Evaluating the performance of inorganic draw solution concentrations in an anaerobic forward osmosis membrane bioreactor for real municipal sewage treatment

Effect of substrate concentration on sulfamethoxazole wastewater treatment by osmotic microbial fuel cell: Insight into operational efficiency, dynamic changes of membrane fouling and microbial response

To solve the problems of antibiotic pollution, water resources and energy shortage, an osmotic microbial fuel cell (OsMFC) was adopted innovatively to treat antibiotic wastewater containing sulfamethoxazole (SMX), and achieved SMX removal, water production and electricity generation. Substrate concentration was one of the key factors affecting the performances of OsMFC, but there were few relevant studies This study explored the effect of substrate concentration on system performances, clarified the dynamic changes of membrane fouling under different substrate concentrations, and further revealed the response of microbial communities. The results showed that the stable removal efficiency of SMX exceeded 98.8 % due to the efficient interception of forward osmosis (FO) membrane. Compared with the 1.0 g/L NaAc system, the SMX degradation efficiency and maximum output voltage in the 2.0 g/L NaAc system were only increased by 3.9 % and 6.3 %, respectively. However, the initial water flux decreased by 30.1 % in the 7th cycle due to more serious FO membrane fouling. In addition, there were significant differences in the dynamic formation process of FO membrane fouling. Higher substrate concentration increased the relative abundance of Desulfobacterota and Geobacter. Functional prediction analysis showed that increasing substrate concentration promoted carbohydrate metabolism pathways and relative abundance of sulfur respiration functional groups, thereby improving COD and SMX removal rates. However, the biosynthesis of other secondary metabolites was significantly improved, resulting in increased contents of EPS and SMP, which aggravated membrane fouling. Overall, the system performed better when the substrate concentration was 1.0 g/L. This study would provide certain guidance for the performance optimization and membrane fouling mitigation of OsMFC, thereby promoting its practical application in antibiotic wastewater treatment.

Smart utilisation of reverse solute diffusion in forward osmosis for water treatment: A mini review

Forward osmosis (FO) has been widely studied as a promising technology in wastewater treatment, but undesirable reverse solute diffusion (RSD) is inevitable in the FO process. The RSD is generally regarded as a negative factor for the FO process, resulting in the loss of draw solutes and reduced FO efficiency. Conventional strategies to address RSD focus on reducing the amount of reverse draw solutes by fabricating high selective FO membranes and/or selecting the draw solute with low diffusion. However, since RSD is inevitable, doubts have been raised about the strategies to cope with the already occurring reverse draw solutes in the feed solution, and the feasibility to positively utilise the RSD phenomenon to improve the FO process. Herein, we review the state-of-the-art applications of RSD and their benefits such as improving selectivity and maintaining the stability of the feed solution for both independent FO processes and FO integrated processes. We also provide an outlook and discuss important considerations, including membrane fouling, membrane development and draw/feed solution properties, in RSD utilisation for water and wastewater treatment.

A Sequential Membrane Process of Ultrafiltration Forward Osmosis and Reverse Osmosis for Poultry Slaughterhouse Wastewater Treatment and Reuse

To address some challenges of food security and sustainability of the poultry processing industry, a sequential membrane process of ultrafiltration (UF), forward osmosis (FO), and reverse osmosis (RO) is proposed to treat semi-processed poultry slaughterhouse wastewater (PSWW) and water recovery. The pretreatment of PSWW with UF removed 36.7% of chemical oxygen demand (COD), 38.9% of total phosphorous (TP), 24.7% of total solids (TS), 14.5% of total volatile solids (TVS), 27.3% of total fixed solids (TFS), and 12.1% of total nitrogen (TN). Then, the PSWW was treated with FO membrane in FO mode, pressure retarded osmosis (PRO) mode, and _L-DOPA coated membrane in the PRO mode. The FO mode was optimal for PSWW treatment by achieving the highest average flux of 10.4 ± 0.2 L/m²-h and the highest pollutant removal efficiency; 100% of COD, 100% of TP, 90.5% of TS, 85.3% of TVS, 92.1% of TFS, and 37.2% of TN. The performance of the FO membrane was entirely restored by flushing the membrane with 0.1% sodium dodecyl sulfate solution. RO significantly removed COD, TS, TVS, TFS, and TP. However, TN was reduced by only 62% because of the high ammonia concentration present in the draw solution. Overall, the sequential membrane process (UF-FO-RO) showed excellent performance by providing high rejection efficiency for pollutant removal and water recovery.

Anaerobic membrane bioreactors for pharmaceutical-laden wastewater treatment: A critical review

Pharmaceuticalsare a diverse group of chemical compounds widely used for prevention and treatment of infectious diseases in both humans and animals. Pharmaceuticals, either in their original or metabolite form, find way into the wastewater treatment plants (WWTPs) from different sources. Recently, anaerobic membrane bioreactors (AnMBR) has received significant research attention for the treatment of pharmaceuticals in various wastewater streams. This review critically examines the behaviour and removal of a wide array of pharmaceuticals in AnMBR with primary focus on their removal efficiencies and mechanisms, critical influencing factors, and the microbial community structures. Subsequently, the inhibitory effects of pharmaceuticals on the performance of AnMBR and membrane fouling are critically discussed. Furthermore, the imperative role of membrane biofouling layer and its components in pharmaceuticals removal is highlighted. Finally, recent advancements in AnMBR configurations for membrane fouling control and enhanced pharmaceuticals removal are systemically discussed.

Effects of Recycled Sponge Iron on Phosphorus Recovery from Polluted Water

Phosphorus in water not only degrades water quality but also leads to a waste of resources. In this study, adsorption thermodynamics and kinetics were used to study the effect of sponge iron on phosphorus removal, and a filtration bed was used to simulate the phosphorus removal in polluted water. The results showed that the maximum theoretical adsorption capacity of the modified sponge iron was increased from 4.17 mg/g to 18.18 mg/g. After desorption with 18.18 mol/L of sodium hydroxide and reactivation with 6% (w%) sulfuric acid, the activation rate of modified sponge iron can reach 98%. In a continuous operation experiment run for approximately 200 days, the sponge iron phosphorus removal percolation bed showed a good phosphorus removal ability. Under the condition of TP = 10 mg/L, HRT = 1 H, the comprehensive phosphorus removal rate was 30–89%, and the accumulated phosphorus adsorption per unit volume was 6.95 kg/m3. Wastewater from the regeneration of the sponge iron base can be used to recover guano stone. The optimum conditions were pH = 10, n (Mg2+):n (PO43−):n (NH4+) = 1.3:1:1.1. Under the optimum conditions, the phosphorus recovery rate could reach 97.8%. The method provided in this study has theoretical and practical significance for the removal and recycling of phosphorus in polluted water.

State-of-the-Art and Opportunities for Forward Osmosis in Sewage Concentration and Wastewater Treatment

The application of membrane technologies for wastewater treatment to recover water and nutrients from different types of wastewater can be an effective strategy to mitigate the water shortage and provide resource recovery for sustainable development of industrialisation and urbanisation. Forward osmosis (FO), driven by the osmotic pressure difference between solutions divided by a semi-permeable membrane, has been recognised as a potential energy-efficient filtration process with a low tendency for fouling and a strong ability to filtrate highly polluted wastewater. The application of FO for wastewater treatment has received significant attention in research and attracted technological effort in recent years. In this review, we review the state-of-the-art application of FO technology for sewage concentration and wastewater treatment both as an independent treatment process and in combination with other treatment processes. We also provide an outlook of the future prospects and recommendations for the improvement of membrane performance, fouling control and system optimisation from the perspectives of membrane materials, operating condition optimisation, draw solution selection, and multiple technologies combination.

Characterization of preconcentrated domestic wastewater toward efficient bioenergy recovery: Applying size fractionation, chemical composition and biomethane potential assay

Domestic wastewater (DWW) can be preconcentrated to facilitate energy recovery via anaerobic digestion (AD), following the concept of "carbon capture-anaerobic conversion-bioenergy utilization." Herein, real DWW and preconcentrated domestic wastewater (PDWW) were both subject to particle size fractionation (0.45-2000 μm). DWW is a type of low-strength wastewater (average COD of 440.26 mg/L), wherein 60% of the COD is attributed to the substances with particle size greater than 0.45 μm. Proteins, polysaccharides, and lipids are the major DWW components. PDWW with a high COD concentration of 2125.89 ± 273.71 mg/L was obtained by the dynamic membrane filtration (DMF) process. PDWW shows larger proportions of settleable and suspended fractions, and accounted for 63.4% and 33.8% of the particle size distribution, and 52.4% and 32.2% of the COD, respectively. The acceptable biomethane potential of 262.52 ± 11.86 mL CH₄/g COD of PDWW indicates bioenergy recovery is feasible based on DWW preconcentration and AD.

Water and nutrient recovery by a novel moving sponge - Anaerobic osmotic membrane bioreactor - Membrane distillation (AnOMBR-MD) closed-loop system

For the first time, a novel sponge-based moving bed-anaerobic osmosis membrane bioreactor/membrane distillation (AnOMBR/MD) system using mixed Na₃PO₄/EDTA-2Na as the draw solution was employed to treat wastewater for enhanced water flux and reduced membrane fouling. Results indicated that the moving sponge-AnOMBR/MD system obtained a stable water flux of 4.01 L/m² h and less membrane fouling for a period lasting 45 days. Continuous moving sponge around the FO module is the main mechanism for minimizing membrane fouling during the 45-day AnOMBR operation. The proposed system's nutrient removal was almost 100%, thus showing the superiority of simultaneous FO and MD membranes. Nutrient recovery from the MF permeate was best when solution pH was controlled to 9.5, whereby 17.4% (wt/wt) of phosphorus was contained in precipitated components. Moreover, diluted draw solute following AnOMBR was effectively regenerated using the MD process with water flux above 2.48 L/m² h and salt rejection > 99.99%.