Organic Matter Removal Rates Research Articles

Effect of aeration pretreatment on anaerobic digestion of swine manure

ABSTRACT To investigate the effects of aeration pretreatment on the anaerobic digestion (AD) of swine manure, five pretreatment groups were established with dissolved oxygen (DO) in each group set to 0.0, 0.4, 0.8, 1.4, and 2.0 mg/L, respectively. The results demonstrated that compared to the non-aeration group, methane production increased to varying degrees with different aeration pretreatments (AP), with a maximum increase of 27.98% (DO = 2.0 mg/L). AP reduced the hydrogen sulfide (H2S) content of biogas. The H2S concentration in the DO = 2.0 mg/L was only 0.209%, and this represented an increased H2S removal rate of 49.27% compared to that of the DO = 0.0 mg/L (0.412%). Simultaneously, AP increases the hydrolysis rate. When the DO concentration reached 2.0 mg/L, the hydrolysis rate reached its maximum. An increase in the hydrolysis rate further enhanced the removal rate of organic matter. The organic matter removal rate was highest (36.96%) at DO = 2.0 mg/L. AP effectively prolonged the methane generation time and shortened the lag time of methane generation. AP creates a brief micro aerobic environment, accelerates substrate hydrolysis, and promotes the production and consumption of total volatile fatty acids, particularly acetic acid. Additionally, AP promoted the symbiotic relationship between Caldicoprobacter (20.93%–34.96%) and Metanosaeta (14.73%–18.45%).

Microbial electrochemical enhanced composting of sludge and kitchen waste: Electricity generation, composting efficiency and health risk assessment for land use

To realize the energy and resource utilization from organic solid waste, a two-phase microbial desalination cell (TPMDC) was constructed using dewatered sludge and kitchen waste as the anode substrate. The performance of electricity generation and composting efficacy was investigated, along with a comprehensive assessment of the potential health risks associated with the land use of the resulting mixed compost products. Experimental outcomes revealed a maximum open-circuit voltage of 0.893 ± 0.005 V and a maximum volumetric power density of 0.797 ± 0.009 W/m³. After 90 days of composting enhanced by microbial electrochemistry, a significant organic matter removal rate of 31.13 ± 0.44 % was obtained, and the anode substrate electric conductivity was reduced by 30.02 ± 0.04 % based on the anode desalination. Simultaneously, there was an increase in the content of available nitrogen, phosphorus, and potassium, as well as an improvement in the seed germination index. The forms of heavy metals shifted from bioavailable to stable residual states. The non-carcinogenic hazard index (HI) values for heavy metals and polycyclic aromatic hydrocarbons (PAHs) during the land use of compost products were less than 1, and the total carcinogenic risk (TCR) values for heavy metals and PAHs were below the acceptable threshold of 10−4. The occupational population risk of infection from five pathogens was higher than that of the general public, with all risk values ranging from 8.67 × 10−8 to 1, where the highest risk was attributed to occupational exposure to Legionella. These outcomes demonstrated that the mixture of dewatered sludge and kitchen waste was an appropriate anode substrate to enhance TPMDC stability for electricity generation, and its compost products have promising land use suitability and acceptable land use risk, which will provide important guidance for the safe treatment and disposal of organic solid waste.

Enhancing gravity-driven membrane system performance in shale gas wastewater treatment: Effect and mechanism of sodium acetate solution backwashing

The low-carbon gravity-driven membrane (GDM) filtration technology has great potential for treating highly decentralized shale gas wastewater (SGW), but its performance requires further enhancement. This study explores the effects and underlying mechanisms of sodium acetate (NaAc) solution backwashing on enhancing GDM system performance in SGW treatment. Results indicated that NaAc solution backwashing for 30 min per day significantly improved the stable flux, organic matter removal rate, and total organic nitrogen removal rate by 64%, 176%, and 1085%, respectively. Structural and compositional analysis of the biofouling layer revealed that NaAc solution backwashing effectively reduced its thickness and coverage, thereby diminishing filtration resistance and enhancing stable flux. Furthermore, comparative analysis with pure water backwashing and evaluations of microbial community structures demonstrated that NaAc solution, as a carbon source, substantially stimulated microbial activity and growth, and optimized the microbial community within the biofouling layer. Specifically, NaAc solution backwashing selectively enriched functional microbes with denitrification and organic degradation abilities, such as Roseovarius, Marinobacter, Bacillus, and Citreitalea, thereby augmenting the GDM system’s nitrogen and carbon removal capabilities. Overall, the performance improvements observed were primarily attributed to the physical cleaning effects and bioaugmentation function provided by NaAc solution. This study offered valuable insights for designing and optimizing backwashing strategies in the GDM system.

Hybrid electrochemical/membrane couplings processes for enhancing seawater pretreatment and desalination.

This research focuses on boosting seawater pretreatment and desalination through electrocoagulation (EC)/ultrafiltration (UF) and electrocoagulation (EC)/nanofiltration (NF) processes. We first optimized the key parameters of the EC process using aluminum (Al) and iron (Fe) electrodes. Experimental results show EC process is efficient under optimal conditions. Second, membrane filtration using UF (ES10B), NF(UTC60) and NF(200) as post-processing steps to the EC process were experimented with. EC(Al)/NF(UTC60) combination resulted in the highest removal rate of organic matter (COD 98%, TOC 95%, fluorescence [humic and fulvic acids] 68%), optical density (OD600nm 75%, turbidity 70%, conductivity 64%). In terms of major ions removal, up to 55% was achieved as NF decreases conductivity, salinity, and hardness. EC(Al)/NF(UTC60) seawater permeate demonstrated the best results in terms of lowest flux decline (J/Jo = 0.9) and fouling, which was realized by resistance in series and recovery factor rate (%). Additionally, NF(UTC60) fouling reversibility led to a longer lifetime and higher recovery factor (93%). PRACTITIONER POINTS: Pretreatment by hybrid processes was experimented with to enhance the saline water treatment. Organic matter (COD 98%, TOC 95%, fluorescence [humic and fulvic acids] 68%) and turbidity were successfully removed. Salinity and hardness (conductivity 64%) were highly reduced by NF. Flux decline, retention rate, and membrane fouling were studied.

Study on the Effectiveness of Constructed Wetlands in Purifying Polluted Water from Rivers and Greenhouse Gas Emissions

In order to investigate the effect of different substrates of constructed wetlands on the purification of polluted water in rivers and their greenhouse gas emissions, this study designed three small-scale constructed wetland experimental systems with traditional gravel (CW-G), volcanic rock (CW-V) and biomass carbon (CW-B) as filler substrates to investigate the effect of different constructed wetland systems on the removal of COD and nitrogen pollutants and to further analyse their effect on greenhouse gas emissions. The results showed that the removal rates of organic matter in all three groups of constructed wetlands reached over 90%. and 49.29% to 58.71%, respectively, with CW-V and CW-B significantly improving the removal of NH4 + -N and NO3− -N compared to CW-G (P < 0.05). A comparison of greenhouse gas emissions reveals that although CW-B resulted in the highest N2O emissions due to its better removal of NO3− -N, its share in nitrogen removal was still the smallest. In addition, the rapid consumption of organic matter in the influent water and the oxidation of some CH4 to CO2 resulted in no detectable CH4 in any of the three groups of constructed wetlands. The results of this study show that the differences in treatment effects and greenhouse gas emissions between the three types of substrate constructed wetlands are significant, and this study can provide some scientific reference for the construction and operation of wetlands for the purification of polluted water bodies in rivers.

Carbon-based materials boost the anaerobic treatment of slaughterhouse wastewater

Carbon-based materials were tested as methanogenic boosters to enhance the anaerobic treatment slaughterhouse wastewater, which included an organic xerogel (OX) doped with graphene oxide, a peach stone carbon (PSC), and a monolithic whey carbon (MWC). Enhanced treatment by the carbon-based boosters was evident in terms of organic matter removal and methane production rate, which was globally reflected on a superior methanogenic conversion efficiency as compared to the unamended control. OX appeared as the best methanogenic booster increasing up to 77 % and 12 % the methane production rate and organic matter removal, respectively. The obtained results suggest that hydrolysis and acidification of the complex wastewater were the limiting steps during the treatment of this industrial effluent. This observation is consistent with the higher production of ammonium, derived from protein hydrolysis, which occurred in bioreactors amended with carbon-based materials, as compared to the unamended control. Several changes in the relative abundance of key microbial taxa occurred; particularly, members of the bacterial families Synergistaceae and Anaerolineaceae, as well as the archaeal Methanolinea and Proteiniclasticum genera, increased significantly in the presence of OX. The synthesized materials are proposed to improve the performance of anaerobic treatment systems dealing with complex wastewaters.

Safe Reuse of Landfill Leachates for Irrigation Purposes

The purpose of the present study was the assessment of the potential reusability of landfill leachates for agricultural irrigation, after advanced oxidation treatments. The UV/Fenton and Fenton processes were applied to the treatment of two different landfill leachate samples, L1 and L2, classified as intermediates, collected from two different landfills located in Macedonia, Greece. Samples were characterized by high COD and TOC values, ranging from 5500-6100 mg/l and 1700-1780 mg/l, respectively. The treatment efficacy and toxicity characteristics were evaluated by conducting phytotoxicity tests. Sorghum saccharatum seeds were used and the germination index (GI) was estimated. The results showed that the UV/Fenton process achieved better organic matter removal rates for both samples. The untreated undiluted leachates L1 and L2 were highly toxic, resulting in GI values of 0. The results of the study showed that Sorghum saccharatum seed germination depends on the nature of the irrigation media and that optimum germination rates were achieved at dilutions of treated leachates with ratios higher than 1:4.

Evaluating the Bioremediation Capacity of the Polychaete Perinereis gualpensis (Jeldes, 1963) for Atlantic Salmon Aquaculture Sludge

The potential of polychaetes for the bioremediation of aquaculture sludge gained more attention in recent years. These organisms can reduce organic matter and nutrients contained in the sludge of several aquaculture species, improving the sustainability of these activities. The aim of this study was to evaluate the removal performance of Perinereis gualpensis (Jeldes, 1963) being fed with aquaculture sludge produced by a recirculating system cultivating Atlantic salmon. The experiment involved adding different amounts of sludge (10% and 20% with respect to total substrate) at a density of 300 organisms m−2 during 30 days. A treatment without sludge served as a control, using natural substrate. The highest removal rate of total organic matter (TOM) (23.95 ± 13.19 g m−2 day−1) was achieved by P. gualpensis with 20% sludge addition, a reduction of about 36% compared to the total amount added at the beginning of the trials. The organisms fed with aquaculture sludge presented higher nitrogen (8–9%) and carbon (40–43%) contents, with a maximum organic carbon assimilation of 32% in relation to the total content in the sludge. The high survival (88–95%) and positive growth rates (0.28% day−1) achieved by P. gualpensis indicated that this species can be sustained with salmon sludge as the only source of food. These results indicate that P. gualpensis is a promising candidate for removing nutrients from salmon effluents. Moreover, the protein contents achieved by the organisms (52–58%) meet the dietary protein requirements of several aquaculture species. Further research is needed to determine the maximum bioremediation capacity of this species and to evaluate the lipid content and fatty acid profiles of P. gualpensis to determine its potential application in aquaculture feed.

Metagenomic characterization of the enhanced performance of multicomponent synergistic thermophilic anaerobic co-digestion of food waste utilizing kitchen waste or garden waste as co-substrate

Food waste (FW) single-substrate anaerobic digestion usually suffers from rapid acidification and inhibition of oil and salt. To overcome these problems and improve the process efficiency, supplementing other substrates has been used in FW anaerobic digestion. This study investigated the biogas production potential through co-digestion of FW with kitchen waste (KW) or garden waste (GW) in different ratios under thermophilic conditions. The results showed that the optimal ratios were FW:KW=60:40 and FW:GW=80:20 which biogas production improved 73.33% and 68.45% compared with single FW digestion, respectively. The organic matter removal rate of co-digestion was 84.46% for FW+KW group (RFK) and 65.64% for FW+GW group (RFG). Co-digestion increased the abundance of the dominant hydrolytic bacteria Defluviitoga and Hydrogenispora and hydrogenotrophic methanogen Methanoculleus. Furthermore, glycoside hydrolases (GHs), vital carbohydrate-active enzymes (CAZymes), were improved by co-digestion. Co-digestion could also effectively promote the function of cellulase and hemicellulose. This strategy for utilizing different organic wastes together as co-substrate provides a new avenue for bioenergy production.

Microbial indicators of efficient performance in an anaerobic/anoxic/aerobic integrated fixed-film activated sludge (A2O-IFAS) and a two-stage mesophilic anaerobic digestion process.

An analysis of the community structure, diversity and population dynamics of Bacteria and Archaea in the suspended and attached biomass fractions of a pilot-scale anaerobic/anoxic/aerobic integrated fixed-film activated sludge (A2O-IFAS) was executed. Along with this, the effluents of the acidogenic (AcD) and methanogenic (MD) digesters of a two-stage mesophilic anaerobic (MAD) system treating the primary sludge (PS) and waste activated sludge (WAS) generated by the A2O-IFAS were also analyzed. Non-metric multidimensional scaling (MDS) and Biota-environment (BIO-ENV) multivariate analyses were performed to link population dynamics of Bacteria and Archaea to operating parameters and removal efficiencies of organic matter and nutrients, in search of microbial indicators associated with optimal performance. In all samples analyzed, Proteobacteria, Bacteroidetes and Chloroflexi were the most abundant phyla, while the hydrogenotrophic methanogens Methanolinea, Methanocorpusculum and Methanobacterium were the predominant archaeal genera. BIO-ENV analysis disclosed strong correlations between the population shifts observed in the suspended and attached bacterial communities of the A2O-IFAS and the removal rates of organic matter, N and P. It is noteworthy that the incorporation of carriers combined with a short sludge retention time (SRT = 4.0 ± 1.0 days) enhanced N removal performance of the A2O by favoring the enrichment of bacterial genera able to denitrify (Bosea, Dechloromonas, Devosia, Hyphomicrobium, Rhodobacter, Rhodoplanes, Rubrivivax, and Sulfuritalea) in the attached biomass fraction. In addition, operation at short SRT enabled the generation of a highly biodegradable WAS, which enhanced the biogas and methane yields in the two-stage MAD. An increase in the relative abundance of Acetobacteroides (uncultured Blvii28 wastewater-sludge group of Rikenellaceae family) correlated positively with the volatile solids removal rate (%VSR), CH4 recovery rate and %CH4 in the biogas (r > 0.8), supporting their relevance for an efficient methanogenesis in two-stage systems.

Enhanced Simultaneous Nitrogen and Phosphorus Removal Performance of the AGS-SBR Reactor Based on the Effects of the C/N Ratio and Microbial Community Change

In recent years, the development of AGS technology will likely lead to a new direction in wastewater treatment development in the future. Traditional sewage treatment technology has been unable to meet the increasingly strict quality standards of wastewater treatment and limited land requirements. AGS technology may be a new method to replace traditional sewage treatment technology. However, the stable operation of AGS technology is a major obstacle to the popularization and development of this technology. The C/N ratio is an important parameter affecting the stability and simultaneous nitrogen and phosphorus removal of AGS technology. In order to enhance the nitrogen and phosphorus removal capacity of a low-load aerobic granular sludge SBR (AGS-SBR) system, changes in the morphology, EPS, and simultaneous removal of organic matter, nitrogen, and phosphorus in the AGS system were studied by regulating different C/N ratios (20, 15, 10, 5). The changes in the microbial community in the system were deeply analyzed by high-throughput sequencing technology. The results showed that different C/N ratios have a significant effect on the nitrogen removal rate of AGS but have little effect on the removal rate of organic matter and phosphorus. When the C/N ratio was reduced to 10, it was conducive to the stability of the low-load AGS-SBR system. An effective C/N ratio promoted the secretion of EPS by microorganisms, and the increase in the PN value contributed to the stability of the granular sludge, which became smooth and compact. The main functional genus in the system were norank_f__Saprospiraceae, Tetrasphaera, Ellin6067, and Pseudomonas. In addition, the simultaneous nitrogen removal performance of the system was significantly improved.

Study on the Extraction Method of Microplastic System in Textile Wastewater

Microplastic pollution has become a global environmental problem. Textile microplastics are an important component of microplastic pollution, but little is known about their contamination in the industrial environment. The lack of standardized methods for detecting and quantifying textile microplastics is a major obstacle to determining the risks they pose to the natural environment. This study systematically examines the pretreatment options for the extraction of microplastics from printing and dyeing wastewater. The effectiveness of potassium hydroxide, nitric acid-hydrogen peroxide mixed solution, hydrogen peroxide, and Fenton's reagent for the removal of organic matter from textile wastewater is compared. Three textile microplastics, polyethylene terephthalate, polyamide, and polyurethane, are studied. The effects of the digestion treatment on the physicochemical properties of textile microplastics are characterized. The separation efficiency of sodium chloride, zinc chloride, sodium bromide, sodium iodide, and sodium chloride-sodium iodide mixed solution on the textile microplastics is tested. The results showed that Fenton's reagent achieved a 78% removal rate of organic matter from printing and dyeing wastewater. Meanwhile, it has less of an effect on the physicochemical properties of textile microplastics after digestion and is the best reagent for digestion. The zinc chloride solution achieved a 90% recovery for separating textile microplastics with good reproducibility. It does not affect the subsequent characterization analysis after separation and is the best solution for density separation.

Cascade utilization of rice straw for biogas production.

To improve the biogas yield of rice straw, an innovative cascade utilization process for biogas production was proposed using a method referred to as "the first digestion + NaOH treatment + the second digestion" (labeled FSD). Both the first digestion and the second digestion of all treatments were conducted at the initial total solid (TS) loading of straw of 6%. A series of lab-scale batch experiments were conducted to investigate the effect of first digestion time (5, 10, and 15days) on biogas production and lignocellulose structure destruction of rice straw. The results showed that the cumulative biogas yield of rice straw using the FSD process was increased by 13.63-36.14% compared with the control (CK), and the highest biogas yield of 233.57mLg-1 TSadded was obtained when the first digestion time was 15days (FSD-15). The removal rates of TS, volatile solids, and organic matter were increased by 12.21-18.09%, 10.62-14.38%, and 13.44-16.88%, respectively, compared with those of CK. The results of Fourier transform infrared spectroscopy analysis revealed that the skeletal structure of rice straw was not significantly destroyed after the FSD process, but the relative contents of functional groups in rice straw were changed. The FSD process accelerated the destruction of crystallinity of rice straw, and the lowest crystallinity index of 10.19% was obtained at FSD-15. The abovementioned results indicated that the FSD-15 process is recommended for cascade utilization of rice straw in biogas production.

Degradation of refractory organic matter in MBR effluent from treating landfill leachate by the UV-nZVI-H2O2 system.

In this study, nano zero-valent iron (nZVI) was used as the Fe2+ source in the Fenton reaction, and a UV-nZVI-H2O2 system was constructed to efficiently degrade and mineralize refractory organic matter in landfill leachate. The results showed that under the optimal conditions (initial pH = 3, UV = 14W, nZVI = 0.5g/L, and [H2O2] = 30mM), the removal efficiencies of total organic carbon, absorbance at 254nm, and color number were 61.38%, 83.89%, and 85.79%, respectively. Control experiments show that the UV-nZVI-H2O2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H2O2 system is related to a higher H2O2 utilization rate. The H2O2 residue in the UV-nZVI-H2O2 system was the lowest, and the effective utilization rate of H2O2 was as high as 98.80%. Alcohol quenching experiments and hydroxyl radical quantitative experiments showed that the dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO• and the yield of HO• was as high as 2007.80μM, which was much higher than that in other systems. The results of spectra analysis showed that the low molecular weight, high fluorescence frequency organic matter, and relatively stable aromatic organic matter were significantly degraded after treatment with the UV-nZVI-H2O2 system and the aromatic degree, humification degree, molecular weight, and molecular polymerization degree of refractory organic matter were also significantly decreased. The mechanism of the UV-nZVI-H2O2 reaction includes homogeneous and heterogeneous Fenton reactions and adsorption and precipitation of organic matter by iron-based colloids. This study can provide theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate.

Characterising operational performance and oxygen crossover of the low-cost cylindrical cathode in microbial fuel cells

The cylindrical cathode has been used in microbial fuel cells (MFC) to achieve a large cathode area and high operational performance. However, the high material cost of cylindrical cathodes limits their practical application. To overcome this, a low-cost cylindrical cathode was successfully developed by coating activated carbon-based catalysts uniformly on the surface of cylindrical stainless steel mesh. The MFCs with the low-cost cylindrical cathodes could obtain a large surface area (up to 509 m2/m3), high power density (81.4 W/m3) and fast organic matter removal rate (−0.32 h−1). However, long-term operation showed that a cathode area larger than 104 m2/m3 could induce excessive oxygen crossover and substantially reduce the power stability of MFC. A numerical study showed that the oxygen crossover was affected by cathode properties such as surface area, current and biofilm. Accordingly, potential controlling methods were proposed. This study will benefit the practical application of cylindrical cathodes.

Optimization of an Empirical Model for Microorganism-Immobilized Media to Predict Nitrogen Removal Efficiency

The purpose of this study was to develop a model to predict the total nitrogen (T-N) concentration in treated wastewater effluent when microorganism-immobilized media are applied. The operational data for this study were obtained using synthetic wastewater and actual wastewater within a lab-scale reactor. The organic matter removal, nitrification, and denitrification rates were 81.8, 87, and 82.9%, respectively. These rates adequately satisfied the effluent water quality standard. The observed parameters from the lab-scale reactor operation were applied to develop the optimization model, and the model showed correlation coefficients as 0.9785 and 0.9811 for nitrification and denitrification efficiencies, respectively. The model predicted that T-N concentration could be reduced to <10 mg/L with the injection of the external carbon source. The predicted value for the T-N concentration was higher than the observed value from the lab-scale reactor, which operated under the same conditions. The model showed comparable values to the observed data, and the model seems to be useful for predicting related parameters in effluent water quality, with further development of the specifications required in the treatment facilities under various operating conditions.

Effect of different mixed light-emitting diode light wavelengths on CO2 absorption from biogas and nutrient removal from biogas slurry by microalgae and fungi induced using strigolactone and endophytic bacteria.

In this study, biogas and biogas slurry were simultaneously treated using two symbiotic systems: Chlorella vulgaris-Ganoderma lucidum-S395-2 (endophytic bacteria) and Scenedesmus obliquus-G. lucidum-S395-2. The influence of different mixed illumination (red and blue) intensity ratios on the algal symbionts' extracellular carbonic anhydrase activities was investigated, as well as the rates of microalgal growth and photosynthesis. The treatment performance was simultaneously assessed in terms of the efficiency of organic matter or nutrient removal and the level of CO2 absorption. The results indicated that red-blue light combinations with an intensity ratio of 5:5 were optimal. When comparing the performance of the two symbiotic systems, the C. vulgaris-G. lucidum-S395-2 symbiont co-culture system achieved significantly improved photosynthetic rates, biomass growth, and treatment effects. Under the optimal treatment conditions, the organic matter and nutrient removal rates were 81.06% ± 7.06% for chemical oxygen demand, 82.32% ± 7.18% for total nitrogen, and 82.98% ± 7.26% for total phosphorus. In addition, the rate of CO2 removal from biogas was 63.38% ± 5.35%. PRACTITIONER POINTS: The red and blue light intensity ratio of 5:5 showed the best removal performance. C. vulgaris-G. lucidum-S395-2 system obtained the best photosynthetic performance. The carbonic anhydrase activity had positive effects on CO2 removal performance.

Performance of a novel granular activated carbon and gravity-driven membrane hybrid process: Process development and removal of emerging contaminants

In this study, a novel granular activated carbon (GAC) gravity-driven membrane (GDM) hybrid system with a ceramic membrane was developed for the production of high quality water. The operational performance in water permeability; removal of organic matter; and contaminants of emerging concern (CECs) including microplastics, larvae, and perfluorinated compounds (i.e., perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid(PFOS)) was evaluated. The experimental results indicate that the GAC-GDM hybrid system can overcome the limitations of the GAC (i.e., low rejection efficiency of particulates) and GDM (i.e., low rejection efficiency of organics) processes. The GDM process showed higher removal rates of microplastics and larvae than the GAC process (i.e., 77.9% and 100% vs. 16.6% and 70%, respectively), and the GAC process exhibited higher removal rates of organic matter and perfluorinated compounds (PFOA and PFOS) than the GDM process (i.e., 54.8%, 90.9% and 99.1% vs. 17.6%, 23% and 31.8%, respectively). In the GAC-GDM hybrid system, stable water flux was observed with the efficient removal of CECs and organic matter during operation. This study implies that the GAC-GDM system can be used as a distributed water treatment system in remote areas such as islands and mountains because the GAC-GDM system is able to minimize the operation scale.

The importance of rest phase and pollutant removal mechanism of tidal flow constructed wetlands (TFCW) in rural grey water treatment

This paper explored the effects of the rest phase of tidal flow constructed wetlands (TFCW) on pollutant removal and microbial communities, and further analyzed the mechanism of TFCW removal of pollutants from grey water. The results showed that the removal rate of organic matter was 69.91 ± 2.44% in the control group (NR-TFCW) without the rest phase, 94.95 ± 1.17% in the experimental group (TFCW), and 96.95 ± 2.43% in the control group (P-TFCW) with the ventilation pipe enhanced rest phase. Limiting and enhancing the oxygen supply in the emptying stage of TFCW will enhance the overlap rate of microorganisms in the upper, middle and lower layers of the reactor. Enhancing the rest phase of TFCW leaded to better aerobic removal of organic matter in the microbial community, while limiting the rest phase of TFCW results in the opposite. In addition, the species overlap rate of the top, middle and bottom layers of NR-TFCW (69.98%) and P-TFCW (54.29%) was higher than that of TFCW (11.34%). The removal of organic matter by TFCW mainly relied on the adsorption of biochar in the flood phase, and the microorganisms aerobic degraded the organic matter adsorbed on the biochar in the rest phase. And thus form a continuous cycle of adsorption and biological regeneration. The microbial community in TFCW did not have the ability to nitrify, but had the ability to remove phosphorus. Ammonia nitrogen in the influent was adsorbed by biochar or converted into cytoplasm. While the phosphorus in the influent was adsorbed by the biochar, it was also being biologically removed.

Effect of Electrode Distances on Remediation of Eutrophic Water and Sediment by Sediment Microbial Fuel Cell Coupled Floating Beds.

Efficient and sustainable technologies for cleaning of contaminated water and sediments are in urgent demand. In this study, a new type of sediment microbial fuel cell coupled floating bed (FB-SMFC) was developed to repair eutrophic water and sediment in a cleaner way. The effect of electrode spacing on the power generation capacity and the synchronous remediation of pollutants from eutrophic water and sediment were studied. When the electrode distance was 60 cm, the maximum power generation and pollutant removal effects were obtained. At the end of the experiment, the maximum output voltage was 0.4 V, and the chemical oxygen demand (CODCr, potassium dichromate method), total nitrogen (TN), and total phosphorus (TP) contents in the overlying water were 8 mg/L, 0.7 mg/L, and 0.39 mg/L. The corresponding removal rates were 88.2%, 78.8%, and 59.0%, respectively. The removal rates of organic matter and TN in the sediment were 12.8% and 86.4%, respectively, and the fixation rate of TP was 29.2%. Proteobacteria was the dominant phylum of bacteria in the sediment and anode. Many anaerobic bacteria were found in the overlying water, which facilitated denitrification. Overall, the results of this research revealed a highly efficient and reliable strategy for eutrophic water and sediment remediation, aquatic ecosystems restoration, and human health protection.