Search Results (40)

Mariculture wastewater is an intractable wastewater, owing to its high salinity inhibiting microbial metabolism. The biocarrier bacterial–microbial consortium (BBM) and bacterial–microbial consortium (BM) were developed to investigate the mechanism of pollutant degradation and microbial community evolution. The BBM exhibited excellent mariculture wastewater treatment, with the highest removal for TOC (91.78%), NH₄⁺-N (79.33%) and PO₄³⁻-P (61.27%). Biocarriers accelerated anaerobic region formation, with the levels of denitrifying bacteria accumulation improving nitrogen degradation in the BBM. Moreover, the biocarrier enhanced the production of soluble microbial products (SMPs) (11.53 mg/L) and extracellular polymeric substances (EPSs) (370.88 mg/L), which accelerated the formation of bacterial and microalgal flocs in the BBM. The fluorescence excitation–emission matrix (EEM) results demonstrated that the addition of biocarriers successfully decreased the production of aromatic-like components in anoxic and aerobic supernatants. Additionally, the biocarrier shifted the bacterial community constitutions significantly. Biocarriers provided an anoxic microenvironment, which enhanced enrichments of Rhodobacteraceae (66%) and Ruegeria (70%), with a satisfying denitrification in the BBM. This study provided a novel biocarrier addition to the BBM system for actual mariculture wastewater treatment. Full article

This study assesses the impact of hydraulic retention time (HRT) on the performance of an anaerobic dynamic membrane bioreactor (AnDMBR) system using a carbon fabric membrane for treating high-strength wastewater. The evaluation of AnDMBR performance encompasses the removal of soluble chemical oxygen demand (sCOD), biogas/methane production, and membrane fouling. The average influent sCOD concentration was 11,814 ± 1064 mg/L, with two HRT applications at 8 and 5 days and high biomass concentration (MLVSS 14,600 ± 500 mg/L). An impressive sCOD removal efficiency exceeding 98% was achieved throughout the operation period. The AnDMBR system exhibited the highest biogas production, reaching 4.33 ± 0.51 L/day, with a methane content of approximately 67.77 ± 2.9% during the 5-day HRT stage. Transmembrane pressure (TMP) increased gradually at the 8-day HRT stage, leading to membrane fouling, whereas fouling occurred more rapidly at the 5-day HRT stage. Biomass analysis showed minimal variations in MLVSS, extracellular polymeric substance (EPS), and soluble microbial product (SMP) concentrations (protein and carbohydrate) across both HRT application stages. This study suggests that the AnDMBR system can be adopted effectively for treating high-strength wastewater, maintaining high COD removal efficiency and biogas production with 5-day HRT. Full article

Using a laboratory-scale system, consisting of a primary disinfection tank (PDT) and three intermittently mixed reactors (R1–R3) in series, bulk water and biofilm contributions to chlorine decay were quantified. The reactors (surface-to-volume ratio: 23.7 m⁻¹; retention time in each reactor: 42.6 ± 1.18 h) were fed with plant-filtered water (PFW). Secondary disinfection was carried out in R1. Free chlorine concentration decreased with travel time (R1: 1.2 mg/L; R2: 0.6 mg/L; and R3: 0.12 mg/L). The bacterial number (ATP) decreased from 67 pg/mL in PFW and remained at ~2–3 pg/mL in R1 and R2 but increased back to 68 pg/mL in R3. First-order chlorine decay rate coefficients decreased from R1 to R2, as expected, but increased by five-fold from R2 to R3. The increased bacterial number (ATP) in R3 and batch chlorine decay tests confirmed that bulk water (soluble compounds, microbes, and sediments) contributed approximately 40% of the decay, and the biofilm contributed 60% in R3. When ATP levels in the reactors were combined with literature data, the bacterial number increased significantly when free chlorine decreased below 0.2 mg/L, but data between 0.2 and 0.5 mg/L are limited. More investigation is needed in the future for chlorine < 0.5 mg/L regarding bacterial regrowth and its effect on bulk water chlorine decay. Full article

Hydrogen is a well-known clean energy carrier with a high energetic yield. Its versatility allows it to be produced in diverse ways, including biologically. Specifically, dark fermentation takes advantage of organic wastes, such as agro-industrial residues, to obtain hydrogen. One of these harmful wastes that is poorly discharged into streams is sugarcane bagasse pentose liquor (SBPL). The present study aimed to investigate hydrogen generation from SBPL fermentation in batch reactors by applying different food/microorganism (2–10 F/M) and carbon/nitrogen (10–200 C/N) ratios under mesophilic and thermophilic conditions. Biohydrogen was produced in all pentose liquor experiments along with other soluble microbial products (SMPs): volatile fatty acids (VFAs) (at least 1.38 g L⁻¹ and 1.84 g L⁻¹ by the average of C/N and F/M conditions, respectively) and alcohols (at least 0.67 g L⁻¹ and 0.325 g L⁻¹ by the average of C/N and F/M conditions, respectively). Thermophilic pentose liquor reactors (t-PLRs) showed the highest H₂ production (H₂ maximum: 1.9 ± 0.06 L in 100 C/N) and hydrogen yield (HY) (1.9 ± 0.54 moles of H₂ moles of substrate⁻¹ in 2 F/M) when compared to mesophilic ones (m-PLRs). The main VFA produced was acetate (>0.85 g L⁻¹, considering the average of both nutritional conditions), especially through the butyrate pathway, which was the most common metabolic route of experimental essays. Considering the level of acid dilution used in the pretreatment of bagasse (H₂SO₄ (1%), 1.1 atm, 120 °C, 60 min), it is unlikely that toxic compounds such as furan derivatives, phenol-like substances (neither was measured), and acetate (<1.0 g L⁻¹) hinder the H₂ production in the pentose liquor reactors (PLRs). Sugarcane bagasse pentose liquor fermentation may become a suitable gateway to convert a highly polluting waste into a renewable feedstock through valuable hydrogen production. Full article

The main purpose of this paper was to reveal the effect of aluminum (Al)-based coagulants on enhanced coagulation for the removal of algae and the synergistic optimization mechanism among different Al species. The formation, breakage, and regrowth processes of algal coagulation flocs formed by a series of monomeric Al-based coagulants (Al₂(SO₄)₃, Al₁₃, and Al₃₀), Al₁₃/Al₃₀ composite coagulant and poly(diallyldimethylammonium chloride)/Al₁₃ (PDADMAC/Al₁₃) composite coagulant were studied. Results indicated that Al₁₃ mainly employed a charge neutralization mechanism, which was conducive to the destabilization of algae and the regeneration of flocs, while Al₃₀ mainly employed a sweep flocculation mechanism, which was conducive to the formation of algae and the strength of flocs. Meanwhile, the charge neutralization was the main mechanism during the algae coagulation process because it could effectively remove the soluble microbial products (SMP) component in the extracellular organic matter (EOM). Therefore, Al₁₃ could achieve a higher coagulation performance than other monomeric Al-based coagulants. The Al₁₃/Al₃₀ composite coagulant could make up for the deficiency of the sweep flocculation mechanism in Al₁₃ and charge neutralization mechanism in Al₃₀, and achieve the best synergistic optimization performance at Al₁₃:Al₃₀-7:3. Additionally, PDADMAC, as a polymer, could further enhance the charge neutralization ability of Al₁₃ at low dosages and the sweep flocculation ability of Al₁₃ at high dosages, respectively. However, an excessive dosage would lead to charge reversal and thus reduce the coagulation effect. Therefore, controlling the dosage was key when using Al-composite coagulants. The findings of our research could offer a certain theoretical foundation for the development of inorganic polymer flocculants. Full article

The effluent discharged from wastewater treatment facilities frequently enters the ocean, posing a considerable threat to the health of marine life and humans. In this paper, an alkali lignin-based biochar-loaded modified Fe–Cu catalyst (FeCu@BC) was prepared to remove soluble microbial products (SMP) from secondary effluent as disinfection by-products precursors at ambient temperature and pressure. The humic acid (HA) was taken as the representative substance of SMP. The results showed that the maximum removal efficiency of HA reached 93.2% when the FeCu@BC dosage, pH, initial HA concentration, and dissolved oxygen concentration were 5.0 g/L, 7, 100 mg/L, and 1.75 mg/L, respectively. After three cycles, the removal efficiency of HA could be maintained at more than 70%. The quenching experiments and electron spin resonance (EPR) results showed that •OH and ¹O₂ were involved in the degradation of HA in the FeCu@BC catalyst reaction system, with ¹O₂ playing a dominant role. Theoretical calculations confirmed that •OH and ¹O₂ were more prone to attack the C=O bond of the side chain of HA. After processing by the FeCu@BC catalyst, the yield of chlorinated disinfection by-products from secondary effluent had decreased in an obvious manner. This study provides a new solution to efficiently solve the problem of chlorinated disinfection by-products from HA. Full article

Filtration backwashing is necessary for the effective operation of membrane modules, and intermittent aeration helps to remove nutrients, which can save energy and effectively control the occurrence of membrane contamination. In this study, membrane contamination was controlled using an MBR in intermittent aeration operation mode and a filtration backwash cycle; difficult organic matter and nitrogen (COD and NH₄⁺-N) were used as the main contamination indicators for this study; and the main membrane contamination components, extracellular polymers (EPs), and soluble microbial products (SMPs) were detected. The results show that the average removal of COD and NH₄⁺-N could reach 86.45% and 92.47%, respectively, with a 2.0 day intermittent aeration time and 9/1 min filtration backwash cycle mode, and it also helped to reduce the membrane contamination, as shown by a decrease of 11.87% in bound EPs (EPS_Bound) and an increase of only 5.32% in SMPs. Microbiological analyses revealed that Proteobacteria and Acinetobacter, as dominant bacteria (50.90%), were the main causes of membrane contamination. Full article

Moving bed biofilm reactor combined with membrane bioreactor (MBBR-MBR) constitute a highly effective wastewater treatment technology. The aim of this research work was to study the effect of commercial K1 biocarriers (MBBR-MBR K1 unit) and 3D-printed biocarriers fabricated from 13X and Halloysite (MBBR-MBR 13X-H unit), on the efficiency and the fouling rate of an MBBR-MBR unit during wastewater treatment. Various physicochemical parameters and trans-membrane pressure were measured. It was observed that in the MBBR-MBR K1 unit, membrane filtration improved reaching total membrane fouling at 43d, while in the MBBR-MBR 13X-H and in the control MBBR-MBR total fouling took place at about 32d. This is attributed to the large production of soluble microbial products (SMP) in the MBBR-MBR 13X-H, which resulted from a large amount of biofilm created in the 13X-H biocarriers. An optimal biodegradation of the organic load was concluded, and nitrification and denitrification processes were improved at the MBBR-MBR K1 and MBBR-MBR 13X-H units. The dry mass produced on the 13X-H biocarriers ranged at 4980–5711 mg, three orders of magnitude larger than that produced on the K1, which ranged at 2.9–4.6 mg. Finally, it was observed that mostly extracellular polymeric substances were produced in the biofilm of K1 biocarriers while in 13X-H mostly SMP. Full article

Submerged membrane bioreactors (SMBRs) are a promising technology for municipal sewage treatment, but membrane fouling has limited their development. In this study, biochar (BC), which has a certain adsorption capacity, was added to an SMBR to investigate its potential in treating municipal sewage and alleviating membrane fouling. The results showed that the average removal rates of ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) were 94.38%, 59.01%, 44.15% and 83.70%, respectively. After BC was added and operation was stable, the ratio of mixed liquor volatile suspended solids to mixed liquor suspended solids (MLVSS/MLSS) was maintained between 0.78 and 0.81. The concentrations of soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) were stabilized between 63.05 ± 8.49 mg/L and 67.12 ± 1.54 mg/L. Trans-membrane pressure (TMP) and scanning electron microscopy (SEM) analyses showed that BC reduced the TMP by reducing the thickness and compactness of the cake layer on the membrane surface. The high-throughput sequencing results showed that the microorganisms associated with biofilm formation (proteobacteria, γ-proteobacteria and α-proteobacteria) were significantly reduced in the BC-enhanced SMBR system. BC promoted the enrichment of functional microorganisms such as Chloroflexi, Acidobacteriota, Anaerolineae and Planctomycetes. Compared with traditional anti-fouling methods, the results of this study may provide a low-cost membrane fouling mitigation method for industrial applications of SMBRs. Full article

The reuse of wastewater has been identified as an important initiative for the sustainable development of the environment; thus, the removal of secondary effluent organic matter (EfOM) to ensure the safety of reused wastewater is the key step and a subject of extensive research. In this study, Al₂(SO₄)₃ and anionic polyacrylamide were selected as coagulant and flocculant, respectively, for the treatment of secondary effluent from a food-processing industry wastewater treatment plant to meet the standard regulatory specifications for water reuse. In this process, the removal efficiencies of chemical oxygen demand (COD), components with UV₂₅₄, and specific ultraviolet absorbance (SUVA) were 44.61%, 25.13%, and 9.13%, respectively, with an associated reduction in chroma and turbidity. The fluorescence intensities (Fmax) of two humic-like components were reduced during coagulation, and microbial humic-like components of EfOM had a better removal efficiency because of a higher Log Km value of 4.12. Fourier transform infrared spectroscopy showed that Al₂(SO₄)₃ could remove the protein fraction of the soluble microbial products (SMP) of EfOM by forming a loose SMP protein complex with enhanced hydrophobicity. Furthermore, flocculation reduced the aromaticity of secondary effluent. The cost of the proposed secondary effluent treatment was 0.034 CNY t⁻¹ %COD⁻¹. These results demonstrate that the process is efficient and economically viable for EfOM removal to realize food-processing wastewater reuse. Full article

In the process of sewage treatment, the characteristics of dissolved organic matter (DOM) are always changed during chemical and biological processes, affecting the generation of disinfection by-products (DBPs) compositions at the following disinfection stage. The present study systematically investigated the effect of DOM characterization on C- and N-DBPs formation at AAO-MBR reactor when treating wastewater. The results showed that the AAO-MBR treatment process could efficiently eliminate dissolved organic carbon (DOC) and ammonium nitrogen (NH₄⁺-N) from wastewater with an elimination rate of 89% and 98%, respectively. Most of the precursors (i.e., 56.8% C-DBPs and 78.1% N-DBPs) were removed at the MBR unit, while AGC and AAO units promoted the formation of DBPs precursors. More specifically, soluble microbial products (SMPs) and humus acid were increased, which led to improved C- and N-DBPs via aerated grit chamber (AGC) treatment. At the AAO treatment unit, the content of low MW hydrophobic SMPs, humus acid, and polysaccharides was increased, indicating low MW and HPO fractions dominating the C- and N-DBPs. MBR treatment improved C-DBPs in high MW and HPO fractions and N-DBPs in low MW and HPO fractions, which is explained by higher MW hydrophobic SMPs and humus acids, compared to the AAO unit. The present study provided deep insight into the linkage of DOM characteristics and C- and N-DBPs formation at each treatment unit during the AAO-MBR process. Full article

Quorum quenching (QQ) is a novel anti-biofouling strategy for membrane bioreactors (MBRs) used in wastewater treatment. However, actual operation of QQ-MBR systems for wastewater treatment needs to be systematically studied to evaluate the comprehensive effects of QQ on wastewater treatment engineering applications. In this study, a novel QQ strain, Acinetobacter pittii HITSZ001, was encapsulated and applied to a MBR system to evaluate the effects of this organism on real wastewater treatment. To verify the effectiveness of immobilized QQ beads in the MBR system, we examined the MBR effluent quality and sludge characteristics. We also measured the extracellular polymeric substances (EPS) and soluble microbial products (SMP) in the system to determine the effects of the organism on membrane biofouling inhibition. Additionally, changes in microbial communities in the system were analyzed by high-throughput sequencing. The results indicated that Acinetobacter pittii HITSZ001 is a promising strain for biofouling reduction in MBRs treating real wastewater, and that immobilization does not affect the biofouling control potential of QQ bacteria. Full article

Membrane bioreactors (MBRs) are frequently used to treat municipal wastewater, but membrane fouling is still the main weakness of this technology. Additionally, the low carbon-nitrogen (C/N) ratio influent has been shown to not only increase the membrane fouling, but also introduce challenges to meet the effluent discharge standard for nitrogen removal. Herein, the authors addressed the challenges by adding cost-effective biochar. The results suggested that the biochar addition can enable membrane fouling alleviation and nitrogen removal improvement. The reduced membrane fouling can be ascribed to the biochar adsorption capacity, which facilitates to form bigger flocs with carbon skeleton in biochar as a core. As a result, the biochar addition significantly altered the mixed liquor suspension with soluble microbial product (SMP) concentration reduction of approximately 14%, lower SMP protein/polysaccharide ratio from 0.28 ± 0.02 to 0.22 ± 0.03, smaller SMP molecular weight and bigger sludge particle size from 67.68 ± 6.9 μm to 113.47 ± 4.8 μm. The nitrogen removal is also dramatically improved after biochar addition, which can be due to the initial carbon source release from biochar, and formation of aerobic–anaerobic microstructures. Microbial diversity analysis results suggested more accumulation of denitrification microbes including norank_f__JG30-KF-CM45 and Plasticicumulans. Less relative abundance of Aeromonas after biochar addition suggested less extracellular polymer substance (EPS) secretion and lower membrane fouling rate. Full article

In order to efficiently remove NOMs in natural surface water and alleviate membrane pollution at the same time, a flat microfiltration ceramic membrane (CM) was modified with MnFeO_X (Mn-Fe-CM), and a coagulation–precipitation–sand filtration pretreatment coupled with an in situ ozonation-ceramic membrane filtration system (Pretreatment/O₃/Mn-Fe-CM) was constructed for this study. The results show that the removal rates of dissolved organic carbon (DOC), specific ultraviolet absorption (SUVA) and NH₄⁺-N by the Pretreatment/O₃/Mn-Fe-CM system were 51.1%, 67.9% and 65.71%, respectively. Macromolecular organic compounds such as aromatic proteins and soluble microbial products (SMPs) were also effectively removed. The working time of the membrane was about twice that in the Pretreatment/CM system without the in situ ozone oxidation, which was measured by the change in transmembrane pressure, proving that membrane fouling was significantly reduced. Finally, based on the SEM, AFM and other characterization results, it was concluded that the main mitigation mechanisms of membrane fouling in the Pretreatment/O₃/Mn-Fe-CM system was as follows: (1) pretreatment could remove part of DOC and SUVA to reduce their subsequent entrapment on a membrane surface; (2) a certain amount of shear force generated by O₃ aeration can reduce the adhesion of pollutants; (3) the loaded MnFeO_X with a higher catalytic ability produced a smoother active layer on the surface of the ceramic membrane, which was conducive in reducing the contact among Mn-Fe-CM, O₃ and pollutants, thus increasing the proportion of reversible pollution and further reducing the adhesion of pollutants; (4) Mn-Fe-CM catalyzed O₃ to produce ·OH to degrade the pollutants adsorbed on the membrane surface into smaller molecular organic matter, which enabled them pass through the membrane pores, reducing their accumulation on the membrane surface. Full article

Fouling is considered one of the main drawbacks of membrane bioreactor (MBR) technology. Among the main fouling agents, extracellular polymeric substances (EPS) are considered one of the most impactful since they cause the decrease of sludge filterability and decline of membrane flux in the long term. The present study investigated a biological strategy to reduce the membrane-fouling tendency in MBR systems. This consisted of seeding the reactor with activated sludge enriched in microorganisms with polyhydroxyalkanoate (PHA) storage ability and by imposing proper operating conditions to drive the carbon toward intracellular (PHA) rather than extracellular (EPS) accumulation. For that purpose, an MBR lab-scale plant was operated for 175 days, divided into four periods (1–4) according to different food to microorganisms’ ratios (F/M) (0.80 kg COD kg TSS⁻¹ d⁻¹ (Period 1), 0.13 kg COD kg TSS⁻¹ d⁻¹ (Period 2), 0.28 kg COD kg TSS⁻¹ d⁻¹ (Period 3), and 0.38 kg COD kg TSS⁻¹ d⁻¹ (Period 4)). The application of the feast/famine strategy favored the accumulation of intracellular polymers by bacteria. The increase of the PHA accumulation inside the cells corresponded to the decrease of EPS and an F/M of 0.40–0.50 kg COD kg TSS⁻¹ d⁻¹ was found as optimum to maximize the PHA production, while minimizing EPS. The lowest EPS content in the sludge (18% of total suspended solids) that corresponded to the maximum content of PHA (9.3%) was found in Period 4 and determined significant mitigation of the fouling rate, whose value was close to 0.10 × 10¹¹ m⁻¹ h⁻¹. Thus, by imposing proper operating conditions, it was possible to drive the organic matter toward PHA accumulation. Moreover, a lower EPS content corresponded to a decrease in the irreversible fouling mechanism, which would imply a lower frequency of the extraordinary cleaning operations. This study highlighted the possibility of obtaining a double benefit by applying an MBR system in the frame of wastewater valorization: minimizing the fouling tendency of the membrane and recovery precursors of bioplastics from wastewater in line with the circular economy model. Full article