Treatment Of High-concentration Wastewater Research Articles

Citric acid steam-assisted decomposition method for the synthesis of meso-macroporous magnesium oxide with rich oxygen defects: Efficient removal and convenient recovery property of Congo red and Ni(II)

The removal of Congo red (CR) and heavy metal ion nickel (Ni(II)) from wastewater is a critical concern for safeguarding the aquatic environment and promoting sustainable development. Herein, a novel citric acid steam-assisted decomposition method is applied to form meso-macroporous magnesium oxide (MgO) with rich oxygen defects. As the gelation process of xerogel precursor could be significantly promoted by the steam-assisted process with citric acid solution as steam source, the morphology structure of MgO changes into loose aggregates with sharp edges and is covered by a layer of MgO nanoparticles. The synthesized MgO, with a high surface area (103.60 m2 g−1), meso-macroporous structure and abundant oxygen defects, exhibits super adsorption capacities for CR (7109.85 mg g−1) and Ni(II) (1405.88 mg g−1). The MgO (0.4 g L−1) could completely remove CR (200 mg L−1) in 30 min, while 10 min for Ni(II) (200 mg L−1) adsorption. The adsorption mechanism of MgO for CR and Ni(II), including electrostatic interaction, oxygen vacancy capture, hydrogen bonding and ion exchange, is effectively enhanced due to the appearance of meso-macroporous structure and oxide defects, such as 5-coordinated oxygen anion (O5C2−) for terrace, 4-coordinated oxygen anion (O4C2−) for edge and 3-coordinated oxygen anion (O3C2−) for corner. The easy calcination is applied to recycle MgO after CR adsorption and the CR removal efficiencies are above 98 % after five cycles. Meanwhile, a nickel chelator (Na2EDTA) and calcination are used to regenerate the MgO after Ni(II) adsorption and the adsorbent shows an insignificant removal efficiency loss after three cycles. The meso-macroporous MgO with rich oxygen defects has the characteristics of high adsorption speed, high adsorption capacity and convenient recovery property, and is expected to become an ideal material for the rapid treatment of high concentration wastewater.

Transitional bimetallic heterostructure catalyst modified anode for microbial fuel cell treatment of high-intensity wastewater

In this paper, transitional bimetallic catalysts (FeS2/MoS2) were prepared by a simple one-step hydrothermal method, which were directly applied to MFC anodes for the treatment of high-concentration wastewater with simultaneous biopower generation. The obtained catalysts were highly biocompatible and favorable for inducing the enrichment of electroactive microorganisms and shortening the initiation cycle. The maximum power density (Pmax) and current density of the obtained anode reached 2.87 W·m−2 and 4.37 A·m−2 under 4000 mg·L−1 influent, which were 171% and 65% higher than that of bare carbon cloth, respectively. The chemical oxygen demand (COD) removal rate reached 98.82%. 16 S rRNA gene sequence analysis showed that the main electrophilic microorganisms induced by FeS2/8%MoS2-modified anodes were Synergistota (30.94%) and Geoalkallbacter (15.93%) compared to CC anodes. The resulting anode possesses excellent redox activity and high biocompatibility, and is simple and inexpensive to prepare. More importantly, it accelerated the extracellular electron transfer rate at the interface between the electroactive bacteria and the anode, providing a new idea of choice for single-chamber microbial fuel cells for low-cost treatment of high-concentration wastewater.

Performance optimization of novel multi-unit green wall system for blackwater treatment and reuse on-site

Blackwater constitutes a primary component of environmental pollution posing serious risk to human health; however, reusing the nutrients found in blackwater diminishes the associated pollution and promotes resource recycling. Conventional green-wall systems are not suitable for in situ treatment of high-concentration wastewater. Thereby, a novel multi-unit green-wall system with six independent treatment units was designed to achieve a cost-effective and eco-friendly in situ treatment of blackwater with high organic load. Zeolite carriers were selected for the matrix with carrier depth of 14.5 cm, ivy and chlorophytum were selected as the greening plants. Various pollutants were rapidly reduced at the initial stage and the concentration of the pollutants decreased as the number of treatment units increased. Overall, the green-wall system was more effective in removing COD and NH4+–N with the removal rates of 98.5% and 98%, which may be due to the good buffering capacity of the media and the roles of Firmicutes and Bacteroidetes in COD degradation and ammoniated nitrification reactions. In addition, the maximum TP and TN removal rates were observed with a value of 85% and 42%, respectively. Consequently, the novel multi-unit green-wall system is an effective method for in situ blackwater reuse.Graphical

Bi-element gradient doped B/N-TiO2-x synthesized by one-step solvothermal method enhances the photocatalysis of Cr(VI)

Studying the influence of non-uniform distribution of bi-element doping on the surface structure and photocatalytic performance of TiO2 in interface photocatalytic processes can be an interesting research topic. Taking B/N bi-element doped TiO2 as an example, this article reports an extremely simple gradient doping method of TiO2 and its enhancement mechanism for high concentration wastewater treatment. The surface enrichment and doping of B caused by electrostatic and atomic radius factors changed the charge properties of the complex during the induction of in-situ reduction of Ti4+. The defects in gap N and Ti3+ lead to the formation of intermediate states, resulting in a narrowing of the band gap of the composite to 2.58 eV. The gradient doping of two atoms endows the optimal photocatalyst with a larger specific surface area (114 m2∙g), stronger photocurrent response (0.179 mA·cm−2), suitable Ti3+/Ov double defect structure, and surface positive charge properties. These characteristics improve the effective treatment of high-concentration pollutants by the preferred B2/N-TiO2-x [e.g., 0.0059 min−1 for 0.5 g·L-1 Cr(VI)] and sustainable treatment (removal efficiency > 90 % within 5 cycles). The synthesis strategy will provide a fast, simple, and safe method for the design and synthesis of new TiO2 based catalysts in the future.

AnCMBR-AFB-integrated process for the treatment of high nitrogen and phosphorus wastewater.

Improving the nitrogen and phosphorus removal rates and efficiently controlling membrane fouling are the keys to fully exploiting the applicability of anaerobic membrane bioreactor (AnMBR) process in high-concentration wastewater treatment. To that purpose, an integrated reactor composed of an anaerobic ceramic membrane bioreactor and N anaerobic fluidized bed (AnCMBR-AFB) was built and pollutant removal efficiency, nitrogen and phosphorus recovery characteristics, and membrane pollution features of this integrated reactor were investigated. The results revealed that the integrated reactor had good pollutant removal efficiency, with turbidity, chromaticity, and UV254 average values of the effluent being 0.470 NTU, 0.011 A, and 0.057 cm-1, respectively, and the average CODCr removal rate was 80%. The nitrogen and phosphorus recoveries were significantly higher than the nitrogen and phosphorus removal rates of conventional AnMBR at 23.20 ± 1.17% and 43.34 ± 1.54%, respectively. Microscopic analysis revealed the formation of magnesium ammonium phosphate (MAP) crystals on the carrier's surface, and friction between the carrier and the membrane surface could delay membrane fouling while allowing the contaminated membrane surface to retain significant roughness. Membrane fouling was mostly brought on by amides and saturated hydrocarbons, and inorganic metal ions also played a role to some extent.

Performance optimization of two-stage constructed wetland-microbial fuel cell system for the treatment of high-concentration wastewater.

Constructed wetland-microbial fuel cell (CW-MFC) has attracted much attention because of its dual functions of wastewater treatment and energy recovery. However, its performance in treating high-concentration wastewater is degraded by the decreased dissolved oxygen at the cathode and insufficient electron acceptors. In this study, two CW-MFC systems with cathodic aeration were connected in series to investigate the effects of aeration rate and hydraulic retention time (HRT) on the removal of pollutants and the performance of electricity production in high-concentration wastewater. Results showed that aeration enhanced NH4+-N and TP removal by 45.0-49.8% and 11.5-18.0%, compared with the unaerated condition, respectively. Meanwhile, no significant change regarding COD removal was observed. Aeration enhances the output voltage and power density of the system, especially the first stage CW-MFC, which improved the power production performance by 1 to 2 orders-of-magnitude. Increasing HRT improves the system's pollutant treatment efficiency and power generation performance for high-concentration wastewater. Still, the extension of HRT to 2days will not contribute much to improving the removal efficiency. Under optimized conditions, the maximum total removal rates of COD, NH4+-N, and TP for the two-stage tandem CW-MFC system were 99.3 ± 0.2%, 92.4 ± 1.6%, and 79.5 ± 3.4%, respectively. Meanwhile, the maximum output voltage and maximum power density of the first-stage CW-MFC were 405mV and 138.0mW/m3, respectively. In contrast, the maximum output voltage and maximum power density of the second stage are 105mV and 14.7mW/m3, respectively.

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.

Treatment of High-Concentration Wastewater from an Oil and Gas Field via a Paired Sequencing Batch and Ceramic Membrane Reactor.

A sequencing batch reactor (SBR) and a ceramic membrane bioreactor (CMBR) were used in conjunction (SBR+CMBR) to treat high-concentration oil and gas field wastewater (HCOGW) from the China National Offshore Oil Corporation Zhanjiang Branch (Zhanjiang, Guangdong, China). The chemical oxygen demand (COD) and the oil concentrations in the wastewater were 20,000–76,000 and 600–2200 mg/L, respectively. After the SBR+CMBR process, the effluent COD and oil content values were less than 250 mg/L and 2 mg/L, respectively, which met the third level of the Integrated Wastewater Discharge Standards of China (GB8978-1996). Through microbiological analysis, it was found that the CMBR domesticated a previously unreported functional microorganism (JF922467.1) that successfully formed a new microbial ecosystem suitable for HCOGW treatment. In conjunction with the SBR process, the CMBR process effectively reduced pollutant concentrations in HCOGW. Moreover, economic analyses indicated that the total investment required to implement the proposed infrastructure would be approximately 671,776.61 USD, and the per-unit water treatment cost would be 1.04 USD/m3.

The Controlling Factors and Ion Exclusion Mechanism of Hydrate-Based Pollutant Removal

Theoretically, impurities can be excluded from hydrate structure and pure water can be extracted during hydrate formation. We achieved the heavy metal (Cu2+ in this study) removal from aqueous solution by hydrate process. The hydrate samples were analyzed by X-ray computed tomography (CT). Boundary layer analysis was conducted to reveal the mechanism of ion exclusion. Moreover, the effect of initial concentrations on removal characteristics was analyzed and the solid–liquid separations were optimized. The main findings were as follows: (1) Solution pockets and trapped solution were identified as the limiting and controlling factors for the removal efficiency; (2) nonguest molecule exclusion and directed substance migration occur during hydrate formation; and (3) this method was suitable for relatively high concentration wastewater treatment application, and a removal efficiency of 96.63% could be achieved. We then proposed a theory in regard to the concentration gradient and directed substance migration d...

Premagnetization enhancing the reactivity of Fe0/(passivated Fe0) system for high concentration p-nitrophenol removal in aqueous solution

In order to strengthen the treatment efficiency of Fe0 based system for high concentration wastewater treatment, Fe0 particles were passivated by concentrated nitric acid, and a premagnetization Fe0/(passivated Fe0) system was setup for high concentration p-nitrophenol (PNP) removal in this study. The significant parameters of this system were optimized. Under the optimal conditions, the premagnetization Fe0/(passivated Fe0) system could obtain high kobs value for PNP removal (0.100 min−1) and COD removal (15.0% after 60 min) for high concentration PNP (500 mg/L) treatment. In addition, five control experiments were set up to confirm the advantage of the premagnetization Fe0/(passivated Fe0) system. The results suggest that passivated Fe0 particles could be stimulated better than Fe0 particles by premagnetization process, and the premagnetization Fe0/(passivated Fe0) systems is much superior to the other five control systems. Furthermore, the pathway for PNP destruction treated by 6 different systems was also proposed according to intermediates determination by High Performance Liquid Chromatography (HPLC) and UV–vis spectrum, and the carbon mass balance was demonstrated according to the COD and HPLC analyses. Finally, the characteristics of (premagnetization) Fe0 and passivated Fe0 was detected by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and vibrating sample magnetometer (VSM), and the mechanism of premagnetization effectively enhancing the reactivity of Fe0/(passivated Fe0) system (better than that of Fe0 system) was proposed. Consequently, the premagnetization for reactivity improvement of Fe0/(passivated Fe0) system is a promising technology to enhance the efficiency of this system for high concentration wastewater treatment.

Application of Process on Furfural Wastewater Treatment

The furfural wastewater is kind of highly concentrated organic wastewater. According to its quality and quantity characteristics, this process of micro-electrolysis - photosynthetic bacterial oxidation - biological contact oxidation - biological carbon has been used for treating furfural wastewater. Under the condition that, the mass concentration of influent COD, BOD5 and SS were 8337~15692, 2100~4030, 100~300mg/L respectively, the pH value was 2~3, the effluent water after the treatment met the specification for grade 1 in Integrated Wastewater Discharge Standard GB(8978-1996), which practical proved that, the effect of the treatment process had a high efficiency, impact load is strong and stable operation; using it in furfural wastewater treatment, other high concentration wastewater treatment would be application reference.

Design of Impinging Stream-Cavitations and Micro-Electrolysis Reactor and Treatment of High Concentration Wastewater

A micro-electrolysis reactor combined with the technology of impinging stream-cavitations drum was designed. Then it was used in the treatment of high concentration wastewater. Under the conditions of reaction time is 60 min, ratio of iron to carbon is 1 and the pressure of the air compressor is 8Mpa, the COD and chromaticity could remove 95.7% and 85.9% respectively. The biodegradability was improved obviously with 0.55 of BOD5/COD. The determinations of kinetics under the best conditions show that, the mode of COD removal basically conforms to the rule of first order kinetics. The reaction rate in our reactor was faster than only micro-electrolysis or only cavitations obviously. The conjunction of impinging stream-cavitations and micro-electrolysis has good synergism and facilitation.

Treatment of high-concentration wastewater using double-effect mechanical vapor recompression

A double-effect mechanical vapor re-compression (MVR) evaporation system for the treatment of highly concentrated inorganic salt wastewater was investigated, and its characteristics were analyzed taking ammonium sulfate wastewater as the treated solution. Mathematical models were established based on the energy and mass balance equations as well as correlations of the thermophysical properties and the heat-transfer coefficients. A parametric study was performed to observe the effects of the temperature rise in the heater, the emission concentration of the first effect, the evaporation temperature and the temperature difference between the condensing steam and the boiling solution on the power consumption and on the heat-transfer area. The results showed that the temperature rise should be in the range of 2.5 to 4°C. The power consumption increased as the evaporation temperature decreased and reached a minimum when the first effect emission concentration was approximately 32%. The heat-transfer area decreased as the emission concentration of first effect, the evaporation temperature or the temperature difference between the condensing steam and the boiling solution increased. The model results were found to be consistent with published industrial data. Compared to the single-effect MVR system, the power consumption of double-effect MVR system was lower. Therefore, the system can be used to treat highly concentrated inorganic salt wastewater and can save energy.

Photocatalysis-enhanced electrosorption process for degradation of high-concentration dye wastewater on TiO 2/carbon aerogel

TiO 2/carbon aerogel (TiO 2/CA) electrode was prepared by ambient drying and sol–gel method. Its morphology and surface chemical composition were characterized with SEM, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and Raman spectra. The electrosorption characteristics were investigated with N 2 adsorption, electrochemical impedance spectrum (EIS) and physical resistance. The photocatalytic activity of TiO 2/CA was evaluated by measuring the photocurrent response. The electrode was used in photocatalysis-enhanced electrosorption (PES) treatment of high-concentration (400 mg L −1) alizarin red (AR) wastewater. Results revealed that the efficiency in the PES process with TiO 2/CA electrode was much better than that in traditional electrosorption with CA. In 240 min, AR removal by PES is 97.3%, 3.1 times that of electrosorption. It was found that the in situ photocatalytic regeneration of the adsorbent enhanced the removal capability and stability in treatment of high-concentration wastewater. The degradation intermediates and reaction pathway were also investigated. The AR molecules and intermediates were degraded effectively and mineralized in the PES process. The TOC removal in 240 min was 90.2%.

PCA를 이용한 하폐수처리시설 운전상태진단

축산폐수는 축사가 대부분 상수원보다 상류지역에 산재하고 있어 이를 효과적으로 관리하기 어려우나, 연속 회분식 반응기(Sequencing Batch Reactor, SBR)는 장치가 간단하고 경제성이 우수하여 축산폐수처리에서 효율적으로 적용될 수 있다. 본 연구에서는 DO(Dissolved Oxygen)과 ORP(Oxidation-Reduction Potential)을 이용하여 지식기반 고장진단 시스템을 제안하였다. 실시간으로 얻어진 ORP, DO값들을 전처리하여, [ORP], [DO]외에 [ORP DO]합성data와 ORP, DO의 특징벡터의 합에서 얻어진 fusion data의 총 4개의 data set을 이용하여 각각에 대한 진단과 분류성능을 검토하였다. 이 값을 이용하여 FCM (fuzzy C-mean) 클러스터링 한 후, K-PCA과 LDA로 차원축소시켜 특징벡터를 추출하였다. 그리고 Hamming distance로 test data와 특징벡터의 거리를 계산하여 각 class를 F1에서 F8까지 분류하였다. 그 결과 데이터를 그대로 이용하는 것 보다 차분데이터형태로 이용하는 것이 우수했으며 그 중 fusion 데이터의 결과가 다른 것들보다 향상된 결과를 보였다. 그리고 K-PCA와 LDA를 결합한 결과가 다른 방법에 비해 우수한 결과를 보였으며 fusion method를 이용한 최고인식율은 98.02%를 나타내었다. SBR is one of the most general sewage/wastewater treatment processes and, particularly, has an advantage in high concentration wastewater treatment like sewage wastewater. A Kernel PCA based fault diagnosis system for biological reaction in full-scale wastewater treatment plant was proposed using only common bio-chemical sensors such as ORP(Oxidation-Reduction Potential) and DO(Dissolved Oxygen). During the SBR operation, the operation status could be divided into normal status and abnormal status such as controller malfunction, influent disturbance and instrumental trouble. For the classification and diagnosis of these statuses, a series of preprocessing, dimension reduction using PCA, LDA, K-PCA and feature reduction was performed. Also, the diagnosis result using differential data was superior to that of raw data, and the fusion data show better results than other data. Also, the results of combination of K-PCA and LDA were better than those of LDA or (PCA+LDA). Finally, the fault recognition rate in case of using only ORP or DO was around maximum 97.03% and the fusion method showed better result of maximum 98.02%.

Kinetic and Performance Characteristics of Wet Air Oxidation of High-Concentration Wastewater

Treatment of high-concentration wastewater from a chemical company by wet air oxidation (WAO) is studied. Experiments were conducted to investigate the effects of the operating pressure and temperature on the chemical oxygen demand (COD) removal. Both air and oxygen were employed as the oxygen supply for the WAO treatment process. Catalytic effects of copper sulfate, cobalt oxide, and zinc oxide on the WAO efficiency were also examined. It was found that over 50% of COD removal can be easily realized in an hour of WAO oxidation. Two kinetic models (first-order and generalized) were employed to represent the experimental data, and their fit to those experimental data was compared. The rate coefficients and the kinetic parameters of the two models were determined also.

多孔性セラミックス充填嫌気性固定床による高濃度排水処理

多孔性セラミックス充填嫌気性固定床による高濃度排水処理