High-concentration Wastewater Research Articles

Enhanced permeability and stability of PVDF hollow fiber membrane in DCMD via heat-stretching treatment

Membrane distillation (MD) demonstrates excellent desalination application potential for high salt concentration wastewater. However, keeping the membrane flux and rejection high during long-term operation remains one of the critical challenges. In this work, a heat-stretching treatment method was proposed to improve the structure of polyvinylidene fluoride (PVDF) hollow fiber membrane and enhance its stability in the MD process. The membrane's pore size decreased after a heat-stretching treatment in water at 120 °C for 1 h. However, the liquid entry pressure of water (LEPw) value and membrane strength increased significantly, making it less prone to pore deformation during the drying or MD process and thus improving the membrane flux and stability in the MD process. The heat-stretching treatment made the PVDF chain arrangement more compact and oriented, avoiding shrinkage in the length direction. Besides stretching, the shrinkage of hollow fiber can be constricted by the combinedeffects of pore filling and stretching due to water or glycerol filling in the membrane pores, thus eliminating the capillary stress caused by liquid evaporation during the air-drying. Consequently, the heat-stretching treatment broke the trade-off between high permeate flux and high stability in the MD process.

Removal of COD and TSS from tomato ketchup industrial wastewater using cylindrical electrocoagulation method

Tomato ketchup industrial sector is associated with various environmental problems including high concentration wastewater containing organic pollutant and suspended solid. While the industry always considers from an economic point of view, electrocoagulation can be the best alternative of treat wastewater which has the advantage easy in operation, minimum space requirements, low volumes of sludge produced, and can be used in high concentration wastewater. This paper investigated the effect of pH and current electricity on performance of removal of COD and TSS in tomato ketchup wastewater treatment. The research was conducted in continuous flow using cylindrical reactor with rod aluminum anode dan helical stainless-steel cathode, while the pH and current variations were 6, 7, 8 and 30 A, 35 A, and 40 A respectively. Based on analyzed data, aluminum has an effectiveness in COD and TSS removal. On the other hand, pH and current has a significant role on the process of removing COD and TSS. The best removal of COD and TSS was under the 35 A and pH 8 condition with 81,86 % (103.24 gCOD) and 82.61% (6.48 gTSS).

Removal Performance of Suspended Solid (SS) and Organic Compounds in the Pre-treatment of Actual Pharmaceutical Wastewater by Microbubble Ozonation

Actual pharmaceutical wastewater was pretreated with ozone microbubbles and compared with the treatment processes of nitrogen microbubbles, ozone common bubbles, and nitrogen common bubbles. The removal process and performance of suspended solids (SS) and organic compounds were investigated. The results showed that ozone microbubble treatment with strong adsorption-flotation-oxidation effects could enhance SS removal significantly, and the corresponding SS removal efficiency reached 81.67% at 60 min. The SS particle size was reduced, and the negative charge on the SS surface was simultaneously changed into a positive charge. Microbubble ozonation with a strong·OH oxidation effect also significantly enhanced the degradation and removal of organic compounds. The removal efficiency of soluble COD (SCOD) reached 36.60% at 60 min, and the SCOD removal was accelerated after the SS removal. The removal efficiency of UV254 also reached 36.91%. The biodegradability was improved, and the biological toxicity was obviously eliminated. The analysis of three-dimensional fluorescence and GC-MS showed that the macromolecular organic compounds with complex structure could be oxidized and decomposed efficiently with microbubble ozonation, resulting in the aromatic reduction in organic compounds in wastewater. Therefore, microbubble ozonation could be considered as an efficient and feasible pretreatment method for high concentration and refractory pharmaceutical wastewater.

Influence of Wastewater Content on Mechanical Properties, Microstructure, and Durability of Concrete

In this study, high concentration wastewater from ready-mixed concrete plants was used to replace potable water as mixing water of concrete, with replacement rates of 0%, 25%, 50%, 75%, and 100%, by weight. The solid content of the wastewater was 12%. Five groups of C20 concrete mix proportions were designed. Different concrete properties, including workability, compressive strength and durability under freeze–thaw cycles, carbonization, and drying conditions, were studied, and the effect of the increase in the proportion of wastewater as a replacement for potable water was investigated. The microstructural attributes of the developed C20 concrete were studied through X-ray diffraction (XRD), thermal analysis (TG-DSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), and mercury intrusion porosimetry (MIP). Finally, the economic benefits of replacing potable water with wastewater were analyzed. The results indicate that using wastewater for concrete mixing reduces workability and a superplasticizer is needed to ensure adequate concrete workability. At the ages of 7, 28, and 56 days, with the increase in the proportion of wastewater as a replacement for potable water (0, 25%, 50%, 75%, 100%), the compressive strength of concrete shows a trend of first decreasing, then increasing, and then decreasing. When the proportion of wastewater replacing potable water is 75%, the concrete compressive strength is the highest. The microstructure showed that the main products of wastewater-mixed concrete are calcite (CaCO3), portlandite (Ca(OH)2), ettringite (Aft), and calcium silicate hydrate (C-S-H). Adding wastewater to concrete does not lead to the formation of new products in the concrete. Wastewater can fill the concrete pores well, thus optimizing the pore structure. When the proportion of wastewater replacing potable water is 75%, C20 concrete has the densest microstructure, lower porosity, and better pore structure. Durability properties further indicate that 25%, 50%, and 75% of wastewater replacing potable water can improve the concrete’s frost resistance. However, there is a negative impact on the carbonation resistance of wastewater. Wastewater replacing 75% potable water by weight can improve the drying shrinkage of concrete. The recycling of wastewater is not only green and environmentally friendly but also has good economic and environmental benefits.

막증발법 공정에서 셰일가스 플랜트 용수 처리: 막 오염 효과

The increase in shale gas production in recent years has resulted in environmental and water management challenges because the water utilized in hydraulic fracturing contains many pollutants. Therefore, the treatment of this wastewater has received significant attention. In the present study, the feasibility of membrane distillation for the treatment of wastewater from shale gas plants was examined. The results indicated that direct-contact membrane distillation (DCMD) is suitable for treating both low-range and high-range flowback water. Based on theoretical calculations and long-term experiments, DCMD was shown to achieve a recovery rate of over 70%. However, the flux abruptly decreased above this critical recovery rate due to membrane fouling. The examination of fouled membranes using scanning electron microscopy revealed that scale was the major source of fouling. In order to ensure that DCMD can become a reliable next-generation desalination technology, the membrane fouling mechanisms were investigated in more detail. This study confirmed that DCMD could be used to treat high-concentration wastewater, but membrane wetting occurred due to scale formation, oil, and grease. Moreover, oil and surfactants were identified as serious obstacles to the use of DCMD because they cause membrane wetting.

Enhancement of the immobilization on microalgae protective effects and carbamazepine removal by Chlorella vulgaris.

Carbamazepine (CBZ) has drawn extensive attention due to their environmental threats. In this study, polyvinyl alcohol-sodium alginate polymers to immobilize Chlorella vulgaris (FACHB-8) were used to investigate whether immobilization can facilitate microalgae to alleviate the CBZ stress and enhance CBZ removal. The results showed that after immobilized treatment, the biomass of microalgae increased by approximately 20%, the maximum level of malondialdehyde content decreased from 28 to 13 μmol/g, and the photosynthetic capacity of FV/FM recovered to 90% of the control group. The CBZ removal rate increased from 67 to 84% by immobilization at a CBZ concentration of 80 mg·L-1. The results indicated that immobilization technology can effectively protect microalgae from CBZ toxicity and improve the removal of CBZ, especially at high concentrations (> 50 mg/L). Biodegradation was the dominant pathway for microalgae to remove carbamazepine. This study added the understanding of the microalgae responses under immobilization and the interactions between immobilized microalgae and CBZ removal, thereby providing a novel insight into microalgae technology in high concentration wastewater treatments.

Performance of Ti/RuO2-IrO2 electrodes and comparison with BDD electrodes in the treatment of textile wastewater by electro-oxidation process

Electrochemical oxidation (EO) technology, which may directly reduce refractory contaminants into simple inorganic molecules like H2O and CO2, is an efficient approach for treating high-concentration wastewater. Boron doped diamond (BDD) electrodes has been extensively researched and used to degrade organic contaminants from real textile wastewater. In this study, two-dimensionally stable anodes, Ti/RuO2-IrO2, were produced and compared with BDD electrodes for the treatment of textile wastewater. This study focuses on the optimization of the produced electrode under different pH and current densities. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that the oxide coating on the Ti plate’s surface was effectively produced. The EO process parameters were optimized using central composite design (CCD) under response surface methodology (RSM), with total organic carbon (TOC), chemical oxygen demand (COD), and color removals as responses and pH, current density, and reaction time as control variables. The analysis of variance (ANOVA) revealed good coefficients of determination (R2) values of.0.90, indicating that the second-order regression model matched the experimental data satisfactorily. In optimized conditions, pH 4 was shown to have the maximum effectiveness for both electrodes. The best treatment efficiency was obtained by applying an 800 A/m2 current for 5 h, taking into account the time component in the different current values employed. BDD had a color, TOC, and COD removal of 93%, 75%, and 48%, respectively, whereas Ti/RuO2-IrO2 had a color, TOC, and COD removal of 88%, 62%, and 41%, respectively. In addition, the toxicity of water treated with the BDD electrode was found to be lower, whereas the toxicity of water treated with the Ti/RuO2-IrO2 electrode was found to be higher.

Visible-light-driven photocatalytic degradation of dye and antibiotics by activated biochar composited with K+ doped g-C3N4: Effects, mechanisms, actual wastewater treatment and disinfection

To improve the performance of graphitic carbon nitride (g-C3N4), a hotly researched metal-free photocatalyst, for better application in the efficient removal of organic pollutants, adsorption synergistically enhanced photocatalysis mechanism was thoroughly explored. Based on KOH pore-forming activated biochar (ACB) and K+ doped g-C3N4 (K-gC3N4), the novel activated biochar-based K-gC3N4 composite (ACB-K-gC3N4) was synthesized via the innovative ultrasonic-milling method. Rhodamine B (RhB), tetracycline (TC), norfloxacin (NOR), and chloramphenicol (CAP) were selected as target pollutants, and the effects of environmental factors, recycling and actual wastewater tests, disinfection effects, and various enhancement strategies were investigated. The results showed that K-gC3N4 was successfully composited with ACB by various characterizations, where the loading mass ratio of 1:2 exhibited the best performance. ACB-K-gC3N4 possessed a larger specific surface area, richer functional groups, suitable band gap (2.29 eV), and broader visible light absorption (~716 nm) than K-gC3N4. ACB-K-gC3N4 presented effective removal efficiency over K-gC3N4 for four pollutants, in which the removal efficiency of RhB reached 93.26%, and the degradation rate constant of 0.0119 min−1 was four times higher than K-gC3N4 (0.0029 min−1). Moreover, ACB-K-gC3N4 was superior to K-gC3N4 in disinfecting S. aureus and E. coli, with a sterilization rate of exceeding 90% for 12 h. The photodegradation activity was dominated by ·O2−, h+, and ·OH, and the mechanisms involved in the three stages. This was attributed to the unique structure and surface properties (defects and persistent free radicals) of ACB, as evidenced by improved adsorption stage and transfer of degradation intermediates, facilitated the generation of active species, accelerated migration of photogenerated electrons, and inhibited photogenerated carriers recombination by the heterojunction. The good reusability and stability, enhancement strategies (blowing air and heating), and satisfactory feasibility for actual wastewater allow ACB-K-gC3N4 possible to promote high-concentration wastewater treatment and disinfection.

P/N co-doped carbon sheet for peroxymonosulfate activation: Edge sites enhanced adsorption and subsequent electron transfer

A controllable synthetic route of carbon nanosheets co-doped with phosphorus and nitrogen was developed by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and carbon sheet. The as-prepared catalyst has shown a substantially increased efficiency for peroxymonosulfate (PMS) activation in the degradation of tetracycline (TC). The roles of dopants and edge sites were systematically investigated by both experimental characterizations and theoretical simulations. Compared with the undoped catalyst, the P/N co-doped catalyst has substantially enhanced the adsorption of PMS/TC and the subsequent electron transfer process, which is recognized as the dominant nonradical mechanism. Consequently, an efficient catalytic activity was obtained for the degradation of TC as well as other pollutants even under high salinity (500 mM) and high concentration wastewater (500 ppm). This work not only presents a non-metallic carbocatalyst with high catalytic activity for extensive environmental remediation, but also provides new insights into the edge P/N co-doping effects on the electron-transfer dominated nonradical activation of PMS.

Influence of aeration intermittency on nitrogen removal in a reactor with aerobic granular sludge treating wastewater

The process of aerobic granular sludge (AGS) has been considered an alternative of great interest for the tertiary wastewater treatment mainly due to the great capacity of granule densification, which makes the system very compact. The simultaneous nitrification and denitrification (SND) occurrence guarantees nitrogen removal at a high level of efficiency and biological phosphorus removal can be optimized in this arrangement with a single treatment stage in sequential batches. In this study, the general behavior of a sequential batch reactor (SBR)/AGS in wastewater treatment and the effect of the air supply regime on nitrogen removal were evaluated. A pilot scale system supplied by relatively high concentration wastewater in a warm climate region was set up over 525 days. The study was divided into three main phases. In Phase I, a cycle of 3 h of total duration and continuous aeration of the sludge was applied with high efficiency in the removal of soluble chemical oxygen demand (sCOD) from the wastewater, but excessive drag of total suspended solids (TSS) with the effluent persistently occurred throughout the cycle. Nitrification went well, but wastewater denitrification was only partial with a notorious and worrisome accumulation of nitrite. In Phase II, the total cycle duration was increased to 4 h, but this increase in the time available for the anoxic and aerobic reactions was not enough to control the problem and the nitrite and nitrate residuals remained high in the effluent. In Phase III, the implementation of an intermittent aeration regime led to the production of an effluent from the treatment system with ammoniacal nitrogen, nitrite and nitrate average concentrations of 4.3 mg N·L−1, 0.4 mg N·L−1 and 5.5 mg N·L−1, respectively. Surveys of concentration profiles were carried out over some batches and it was observed that denitrification occurs mostly simultaneously with nitrification during the aeration period. The general conclusion of this study is that the application of intermittency regime in the air supply of AGS is of great importance for the improvement of nitrogen removal in this process.

Functionalized polymethyl methacrylate-modified dialdehyde guar gum containing hydrazide groups for effective removal and enrichment of dyes, ion, and oil/water separation

In the study, a novel polymethacryloyl hydrazone modified guar gum adsorption material (GSA) was prepared via condensation between polyhydrazide and dialdehyde guar gum. GSA exhibited an abundant porous structure, higher selectivity for cationic pollutants in high-concentration wastewater like methylene blue (MB), malachite green (MG) dyes, and Cu2+. Under optimized experimental conditions, the maximum equilibrium adsorption capacity of MB, MG, and Cu2+ were 1418.36 mg/g, 1375.58 mg/g, and 196 mg/g, respectively. Adsorption isotherms and kinetics were well fitted with the Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic analysis demonstrated that the adsorption process was endothermic, feasible, and spontaneous. Correspondently, the adsorption mechanism was explored by FTIR, SEM-EDS and XPS. The adsorbent was employed in disposing of local sewage water. Additionally, GSA successfully achieves efficient water/oil separation in different salt concentrations with a separation efficiency exceeding 99%.

New Technology for Degradation of Wastewater Containing High Concentrations of COD and Boron Based on Manganese-Iron Oxide Catalytic Support

The existing methods for simultaneous treatment of wastewater containing high concentrations of chemical oxygen demand (COD) and boron are too cumbersome and require a relatively long treatment time. The traditional oxidation method is easy to cause a large amount of sludge and other secondary pollution. Therefore, in this research, the wastewater was oxidized by the self-synthesized manganese-iron oxide catalytic support. This oxidation and adsorption combined method significantly increased the efficiency of wastewater treatment, reduced the treatment time and the replacement frequency of consumables. The efficiency in degradation of high-concentration COD (25,250 mg/L) was more than 90%, which could be reached within 40 min, while that of boron (500 mg/L) could reach above 95% within 20 min. After optimization of the parameters (daily treatment capacity: 5CMD) was combined to treat high-concentration wastewater containing high concentrations of COD (14,700 mg/L) and boron (486 mg/L), with treatment efficiency approaching 100% within 20 min. As proved by the research results, after being treated by the new manganese-iron oxide catalytic support and activated carbon, the wastewater has reached the emission standard and can be discharged directly. This combined method provides a new way for the treatment of wastewater containing high concentrations of COD and boron.

Preparation of Magnetic Alginate-Based Biogel Composite Cross-Linked by Calcium Ions and its Super Efficient Adsorption for Direct Dyes

Magnetic sodium alginate (SA)-based biosorbent Fe₃O₄@SA-Ca gel beads were synthesized by droplet polymerization using Ca2+ ions as crosslinking agent, and characterized by Scanning Electron Microscopy (SEM). Fe₃O₄@SA-Ca polymer was used for the removal of Direct Orange 26 (DO-26) dye from water. The ratio of raw materials and some important conditions affecting the adsorbent performance were carefully examined. The adsorption kinetics, isotherms and thermodynamics were investigated. When the concentrations of SA, CaCl2 and Fe3O4 solutions were 1.9, 10 and 10 g/L, respectively, the black Fe₃O₄@SA-Ca gel beads with about 3 mm diameter were successfully prepared by curing 6h at room temperature. The polymer gel exhibits ultra-high adsorption capacity of 1252 mg/g and removal efficiency of 96.2 % for DO-26 under the conditions of 0.05 g polymer dosage, 2600 mg/L of dye initial concentration, solution pH 2.0 and 90 min of the adsorption time at 298 K. The dye removal efficiency can be all over 92 % in a wide pH range of 2.0 to 10.0. The adsorption process completely accorded with the pseudo-second-order rate model at different temperatures (298 ~ 328 K). The dye adsorption behavior was well in line with Freundlich model. The thermodynamic study indicated that the adsorption reaction was of spontaneous and exothermic nature. SEM analysis showed that the Fe₃O₄@SA-Ca gel beads appeared uneven surface with irregular folds and grooves. A high-cost-effective magnetic biosorbent, Fe₃O₄@SA-Ca can super effectively remove direct dyes from high-concentration wastewater in a wide range of acidity, and can be easily separated and recovered from water after adsorption without secondary pollution, and would have a good application prospect.

Degradation of enrofloxacin by photocatalysis using titanium dioxide nanomaterials

This work evaluates the ability to degrade Enrofloxacin (ENR) in synthetic high concentration wastewater by the photocatalytic method using pure TiO2 nanomaterials. The material properties, including morphology, crystalline structure, UV-Vis absorption, and surface acidity-basicity, were also characterized. The treatment efficiency of 50 mgENR/L reached over 80% after 2 h of UVA irradiation, at pH 6 and 1 gP25/L. The antibacterial level of ENR after treatment was checked by Bacillus subtilis activity. After treatment, the activity of ENR residue was no longer sufficient to cause inhibition of the bacteria while the degraded product was not toxic to it. The research results show that the photocatalysis material has a good ability to degrade ENR as well as other antibiotic residues in the water environment.

A novel pretreatment biotechnology for increasing methane yield from lipid-rich wastewater based on combination of hydrolytic enzymes with Candida rugosa fungus

Lipid-rich wastewater from the local dairy industry (cheese whey) in the Galilee, Israel was hydrolyzed by using two different sources of lipase as hydrolytic enzymes: fungal (Candida rogusa lipase-AY) and animal porcine pancreatic lipase(PPL). Pretreatment efficiency was verified by comparative biodegradability tests of raw and treated wastewater samples. Simultaneous hydrolysis and anaerobic digestion in the same reactors were also tested. Enzymatic pretreatment of these samples at a concentration of 0.05 w v−1 showed organic matter removal of 90% and methane formation increases of 140% for the fungal source enzyme (i.e., AY), while for the animal source enzyme (i.e., PPL) was 86 and 130%, respectively. Enzymatic pretreatment led to significant methane formation which was obtained only for moderate substrate concentration (initial chemical oxygen demand of 15 gL−1); While in high concentrated lipid-rich wastewater led to methane yield inhibition. The main finding was that the combination of AY enzyme with Candida rugosa fungus (i.e., enzyme mixture) led to a high efficiency in methane production (+152%) and organic materials removal (more than 90%). In summary, the use of fungal hydrolytic lipase mixed with Candida rugosa fungus is a promising method for enhancing methane production during the biodegradation of fat and grease-rich wastewaters.

A coupled system of flow-through electro-Fenton and electrosorption processes for the efficient treatment of high-salinity organic wastewater

The traditional high-salinity organic wastewater treatment process is cumbersome and costly, and involves an independent process for removing pollutants and salinity. A flow-through coupled system of electro-Fenton and electrosorption processes was designed in this work. The simultaneous purification and desalination of high concentration wastewater were effectively achieved through the cooperation of various electrochemical reactions, which avoids the complex processes of desalination and dilution in advance when treating high-salinity organic wastewater, and the removal performance was improved. The influence of key parameters, including voltage, initial pH, plate spacing, H2O2 concentration, and flow rate, were systematically investigated. The findings show that actual wastewater passing through the coupled system promptly turns to clean water with significantly decreased COD, TN, and salinity, with removal efficiencies reaching 96.5%, 98.2%, and 46.2%, respectively, under the optimal conditions (voltage intensity 1.5 V, initial pH 4, plate spacing 1 cm, flow rate 40 mL/min, H2O2 concentration 50 mM). The reaction mechanism study suggested that both the Fenton reaction, direct electron transfer, and indirect oxidation by active chlorine contributed to the removal of COD and TN, while the decrease in salinity mainly occurred in the process of electrosorption. Moreover, the regeneration of the ACF and the operational stability of the coupled system were good after five cycles. The economic analysis indicated that the cost of the flow-through coupled system was only $1.18/m3, which has important benefits.

Enhancing High-concentrated Wastewater Quality on Evaporation Rate from Five-Consecutive Oxidation Ponds as Located in Phetchaburi, Southerly Thailand

This research aimed to examine the environmental factors determining the rates of evaporation, a natural phenomenon contributing to the treatment of wastewater of 5-consecutive oxidation ponds of the King’s Royally Initiated Laem Phak Bia Environmental Research and Development Project. Data collected from the 17th of April to 30th of May 2019 by US Class A Evaporation Pan revealed that the sedimentation pond (Pond 1) has the highest rate, 7.22 mm d-1, the oxidation pond 1 (Pond 2), 5.70 mm d-1, the oxidation pond 3 (Pond 4), 5.56 mm d-1, the stabilization pond (Pond 5), mm d-1, the reference pond at 5.07 mm d-1 and the oxidation pond 2 (Pond 3), 3.59 mm d-1. Concluding the evaporation in domestic wastewater treatment plants is characterized by 1) heat generated from short and long wave radiation emitted by earth and the sun, 2) local wind profiles of the area affected the height differences of the roughness length, and 3) heat generated by the respiration and digestion process of microbial activities and other grey body contaminants. Presenting the day and night variations made for the analysis, the day evaporation was significantly higher resulted by the net radiation were accountable. Wind profile generated from the measurement of speeds and directions at two different sites at 3 and 10 m has explained for the roughness length heights over each pond as lower roughness height have cause the increased in the rates of evaporation in Pond 4 and 5 however, these process were also suppressed by high ionic bonding molecules effected suggested by the high TDS and EC values. The vertical temperature profile has conveyed the movement in the heat flux that dominated an upward flux movement in Pond 1. This is the exothermic reaction from the digestion process have suggested that extra heat has been added.

Ti/RuO2-IrO2-SnO2 Anode for Electrochemical Degradation of Pollutants in Pharmaceutical Wastewater: Optimization and Degradation Performances

Electrochemical oxidation technology is an effective technique to treat high-concentration wastewater, which can directly oxidize refractory pollutants into simple inorganic compounds such as H2O and CO2. In this work, two-dimensionally stable anodes, Ti/RuO2-IrO2-SnO2, have been developed in order to degrade organic pollutants from pharmaceutical wastewater. Characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) showed that the oxide coating was successfully fabricated on the Ti plate surface. Electrocatalytic oxidation conditions of high concentration pharmaceutical wastewater was discussed and optimized, and the best results showed that the COD removal rate was 95.92% with the energy consumption was 58.09 kW·h/kgCOD under the electrode distance of 3 cm, current density of 8 mA/cm2, initial pH of 2, and air flow of 18 L/min.

Microbial Community Analysis of Different DN and PN-ANAMMOX Coupling Modes for Mature Landfill Leachate Treatment

To promote the application of ANAMMOX process in landfill leachate treatment, a pilot reactor based on the ANAMMOX process was established at a landfill site. In this paper, we aim to further analyze the influence of different coupling modes of denitrification (DN) and partial nitrification and ANAMMOX (PN-ANAMMOX) on the diversity of microbial community. The DN+(PN-ANAMMOX) process could effectively treat the mature leachate. However, with an increase in organic matter in the influent, the oxygen demand of PN zone increased, and the enrichment of Nitrosomonadaceae in the PN zone was limited. The lack of substrate supply for ANAMMOX zone further limited the enrichment of Brocadiaceae as well; thus, the total nitrogen removal rate (TNRR) remained at 0.44 kg ·(m3 ·d)-1. In the DN-(PN-ANAMMOX) process, Saprospiraceae with denitrifying ability was enriched in the DN zone, and the organic matter was gradually degraded and removed; thus, a good low-carbon environment was provided for the subsequent PN-ANAMMOX process. Nitrosomonadaceae and Brocadiaceae were enriched in the functional zones, and the TNRR and total nitrogen removal efficiency (TNRE) of the DN-(PN-ANAMMOX) were further elevated to 0.55 kg ·(m3 ·d)-1 and 94.65%, respectively. Moreover, the direct treatment of mature leachate with 2233 mg ·L-1 NH4+-N and 2712 mg ·L-1 COD was finally realized. In addition, Candidatus Kuenenia was better adapted to leachate and high substrate concentration wastewater, and it became the dominant genus in the ANAMMOX zone.

Micro-pressure swirl reactor (MPSR) for efficient COD and nitrogen removal of high-concentration wastewater.

A micro-pressure swirl reactor (MPSR) was developed for carbon and nitrogen removal of wastewater, in which dissolved oxygen (DO) gradient and internal circulation could be created by setting the aerators along one side of the reactor, and micro-pressure could be realized by sealing most of the top cap and increasing the outlet water level. In this study, velocity and DO distribution in the reactor was measured, removal performance treating high-concentration wastewater was investigated, and the main functional microorganisms were analyzed. The experiment results indicated that there was stable swirl flow and spatial DO gradient in MPSR. Operated in sequencing batch reactor mode, distinct biological environments spatially and temporally were created. Under the average influent condition of chemical oxygen demand (COD) concentration of 2,884 mg/L and total nitrogen (TN) of 184 mg/L, COD removal efficiency and removal loading was 98% and 1.8 kgCOD/(m3·d) respectively, and TN removal efficiency and removal loading reached up to 90% and 0.11 kgTN/(m3·d) respectively. With efficient utilization of DO and simpler configuration for simultaneous nitrification and denitrification, the MPSR has the potential of treating high-concentration wastewater at lower cost.