COD Removal Research Articles

Optimal carbofuran degradation via CWPO in NOM-doped water by a framework Cu-doped aluminate perovskite catalyst derived from aluminum saline slags

This study is the first to propose the synthesis of LayAl1–xCuxO3–δ perovskite catalysts using Al recovered from acid leaching of saline slags. The effect of parameters such as the La/Al molar ratio was explored during the synthetic process. A suite of characterization techniques—including XRF, XRD, N2 adsorption, H2-TPR, FTIR, TGA-DTA, TEM, SEM, EDX, and XPS—confirmed the successful synthesis of high-purity (up to 90 %) perovskites with La and O vacancies, and a high concentration of Cu(I) active sites dispersed within the perovskite lattice. The best catalyst was used to optimize the degradation of carbofuran (CBF) in water doped with synthetic dissolved natural organic matter (NOM) using the Fenton-like catalytic wet peroxide oxidation (CWPO) approach. The effects of catalyst concentration, H2O2 dose, and pH on catalytic performance were investigated. Degradation, mineralization (COD removal), and H2O2 consumption were maximized, while Cu leaching was minimized using a statistical desirability function for multiple responses. Optimal conditions were found to be a catalyst concentration (mg Cu/mg H2O2) of 0.234 (2.0 g L–1), an H2O2 dose of 73.3 % (0.73 times the stoichiometric dose for full COD mineralization), and a remarkable circumneutral pH of 6.2. Under these conditions, degradation reached 94.1 %, and COD mineralization was 51 % under room temperature. Notably, the perovskite catalyst exhibited remarkable stability during reuse in up to three cycles, as demonstrated by the low Cu leaching (<1.30 mg L–1).

Valorization of paper-mill sludge laden with 2-chlorotoluene using hydroxyapatite@biochar nanocomposite to enrich methanogenic community: A techno-economic approach

While several studies have investigated the anaerobic digestion of paper-mill sludge (PMS), this technology suffers from nutrient insufficiency, inhibition by aromatic compounds, and low bio-CH4 yield. Hence, PMS was anaerobically co-digested with chicken manure (CM) and supplemented by hydroxyapatite@biochar (HAP@BC) nanocomposite for enhancing 2-chlorotoluene degradation and enriching the methanogenic archaea. Multiple continuous stirred tank reactors (CSTRs) were operated at 12.6 h hydraulic retention time (HRT), using PMS (R1), CM (R2), PMS + CM (R3), PMS + CM+100 mg HAP/L (R4), and PMS + CM+100 mg HAP@BC/L (R5). The maximum bio-CH4 yield of 147.5 ± 9.1 mL/g COD and 2-chlorotoluene removal of 91.2 ± 6.8 % were obtained from R5, experiencing a sufficient C/N ratio of 14.7 and the highest activities of acidogenesis (42.0 %), acetogenesis (37.9 %), and methanogenesis (42.1 %). The abundances of Euryarchaeota, Bacteroidota, and Chloroflexi at the phylum level, and Pseudomonas, and Bacillus at the genus level could highly contribute to the dechlorination mechanism and acetate transformation into CH4. This biomass-to-bioenergy project (10 m3/d capacity) could benefit from pollution reduction, biogas recovery, and carbon credit, giving 5.6 yr payback-period, 3503 USD net present value, and 12.1 % internal rate of return. Because R5 exhibited an efficient techno-economic anaerobic biodegradation performance, future studies are required to optimize its HRT condition and HAP@BC dosage.

Thermophilic and mesophilic anaerobic digestion of soybean molasses: A performance vs. stability trade-off

One of the factors that has a direct impact on anaerobic digestion is the applied organic loading rate (OLRA). Increasing OLRA can boost methane production but can also cause process failure. As a result, establishing the appropriate OLRA for the procedure is critical. This study evaluated the effect of increasing the OLRA using soybean molasses in a thermophilic anaerobic reactor (R-Thermo), as well as the effect of feeding strategy and co-processing with okara. Furthermore, the performance versus stability trade-off between R-Thermo and mesophilic anaerobic digestion (R-Meso) was investigated. The increase of OLRA from 10 to 15 and 20 kg-COD/m³/d led to a decrease in COD removal efficiency (90, 86, and 75%), methane yield (12.0, 11.6, and 9.9 mol-CH4/kg-COD) and an increase in total volatile acids concentration (251, 456, and 1393 mg-HAc/L, respectively). At 15 kg-COD/m³/d, R-Meso performed similarly to R-Thermo, and at 20 kg-COD/m3/d, R-Meso outperformed (81% COD removal efficiency, 9.3 mol-CH4/kg-CODrem and 154.5 mol-CH4/m3/d). Temperature greatly influenced the distribution of metabolic pathways, as shown by thermodynamic and kinetic analyses, thus impacting bacterial diversity. At 55 °C, amongst the bacterial genera, Tepidiphilus stood out (>28.2%), followed by Acetomicrobium, Coprothermobacter and Candidatus_Caldatribacterium. The OLRA clearly impacted the archaeal community; Methanothermobacter (77.4%) was favored over Methanosarcina (14.8%). Under thermophilic temperature, it seems that syntrophic acetate oxidation (SAO) bacteria might have competed for substrate with acetoclastic methanogens, while in R-Meso microorganisms responsible for the initial steps of organic matter breakdown, such as members of the Firmicutes and Proteobacteria phyla (at least 67%), were dominant. In summary, R-Meso, characterized by a more uniform distribution of metabolic pathways, as well as a diverse and well-adapted microbial consortium, have exhibited enhanced stability and outperformed R-Thermo at high-loads.

Microbial approach towards anode biofilm engineering enhances extracellular electron transfer for bioenergy production

Applying microbial electrolysis cells (MEC) is a biological approach to enhance the growth of high amounts of electroactive biofilm for extracellular electron transfer. The electroactive biofilm degrades the organics by oxidizing them at the anode and producing electrical energy. Addition of waste-activated sludge (WAS) with fat grease oil (FOG) produces an optimal reactor environment for microbial growth to enhance the exchange of electrons between cells via microbial electrolysis. The present work aimed to investigate the microbial approach to increase the extracellular electron transfer (EET) in microbial electrolysis cells. Results revealed that metabolites in electroactive microbes (EAM) grow viable cells that initiate high EET at anode sites. At optimum WAS with FOG addition, volatile fatty acid and current generation yield production was 2.94 ± 0.19 g/L and 17.91 ± 7.23 mA, accompanied by COD removal efficiency of 89.5 ± 14.4%, respectively. This study introduces a novel approach to anode biofilm engineering that significantly enhances extracellular electron transfer, offering a fresh perspective on bioenergy production. Our approach, which demonstrates that anodic biofilm enhances intercellular electron transfer, increases NADH-NAD ratio, and increases metabolite yield-fluxes, has the potential to revolutionize bio-electricity production. Results indicated that the electrolysis highlights MEC performance in power generation of 788 mV with 200 mL of anode volume of active viable cells by utilizing WAS with 11% FOG. The achievements of this study provide critical parameters for the anode biofilm engineering, demonstrating how growth cell volume, intercellular electron transfer, and increases in NADH-NAD ratio are evidence of an increase in the EET, compelling evidence for the resilience treatment and efficient current production. These findings are significant in advancing our understanding of bioenergy production.

Wastewater Treatment through Sequencing Batch Reactor: Adaptation of a Hydro-cyclone Decanter to Enhance Particle Segregation

Objectives:This study investigates the integration of a hydro-cyclone decanter into Sequencing Batch Reactor (SBR) systems to enhance particle segregation during the decanting phase, aiming to improve removal efficiencies of suspended particles in SBR. Methods:A hydro-cyclone separator was designed for the SBR reactor, optimizing particles separation using centrifugal forces without extensive process modifications. Experiments were conducted to evaluate the performance with synthetic and actual wastewater at different concentrations and flow rates.Results and Discussion:The hydro-cyclone decanter achieved removal efficiencies of up to 32.3% for synthetic wastewater and approximately 73.2% for actual wastewater, demonstrating significant particle segregation capabilities. However, its impact on dissolved pollutants like total nitrogen (T-N) and total phosphorus (T-P) was limited.Conclusion:Integrating a hydro-cyclone decanter in SBR systems significantly enhances particle segregation, particularly for larger particles, while moderately improving COD removal, suggesting its effective use in wastewater treatment processes.

Use of native macrophyte Echinodorus subalatus for grey water treatment applying alternative bed substrate in constructed wetlands

ABSTRACT Two vertical flow constructed wetland (VFCW 1 and VFCW 2) with native macrophyte Echinodorus subalatus (Mart.) were operated. In VFCW 1, the substrates used were ceramic brick, washed sand, seashells (Anomalocardia brasiliana), and ceramic brick and sand in VFCW 2. The system was operated for 74 days, in batches, with cycles of 168 h, and fed with synthetic grey water. The presence of seashells in VFCW 1 was a differential factor (p < 0) for the removal of anionic surfactant (94.09 ± 7.77%), COD (88.43 ± 5.43%) and total phosphorus (45. 98 ± 9.86%) when compared to VFCW 2. The Langmuir isotherm was used to calculate the substrate adsorption capacity for total phosphorus, anionic surfactant, and COD. The results showed that adsorption on support materials was not the primary mechanism of pollutants removal. From 16S sequencing, it was observed that phylum Firmicutes was the most abundant (96.5%), followed by phylum Proteobacteria (3.5%). The results suggest that using seashells as an alternative substrate improved pollutant removal efficiency.

Boosting BOD/COD biodegradability of automobile service stations wastewater by electrocoagulation

ABSTRACT This study investigates the application of electrocoagulation for enhancing the biodegradability of organic matter in automobile service station wastewater, notorious for its contamination with polyaromatic hydrocarbons, heavy metals, and surfactants. Optimization of key variables such as electrode material, current density, and electrical consumption is conducted, with correlation analysis assessing their impact on water quality. Experimental setups utilize a vertical configuration comprising eight monopolar steel electrode plates as cathodes and eight counter electrodes (either iron or aluminum) connected in parallel. Results indicate that employing iron as the sacrificial electrode significantly increases the biochemical oxygen demand/chemical oxygen demand (BOD/COD) ratio, highlighting the efficacy of heightened power levels in enhancing organic matter degradation. Optimal removal efficiencies, including 87.5 for COD, 96.01 for BOD, and 92.2% for total solids, are achieved at a current density of 42 A/m2 and energy consumption of 360 kWh/m3, while maintaining pH levels between 6 and 9. The findings underscore the potential of electrocoagulation with Fe, Al as anodes, and stainless-steel cathodes as an efficient wastewater treatment approach, particularly for COD, BOD, and solid particle removal, thus contributing significantly to environmental sustainability.

Application of Bioelectrochemical System in Nitrogen Removal via Simultaneous Autotrophic Nitrification and Denitrification from Wastewater

AbstractBioelectrochemical systems (BES) is a new and expanding technology that can simultaneously convert chemical energy into electrical energy by removing nutrients. The present study investigated the BES in removing nitrogen compounds and produce electricity. To this end, a BES reactor with two chambers of cathode and anode and nafion 117 membrane was used as a separator between the two chambers. Then, the BES performance at different concentrations of COD and primary ammonium at different retention times was investigated to remove nitrogen compounds and organic matter. Voltage, current and power density were measured. The results showed that the maximum COD removal efficiency was 73.2 % for the substrate concentration of 2000 mg/L, which decreased to 72.6 % when the substrate concentration increased to 10000 mg/L. The maximum removal efficiency of nitrogen compounds was 83.4 % at COD 10000 mg/L and the initial ammonium concentration was 50 mg/L. The maximum voltage, current and power density in this phase were 391 mV, 460 mA/m2, 63/48 mW/m2, respectively. The results of the study showed that BES can be used as a suitable method to remove high amounts of ammonium in wastewater and organic materials and simultaneously produce electricity.

Sustainable bioenergy potential of peat-moss derived hydrothermal aqueous phase: Insights into methane production and organic transformation

Achieving Sustainable Development Goal 7 (SDG-7) by exploring bioenergy production from peat-moss derived hydrothermal aqueous phase (HAPs) through anaerobic digestion (AD). This study investigated six combinations of hydrothermal conversion temperature (HCT) and residence time (HCRT). Methane yields varied significantly, with the highest (256 mL/g COD) achieved at 200 °C:4h, while the lowest (97 mL/g COD) was at 320 °C:4h due to formation of toxic and refractory organics. Microtox analysis showed acute toxicity > 98 % for all HAPs. Notably, higher HCT and HCRT led to more complex and diverse organic patterns, promoting the formation of humus-like substances, ester, alkane alcohols, and aromatics. GC–MS analysis revealed a 23 % increase in aldehyde and ketone compounds at 320 °C:4h. Continuous experiments confirmed 29 % COD removal efficiency at 320 °C:4h and identified 13 refractory organics, highlighting challenges in biodegradability. These findings provided valuable insights for optimizing AD processes, enhancing bioenergy production, and advancing sustainable energy solutions in alignment with SDG-7.

Biochar for wastewater treatment: Addressing contaminants and enhancing sustainability: Challenges and solutions

In recent years, biochar has gained interest for its potential use in treating and removing contaminants from domestic, municipal, and industrial wastewater. When applied in fixed filter columns (BFCs), biochar can effectively immobilize, filter, and recover contaminants with high treatment efficiency. On average, COD removal is 80 %, nutrient removal is 71 % for nitrogen-ammonium and 57 % for phosphorus-phosphate, and pathogen reduction averages 2.4 log10 units. These results vary depending on factors such as the biochar's surface area, the conditions under which it was pyrolyzed, and operational parameters like hydraulic loading and retention time. Biochar addresses limitations in traditional wastewater treatment by leveraging adsorption, ion exchange, and biological degradation mechanisms. The larger surface area and functionalized surface of engineered biochar make it particularly effective in treating diverse pollutants, including heavy metals, nutrients, and emerging contaminants, such as antibiotic-resistant bacteria. As the global population and industrial activities increase, there is a pressing need for sustainable wastewater treatment technologies. Biochar addresses this need and serves as a waste valorization tool, contributing to bioenergy production, soil improvement, and other applications. The present review focuses on improving biochar's performance and durability in real-world applications by addressing challenges like physical degradation. It also proposes strategies to enhance biochar's properties and reuse potential.

Efficient hydrogen production from food waste leachate using single-chamber microbial electrolysis cell

The aim of this study was to develop an efficient strategy for enhancing H2 production in the single-chamber microbial electrolysis cell (MEC) using food waste leachate as a substrate. Different pH (8.5, 9.5, 10.5, and 11.2), applied voltage (0.8, 1.2, 1.5, 1.8, 2.0, 2.2, 2.3, and 2.4 V) and negative pressure control (−50 kPa) were tested in the single-chamber MEC. Suitable pH adjustment could greatly promote electricity generation and H2 production rather than negative pressure control. Under pH of 11.5 and 2.4 V, the maximum current density reached 121.9 ± 10.9 A/m³ with an average H2 concentration of 91.9 ± 3.2% in a 1.2-L single-chamber MEC within 30 continuous cycles of operation (∼607 h), which was constructed with carbon brushes as the anode and stainless steel brushes as the cathode. The maximum H2 production rate reached 853.2 ± 70.3 L/m³•d with an H2 yield of 26.3 mmol•H2/g•COD. The COD removal of 68.3 ± 6.8% and three-dimensional excitation-emission matrix spectra of the effluent in the MEC within 21 ± 3h indicated efficient organics degradation in the leachate. Our results should provide a promising way to enhance the H2 production of MEC during leachate treatment.

Electrochemical removal of ethylene glycol monobutyl ether in aviation industry wastewater using a porous Ti4O7/Ti electrode

Titanium alloy chemical milling wastewater contains a significant amount of ethylene glycol monobutyl ether (EGBE), which is toxic and difficult to be degraded by microorganisms, and the emission will lead to severe environmental pollution. To solve this problem, the electrocatalytic oxidation method was employed to remove EGBE in the wastewater, in which a porous Ti4O7/Ti electrode were prepared and employed as the anode, while stainless steel acted as the cathode. The effects of current density, interelectrode distance, and stirring mode on the COD removal rate were also investigated. Results show that the COD of the wastewater significantly decreases from 12410 to 15 mg L−1 after 16 h of electrolysis at 10 mA cm−2 and electrode spacing of 1.0 cm as well as aeration stirring at 100 mL min−1. Moreover, pilot-plant scale testing reveals that the COD decreasing from 11980 to 183 mg L−1 after 24 h of electrolysis. Consequently, the utilization of porous Ti4O7/Ti electrode as anode in the electrocatalytic oxidation method presents significant potential in removal of EGBE in aviation industry wastewater.

Remoción de cromo (VI) de agua residual de curtiembre empleando biomasa orgánica vegetal en un reactor biológico secuencial aerobio

[Introduction]: In the removal of chromium (VI) from tannery wastewater, physicochemical methods are the most used. However, these require high operating costs, and worse still, generate secondary pollutants that again require complementary treatments for their elimination. Given this, the applicability of plant organic biomass (VOB) emerges as an environmental alternative based on the adsorption of chromium (VI), the simplicity of obtaining it, the reduction as waste and, above all, it does not generate secondary pollutants. [Objective]: Use VOB waste in an aerobic sequential biological reactor (SBR) for the removal of chromium (VI) in the treatment of tannery wastewater. [Methodology]: 3 aerobic SBR systems were implemented; 2 controls (SBR1 and SBR2) and 1 study subject (SBR+VOB). Each system was fed with tannery wastewater (18 L) and connected to an aeration system (12.7 L/min). The bacterial inoculum, a fundamental part of an SBR system, was obtained from the selective culture of chromium (VI) reducing bacteria (RBCrVI) taken from the wastewater under study, and integrated into SBR2 and SBR+VOB at 0.6 g/L. The VOB was obtained from Stenotaphrum secundatum residues, fragmented, sieved, sterilized and integrated into the SBR+VOB at 1.5 g/L. [Results]: The SBR+VOB system achieved the highest percentage of chromium (VI) removal (93 %), followed by SBR2 (80.1 %), and finally SBR1 (2.8 %). With respect to COD and TSS, the statistical test (Tukey) showed that there was no significant difference between the system under study and the controls, recording COD removal percentages ranging from 87.8 % to 88.4 %, and TSS ranging from 63.8 % to 69.2 %. [Conclusions]: The viability of using VOB waste to remove chromium (VI) in the treatment of tannery wastewater has been evidenced. The results of this research create a promising panorama to mitigate the effects derived from inadequate management of tannery wastewater and organic solid waste.

Urban wastewater treatment at ambient conditions using microalgae-bacteria consortia in a membrane high-rate algal pond (MHRAP): The effect of hydraulic retention time and influent strength

The effects of hydraulic retention time (HRT) and influent wastewater strength on microalgae-bacteria performance were studied in two sets of experiments in a 6-day biomass retention time membrane high-rate algal pond (MHRAP) pilot plant to assess its pollutants removal potential. In the first set of experiments, the MHRAP was continuously fed with effluent from primary settling and operated at 6-, 4- and 2-days HRT and in the second set, the MHRAP was operated at 4-, 2-, and 1-day HRT using pre-treatment effluent. Results showed a complex interaction between algae-bacteria consortium, ambient conditions and MHRAP operation. In set 1, the highest total nitrogen (T-N) and total phosphorus (T-P) removal efficiencies were reached with 6-day HRT (23.6±0.6 % and 32±4 %, respectively), partially due to free ammonia nitrogen stripping and phosphorus precipitation, because of abiotic factors, which reduces the activity of nitrite-oxidizing bacteria and led to partial-nitrification. On the other hand, the 4 and 2-day HRT T-N and T-P removal efficiencies were reduced (below 10 % and 5 %, respectively) because the abiotic factors limited the physicochemical processes, and less biomass was taken up. In set 2, a suitable equilibrium between the microalgae and bacterial communities at 2-days HRT achieved high T-N (91±5 %) and T-P (71±8 %) removal efficiencies. Mass balances indicated that the nitrogen was mostly removed by nitrification-denitrification (87 % of T-N) and T-P predominant removal mechanism was precipitation. The COD removal efficiencies were higher than 86 % in both sets, since the particulate COD and colloids were removed by ultrafiltration. The obtained results showed that MHRAP technology would allow reducing COD and nutrient loads in the effluent under certain operating conditions, demonstrating the potential for resource recovery and wastewater treatment of microalgae-bacteria consortia.

Semi-continuous cultivation of microalgae to treat coal mine effluent in pilot scale: Nutrient removal, biodesalination and fatty acid composition analysis

Coal excavation is associated with discharge of an enormous amount of mine water rich in salt and trace metal ions, which require efficient treatment before use. Considering the potentiality of microalgae for high salt tolerance, salt removal and metallic pollutant removal from aqueous system, present study focuses semi-continuous cultivation of candidate microalgae Chlorella pyrenoidosa (NCIM 2738) in bubble column reactor (BCR) and open raceway pond (ORP) for nutrient supplemented coal mine effluent (NSCME) treatment. In between different hydraulic retention times (HRTs), HRT 6 d provide maximum average biomass productivity of 950 mg L−1 d−1 in BCR and 728.4 mg L−1 d−1 in ORP. HRT 9 d facilitates a maximum lipid content of 1.8 g L ̶ 1 in BCR and 1.4 g L ̶ 1 in ORP. Further, HRT 9 d had the maximum COD removal efficiency (96.5 % in BCR and 94.2 % in ORP) and maximum salinity removal efficiency (93 % in BCR and 92 % in ORP). Fatty acid methyl esters (FAME) characterization highlighted potential biodiesel applicability with cetane number (CN) of 53.94. Energy dispersive X-ray spectroscopy (EDS) revealed an excess amount of salt and metal ions deposition on the surface of harvested microalgae samples. Outdoor large-scale C. pyrenoidosa cultivation can be integrated with coal mine closure plans to meet sustainable development goals (SDGs) 6, 7 and 13.

Electrical stimulation improves the efficiency of treating typical reclaimed water in biofilters

ABSTRACT To conduct advanced treatment on reclaimed water with a low C/N ratio and a low content of biodegradable organic matter, this paper established an electrically coupled biological filter system (biofilter-microbial electrolysis cell, BF-MEC). Through two-stage influent, the influence of electrical stimulation and electrochemical structure on the nitrogen and carbon removal of the system was explored, and the following results were obtained. The optimal externally applied voltage for the BF-MEC system is 0.55 V. The optimal structure of the BF-MEC system is an electrode spacing of 100 mm, and the optimal electrode position is when the electrode is located at the bottom of the system. Compared with the BF system, in the first stage, the removal rates of chemical oxygen demand, total ammonia nitrogen (TAN), and total nitrogen (TN) in the optimal structure BF-MEC system are increased by 13.4, 118.1, and 273.65%, respectively. In the second stage, COD, TAN, and TN removal rates are increased by up to 277.98, 115, and 722.98, respectively. The optimal electrode position is when the electrode is located at the lower part of the system. At this time, the microbial community is more abundant, the microbial activity and lifespan are longer, and the system efficiency is optimal. optimal.

Impact of water depth and flow velocity on organic matter removal and nitrogen cycling in floating constructed wetlands

The configuration of water depth (WD) and flow velocity (FV) in floating constructed wetlands (FCWs) reflects the complex interactions between hydraulic conditions and wastewater treatment performance. Properly configuring hydraulic conditions can optimize performance. This study explored the removal and degradation of organic matter and nitrogen (N) in FCWs with three different WDs (50 cm (SD), 70 cm (MD), and 95 cm (DD)) under four FV conditions (0, 0.3, 1.0, and 1.5 m/d). It also analyzed the regulatory effects of hydraulic conditions on microbial community structure to provide new insights for configuring hydraulic conditions in FCWs. The results indicate that variations in WD and FV do not significantly affect COD removal (p > 0.05), with removal efficiency (RE) consistently reaching 90 % across all conditions. However, hydraulic conditions do influence the degradation rate (k) of COD, with increased FV enhancing the k in MD and DD. In contrast, WD significantly impacts the removal of NH4+−N (p < 0.05), with RE in SD exceeding 80 % across all four FVs. The primary reason is that increased WD reduced the abundance of nitrifying bacteria (Nitrosomonas and Nitrospira) and functional genes (hao and pmoABC-amoABC). Meanwhile, increased WD and FV significantly enriched the denitrifying bacteria genera (such as Massilia, Bacillus, Ensifer, and Rhodobacter) and certain functional genes (nap and nir), favoring the denitrification process and enhancing the dissimilatory nitrate reduction to ammonium (DNRA) process. Furthermore, microbial community diversity, richness, and the number of operational taxonomic units (OTUs) were highest in SD, but decreased with increased WD. This is mainly related to changes in oxygen (O2) transmission and nutrient concentration. These findings help us understand the mechanisms by which hydraulic regulation affects the removal of organic matter and N in FCWs. They also propose potential solutions from a hydraulics perspective to enhance N removal.

Acclimatisation process of biogas production from tofu industrial wastewater using biofilter in anaerobic baffled reactor (ABR)

A biofilter is a simple technology used in an anaerobic baffled reactor (ABR) to keep biological solids (inoculum) from being easily carried by the inlet substrate and to shorten the hydraulic retention time (HRT). The principle of a biofilter is to form a biofilm on the packed bed of the biofilter in ABR so that it contains immobilised microorganisms. This study aims to know the performance of the biofilter reactor on biogas production during the acclimatisation process. The results show biofilters shorten the HRT and effectively remove pollutants, increasing biogas production and methane quality. The total solid content decreases by around 44 %, from 0.38 % to 0.17 %. The biogas production during acclimatisation was 1806.41 L and COD removal was 95 %. The biogas composition of CH4 was 58.05 %, CO2 38.23 %, and N2 3.2 %. This study provides preliminary findings for further studies on the use of tofu wastewater as a biogas feedstock with different concentrate substrates, which is very useful for sustainability activities and improving the industry to become green.

Near-Complete Phosphorus Recovery from Challenging Water Matrices Using Multiuse Ceramsite Made from Water Treatment Residual (WTR)

Water treatment residual (WTR) is a burden for many water treatment plants due to the large volumes and associated management costs. In this study, we transform aluminum-salt WTR (Al-WTR) into ceramsite (ASC) to recover phosphate from challenging waters. ASC showed remarkably higher specific surface area (SSA, 70.53 m2/g) and phosphate adsorption capacity (calculated 47.2 mg P/g) compared to previously reported ceramsite materials (< 40 m2/g SSA and < 20 mg P/g). ASC recovered over 94.9% of phosphate across a wide pH range (3 – 11) and generally sustained > 90% of its phosphate recovery at high concentrations of competing anions (i.e., Cl-, F-, SO42-, or HCO3-) or humic acid (HA). We challenged the material with real municipal wastewater at 10°C and achieved simultaneous phosphate (>97.1%) and COD removal (71.2%). Once saturated with phosphate, ASC can be repurposed for landscaping or soil amendment. The economic analysis indicates that ASC can be a competitive alternative to natural clay-based ceramsite, biochar, or other useful materials. Therefore, ASC is an eco-friendly, cost-effective adsorbent for phosphate recovery from complex waters, shedding light upon a circular economy in the water sector.

Synergistic Enhancement in Hydrodynamic Cavitation combined with Peroxymonosulfate Fenton-like Process for BPA Degradation: New Insights into the Role of Cavitation Bubbles in Regulation Reaction Pathway

The combination of hydrodynamic cavitation (HC) and Fenton-like oxidation technology can dramatically enhance the pollutant removal capacity, however, the synergistic effect of cavitation and catalyst on reactive oxygen species (ROS) generation remained enigmatic. In this study, we established a combined system based on HC and Ce-MnFe2O4 activated peroxymonosulfate (PMS) for BPA removal, and attentions were paid on the role of cavitation bubbles. Study results show that the combination of HC in Ce-MnFe2O4 activated PMS could mediate the degradation of BPA from the non-radical pathway dominated by 1O2 to •O2− dominated radical pathway. Both controlled experiments and theoretical calculations revealed that the cavitation bubbles with different sizes play the dominant role in ROS generation. The microjets produced by the collapse of cavitation bubbles could create a large number of oxygen vacancy defects on Ce-MnFe2O4 surface, which modify the activation barrier of PMS and facilitate the generation of •O2− thermodynamically. The stable existing cavitation bubbles with the size of 100∼400 nm could create considerable gas-liquid interface. The molecular dynamics simulations show that the nano bubbles can concentrate the BPA and increase the probability of contacts between BPA and Ce-MnFe2O4, hence effectively solve the issues of short lifetime of •O2− radicals and limited mass transfer distance to strengthen the reaction. In addition, the PMS/Ce-MnFe2O4/HC system not only achieves the satisfied COD (95%) and TOC (65%) removal efficiency but also enabled the BPA-contaminated water with a low energy cost of 0.065 kWh·m−3 and oxidant cost, highlighting the application potential of the HC technology for contaminated water.