN), and total phosphorus (TP) in high-strength food waste anaerobic digestion effluent (ADE), with high-throughput sequencing conducted to analyze bacterial community dynamics and microbial ecological shifts, coupled with carbon accounting model integration to quantify system-specific carbon emission reduction capacities. Experimental results demonstrated that the bacteria-algae symbiotic system achieved removal efficiencies of 58.89 %, 91.94 %, and 78.89 % for sCOD, AN, and TP, respectively, when treating ADE. Notably, the sCOD degradation rate was approximately 8 % higher than that of the pure algal system. At the phylum level, the bacterial community structure within the symbiotic system exhibited greater diversity and balanced phylum distribution. At the class level, the relative abundances of Gammaproteobacteria, Anaerolineae, and Microgenomatia increased by 5-12 %, 11-14 %, and 2-6 %, respectively, compared to the pure algal system. Carbon footprint analysis revealed that treating 1 m3 of ADE with the symbiotic system reduced CO2 emissions by 51.2 g compared to conventional aerobic processes and lowered CH4 emissions (expressed as CO2 equivalents) by 111.94 g relative to anaerobic processes. These findings indicate that the bacteria-algae symbiotic technology synergistically combines high-efficiency pollutant removal with carbon sequestration capabilities, providing a viable solution for wastewater treatment aligned with carbon neutrality objectives.

Performance and mechanisms of constructed wetland integrated microbial fuel cell for remediation and detoxification of leather tannery wastewater

Several previous studies concerned of microbial fuel cells integrated into constructed wetlands, nevertheless, their application as a convenient treatment for wastewater is still developing. In this experimental investigation, five CW-MFC systems were similarly designed, setup, and operated in a batch mode for two subsequent cycles. Each cycle lasted for 10 days to evaluate the performance of CW-MFC system for the remediation of real leather tannery wastewater (LTW). Four CW-MFCs were planted, each with different type of vegetation including Conocarpus, Arundo donax, Canna lily, and Cyperus papyrus in CW1-MFC, CW2-MFC, CW3-MFC, and CW4-MFC, respectively. The fifth CW5-MFC was maintained unplanted and considered as the control system. The performance of each CW-MFCs systems was evaluated mainly based on the removal of organic content (COD), total dissolved solid (TDS) elimination, and power generation. The results demonstrated that the four types of plants maintained healthy and no sign of wilting was observed during the 20 days of monitoring. For the first cycle of batch operation, maximum removal efficiencies of COD were 99.8%, 99.5%, 99.7%, 99.6% and 99.5% with power outputs of 10,502.8, 10,254.6, 9956.4, 10,029.6, and 9888.0 mW/m3, while, maximum TDS elimination were 46.7%, 39.7%, 60.8%, 55.5%, and 13.8% observed in CW1-MFC, CW2-MFC, CW3-MFC, CW4-MFC, and CW5-MFC, respectively. Very comparable results were observed in the second operation cycle. Results of phototoxicity test indicated that the germination of Hordeum vulgare and Triticum aestivum were 100% watered with treated effluent compared to 90% accomplished with tap water as the control solution for both types of seeds.

Microalgal-bacterial interactions: Research trend and updated review

Microalgae are being recognized as the key contributor to sustainability in many sectors, starting from energy up to food industries. The microorganism has also been utilized as environmental remediator, capable of converting organic compounds into economically valuable biomass. To optimize the use of microalgae in these sectors, researchers have explored various approaches, of which is the use of bacteria. The interaction between bacteria and microalgae can potentially be harnessed, but its complexity requires extensive research. Herein, we present the bibliometric analysis on microalgal-bacterial interactions. The metadata of published literature was collected through Scopus database on August 4, 2023. The downloaded.csv file was uploaded to VOSViewer and biblioshiny for network visualization. We found that the research has gained a lot of attention from researchers since 2012 with an exponential increase of the publication number. The United States and China are leading the research with a strong collaboration. Based on the research sub-topic clusters, the interaction is mostly studied for wastewater treatment, biomass production, and algal bloom control. Updated reviews on this topic reveal that researchers are now focus on optimizing the efficacy of microalgae-bacteria system, investigating the modes of actions, and identifying challenges in its real-world implementation. The microalgal-bacterial interaction is a promising approach for microalgae utilization in wastewater treatment, biomass production, and algal bloom control.

Contaminant removal performance and lipid productivity of a cyanobacteria-bacteria consortium containing exogenous phytohormones during the treatment of antibiotic-polluted wastewater

In this study, a cyanobacteria-bacteria consortium containing native wastewater bacteria and immobilized Synechococcus sp. was constructed. The cyanobacterial cellular responses (including growth, biomass and lipid productivity) and contaminant removal ability (for TN, TP, COD and antibiotics) in the consortium were evaluated during the advanced treatment of wastewater containing 10-50 μg/L of mixed antibiotics (amoxicillin, tetracycline, erythromycin, sulfadiazine and ciprofloxacin) with the addition of a certain phytohormone (indole-3-acetic acid, gibberellin A3 or 6-benzylaminopurine) at trace level within a period of four days. Each phytohormone promoted the growth of Synechococcus sp. and increased the tolerance of Synechococcus sp. to mixed antibiotics. Indole-3-acetic acid coupled to moderate antibiotic stress could elevate lipid productivity and lipid content of Synechococcus sp. to 33.50 mg/L/day and 43.75%, respectively. Phytohormones increased the pollutant removal performance of the cyanobacteria-bacteria consortium through the stimulation of cyanobacterial growth and the regulation of cyanobacteria-bacteria interaction, which increased the abundances of microalgae-associated bacteria including Flavobacterium, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Bosea, Sphingomonas and Emticicia. Up to 80.83%, 98.06%, 83.26%, 99.84%, 99.50%, 89.41%, 65.61% and 60.65% of TN, TP, COD, amoxicillin, tetracycline, erythromycin, sulfadiazine and ciprofloxacin were removed by the consortium with the addition of phytohormones. In general, indole-3-acetic acid was the optimal phytohormone for enhancing lipid production and contaminant removal performance of the cyanobacteria-bacteria consortium.

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.

A cleaner leather chemical from feather waste for reducing ammonia-nitrogen pollution and improving biological treatment efficiency of tannery wastewater

Feather waste is produced in millions of tons globally every year, resulting in a waste of biomass resources and even environmental pollution. A sustainable strategy for utilizing feather waste was proposed by preparing a clean deliming agent for ammonia-nitrogen (NH₃-N) reduction in leather manufacture and biological treatment efficiency improvement of tannery wastewater. Briefly, chicken feather wastes were deeply hydrolyzed with sulfuric acid, and the optimized keratin hydrolysate (KH_opt) that contained 53.6% crude protein and 41.2% amino acids, such as glutamic acid, serine, proline, leucine, phenylalanine, glycine, valine, and arginine, was obtained and used to delime limed cattle hides. The appropriate ratio of amino acids in KH_opt gave KH_opt a great pH-buffering capacity and maintained a stable float pH of approximately 9 throughout the deliming process. The isoelectric points of KH_opt (3.8) and the limed hide (6.3) were both lower than the float pH, thereby bringing about an electrostatic repulsion between the KH_opt and the hide surface, which is helpful for KH_opt to penetrate and deswell the limed hide rapidly. Moreover, the KH_opt deliming effectively removed calcium from the limed hide and achieved leather comparable to conventional leather for commercial applications. KH_opt reduced the NH₃-N concentrations of deliming effluent and tannery wastewater by 91.1% and 80.6%, respectively, compared with the conventional deliming agent (ammonium sulfate), and dramatically increased the biological treatment efficiency of tannery wastewater. The results showed that efficient and high-value use of feather waste was made by preparing KH_opt for sustainable leather manufacturing.