OBJECTIVEThis study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic (A²/O) processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity.

METHODSA luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A²/O system.

RESULTSThe optimum operational parameters for toxicity reduction were as follows: anaerobic hydraulic retention time (HRT) = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time (SRT) = 15 days and internal recycle ratio (IRR) = 100%. An important toxicity reduction (%) was observed in the optimized A²/O process, even when the toluene concentration of the influent was 120.7 mg·L⁻¹.

CONCLUSIONSThe toxicity of municipal wastewater was reduced significantly during the A²/O process. A²/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.

Anaerobiosis ; Bioreactors ; Oxygen ; Sewage ; Time Factors ; Waste Disposal, Fluid ; methods

The anaerobic granular sludge from an Internal Circulation (IC) reactor of a paper mill wastewater treatment plant were seeded in an Anammox upflow anaerobic sludge blanket reactor. After 185 days operation, the reactor was finally started up by increasing the influent ammonium and nitrite concentrations to 224 mg/L and 255 mg/L, respectively, with volumetric nitrogen removal rate increasing to 3.76 kg/(m3·d). The physicochemical characteristics of the cultivated Anammox granules were observed by scanning electron microscope, transmission electron microscope and Fourier Transform infrared spectroscopy (FTIR). Results suggested that during the start-up course, the granular sludge initially disintegrated and then re-aggregated. FTIR spectra results revealed that the Anammox granular sludge contained abundant functional groups, indicating that it may also possess good adsorption properties. The ecological structure of the granular sludge, analyzed by the metagenomic sequencing methods, suggested that the relative abundance of the dominant bacterial community in the seeding sludge, i.e., Proteobacteria, Firmicutes, Bacteroidetes, significantly reduced, while Planctomycetes which contains anaerobic ammonium oxidation bacteria remarkably increased from 1.59% to 23.24% in the Anammox granules.
Ammonia ; chemistry ; Bacteria ; Bioreactors ; Nitrogen ; chemistry ; Sewage ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

Municipal wastewater is usually problematic for the environment. The process of oleaginous microalgal culture requires large amounts of nutrients and water. Therefore, we studied the feasibility of oleaginous microalgal culture of Scenedesmus dimorphus in bubbled column photobioreactor with municipal wastewater added with different nutrients. S. dimorphus could adapt municipal nutrient-rich wastewater by adding some nutrients as nitrogen, phosphorus, ferric ammonium citrate and trace elements, and the amounts of such nutrients have significant effects on cell growth, biomass yield and lipid accumulation. At optimum compositions of wastewater medium, the algal cell concentration could reach 8.0 g/L, higher than that of 5.0 g/L in standard BG11. Furthermore, S. dimorphus had strong capacity to absorb inorganic nitrogen and phosphorus from its culture water. There was almost no total nitrogen and phosphorus residues in culture medium after three or four days culturing when the adding mounts of nitrate and phosphate in wastewater medium were no more than 185.2 mg/L and 16.1 mg/L respectively under the experimental conditions. As a conclusion, it was feasible to cultivate oleaginous microalgae with municipal nutrient-rich wastewater, not only producing feedstock for algal biodiesel, but also removing inorganic nitrogen and phosphorus from wastewater.
Biofuels ; Cities ; Culture Techniques ; methods ; Lipids ; biosynthesis ; Microalgae ; metabolism ; Photobioreactors ; Scenedesmus ; growth & development ; metabolism ; Waste Disposal, Fluid ; methods ; Waste Products

In order to broaden the application area of the new nitrogen removal technology, a full-scale system for short-cut nitrification and anaerobic ammonium oxidation (Anammox) was investigated in the nitrogen removal from a strong-ammonium pharmaceutical wastewater. When the influent ammonium concentration was (430.40 ± 55.43) mg/L, ammonia removal efficiency was (81.75 ± 9.10)%. The short-cut nitrification and Anammox system could successfully remove nitrogen from the pharmaceutical wastewater. The start-up of short-cut nitrification system took about 74 d and the nitrite accumulation efficiency was (52.11 ± 9.13)%, the two-step mode using synthetic wastewater and actual wastewater was suitable for the start-up of short-cut nitrification system. The start-up of Anammox system took about 145 d and the maximum volumetric nitrogen removal rate was 6.35 kg N/(m3·d), dozens of times higher than those for the conventional nitrification-denitrification process. The strategy achieving Anammox sludge by self-growth and biocatalyst addition was suitable for the start-up of Anammox system.
Ammonia ; chemistry ; Bioreactors ; Drug Industry ; Nitrification ; Nitrites ; chemistry ; Nitrogen ; chemistry ; Sewage ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

In order to simultaneously remove carbon and nitrogen from organic-rich wastewater, we used an up-flow anaerobic sludge bed/blanket (UASB) reactor that was started up with anammox with high concentration of carbon and nitrogen by gradually raising the organic loading of influent. We optimized the removal of nitrogen and carbon when the chemical oxygen demand (COD) concentration varied from 172 to 620 mg/L. During the entire experiment, the ammonium and total nitrogen removal efficiency was higher than 85%, while the average COD removal efficiency was 56.6%. The high concentration of organic matter did not restrain the activity of anammox bacteria. Based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and tapping sequencing analyses, the Planctomycete, Proteobacteria, Chloroflexi, Chlorobi bacteria are detected in the UASB reactor, which indicated complex removal pathway of carbon and nitrogen coexisted in the reactor. However, a part of Planctomycete which referred to anammox bacteria could tolerate a high content of organic carbon, and it provided help for high performance of nitrogen removal in UASB reactor.
Ammonia ; chemistry ; Biological Oxygen Demand Analysis ; Bioreactors ; Carbon ; chemistry ; Nitrogen ; chemistry ; Sewage ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

Anaerobic ammonium oxidation (ANAMMOX), as its essential advantages of high efficiency and low cost, is a promising novel biological nitrogen elimination process with attractive application prospects. Over the past two decades, many processes based on the ANAMMOX reaction have been continuously studied and applied to practical engineering, with the perspective of reaching 100 full-scale installations in operation worldwide by 2014. Our review summarizes various forms of ANAMMOX processes, including partial nitritation-ANAMMOX, completely autotrophic nitrogen removal over nitrite, oxygen limited autotrophic nitrification and denitrification, denitrifying ammonium oxidation, aerobic deammonification, simultaneous partial nitrification, ANAMMOX and denitrification, single-stage nitrogen removal using ANAMMOX and partial nitritation. We also compare the operating conditions for one-stage and two-stage processes and summarize the obstacles and countermeasures in engineering application of ANAMMOX systems, such as moving bed biofilm reactor, sequencing batch reactor and granular sludge reactor. Finally, we discuss the future research and application direction, which should focus on the optimization of operating conditions and applicability of the process to the actual wastewater, especially on automated control and the impact of special wastewater composition on process performance.
Ammonia ; chemistry ; Bioreactors ; Denitrification ; Nitrification ; Nitrites ; chemistry ; Nitrogen ; chemistry ; Oxygen ; chemistry ; Sewage ; chemistry ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

The performance of a novel anaerobic bioreactor, spiral automatic circulation (SPAC) reactor, was investigated in lab-scale. The results showed that the average COD removal efficiency was 93.6% (91.1%-95.7%), with influent concentration increased from 8000 mg/L to 20 000 mg/L, at 30 degrees C and hydraulic retention time (HRT) of 12 h. The removal efficiency remained at 96.0%-78.7% when HRT was shortened from 5.95 h to 1.57 h, as the influent concentration was kept constantly at 20 000 mg/L. The highest organic loading rate (OLR), volumetric COD removal rate and volumetric biogas production of the SPAC reactor were 306 gCOD/(L x d), 240 g/(L x d) and 131 L/(L x d), respectively. When increasing influent COD concentration (from 8000 mg/L to 20 000 mg/L), the effluent COD concentration maintained at low level (852 mg/L for average) with volumetric COD removal rate increased by 162% and volumetric biogas production increased by 119%. With reduced HRT (from 5.95 h to 1.57 h), the volumetric COD removal rate and volumetric biogas production were increased by 191% and 195%, respectively. The SPAC reactor shows good performances in adapting the continuous change of influent COD and HRT.
Anaerobiosis ; Bacteria, Anaerobic ; metabolism ; Bioreactors ; microbiology ; Computer Simulation ; Waste Disposal, Fluid ; instrumentation ; methods

We studied the effects of the oxygen on partial nitrification in a membrane bioreactor (MBR), to find out critical dissolved oxygen (DO) concentrations for the optimal partial nitrification by monitoring the oxygen uptake rate (OUR) and oxygen supply rate (OSR). The nitrite accumulation occurred at a DO concentration of 1 mg/L, while the ratio of nitrite to ammonia in effluent was close to 1 at a DO concentration of 0.5 mg/L which was suitable to serve as the feed of an ANNAMOX system. When the mixed liquid suspended solids(MLSS) was 20 g/L in MBR, OUR and OSR were 19.86 mg O2/(L·s) and 0.369 mg O2/(L·s) respectively, indicating that the oxygen supply was the bottleneck of partial nitrification. "Low DO and high aeration rate" were suggested as a control strategy to further improve the efficiency of partial nitrification.
Ammonia ; chemistry ; Bioreactors ; Membranes, Artificial ; Nitrification ; Nitrites ; chemistry ; Oxygen ; chemistry ; Waste Disposal, Fluid ; methods

OBJECTIVEDuring present investigation the data of a laboratory-scale anoxic sulfide oxidizing (ASO) reactor were used in a neural network system to predict its performance.

METHODSFive uncorrelated components of the influent wastewater were used as the artificial neural network model input to predict the output of the effluent using back-propagation and general regression algorithms. The best prediction performance is achieved when the data are preprocessed using principal components analysis (PCA) before they are fed to a back propagated neural network.

RESULTSWithin the range of experimental conditions tested, it was concluded that the ANN model gave predictable results for nitrite removal from wastewater through ASO process. The model did not predict the formation of sulfate to an acceptable manner.

CONCLUSIONApart from experimentation, ANN model can help to simulate the results of such experiments in finding the best optimal choice for ASObased denitrification. Together with wastewater collection and the use of improved treatment systems and new technologies, better control of wastewater treatment plant (WTP) can lead to more effective maneuvers by its operators and, as a consequence, better effluent quality.

Bioreactors ; Neural Networks (Computer) ; Oxidation-Reduction ; Sulfates ; chemistry ; Sulfides ; chemistry ; Time Factors ; Waste Disposal, Fluid ; methods

The internal-loop granular sludge bed nitrifying reactor is a new type of aerobic nitrifying equipment and has taken on a good potential for nitrification. The critical aerating flux for liquid loop and critical aerating flux for fluidization of granular sludge are two important parameters for its operation. The relationship between liquid superficial velocity in riser (U1r) and aerating flux(Ugr) was studied, the model parameters were measured by experiment, and the relational expression was established. According to the model, the critical aerating flux for liquid loop and the critical aerating flux for fluidization of granular sludge were calculated as 1.017cm/min and 2.662cm/min, respectively. The experimental data from reactor operation showed that the two calculated critical aerating fluxes near the practical values. So they could be used to direct the design and operating optimization for the internal-loop granular sludge bed nitrifying reactor.
Bacteria, Aerobic ; metabolism ; Bioreactors ; Nitrites ; metabolism ; Sewage ; chemistry ; microbiology ; Waste Disposal, Fluid ; methods