Catalytic Ozonation for Effective Degradation of Coal Chemical Biochemical Tail Water by Mn/Ce@RM Catalyst

An Mn/Ce@red mud (RM) catalyst was prepared from RM via a doping–calcination method. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the surface morphology, crystal morphology, and elemental composition of the Mn/Ce@RM catalyst, respectively. In addition, preparation and catalytic ozonation conditions were optimized, and the mechanism of catalytic ozonation was discussed. Lastly, a fuzzy analytic hierarchy process (FAHP) was adopted to evaluate the degradation of coal chemical biochemical tail water. The best preparation conditions for the Mn/Ce@RM catalyst were found to be as follows: (1) active component loading of 3%, (2) Mn/Ce doping ratio of 2:1, (3) calcination temperature of 550 °C, (4) calcination time of 240 min, and (5) fly ash floating bead doping of 10%. The chemical oxygen demand (COD) removal rate was 76.58% under this preparation condition. The characterization results suggested that the pore structure of the optimized Mn/Ce@RM catalyst was significantly improved. Mn and Ce were successfully loaded on the catalyst in the form of MnO2 and CeO2. The best operating conditions in the study were as follows: (1) reaction time of 80 min, (2) initial pH of 9, (3) ozone dosage of 2.0 g/h, (4) catalyst dosage of 62.5 g/L, and (5) COD removal rate of 84.96%. Mechanism analysis results showed that hydroxyl radicals (•OH) played a leading role in degrading organics in the biochemical tail water, and adsorption of RM and direct oxidation of ozone played a secondary role. FAHP was established on the basis of environmental impact, economic benefit, and energy consumption. Comprehensive evaluation by FAHP demonstrated that D3 (with an ozone dosage of 2.0 g/H, a catalyst dosage of 62.5 g/L, initial pH of 9, reaction time of 80 min, and a COD removal rate of 84.96%) was the best operating condition.

Impact of Temperature on the Performance and Character of the Methanogenic Community of a Fixed-Bed Anaerobic Reactor at Psychrophilic Temperature

To determine the effects of a gradual temperature decrease on reactor performance and the microbial community, four fixed-bed reactors that were packed with a biofilm carrier were operated for 217 days. The temperature of the reactors was decreased from 30 °C to 3 °C. The reactors initially soured at 3 °C and recovered when they were returned to 4 °C, as indicated by the stabilization of biogas production, methane production, VFA concentration, pH, and the COD removal rate. Our results also revealed that methanomicrobiales were the dominant methanogen, the concentration of the 16S rRNA gene in the carbon-fiber carrier sludge exceeded the same gene concentration in the deposited sludge, and that the carbon-fiber carrier played an important role in methanomicrobiale colonization at low temperatures. We suggest that 4 °C is the low-temperature threshold for optimal reactor performance.

Enhance nitrogen removal in bioretention cells with addition of hydrothermal pre-treated pine barks as external carbon source

The problem of poor carbon source is a common factor limiting the nutrients removal in bioretention cells (BRCs). This study aimed to investigate the feasibility of using modified biomass in BRCs filled with a mixture of fly ash ceramsite and pumice fillers to enhance nitrogen removal. Different pretreatment methods (hydrothermal-treated, acid-treated and alkali-treated) were attempted, and hydrothermal pretreatment showed a best performance in carbon release ability. The scanning electron microscopy showed that the lignin in hydrothermal pretreated pine barks (H-PBs) was destroyed, and the fiber structure became thinner with more irregular folds, which improved the accessibility of cellulose and attachment of microorganisms. The addition of H-PBs significantly enhanced the nutrients removal in BRCs, and the removal rates of TN and NO3−-N increased by 23.25% and 38.22% compared with those in BRC-A (without external carbon source), but the removal rate of NH4+-N was inferior to BRC-A. Besides, the large carbon release amount of H-PBs did not deteriorate the effluent quality, with COD removal rate of 87.98% in the 48 d. These results indicate that the BRCs by adding H-PBs could intensify the denitrification process.

Performance of anode materials in electrochemical treatment system for indigo dyeing wastewater

Purpose This study aims to explore suitable anode materials used in the electrochemical system for indigo dyeing wastewater, to achieve optimal treatment performances. Design/methodology/approach The single factor experiment was used to explore the optimum process parameters for electrochemical decolorization of indigo dyeing wastewater by changing the applied voltage, electrolysis time and electrolyte concentration. At the voltage of 9 V, the morphology of flocs with different electrolytic times was observed and the effect of electrolyte concentration on decolorization rate in two electrolyte systems was also investigated. Further analysis of chemical oxygen demand (COD) removal rate, anode weight loss and sediment quantity after electrochemical treatment of indigo dyeing wastewater were carried out. Findings Comprehensive considering the decolorization degree and COD removal rate of the wastewater, the aluminum electrode showed the best treatment effect among several common anode materials. With aluminum electrode as an anode, under conditions of applied voltage of 9 V, electrolysis time of 40 min and sodium sulfate concentration of 6 g/L, the decolorization percentage obtained was of 94.59% and the COD removal rate reached at 84.53%. Research limitations/implications In the electrochemical treatment of indigo dyeing wastewater, the aluminum electrode was found as an ideal anode material, which provided a reference for the choice of anodes. The electrodes used in this study were homogenous material and the composite material anode needed to be further researched. Practical implications It provided an effective and practical anode material choice for electrochemical degradation of indigo dyeing wastewater. Originality/value Combined with the influence of applied voltage, electrolysis time and electrolyte concentration and anode materials on decolorization degree and COD removal rate of indigo dyeing wastewater, providing a better electrochemical treatment system for dyehouse effluent.

The influence of electrode spacing on the performance of bioretention cell coupled with MFC

In order to explore the influence of electrode spacing on the performance of the enhanced bioretention system, four bioretention cells with microbial fuel cell (BRC–MFC) systems with different electrode spacing were designed, and the effect of electrode spacing on system performance was revealed by analysing its water treatment capacity and electricity production efficiency. The results showed that BRC–MFC had good water treatment capacity and could produce electricity simultaneously. Compared with other BRC–MFC systems with spacing, the BRC3 system (with an electrode spacing of 30 cm) had significant water treatment capacity under different organic loads, especially under high organic load (C/N = 10) operation, COD removal rate was as high as 98.49%, NH 4 + − N removal rate was as high as 97%, and it had a higher output voltage of 170.46 ± 6.17 mV. It could be seen that proper electrode spacing can effectively improve the water treatment capacity of the BRC–MFC system. This study provided a feasible method for improving the performance of the BRC–MFC system, and revealed the relevant mechanism. A proper electrode spacing with sufficient carbon sources could effectively improve the water treatment capacity of the BRC–MFC system.

Towards Water and Energy Self-Sufficiency: a Closed-Loop, Solar-Driven, Low-Tech Laundry Pilot Facility (LaundReCycle) for the Reuse of Laundry Wastewater

In the scope of this study, a pilot facility for the recycling of laundry effluent was developed and tested. With the aim to enable nearly complete energy and water self-sufficiency, the system is powered by a photovoltaic plant with second-life batteries, treats the wastewater within the unit and constantly reuses the treated wastewater for washing in a closed cycle. The technology for wastewater treatment is based on a low-tech approach consisting of a physical/mechanical pre-treatment and biological treatment in trickling filter columns. The treatment process is operated in batch mode for a capacity of five washing cycles per day. During five weeks of operation water quality, energy consumption and production, water losses and washing performance were monitored. The system recovered 69% of the used water for the washing machine while treating the wastewater to the necessary water quality levels. The average COD removal rate per cycle was 92%. Energy analysis was based on modelled data of the monitored energy consumption. With the current set-up, an internal consumption rate of 80% and self-sufficiency of 30% were modelled. Future developments aim at increasing water and energy self-sufficiency and optimizing the water treatment efficiency.

Catalytic wet peroxide oxidation degradation of magenta wastewater and preparation of FeOCl/montmorillonite

The iron oxychloride/pillared montmorillonite (FeOCl/MMT) catalyst was prepared by wet impregnation method and solid melting method. Various characterization techniques were used to analyze the microscopic morphology and structure of a series of catalysts. Moreover, the catalysts were used to treat magenta simulated dye wastewater through catalytic wet peroxide oxidation (CWPO) degradation. The magenta removal rate and chemical oxygen demand (COD) removal rate of the magenta simulated dye wastewater were used to evaluate the catalytic performance of the catalyst, and the optimal catalyst preparation conditions were selected. The results showed that the solid melting method was more favorable to the preparation of the catalyst, and the COD removal rate of wastewater can reach 70.8% when the FeOCl load was 3%. Moreover, 96.2% of the magenta in the solution has been removed. The COD removal rate of the magenta wastewater decreased by only 12.4% after the catalyst was repeatedly used six times, indicating that the catalyst has good activity and stability. The Fermi equation can simulate the reaction process of the catalyst treating magenta wastewater at high temperature.

Investigation of the effect of magnetic field on the chemical oxygen demand removal of wastewater

This study investigated the effect of magnetic field on the biological treatment of wastewater at varied liquid volumetric flow rates. Wastewater quality is measured by Chemical Oxygen Demand (COD) which quantifies the amount of oxygen required to chemically oxidize organic compounds present in the water. The results obtained from the present study show that at the flow rate of 6.7 x 10⁻⁵ m³s⁻¹ there was a significant effect on the COD removal. At lower flow rates the magnetic field had more time to act on the microorganisms which in-turn increased the COD removal rate. However at flow rates 3.3 x 10⁻⁴ to 1.2 x 10⁻⁴ m³s⁻¹ the effect of the applied magnetic field on the COD removal decreased slightly.

Investigation of the effect of magnetic field on the chemical oxygen demand removal of wastewater

This study investigated the effect of magnetic field on the biological treatment of wastewater at varied liquid volumetric flow rates. Wastewater quality is measured by Chemical Oxygen Demand (COD) which quantifies the amount of oxygen required to chemically oxidize organic compounds present in the water. The results obtained from the present study show that at the flow rate of 6.7 x 10⁻⁵ m³s⁻¹ there was a significant effect on the COD removal. At lower flow rates the magnetic field had more time to act on the microorganisms which in-turn increased the COD removal rate. However at flow rates 3.3 x 10⁻⁴ to 1.2 x 10⁻⁴ m³s⁻¹ the effect of the applied magnetic field on the COD removal decreased slightly.

Preparation and Application of Sewage Sludge Bio-char/zero Valent Iron (SSBC/ZVI) Composite for Improving the Biodegradability of a Real Chemical Synthesis-based Pharmaceutical Wastewater

A new kind of micro-electrolysis filler sewage sludge biochar/zero violent iron (SSBC/ZVI) composite was prepared for a real chemical synthesis based pharmaceutical wastewater (CSPW) pretreatment for improving the biodegradation index (BI). The optimal operation condition of micro-electrolysis system was obtained at HRT of 2 h, the initial pH of 3.0 and filler dosage of 100 g/L, with COD removal rate of 30.5%. Comparative analysis of raw and used SSBC/ZVI filler, GC-MS analysis of raw and treated pharmaceutical wastewater suggested that the pollutants removal was mainly attributed to the combination of reduction and oxidation, absorption of SSBC and flocculation effect of iron sludge. In addition, SSBC/ZVI exhibited relative high stability and excellent reusability for COD removal and BI improvement of real pharmaceutical wastewater. The results of this study provide new ideas of sewage sludge utilization for real wastewater pretreatment.