[Two-Stage Denitrification Process Performance with Solid Slow-Release Carbon Source].

During wastewater treatment using a traditional biological denitrification process, the excessive concentration of nitrate nitrogen (NO3--N) in the effluent is the primary cause of excessive total nitrogen (TN) generation. By using an external carbon source to increase the carbon to nitrogen ratio (C/N), the denitrification process can be strengthened, which effectively addresses this problem. Using an integrated denitrification reactor developed based on the two-stage denitrification process principle with the addition of polybutylene succinate (PBS) in the second stage, the denitrification process was analyzed using a scanning electron microscope before and after characterization of PBS materials. Moreover, amplicon sequencing was used for in-depth exploration of changes in the microbial community structure in the second denitrification pool before and after the addition of PBS. The data of a continuous 120-day experiment showed that the COD removal rate dropped from 95.7% to 90.8%, the TN removal rate increased from 51.8% to 80%, the relative abundance of Proteobacteria phylum rose from 36.1% to 46.1%, and the relative abundance of Thermomonas rose from 6.47% to 13.48%. The results show that after the addition of PBS, PBS can not only provide carbon source for denitrification, but its surface can also serve as a carrier for microbial growth and attachment, play a good role in filming, and increase the abundance of denitrifying bacteria and strengthen denitrification. During the nitrification process, denitrification performance was significantly enhanced, effectively improving the TN removal rate of the system.

Online prediction of effluent COD in the anaerobic wastewater treatment system based on PCA-LSSVM algorithm.

Since anaerobic wastewater treatment is a nonlinear and complex biochemical process, reasonable monitoring and control are needed to keep it operating stably and efficiently. In this paper, a least-square support-vector machine (LS-SVM) was employed to construct models for the prediction of effluent chemical oxygen demand (COD) in an anaerobic wastewater treatment system. The result revealed that the performance of the steady-state model based on LS-SVM for predicting effluent COD was acceptable, with the maximum relative error (RE) of 11.45%, the mean average percentage error (MAPE) of 0.79% and the root mean square error (RMSE) of 3.08 when training, and the performance fell slightly when testing. Even though, the correlation coefficient value (R) between the predicted value and the actual value of 0.9752 could be achieved, which means this model can predict the variation of effluent COD in general. The dynamic-state models under three kinds of shock loads, which were concentration, hydraulic, and bicarbonate buffer absent, showed good forecasting performance, the correlation coefficient values (R) all excelled 0.99. Among these three shocks, the dynamic LS-SVM model under bicarbonate buffer absent shock achieved the optimal performance and followed by the dynamic-state model under hydraulic shock. This paper provides a meaningful reference to improve the monitoring level of the anaerobic wastewater treatment process.

[Using HKUST-1 as a Template for Copper Oxides Preparation to Activate Peroxymonosulfate for RhB Degradation].

Using Cu-MOF (HKUST-1) as a template, copper oxide was prepared by heat treatment under different temperatures in this study. The effect of treatment temperature on the composition and morphology of the products were studied. The catalytic abilities of the copper oxide products were tested through a series of experiments of activating peroxymonosulfate (PMS) to degrade RhB under different conditions. The results of XRD, SEM, and XPS show that the product is gradually transformed from a Cu2O/CuO mixture into pure CuO with the increase of heat treatment temperature. The original octahedron structure of HKUST-1 was collapsed. Under neutral pH conditions, when the dosage of PMS and CuO-650 was 1.00 mmol·L-1 and 0.20 g·L-1, respectively, the total degradation of RhB (concentration of 0.10 mmol·L-1) could be completed within 90 min. In addition, CuO-650 also has many advantages, such as it can be applied within a wide range of pH values. In addition, the copper ion dissolution rate was low (1.309 mg·L-1 at pH=3 and 0.987 mg·L-1 at pH=7), and it has great recyclability and stability. These characteristics further proved that CuO-650 can be used as a promising catalyst for PMS activation.

Modeling and multi-objective optimization for ANAMMOX process under COD disturbance using hybrid intelligent algorithm.

Anaerobic ammonium oxidation (ANAMMOX) has been regarded as an efficient process to treat nitrogen-containing wastewater. However, the treatment process is not fully understood in terms of reaction mechanisms, process simulation, and control. In this paper, a multi-objective control strategy mixed soft-sensing model (MCSSM) is developed to systematically design the operating variations for multi-objective control by integrating the developed model, a least square support vector machine optimized with principal component analysis (PCA-LSSVM) and non-dominated sorting genetic algorithm-II (NSGA-II). The results revealed that the PCA-LSSVM model is a feasible and efficient tool for predicting the effluent ammonia nitrogen concentration ([Formula: see text]) and the total nitrogen removal concentration (CTN, rem) with determination coefficients (R2) were 0.997 for [Formula: see text] and 0.989 for CTN, rem, and gives us the reasonable solutions in influent by using NSGA-II. To achieve a better removal effect, the influent pH should be kept between 7.50 and 7.52, the COD/TN ratio is suggested to maintain at 0.15 and the NH4+-N/NO2--N ratio is suggested to maintain at 0.61. The developed MCSSM approach and its general modeling framework have a high potential of applicability and guidance to bioprocess in wastewater treatment, and numerical models can be structured for predicting and optimization and experiments can be conducted for data acquisition and model establishment.

[MIL-88A@MIP Activated Persulfate for Targeted Degradation of Dibutyl Phthalate].

MIL-88A@MIP was fabricated for the first time in this experiment with a metal-organic framework of MIL-88A as the precursor based on the molecular imprinting method. It was characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), and N2 adsorption. The catalytic performance of MIL-88A@MIP was tested to activate persulfate (PS) to generate SO4-· for the degradation of dibutyl phthalate (DBP), which was used as a target pollutant. Compared with the precursor MIL-88A, the catalytic activity of MIL-88A@MIP was improved effectively through targeted modification, and the DBP removal rate increased 80.4% after reacting for 480 min. An experiment determining the influencing factors showed that the optimum activation condition of the catalyst was PS:DBP=600:1, MIL-88A@MIP dosage of 0.5 g·L-1,and pH=3.26. Furthermore, MIL-88A@MIP shows a high capability of removing different phthalic acid ester (PAE) contaminants that reflect its targeting selectivity.

[Removal of Sulfate Ions from Aqueous Solution by Adsorption with Hydrotalcite- like Composite].

Hydrotalcite-like composite synthesized by co-precipitation method was used as an adsorbent to remove the sulfate ions in aqueous solution. XRD, FT-IR , SEM and EDS elemental analysis were used to clarify the structure and composition of the hydrotalcite- like composite. The influences of time, initial pH value and coexisting ions on adsorption performance were investigated. The result showed the material was the composite of zinc aluminum nitrate hydrotalcite-like compounds and zinc aluminum phenylalanine hydrotalcite-like compounds. Hydrotalcite-like composite had a good performance in adsorption of sulfate ions, and the maximum adsorption capacity was 52.75 mg · g⁻¹. The data fitted pseudo-second order kinetic model best, which indicated that chemical adsorption was the rate-limiting step. Freundlich isotherm was more suitable to describe the adsorption process, and this meant the adsorption of sulfate ions by hydrotalcite-like composite was multilayered adsorption. Thermodynamic parameters showed that the adsorption process was endothermic and spontaneous at room temperature. Hydrotalcite-like composite adsorbed sulfate ions mainly through ion exchange, electrostatic force and physical adsorption. The experimental results showed that the hydrotalcite-like composite had potential for sulfate ion removal in the aqueous solution.

[Effects of particle size of zero-valent iron on the reactivity of activating persulfate and kinetics for the degradation of acid orange 7].

This research described the heterogeneous reactions of persulfate with different particle sizes of zero-valent iron (including 1 mm-ZVI,150 µm-ZVI,50 nm-ZVI) for degradation of acid orange 7(AO7) , and studied the kinetics and intermediate products of AO7 under these systems. The results demonstrated that these three types of ZVI were efficient in promoting the degradation of AO7, the degradation efficiencies of AO7 were 43% , 97% , and 100% within 90 min respectively, in the 1 mm-ZVI,150 µm-ZVI and 50 nm- ZVI systems, respectively. With the results of kinetic fitting models, the pseudo first-order kinetics exhibited better fitting results in the 1 mm-ZVI,150 µm-ZVI systems, while the second-order kinetics exhibited better fitting results in the 50 nm-ZVI system. And the different ZVI types exhibited difference on the AO7 degradation rate constant, which ranged as 50 nm-ZVI > 150 µm-ZVI > 1 mm-ZVI. The iron corrosion products coating on the ZVI after reaction were composed of α-Fe2 O3 and some Fe3O4 in the 1 mm-ZVI system while that consisted of Fe3O4 and α-Fe2O3, FeOOH respectively, in thel50 µm-ZVI and 50 nm-ZVI systems,. Which were identified by scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and Raman spectroscopy. Some intermediate products, including 2-naphthalenol, 2-methylphenol, 4-ethyl- 3-methyl-phenol, isoindole- 1,3-dione and phthalic acid et al. were identified by GC/MS measurement. Both UV-vis absorbance spectra and GC/MS determination indicated that there was difference in degradation paths of AO7 between the three systems.

[Effect of constructed wetland on the purification of industrial zone rainfall runoff contaminated with phenanthrene].

According to the water characteristics of industrial rainfall runoff in the catchment of Tongsha Reservoir, Dongguan City, a subsurface-flow constructed wetland (SSFCW) was used to treat simulated rainfall and the spatial variation of removal efficiency of contaminants in the wetland bed was analyzed. The longitudinal and vertical variation of removal efficiency of COD, NH4(+) -N, TN, TP and phenanthrene were examined. Enzyme activity of polyphenol oxidase (PPO) and nitrate reductase (NR) along the wetland bed were analyzed as well, meanwhile, four biogeochemical indexes of the wetland system, including DO, pH, ORP and water temperature, were monitored and their influences on the removal efficiency of contaminants and enzyme activity were analyzed. Results showed that DO, pH, ORP, water temperature all presented a decreasing tendency along the wetland bed, and the removal of COD, TP and phenanthrene occurred mainly in the front quarter of the wetland system; in the vertical direction, DO and ORP in the upper wetland bed were significantly higher than those in the ground floor, suggesting that the horizontal subsurface system was in an anaerobic or anoxic condition. The removal rates of COD, TP, TN, NH4(+) -N and phenanthrene were 1.17-1.36, 2.04-2.11, 1.40-1.92, 1.37-2.30, and 1.07-1.36 times higher than those at the bottom, respectively. Therefore, the vertical variation of purification efficiency was more significant than the longitudinal variation. A significant positive correlation was determined between the enzyme activity of NR and the NO3(-) -N concentration, but the longitudinal variation in the enzyme activity of NR and PPO was not obvious.

[Mechanism of reductive dechlorination of trichlorophenol with different electron donors].

A test was conducted to examine the degradation effect and reductive dechlorination pathway of 2, 4, 6-trichlorophenol (2,4,6-TCP) in the presence of different electron donors, such as glucose, sodium lactate, sodium pyruvate and sodium acetate. The results showed that, compared with the effect of glucose, sodium lactate, sodium pyruvate and sodium acetate enhanced the dechlorination of 2, 4, 6-TCP effectively, among which sodium lactate could serve as a kind of hydrogen release compound, and the electrons required for reductive dechlorination were released in a sustained way. Substrate metabolism dehydrogenase activity was improved by the external electron donor; after reaction for 240 h, the activity of dehydrogenase was increased in the four electron donor systems, by 21.49%, 25.78%, 136.85% and 139.3%, respectively. The main reductive dechlorination products of 2,4,6-TCP included 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) and phenol; when sodium acetate was used as the electron donor, 4-CP was the main degradation product, and the transformation ratio from 2,4,6-TCP to 4-CP was more than 22%.

[Treatment studies of industrial rainoff with a new type of constructed wetland].

According to water characteristics of industrial rain runoff in a catchment of Tongsha reservoir, Dongguan city, an improved baffled constructed wetland (BCW) was used for purification experiment study of simulated and on-the-spot rain runoff. The purification effects of simulated rain runoff were compared in different operated phases of BCW. Meanwhile, the variation of the pollutants (COD, SS, TN, TP, NH4(+) -N, Pb, Zn, Cu) along the BCW and their removal mechanism were analyzed and discussed, respectively. In the simulated experiment, the effluent water quality of BCW system met the needs of Environmental Quality Standard for Surface Water( GB 3838-2002) III, besides TN met IV, and most of the pollutants were removed in the front of the BCW. In the purification study of on-the-spot rain runoff, removal rate of COD, SS, TN, TP and NH4(+) -N were 90.9%, 97.0%, 83.4%, 92.2% and 90.0%, respectively; removal rate of Pb, Zn and Cu were 98.4%, 94.1% and 93.6%, respectively. The effluent met the grade III. Results showed that there was remarkable treatment performance of industrial catchment rain runoff when BCW system was used, which also can withstand strong shock load. Moreover, a modest variation of temperature affected the removal of pollutants in the BCW insignificantly.

[Influences of pH and complexing agents on degradation of reactive brilliant blue KN-R by ferrous activated persulfate].

The influences of pH and complexing agents on degradation of reactive brilliant blue KN-R by ferrous activated persulfate were investigated, and finally the complexed and the uncomplexed system were compared. Because the lower the pH the more quickly will be the dissociation of S2O8(2-) to the SO4(-*) and the ORP of the dominant radical SO4(-*) in the acidic condition is higher than the dominant radical *OH in the alkaline condition, KN-R degradation rates in acidic condition are far outweigh in the neutral and alkaline conditions. When pH value was 3, the residual rate of KN-R was 17.0% within 3 hours by EDTA system with the lowest PS consumption rate 32.3%, so EDTA was the best complexing agent choice in acidic condition. When pH value was 7, the residual rates of KN-R were 11.3%, 12.4% within 3 days by EDTA, citric acid system with the PS residual rates 28.9%, 28.0% respectively, so EDTA, citric acid were the better choices in the neutral condition. When pH value was 10, glucose acid, citric acid, EDTA and tartaric acid systems all had the similar KN-R degradation rates and PS residual rates, so all could acted as the complexing agents, when the system contained trace amounts of ferrous, the addition of complexing agent would greatly improve the degradation rate of pollutant, from original 52.5% to 79.3% of 3 d, so PS is suitable for in situ chemical oxidation (ISCO).

[Degradation of azo dye acid orange 7(AO7) by heat, ZVI and heat/ZVI activated persulfate].

Effects of temperatures, PS concentrations and ZVI dosages on AO7 decomposition were investigated in sole heat and ZVI activating systems. The degradation results of two systems were compared for selecting a better activating way for AO7 degradation and finally the two activating ways were combined for getting the optimal AO7 degradation efficiency. The degradation of AO7 by Heat/PS systems followed pseudo first-order kinetics. The reaction rates increased with increasing reaction temperatures (elevated from room temperature to 90 degrees C) and also increased when initial PS concentrations varied from 1 to 12 mmol x L(-1). For ZVI activating systems (ZVI/PS systems), the degradation rate of AO7 was the highest when ZVI dose was 0.2 g, and it reached to 95.6% within 90 min. Comparing ZVI/PS systems with Heat/PS systems, the results showed that the ZVI activation was a more effective way to activate PS than the heat activation for AO7 degradation. AO7 degradation processes by ZVI/heat/PS systems were two-stage pseudo first-order kinetic processes, and the combining of two activating ways significantly increased the reaction rates. By the addition of ZVI to the Heat/PS system, the apparent activation energy E(a) of AO7 degradation reduced from the original 130.26 kJ x mol(-1) to 27.70 kJ x mol(-1).

The fate of di-n-butyl phthalate in a laboratory-scale anaerobic/anoxic/oxic wastewater treatment process.

A laboratory-scale anaerobic/anoxic/oxic (AAO) wastewater treatment system was employed to investigate the effects of hydraulic retention time (HRT) and sludge retention time (SRT) on the removal and fate of di-n-butyl phthalate (DnBP). HRT had no significant effect on DNBP removal between 12 and 30 h. However, longer HRT increased DnBP accumulation in the system and DnBP retention in the waste sludge. When SRT was increased from 15 to 25 d, DnBP removal efficiency stayed above 95%. Compared to the removal of only 90% at SRT of 10d, longer SRT enhanced DnBP degradation efficiency. The optimal HRT and SRT for both nutrients and DnBP removal were 18 h and 15 d. At these retention times, about 72.66% of DnBP was degraded by the activated sludge process, 2.44% was released in the effluent, 24.44% was accumulated in the system, and 0.5% remained in the waste sludge. The anaerobic, anoxic and oxic reactors were responsible for 17.14%, 15.02% and 63.46% of the overall DnBP removal, respectively. Meanwhile a removal degradation model was formulated, and kinetic parameters were evaluated with batch experiments under anaerobic, anoxic, oxic conditions. The model can well forecast the effluent quality of anaerobic/anoxic/oxic reactors of the AAO process.

A fast predicting neural fuzzy model for on-line estimation of nutrient dynamics in an anoxic/oxic process.

In this paper a software sensor based on a fuzzy neural network approach was proposed for real-time estimation of nutrient concentrations. In order to improve the network performance, fuzzy subtractive clustering was used to identify model architecture, extract and optimize fuzzy rule of the model. A split network structure was applied separately for anaerobic and aerobic conditions was employed with dynamic modeling methods such as autoregressive with exogenous inputs and multi-way principal component analysis (MPCA). The proposed methodology was applied to a bench-scale anoxic/oxic process for biological nitrogen removal. The simulative results indicate that the learning ability and generalization of the model performed well and also worked well for normal batch operations corresponding to three data points inside the confidence limit determined by MPCA. Real-time estimation of NO(3)(-), NH(4)(+) and PO(4)(3-) concentration based on fuzzy neural network analysis were successfully carried out with the simple on-line information regarding the anoxic/oxic system.