Aeration Mode Research Articles

Static Culture Combined with Aeration in Biosynthesis of Bacterial Cellulose.

One of the ways to enhance the yield of bacterial cellulose (BC) is by using dynamic aeration and different-type bioreactors because the microbial producers are strict aerobes. But in this case, the BC quality tends to worsen. Here we have combined static culture with aeration in the biosynthesis of BC by symbiotic Medusomyces gisevii Sa-12 for the first time. A new aeration method by feeding the air onto the growth medium surface is proposed herein. The culture was performed in a Binder-400 climate chamber. The study found that the air feed at a rate of 6.3 L/min allows a 25% increase in the BC yield. Moreover, this aeration mode resulted in BC samples of stable quality. The thermogravimetric and X-ray structural characteristics were retained: the crystallinity index in reflection and transmission geometries were 89% and 92%, respectively, and the allomorph Iα content was 94%. Slight decreases in the degree of polymerization (by 12.0% compared to the control―no aeration) and elastic modulus (by 12.6%) are not critical. Thus, the simple aeration by feeding the air onto the culture medium surface has turned out to be an excellent alternative to dynamic aeration. Usually, when the cultivation conditions, including the aeration ones, are changed, characteristics of the resultant BC are altered either, due to the sensitivity of individual microbial strains. In our case, the stable parameters of BC samples under variable aeration conditions are explained by the concomitant factors: the new efficient aeration method and the highly adaptive microbial producer―symbiotic Medusomyces gisevii Sa-12.

In-situ electrolytic oxygen is a feasible replacement for conventional aeration during aerobic composting

Aerobic composting is an effective recycling method for the disposal and resource utilization of organic solid waste. However, the inappropriate aeration mode used during conventional aerobic composting (CAC) often results in low oxygen utilization efficiency and loss of temperature, which further leads to a long maturation period and large odorous gas (NH3) pollution. Herein, a novel electrolytic oxygen aerobic composting (EOAC) process was invented first using in-situ oxygen generation for aeration by the electrolysis of water in compost. Our results demonstrated that the germination index (GI) significantly increased during EOAC, and the maturation time of compost was shortened by nearly 50% during EOAC compared to CAC, indicating higher oxygen utilization efficiency during EOAC. Meanwhile, NH3 emissions, N2O emissions, and nitrogen loss during the EOAC process decreased by 61%, 46%, and 21%, respectively, compared to CAC. The total relative abundance of thermophilic and electroactive bacteria during EOAC increased remarkably. EOAC inhibited ammoniation, nitrification, and denitrification, and weakened N-associated functional genes. A techno-economic analysis indicated that EOAC had greater technical superiority and cost advantages compared to CAC. This study represents proof-of-principle for EOAC and suggests that in-situ electrolytic oxygen is a feasible replacement for conventional aeration during aerobic composting.

Construction of a Microchannel Aeration Cathode for Producing H2O2 via Oxygen Reduction Reaction.

Electrochemical oxygen reduction is a promising method for in situ H2O2 production. Its important precondition is that dissolved oxygen molecules have to diffuse to and arrive at the cathode surface for reacting with electrons. Obviously, shortening the diffusion distance is beneficial to improve the reaction efficiency. In this study, a novel microchannel aeration mode was proposed to confine the diffusion distance of O2 to the micrometer level. For this mode, an aeration cathode was fabricated from a carbon block with microchannel arrays. The diameter of each channel was only 10-40 μm. Oxygen will be pumped into every microchannel from the top entry, while an aqueous solution will permeate into microchannels through the bottom entry and pores in the channel wall. This microchannel aeration cathode exhibited a H2O2 yield of up to 4.34 mg h-1 cm-2, about eight times higher than that of the common bubbling aeration mode. The corresponding energy consumption was only 7.35 kWh kg-1, which was superior to most reported results. In addition to H2O2, this aeration cathode may also produce •OH via a one-electron reduction of H2O2. In combination with H2O2 and •OH, phenol, sulfamethoxazole, and atrazine were degraded effectively. We expect that this microchannel aeration cathode may inspire researchers focused on H2O2 production, water pollutant control, and other multiphase interfacial reactions.

Nitrite Regulation During Start-up of Combined Partial Nitritation and ANAMMOX Process

Two types of full-scale reactors(SBR, 116.6 m3, activated sludge process; SBBR, 64.8 m3, activated sludge and biofilm process) were inoculated with activated sludge from a swine wastewater treatment plant. The effect of NO2--N concentration on ANAMMOX was investigated in the reactors during the start-up of the combined partial nitritation and ANAMMOX(CPNA) process by controlling the dissolved oxygen(DO), aeration mode, and NaNO2 dosing. The results showed that the SBBR was more suitable for rapid start-up of partial nitritation under the same operation conditions. Despite NO2--N inhibition(100-129 mg·L-1, 7 days), the ANAMMOX process was successfully started by the SBR on day 39, and the total nitrogen removal rate and efficiency(TNRR and TNRE) were 0.069 kg·(m3·d) -1 and 23.3%, respectively. However, 17 days of NO2--N inhibition(129-286 mg·L-1) had an unrecoverable effect on ANAMMOX activity in the SBBR. By adding NaNO2, the SBR successfully started the CPNA process on day 77. The TNRR, TNRE, and activity of ANAMMOX from day 51 to 77 increased rapidly from 0.070 to 0.336 kg·(m3·d) -1, 16.0% to 52.2%, and 0.012 to 0.307 kg·(kg·d) -1, respectively. The gene copy concentration of AOB and ANAMMOX bacteria in the SBR increased from the original 8.06×106 and 4.42×104 copies·mL-1 to 1.02×109 and 1.77×107 copies·mL-1, respectively, which indicated that the rapid enrichment of AOB and ANAMMOX bacteria in the SBR was achieved mainly by controlling DO, aeration mode, and NaNO2 dosing. Reasonable nitrite regulation is the key for the start of the CPNA process.

Estimating acceptable exposure time for bioaerosols emission in a wastewater treatment plant by reverse quantitative microbial risk assessment based on various risk benchmarks.

Populations exposed to bioaerosols over time in wastewater treatment plants (WWTPs) will be infected. Then, the reverse quantitative microbial risk assessment (QMRA) provides a quantitative framework for the estimation of acceptable exposure time to protect people from excessive exposure and then manage their health risk. In this study, the acceptable exposure time for staffs and visiting researchers exposed to S. aureus or E. coli bioaerosols emitted from aeration ponds in WWTPs was estimated and analyzed by Monte Carlo simulation-based reverse QMRA (using the 1E-4 pppy suggested by the US EPA or 1E-6 DALYs pppy suggested by the WHO as benchmarks). The 1E-3 and 1E-2 pppy were selected as a series of loose annual infection risk benchmarks to calculate a practical acceptable exposure time. The results showed that for the acceptable exposure time in each specific exposure scenario, the exposure of females was consistently 0.3-0.4 times longer than that of males; the exposure of staffs was 3.6-3.9 times shorter than that of visiting researchers; the exposures of populations in the rotating-disc aeration mode were consistently 6.3-6.6 and 2.8-3.1 times longer than those in the microporous aeration mode for S. aureus and E. coli bioaerosols, respectively. The acceptable exposure time with the use of personal protective equipment (PPE) was 33.4-35.0 times as long as that without PPE. The US EPA benchmark is stricter than the WHO benchmark with regard to the estimation of the acceptable exposure time of S. aureus or E. coli bioaerosols. The 1E-3 pppy is more appropriate and practical than the US EPA benchmark, but the 1E-2 pppy is notably too loose for health risk management. This research can assist managers of WWTPs to formulate a justified exposure time and develop applicable administrative and personal intervention strategies. The results can enrich the knowledge bases of reverse QMRA to elect a series of loose health-based target risk benchmarks for health risk management.

The Use of a Neurocontroller in a Multi-Mode Air Supply Control System at Agricultural and Industrial Facilities

The possibility of using a neurocontroller to control the aeration mode in the air supply circuit with a compressor unit has been investigated. The control algorithm is implemented using a multi-layer feedforward neural network. The control object model in the study included a frequency converter, motor and compressor. The analysis of the properties of the system was carried out by evaluating the obtained transients using MATLAB. The results showed that the system has high quality indicators in stabilization and programmed control modes.

Evaluation of PAO adaptability to oxygen concentration change: Development of stable EBPR under stepwise low-aeration adaptation

Recent research has shown the adaptability of Biological Nutrient Removal (BNR) systems to very low level dissolved oxygen (DO) concentration, mainly focusing in the nitrification ability that maintains the nitrogen oxidation process even at very low DO levels. Although step-wise aeration decrease on Enhanced Biological Phosphorus Removal (EBPR) is not fully comprehended. This study investigated the effect of reaching micro-aeration with adaptation strategies on EBPR performance. A step-wise oxygen concentration decrease, arriving at an average aeration level of 0.4 mgO2/L was evaluated, with an outcome of approximately 90 % phosphorus removal efficiency. Compared with different aeration modes, the highest phosphorus (P)-removal efficiency, P-release and lowest effluent phosphorus was achieved in gradual DO decrease strategy. On the other hand, an instant decrease in aeration from stable EBPR process from 2 mgO2/L to 0.4 mgO2/L adversely impacted P-removal by decreasing the efficiency to average 60 % and deteriorating the phosphorus removing microbial consortium. Comparison of results between instant and gradual DO-decrease, indicated the sensitivity of microorganisms to aeration. Microbial adaptation to decreased oxygen availability is crucial to reach high process performance. This study proposes, a potential aeration mode, which contributes in reduction of energy consumption in BNR systems through wastewater treatment.

Efficient degradation of tetracycline using core–shell Fe@Fe2O3-CeO2 composite as novel heterogeneous electro-Fenton catalyst

Developing efficient heterogeneous electro-Fenton (EF) catalysts for degradation of organic pollutants remains a challenge. Herein, a novel heterogeneous EF catalyst, core–shell Fe@Fe2O3-CeO2 composite, was successfully synthesized in a facile manner for effective degradation of tetracycline (TC) pollutant. The catalytic activity was evaluated by effects of different processes, Fe/Ce molar ratio, catalyst dosage, initial solution pH, applied current and aeration mode. Fe@Fe2O3-CeO2 with 2:1 Fe/Ce molar ratio achieved TC removal efficiency of 90.7% within 1 h and mineralization efficiency of 86.9% within 6 h with such excellent performance attributed to the high utilization efficiency of H2O2 and the synergistic effects between Ce4+/Ce3+ and Fe3+/Fe2+. Moreover, this novel catalyst exhibited good recyclability and stability in successive cycles with low metal leaching. Furthermore, the heterogeneous EF process showed satisfactory catalytic activity towards degradation of other organic pollutants (e.g., metronidazole, diclofenac sodium, and chloramphenicol). Based on the experimental results and analysis, the mechanism of the heterogeneous EF process with Fe@Fe2O3-CeO2 catalyst and possible TC degradation pathways were proposed, which provides insights into the catalytic reaction process and should be of value in facilitating the application of this method in refractory wastewater treatment.

Nitrogen removal in subsurface constructed wetland: Assessment of the influence and prediction by data mining and machine learning

Subsurface constructed wetland (SCW) appears to be an economical and environmental-friendly practice to treat nitrogen-enriched (waste) water. Nevertheless, the removal mechanisms in SCW are complicated and rather time-consuming to conduct and assessment the efficiency of new experiments. This work mined data from literature and developed the machine learning models to elucidate the effect of influent inputs and predict ammonium removal rate (ARR) in SCW treatment. 755 sets and 11 attributes were applied in four modeled algorithms, including Random forest, Cubist, Support vector machines, and K-nearest neighbors. Six out of ten input features including ammonium (NH 4 ), total nitrogen (TN), hydraulic loading rate (HLR), the filter height (i.e., Height), aeration mode (i.e., Aeration), and types of inlet feeding (i.e., Feeding) have posed pronounced influences on the ARR. The Cubist algorithm appears the most optimal model showing the lowest RMSE i.e., 0.974 and the highest R 2 i.e., 0.957. The contribution of variables followed the order of NH 4 , HLR, TN, Aeration, Height and Feeding corresponding to 97, 93, 71, 49, 34, and 34%, respectively. The generalization ability to forecast ARR using testing data achieved the R 2 of 0.970 and the RMSE of 1.140 g/m 2 d, indicating that Cubist is a reliable tool for ARR prediction. User interface and web tool of final predictive model are provided to facilitate the application for designing and developing SCW system in real practice. • Four supervised ML algorithms were utilized to predict ARR by SCW. • Six over ten input variables were found to be the most pronounced parameters. • NH 4 -N (97%), HLR (93%), and TN (71%) contributed the most to model. • Cubist achieved the highest generalization with R 2 of 0.957 and RMSE of 0.974 g/m 2 d. • Strong correlation between the predicted and actual results by Cubist.

Treatment of the actual landfill leachate in different constructed wetlands through intermittent and varied aeration mode.

This study focused on the removal of organic matter and nitrogen and explored the feasible operation strategies to achieve short-cut nitrification and denitrification in two constructed wetlands (CWs), which were designed to treat the actual landfill leachate from a small county in parallel. The two CWs were horizontal sub-surface flow constructed wetlands (HFCW) with partial-area aeration and vertical sub-surface flow constructed wetlands (VFCW) with full-area aeration. The experimental results showed that both CWs could achieve an excellent organic matter and nitrogen removal performance under the conditions of intermittent aeration with high frequency and medium intensity (2 h of aeration and 4 h of rest). The removal efficiencies of COD and total nitrogen by HFCW were 89.08% and 73.22%, and the corresponding values of VFCW were 84.51% and 71.44%, respectively. Meanwhile, the inhibition kinetics model indicated that HFCW with partial-area aeration could enhance the free ammonium (FA) tolerance of ammonium-oxidizing bacteria (AOB) and reduce the conversion percentage of ammonia nitrogen. In addition, the intermittent aeration mode with high frequency and medium intensity could keep the DO concentration below under 0.60 mg L-1 in HFCW, which helped to achieve stable short-cut nitrification and ensure the average nitrite accumulation rate (NAR) reach 50.96%. These results suggested that the intermittent aeration in partial-area could achieve successful short-cut nitrification in HFCW, thereby improving the removal efficiency of nitrogen in landfill leachate.

Enhanced nutrient removal and facilitating granulation via intermittent aeration in simultaneous partial nitrification endogenous denitrification and phosphorus removal (SPNEDpr) process

A novel simultaneous partial nitrification, endogenous denitrification and phosphorus removal (SPNEDpr) system was operated for 213 days in a sequencing batch reactor to treat real domestic sewage. The nutrient removal was achieved under an operation mode of intermittent aeration at unequal intervals with low oxygen concentrations. Through optimizing intermittent aeration conditions, the removal efficiencies of total inorganic nitrogen (TIN), PO43–P and chemical oxygen demand (COD) reached 78.40%, 98.13% and 84%, respectively. Low-oxygen (0.1–0.7 mg/L) and intermittent aeration effectively inhibited nitrite oxidation bacteria (NOB), maintaining stable partial nitrification with nitrite accumulation ratio of 96.45%. Notably, intermittent aeration promoted the formation of aerobic granular sludge, with the sludge particle size increasing from 217.2 ± 5.3 to 351.8 ± 4.8 μm, thereby enhancing the TIN loss efficiency (81.3%). The predominant genus was Candidatus_Competibacter (11.6%), which stored COD as intracellular carbon source and performed the endogenous denitrification. The SPNEDpr process provided a highly efficient and economical method for treating urban sewage.

Study of the oxidation process of divalent iron in aqueous solutions during aeration through ceramic membranes modified by layered double hydroxides

The work considers the issues of intensification of the process of purification of natural waters from compounds of bivalent iron, namely the stage of its oxidation. In the experiments, corundum-based ceramic membranes with a deposited layer of aluminum oxide and the same membranes, but modified with layered double hydroxide (LDH) based on the trivalent iron ion, were used as the aerator material. Experiments were carried out to compare the aeration modes for both types of membranes; an aquarium aerator was taken as a comparison. The contribution of the selective layer with LDH to the oxidation rate of bivalent iron by atmospheric oxygen is shown, which confirms its catalytic activity. The process flow diagram of the aerator is proposed.

MBR공정의 운전조건의 변화에 따른 여과성능 개선연구

Membrane bioreactor (MBR) combining an activated sludge process and membrane filtration could achieve high nutrient removal efficiency and complete biomass retention without a secondary clarifier. Membrane fouling remains the most challenging issue in MBR operation and attracts considerable attention in MBR studies. The objective of this study is to investigate the influence of permeate flux, aeration mode and strength, and mixed liquor suspended solid (MLSS) on membrane filtration of small-scale MBR (the capacity 100㎥/d), which consisted of anaerobic, anoxic, and aeration tank coupled with membrane. Experiments were conducted with real MBR using real wastewater (BOD <250 mg/L, COD <220 mg/L, T-N <65 mg/L, T-P <8 mg/L, E-coli <100,000 no/mL). As a result, the increase of both permeate flux and MLSS increased TMP of MBR while the increase of aeration strength decreased the TMP. Compared to the existing operation conditions of MBR, the operation conditions of shorter filtration time (8 min on/ 2 min off) for a cycle and lower MLSS (<3000 mg/L) in MBR resulted in longer filtration duration time (about two times) as well as the reduction of cleaning chemical.

Constraining nitrification by intermittent aeration to achieve methane-driven ammonia recovery of the mainstream anaerobic effluent

Mainstream anaerobic treatment has the potential to capture organic energy, and represents a sustainable development trend, but with the problems of low biogas quality and dissolved methane emissions. In this study, methane-driven ammonia recovery of anaerobic effluent was proposed. A 380-day long-term experiment, which was divided into four phases according to different aeration modes, was conducted. The ammonia conversion and microbial characteristics shows that ammonia oxidizing bacteria (AOB) were constrained during Phases 2 (DO: <0.2 mg L−1) and 4 (DO: 0.1–1.6 mg L−1), and were active during Phase 3 (DO: 2–4 mg L−1). During phase 4, when the intermittent aeration was used, the total nitrogen removal rate was higher than during Phases 2 and 3, and nearly 100% ammonia was removed. Methylomonas, a genus of methane oxidizing bacteria (MOB), was enriched during Phase 4. The serum bottle experiment confirmed that the ammonia removal occurred through the MOB assimilation. The protein content in the CH4-added group was 35.5%, which was higher than in the group without CH4 (23.3%). The powerful ammonia assimilation and protein synthesis capabilities of MOB give a meaning to the anaerobic effluent for ammonia recovery and protein production. Intermittent aeration could be used to constrain AOB and improve ammonia recovery efficiency.

Intermittent aeration improving activated granular sludge granulation for nitrogen and phosphorus removal from domestic wastewater

Given the large quantity discharge of nutrients in sewage, nitrogen and phosphorus is getting a worldwide concern. This manuscript assigned two different aeration modes of intermittent aeration/anoxia aeration and continuous aeration to study dissolved oxygen (DO) affecting contaminant removal, AGS granulation and microbial community diversity. The results demonstrated that intermittent aeration contributed to higher removal efficiencies of organics, nitrogen and phosphorus and faster granulation process, larger particle size, and more microbial communities than continuous aeration. The temporal lack of DO for intermittent aeration module did not only save approximately 40% energy but also change microbial communities. The intermittent aeration had no growth of filamentous bacteria and more microbial communities consist of Paracoccus, Delftia, Flavobacterium, Brevundimonas, Roseobacter_clade_CHAB-I-5_lineage, which accelerated AGS granulation, and Nitrosopumilus, Nitrospina, Facultative anaerobes, Pelagibacter and UKL 13-1 bacteria, which played crucial roles in N and P removal.

Effect of first-stage aeration on treatment of domestic sewage in different hybrid constructed wetlands.

Two sets of hybrid constructed wetlands (HCWs) with the first-stage aeration were used to treat actual domestic sewage in this paper, where the effects of three important factors of aeration mode, hydraulic loading rates (HLR), and aeration volume on the removal of pollutants in both HCWs were studied in contrasts. In addition, the pollutant removal efficiency, the contribution of plants, and the characteristics of biofilm in both HCWs were explored. The results of 250-day experiment showed that the TN removal capacity of HCW combining vertical flow CW with horizontal flow CW (VF-HF) was better than HCW's converse combination (HF-VF) in treatingsewage, while the removal efficiency of COD and NH4+-N were similar, and the concentrations of TN and COD in the effluent of VF-HF could successfully meet the National discharge requirements. Compared with the continuous aeration, the intermittent aeration only had a little effect on the removal of COD and NH4+-N, but could improve TN removal performance in both HCWs. Meanwhile, increasing the aeration volume was beneficial to remove NH4+-N but not TN in HCWs. In addition, although the pollutant removal performances in both HCWs were impacted, the removal capacity of TN in VF-HF was only affected a little, when HLR was increased by 50%. The contribution of plants' uptake accounted for about 10% to nitrogen removal and 20% to phosphorus removal in both HCWs. The biomass at the filler surface near the plant rhizosphere was greater than that in the non-rhizosphere zones, and the impact of plant rhizosphere on the nitrification activity of biofilm was significantly greater than that on denitrification activity in both HCWs.

Architectural choices aimed at reducing the air pollution by vehicle emissions in residential areas

Introduction. The formation of an optimal microclimate and ensuring the purity of atmospheric air in residential areas is possible in urban planning design practice by regulating the wind regime, which determines the thermal state of a person and the quality of the living environment, the temperature and humidity regime. The aim of the study is to assess the impact of the width, density, and planning techniques of main streets on the aeration regime and reduction of the concentration of motor transport emissions in the air of residential areas. Material and methods. The research was carried out both in full-scale conditions on the streets of large cities and residential buildings’ models at a scale of 1:20 using cup anemometers. Results. The regularities of the formation of the aeration regime and the level of gas contamination of main streets with different planning and development methods are established. The dependences of the coefficient of air flow transformation in terms of the speed on the width of streets and the size of gaps between buildings are obtained. Planning conditions that exclude the possibility of a closed circulation of impurities in street canyons are determined. The spatial and temporal dynamics of air pollution of transport communications in residential areas of settlements is studied. Conclusions. Hygienic standards for the content of motor transport emissions in the air of residential areas are provided by the optimal aeration mode, formed by choosing the width, position of the route, number of floors, planning techniques, and density of development of main streets. Simultaneously, it is necessary to introduce measures aimed at reducing the gross emissions of pollutants into the atmosphere and eliminating foci of atmospheric pollution on the transport networks of cities. When selecting urban planning decisions that ensure the environmental quality of the living environment of settlements in different geographical areas, it is necessary to consider the peculiarities of spatial-temporal dynamics of air pollution by transport and communications, due to changes in meteorological conditions and fluctuations in the intensity of traffic by hour of day, day of week and season of the year.

Aeration ofVitis viniferaShiraz fermentation and its effect on wine chemical composition and sensory attributes

Background and Aims Aeration during fermentation of red wines has the potential to enhance positive red fruit attributes and suppress less desirable reductive characteristics. The implementation of aeration in commercial winemaking, however, is impeded by the lack of a clear understanding of both the major benefits of its use and the nature of the aeration regimes required to modify the finished product. This work aimed to evaluate the impact of different modes of aeration, varying in their timing, duration and intensity, on fermentation duration, chemical composition and sensory properties of Shiraz wine. Methods and Results Forty-eight pilot-scale fermentations (450 kg) were treated with different aeration modalities and compared to non-aerated fermentations across four vintages. This work demonstrated the reproducible effects of aeration, resulting in an enhancement of fruit-related attributes, decreases in colour intensity and a lowering of astringent mouthfeel and bitterness. The development of attributes describing possible oxidation or undesirable volatility were not observed in this work. These effects on wine sensory attributes were correlated with an increase in the concentration of relevant short and branched-chain esters and acetates, and a decrease in the concentration of phenolic substances. No enhancement of fermentation performance was observed in any of the trials. Overall, this work revealed the robustness of red wine fermentations to aeration. Conclusions This work provides strong evidence that aeration does not alter the duration of either alcoholic or malolactic fermentation of red musts. Although there was no impact on fermentation performance, aeration did result in the production of wines with increased red fruit characters, and decreased astringency and reductive off-odours. Significance of the Study This work demonstrates aeration to be a useful oenological tool for the production of red wine and indicates that stylistic impact, rather than fermentation performance, is likely to be more pertinent to the adoption of red wine aeration.

Optimization of biotic and abiotic factors liable for biodegradation of chlorpyrifos and their modeling using neural network approaches

Chlorpyrifos has a substantial risk to human health besides biodiversity. In the present study, a previously isolated bacterial strain Enterobacter sp. SWLC2 has been used to investigate its biodegradation potential in different soil-slurries systems and to optimize culture conditions to achieve enhanced biodegradation of chlorpyrifos. The optimization results indicate that the maximum (87%) spiked-chlorpyrifos biodegradation occurred in a sandy loam soil-slurry system in aeration mode after 18 days of incubation at the optimal temperature (35 °C) and pH (7). The effect of sources of carbon/nitrogen (organic sugars, organic acids, and amino acids, etc.) on the biodegradation of chlorpyrifos has been investigated and their optimal values are estimated. The neural networks have been designed to find the optimal values of earlier factors in the predictive modeling of degradation of chlorpyrifos.

Characteristics of the extracellular products of pure oxygen aerated activated sludge in batch mode.

The effects of pure oxygen aeration on compositional characteristics of soluble microbial products (SMP) and extracellular polymeric substances (EPS) of the activated sludge acclimated in a sequential batch reactor (SBR) were explored in batch mode. The structure of the extracellular products would change with different aeration methods or aeration rates. The proportion of SMP of most oxygen aerated sludge was less than 10%, while that in air aerated sludge was as high as 30-40%. The proportion of TB-EPS decreased from 56.95% to 30.63%, and the proportion of LB-EPS increased obviously with the increase of oxygen aeration rate. The contents of the protein (PN) and the polysaccharide (PS) of extracellular products with oxygen aeration were significantly different, and the PN was much higher than PS (p < 0.05). The zeta potential of each component in activated sludge was negative, gradually decreasing with the progress of biological treatment. The fluorescence peaks in SMP, LB-EPS and TB-EPS with pure oxygen aeration were attributed to tryptophan PN-like and humic acid-like fractions. The results showed that the proportion of the components in the extracellular products could be regulated by adjusting the aeration rate and aeration mode, so as to optimize the treatment process of activated sludge.