Tianlong Zheng

Microbubble enhanced ozonation process for advanced treatment of wastewater produced in acrylic fiber manufacturing industry

This work investigated microbubble-ozonation for the treatment of a refractory wet-spun acrylic fiber wastewater in comparison to macrobubble-ozonation. CODcr, NH3-N, and UV254 of the wastewater were removed by 42%, 21%, and 42%, respectively in the microbubble-ozonation, being 25%, 9%, and 35% higher than the removal rates achieved by macrobubble-ozonation at the same ozone dose. The microbubbles (with average diameter of 45μm) had a high concentration of 3.9×10(5) counts/mL at a gas flow rate of 0.5L/min. The gas holdup, total ozone mass-transfer coefficient, and average ozone utilization efficiency in the microbubble-ozonation were 6.6, 2.2, and 1.5 times higher than those of the macrobubble-ozonation. Greater generation of hydroxyl radicals and a higher zeta potential of the bubbles were also observed in the microbubble ozonation process. The biodegradability of the wastewater was also significantly improved by microbubble-ozonation, which was ascribed to the enhanced degradation of alkanes, aromatic compounds, and the many other bio-refractory organic compounds in the wastewater. Microbubble-ozonation can thus be a more effective treatment process than traditional macrobubble-ozonation for refractory wastewater produced by the acrylic fiber manufacturing industry.

Advanced treatment of wet-spun acrylic fiber manufacturing wastewater using three-dimensional electrochemical oxidation

A three-dimensional electrochemical oxidation (3D-EC) reactor with introduction of activated carbon (AC) as particle micro-electrodes was applied for the advanced treatment of secondary wastewater effluent of a wet-spun acrylic fiber manufacturing plant. Under the optimized conditions (current density of 500A/m2, circulation rate of 5mL/min, AC dosage of 50g, and chloride concentration of 1.0g/L), the average removal efficiencies of chemical oxygen demand (CODcr), NH3-N, total organic carbon (TOC), and ultraviolet absorption at 254nm (UV254) of the 3D-EC reactor were 64.5%, 60.8%, 46.4%, and 64.8%, respectively; while the corresponding effluent concentrations of CODcr, NH3-N, TOC, and UV254 were 76.6, 20.1, and 42.5mg/L, and 0.08Abs/cm, respectively. The effluent concentration of CODcr was less than 100mg/L, which showed that the treated wastewater satisfied the demand of the integrated wastewater discharge standard (GB 8978-1996). The 3D-EC process remarkably improved the treatment efficiencies with synergistic effects for CODcr, NH3-N, TOC, and UV254 during the stable stage of 44.5%, 38.8%, 27.2%, and 10.9%, respectively, as compared with the sum of the efficiencies of a two-dimensional electrochemical oxidation (2D-EC) reactor and an AC adsorption process, which was ascribed to the numerous micro-electrodes of AC in the 3D-EC reactor. Gas chromatography mass spectrometry (GC-MS) analysis revealed that electrochemical treatment did not generate more toxic organics, and it was proved that the increase in acute biotoxicity was caused primarily by the production of free chlorine.

Pilot-scale experiments on brewery wastewater treatment and sludge reduction based on food chain predation

AbstractIn a pilot-scale experiment, hydrolyzation-food chain reactor (H-FCR) system was used to treat brewery wastewater. The performance of the system, including COD, BOD5, NH3-N, SS removal, and sludge reduction, were investigated. The mechanism of sludge reduction and the characteristics of biological community during multilevel contact oxidation process were also explored. The food chain reactor (i.e. four-level contact oxidation reactor with a volume ratio of 4:3:3:2) was found to be contributory to the provision of a suitable environment for the formation of the food chain of bacteria–protozoa–metazoan–larger metazoan. The ratio of metazoan density to protozoa density and metazoan density to bacteria density increased gradually with COD concentration reduction along the flow direction. This change strengthened the role of predation in reducing sludge production from the source. The sludge production decreased to 8.15% kg suspended sludge/(kg COD removed). The formation of the food chain also provid...

Separation of Pollutants from Oil-Containing Restaurant Wastewater by Novel Microbubble Air Flotation and Traditional Dissolved Air Flotation

Novel microbubble air flotation (MAF) and traditional dissolved air flotation (DAF) systems were compared based on the separation ability of pollutants from oil-containing restaurant wastewater, which was used to verify the strengths of MAF system. The results showed that, when the operational parameters were a PAC dosage of 20 mg/L, reaction time of 15 min, operational pressure of 0.35 MPa, and reflux ratio of 25%, the removal efficiencies of oil, CODcr, and turbidity in MAF were 10.3%, 22.6%, and 15.0% higher than that in DAF, respectively. The maximum removal efficiencies of oil and turbidity in the MAF system were 98.0% and 97.5%. In addition, the minimum microbubble diameter in the MAF system was 20 µm under the operational pressure of 0.9 MPa, which could be successively and steadily produced. The maximum oil removal efficiency was achieved in the MAF system when the microbubbles and oil-droplets were similar sizes. Therefore, the application of the MAF technology could alleviate the pressure of downstream treatment of oil-containing wastewater.

Wastewater-nitrogen removal using polylactic acid/starch as carbon source: Optimization of operating parameters using response surface methodology

Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid (PLA)/starch blends as carbon source and carrier for functional bacteria. The exclusive and interactive influences of operating parameters (i.e., temperature, pH, stirring rate, and PLA-to-starch ratio (PLA proportion)) on nitrification (Y1), denitrification (Y2), and COD release rates (Y3) were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous nitrification and denitrification. The carbon release rate of the blends was controllable. The sensitivity of Y1, Y2, and Y3 to different operating parameters also differed. The sequence for each response was as follows: for Y1, pH>stirring rate>PLA proportion>temperature; for Y2, pH>PLA proportion>temperature> stirring rate; and for Y3, stirring rate>pH>PLA proportion>temperature. In this study, the following optimum conditions were observed: temperature, 32.0°C; pH 7.7; stirring rate, 200.0 r ∙min–1; and PLA proportion, 0.4. Under these conditions, Y1, Y2, and Y3 were 134.0 μg-N∙gblend–1∙h–1, 160.9 μg-N∙g-blend–1∙h–1, and 7.6 × 103 μg-O∙g-blend–1∙h–1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.Graphical abstract

Advanced treatment of acrylic fiber manufacturing wastewater with a combined microbubble-ozonation/ultraviolet irradiation process

This work investigated the effectiveness of a combination of microbubble-ozonation and ultraviolet (UV) irradiation for the treatment of secondary wastewater effluent of a wet-spun acrylic fiber manufacturing plant. Under reactor condition (ozone dosage of 48 mg L−1, UV fluence rate of 90 mW cm−2, initial pH of 8.0, and reaction time of 120 min), the biodegradability (represented as BOD5/CODcr) of the wastewater improved from 0.18 to 0.47. This improvement in biodegradability is related to the degradation of alkanes, aromatic compounds, and other bio-refractory organic compounds. The combination of microbubble-ozonation and UV irradiation synergistically improved treatment efficiencies by 228%, 29%, and 142% for CODcr, UV254 removal and BOD5/CODcr respectively after 120 min reaction time, as compared with the sum efficiency of microbubble-ozonation alone and UV irradiation alone. Hydroxyl radical production in the microbubble-ozonation/UV process was about 1.8 times higher than the sum production in microbubble-ozonation alone and UV irradiation alone. The ozone decomposition rate in the combined process was about 4.1 times higher than that in microbubble-ozonation alone. The microbubble-ozonation/UV process could be a promising technique for the treatment of bio-refractory organics in the acrylic fiber manufacturing industry.

Responses of ammonia-oxidizing bacteria community composition to temporal changes in physicochemical parameters during food waste composting

Chemoautotrophic ammonia-oxidizing bacteria (AOB) serve an important function in ecological nitrogen transformation because of their great potential to alleviate ammonia emissions during aerobic composting. However, studies on the influence of specific environmental factors on AOB community dynamics in the food waste composting field are scarce. Hence, this study aimed to identify and prioritize some environmental parameters that affect AOB community composition during food waste composting. The composition and diversity of the AOB community were determined using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). Relationships between the obtained parameters and AOB community composition were simultaneously evaluated by multivariate analysis. Phylogenetic analysis indicated that large amounts of Nitrosomonas-like and Nitrosospira-like lineages existed in different periods. The Nitrosomonas europaea/eutropha were the most dominant AOB species in the thermophilic stage. Redundancy analysis revealed that the dynamics of the AOB community was mainly attributed to temporal changes in nitrate and the pH of the compost material (p < 0.05). Variations (54.7% for AOB species data) were statistically explained by nitrate and pH, suggesting that these parameters were the most likely to influence, or be influenced by AOB community composition, and may further influence nitrogen cycle in the food waste composting ecosystem.

Multilevel contact oxidation treatment of brewery wastewater using spiral biological carriers and their nitrogen removal mechanism

In this study, spiral biological carriers were used to treat brewery wastewater in a multilevel contact oxidation process. The optimal operational conditions are the following: hydraulic retention time of 6.5 h; temperature of above 21°C; pH of 7.2; and dissolved oxygen concentration ranges of 4.0–6.0 mg/L, 3.0–4.0 mg/L, 2.0–3.0 mg/L, and 2.0–3.0 mg/L in four contact oxidation tanks, respectively. Under the optimal conditions, the removal efficiencies of total nitrogen, ammonia, and CODcr of the system were 77.0%, 87.6%, and 92.2% respectively. Effluent quality met the discharge standard of pollutants for the beer industry (GB 19821–2005). In addition, the aerobic-anoxic micro-and macro-environments were formed in the spiral biological carriers. This could be explained by the specific surface character and three-dimensional spiral structure of these carriers which strengthened the simultaneous nitrification and denitrification (SND) process. The removal efficiency of total nitrogen of the reactor was up t...