Aeration Tank Research Articles

Remediation of phenanthrene contaminated soil through persulfate oxidation coupled microbial fortification

The technology of chemical oxidation coupled microbial remediation of polycyclic aromatic hydrocarbons contaminated soil was efficient and friendly, but the research on the compatibility of chemical oxidation and the bioremediation is insufficient. This study was to explore the compatibility of persulfate oxidation coupled microbial degradation and promote the remediation of phenanthrene contaminated soil. The results showed that the addition of persulfate with the participation of Fe2+ caused the soil environment to be acidic and the soil pH with the lower concentrations (20, 50 mmol/L) of persulfate returned to neutral after 14 days. The content of fulvic-like and humic-like increased after adding persulfate at the same time. Persulfate inhibited the activity of soil dehydrogenase and polyphenol oxidase, simultaneously, the oxidation species generated during the persulfate oxidation process and the acidic environment (pH=4.13) led the soil microbial abundance and diversity to decrease significantly. Besides, the phenanthrene degradation bacterial consortium was screened through a gradual domestication process, which derived from activated sludge in the coking plant wastewater aeration tank of Xuzhou Weitian Chemical Co., Ltd. The efficient degrading bacteria were identified as Pantoea (95%) using high-throughput sequencing, with the 84% degradation rate of phenanthrene after the 7th day. Comparing persulfate oxidation, the removal rate of phenanthrene in the soil was increased by 33% after 63 days of the combined remediation. Adding 20 mmol/L persulfate and inoculating domesticated high-efficiency degrading bacteria Pantoea was recommended in the remediation of PAHs contaminated soil.

Influence of substrates concentrations on the dynamics of oxygen demand and aeration performance in ideal bioreactors

The effect of bioreactor configurations on the dynamics of aeration modelling was investigated by incorporating three different correlations from the literature to estimate α-factors into the aeration model. Estimated air flow rates using the three correlations were then validated against experimental data obtained from pilot sequencing batch reactors (SBRs). Two identical SBRs were operated in parallel; one received raw wastewater and the other received primary treated wastewater. The validated aeration model was then used to evaluate aeration dynamics in different bioreactor configurations, both for nitrification only and nitrification/denitrification, with the three different correlations. The current study is the first to investigate the validity of the aforementioned correlations using various bioreactor configurations and to establish that the bioreactor configuration not only impacts spatial and temporal biological oxygen demands as currently understood but also oxygen transfer efficiency. The first correlation based on the real-time bioreactor soluble chemical oxygen demand (sCOD) was able to predict the temporal measured air flow rate in the pilot SBRs. The second correlation based on the influent COD overestimated the air flow rates as it considered the impact of the influent loading rates on the α-factor and overlooked the improvement in α-factor due to biodegradation. The third correlation based on MLSS concentrations underestimated the air flow rates at the beginning of the aeration cycle as it ignored the impact of influent loading rates on the α-factor and considered only the insignificant change in MLSS during the aeration cycle. In terms of bioreactor configuration, the model-based analysis showed that the first correlation is suitable for designing SBR, plug flow reactor (PFR), step-feed PFR, and completely mixed stirred reactor (CSTR) systems, and the third correlation is suitable for designing CSTRs and membrane bioreactors (MBRs), while the second correlation was not accurate in any of the reactors modelled. When nitrification was targeted, the CSTR reduced aeration energy by 44 %–49 % compared to the PFR, and 41 %–43 % when both nitrification and denitrification were targeted. Compared to the plug-flow reactor, the step-feed PFR reduced aeration energy by 9% when nitrification only was targeted. However, when pre-denitrification was added, both systems showed the same aeration energy consumption. Pre-denitrification reduced organic loadings to aeration tanks and decreased aeration energy by 22 %, 11 %, 15 %, and 14 % in PFR, CSTR, PFR step feed and MBR systems, respectively.

Aging microplastics in wastewater pipeline networks and treatment processes: Physicochemical characteristics and Cd adsorption

Despite a wealth of information on removal of the microplastics (MPs) in wastewater treatment plants (WWTPs), little attention has been paid to how wastewater treatment process affect the MP physicochemical and adsorption characteristics. In this study, changes in physicochemical property of three MPs, i.e. polyamide (PA), polyethylene (PE) and polystyrene (PS) through the wastewater pipeline, grit and biological aeration tanks were investigated. The results show that compared with virgin MPs, the treated MPs have higher specific surface area and O content, and lower C and H contents, and glass transition temperature, implying that the three treatments cause the chain scission and oxidation of the MPs. Cd adsorption capacities of the MPs are higher than the corresponding virgin MPs after sulfidation in the pipeline (SWPN) and biological treatment in aeration tank (BTAT). Pearson correlation analysis shows that the increase is mainly resulted from the enhancement of the O-containing groups on the MPs. However, Cd adsorption capacities of the MPs decrease after mechanical abrasion in grit tank (MAGT), corresponding to the decrease in carbonyl index. Two dimensional FTIR correlation spectroscopy demonstrates that the NH bond in the PA plays a more important role than CH bond in the adsorption of Cd, but only change of the CH bond is found in the PE and PS. The findings provide new insights into the effect of WWTPs on the MP aging and physicochemical characteristics.

COMPUTER SIMULATION OF BIOLOGICAL WASTEWATER TREATMENT PROCESSES IN AEROTANKS WITH PLATES

Purpose. Efficiency determination of the aeration tank at the stage of design or reconstruction of bioreactors in which biological wastewater treatment is carried out requires the use of special mathematical models and calculation methods. The main purpose of the article is to develop CFD models for evaluating the operation efficiency of aeration tanks. Methodology. A numerical model has been developed for the computer calculation of the biological wastewater treatment process in aerotanks, taking into account hydrodynamics. The model is based on two-level mass conservation equations for the substrate and activated sludge and the velocity potential equation. The process of biological transformation of the substrate is calculated based on the Monod model. For the numerical integration of the mass transfer equations of activated sludge and substrate, the alternating-triangular difference splitting scheme is used. In this case, the basic equations are divided into two equations of a more simplified form. For the numerical integration of the equations for the velocity potential, it is split into two one-dimensional equations. Further, each equation is solved according to explicit scheme. For the numerical integration of equations that describe the process of substrate transformation based on the Monod model, the Euler method is used. Findings. The software implementation of the constructed numerical model has been carried out. The results of a computational experiment on the study of the wastewater treatment process in an aeration tank with plates are presented. This leads to the conclusion that the quality control of wastewater treatment in aeration tanks is possible with the help of plates. Originality. A multivariate CFD model has been developed, which makes it possible to quickly assess the efficiency of the aeration tank. A feature of the model is the ability to evaluate the operation of the aeration tank, taking into account its geometric shape and location of additional plates in the construction. Practical value. The constructed numerical model can be used during calculations in the case of designing aeration tanks, or in determining the efficiency of wastewater treatment under new operating conditions.

Research on the effects of ferric salt added into aeration tank for phosphorus removal on biochemical system

Abstract In this paper, two iron salts, ferrous chloride (FeCl2) and ferric chloride (FeCl3), are directly added into an aeration tank for phosphorus removal, and their effects on the biochemical system are studied; the water quality parameters such as pH and alkalinity are also investigated. The extent of influence of the added iron salts on the pH and alkalinity of aerated solutions is demonstrated to be FeCl3 > FeCl2. When the dosage of iron ions is 20 mg/L, the decrease in pH and alkalinity caused by FeCl3 is 0.5 and 65 mg/L, which is higher than FeCl2 by 2% and 26%. The initial phosphorus removal effect of FeCl2 is worse than that of FeCl3, but after continued aeration and oxidation, the phosphorus removal effect of FeCl2 can be improved; however, the final phosphorus removal effect is basically the same as that of FeCl3 added directly. The results show that FeCl2 is preferred when iron salt is added directly into the aeration tank to remove phosphorus. The proposed scheme can reduce the effect of iron salts on the alkalinity of the biochemical system on the premise of ensuring the phosphorus removal effect of the system, and is conducive to ensuring the stable operation of the biochemical system.

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.

Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs; Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge.

This is the first study that examines the effect of operating conditions on fouling of Membrane Bio-Reactors (MBRs), which treat municipal wastewater in field conditions, with specific regard to the controlled development of filamentous microorganisms (or filaments). The novelty of the present work is extended to minimize the dissolved oxygen (DO) in recirculated activated sludge for improving the process of denitrification. For this purpose, two pilot-scale MBRs were constructed and operated in parallel: (i) Filament-MBR, where an attempt was made to regulate the growth of filaments by adjustment of DO, the Food-to-Microorganisms (F/M) ratio and temperature, and (ii) Control-MBR, where a gentle stirring tank was employed for the purpose of zeroing the DO in the recycled sludge. Results showed that low temperature (<15 °C) slightly increased the number of filaments in the Filament-MBR which, in turn, decreased the Trans-Membrane Pressure (TMP). As the Soluble Microbial Products (SMP) and the colloids are considered to be the basic foulants of membranes in MBR systems, specific attention was directed to keep their concentration at low values in the mixed liquor. The low F/M ratio in the aeration tanks which preceded the membrane tank was achieved to keep the SMP proteins and carbohydrates at very low values in the mixed liquor, i.e., less than 6 mg/L. Moreover, as a result of the low recirculation rate (2.6∙Qin), good aggregation of the produced excess sludge was achieved, and low concentration of colloids with a size ≤50 nm (nearly the membranes’ pore size used for filtration/separation) was measured, accounted for maximum 15% of the total colloids. Additionally, the increase in filamentous population at the Filament-MBR contributed to the further reduction of colloids in the mixed liquor at 7.9%, contributing beneficially to the reduction of TMP and of membrane fouling. The diminishing of DO in the recirculated sludge improved denitrification, and resulted in lower concentrations of Ν-NO3− and TN in the effluent of the Control-MBR. Furthermore, the recirculation rate of Qr = 2.6∙Qin, in comparison with Qr = 4.3∙Qin, resulted in improved performance regarding the removal of N-NH4+. Finally, high organics removal and ammonium nitrification was observed in the effluent of both pilots, since COD and Ν-ΝH4+ concentrations were generally in the range of 10–25 mg/L and <0.1 mg/L, respectively.

Evaluating the performance of fine bubble diffused aeration systems in cylindrical aeration tanks by fuzzy c-means algorithm.

In order to make a comprehensive evaluation of the performance of fine bubble diffused aeration systems in cylindrical aeration tanks, the following parameters are considered: distribution of DO concentration in the horizontal direction of the different water depth of an aeration tank, distribution of DO concentration in the vertical direction of the aeration tank, distribution of DO concentration in all the points of the aeration tank and ratio of total mass increment of DO in the aeration tank to total mass of oxygen in aeration air. The aeration characteristic criterion (ACC) is proposed to synthesize these parameters, and weighted sums of the similarity degrees derived from the extensions of fuzzy c-means (FCM) are used to construct ACC. The results show that compared with total volumetric oxygen transfer coefficient (KLα) and specific standard oxygen transfer efficiency (SSOTE), ACC is demonstrated to be more marked and sensitive for the performance evaluation of the fine bubble diffused aeration systems equipped with fine-pore aeration tubes. Moreover the performance of aeration systems equipped with different layouts of fine-pore aeration tubes is comparatively studied, and their performance from best to worst is ring-type diffuser > square-type diffuser > parallel-lines-type diffuser > cross-type diffuser.

An Analysis of Operation Conditions and Microbial Characteristics in Swine Wastewater Treatment Plants with Spontaneously Enriched Anammox Bacteria

The spontaneous enrichment of anammox bacteria has been reported in swine wastewater treatment facilities. However, their causative conditions and microbial characteristics, which this study aims to explain, are poorly understood. We discovered eight treatment facilities where the collected red biofilms exhibited high anammox activity levels at 57–843 µmol-N2/g-ignition loss (IL)/h and anammox DNA concentrations of 4.3 × 108–1.6 × 1012 copies/g-IL. The facilities used various wastewater treatment methods—six of them employed a multi-stage continuous reactor, whereas aeration tanks were continuously aerated at another combination of six facilities. Levels of dissolved oxygen (DO) in these tanks were fairly low at ≤1 mg/L. Pyrosequencing of the biofilms indicated the presence of 3–62.5% Planctomycetes, and the dominant anammox in each biofilm comprised three operational taxonomic units (OTUs) similar to Candidatus Jettenia asiatica, Ca. Brocadia fulgida, and Ca. B. caroliniensis. This suggested that some particular species of anammox bacteria naturally thrive when operating a swine wastewater treatment facility at low DO levels. The frequent enrichment of anammox biofilms at the sampled sites indicated that these treatment facilities were good seed sources of anammox; therefore, anammox treatment would be a viable method for the removal of nitrogen from swine wastewater.

Application of effective microorganisms technology on dairy wastewater treatment for irrigation purposes

Due to the massive amounts of freshwater consumed in dairy industries, as a result, thousands of liters of wastewater were produced as one liter of milk produces 10 liters of wastewater which represents a major threat to the surrounding environment and aquatic life. The application of a promising technology called “effective microorganism (EM)” was the key solution due to its low operating cost, low technology, and eco-friendly condition. Three different effective microorganisms were used, such as Bacillus bacteria (EM1), Staphylococcus bacteria (EM2), and EM stoste + Molasses (EM3). EM1 and EM2 were isolated from the dairy wastewater by using streaking for isolation on an agar plate process, while EM3 was prepared by mixing 12 % EM stoste, 6% molasses, and 82% distilled water. A laboratory pilot consists of aeration and final settling tanks, both tanks followed by an activated carbon filter. Four trials were performed, the first trial was without any EM, the second trial was adding EM1 with a dose of 50 ml to the aeration tank, the third trial was EM2 with a dose of 50 ml to the aeration tank, finally adding EM3 with a dose of 30 ml to the aeration tank. Results showed that using Bacillus bacteria (EM1) was the most effective trial as it was effective in reducing TSS (total suspended solids), BOD (biological oxygen demand), COD (chemical oxygen demand), TN (total nitrogen), and TP (total phosphorous) concentrations by removal efficiency of 93%, 96.2%, 95.9%, 94%, and 64%, respectively which were below the limitations of the Egyptian code for reuse for irrigation purposes.

Use of silt sludge after biological wastewater treatment for crop yields increasing

Researching the possible use of the silt sludge after biological wastewater treatment from the industrial enterprises for increasing the agricultural crops’ yield was spent. Silt sludge is obtained as a result of biological wastewater treatment in column-type aeration tanks. Founded the concentration’s increase of macro - and microelements in the silt sludge, improvement of the sanitary status and decrease of the heavy metals content after its treatment by the enzyme-cavitation method. Low-intensity cavitation with a cavitation number (0.01-0.05) with air oxygen saturation of the sediment (at least 10 mg/m3) allows for deep organic matter mineralization, dehydration pathogenic microflora’s destruction and dehilmintization. Shown the obtained complex fertilization into soil gives it nitrogen, humus and sulfur and increases the winter wheat’s yield.

Сравнение результатов расчета аэротенков по моделям НИИ ВОДГЕО/СамГТУ и ASM2d

Проведено сравнение результатов расчета аэротенков, реализующих процессы аэробного окисления органических соединений, нитрификации, денитрификации и удаления фосфора (химического и биологического) по двум различным математическим моделям (методикам): ВОДГЕО/СамГТУ (Самарского государственного технического университета)и ASM2d. Эти модели относятся к теоретическим и описывают процессы биологической очистки сточных вод с помощью формул ферментативной кинетики. Расчеты для одних и тех же входных и выходных данных показали высокую сходимость результатов по объемам технологических зон аэротенков. Для качества очищенных вод до требований ПДК для водных объектов рыбохозяйственного значения (вариант 1) расхождение составляет –0,3 и 3,3% соответственно для аноксидной и аэробной зон. При показателях на сброс в водный объект категории Б (вариант 2) для сооружений от больших до сверхкрупных разница в результатах расчета объемов составила соответственно 13,8 и 15,4%. При расчете с учетом качества очищенной воды до значений технологических показателей на сброс в водный объект категории Г (вариант 3) для очистных сооружений от больших до сверхкрупных расхождение в значениях объемов аэробных зон составило 48%, что обусловлено целесообразностью обеспечения устойчивой нитрификации при высоких нагрузках. Поэтому вариант 3 по методике ВОДГЕО/СамГТУ фактически выполнен на более низкую нагрузку на ил и более глубокую нитрификацию, чем по методике ASM2d (1 вместо 2 мгN–NH4/л). Показано, что лежащие в основе обеих методик математические модели, базирующиеся на фундаментальных уравнениях ферментативной реакции, весьма высокая сходимость и логичность результатов расчетов дают основание утверждать, что обе эти модели в наибольшей степени из известных приемлемы для расчета сооружений биологической очистки сточных вод с удалением азота и фосфора. The paper presents a comparison of the results of calculating aeration tanks where the processes of aerobic oxidation of organic compounds, nitrification, denitrification and phosphorus removal (chemical and biological) according to two different mathematical models (methods): VODGEO/SamGTU (Samara State Technical University) and ASM2d have been implemented. These models are theoretical and describe the processes of biological wastewater treatment using enzymatic kinetics formulas. Calculations for the same input and output data showed a high reproducibility in terms of the volumes of the process zones of aeration tanks. For the quality of effluent meeting the MPCs for fishery water bodies (option 1), the discrepancy is –0.3 and 3.3%, respectively, for the anoxid and aerobic zones. With indicators for effluent discharge into a water body of category B (option 2) for large-scale to extremely large-scale facilities, the difference in the results of calculating the volumes was 13,8 and 15.4%, respectively. While making calculations with account of the effluent quality reaching the process indicators for discharge into a water body of category G (option 3) for large-scale to extremely large-scale facilities, the discrepancy in the values of the volumes of aerobic zones was 48% owing to the expediency of ensuring stable nitrification at high loads. Therefore, option 3 according to the VODGEO/SamGTU method was actually performed for a lower sludge load and more enhanced nitrification than according to the ASM2d method (1 instead of 2 mgN–NH4/l). It is shown that the mathematical models underlying both methods, based on the fundamental equations of the enzymatic reaction, a very high reproducibility and consistency of the calculation results give grounds to assert that both of these models are, to the greatest extent known, acceptable for calculating biological treatment facilities with the removal of nitrogen and phosphorus.

Design of the Reactor and the Clarifier of an Activated Sludge Water Resource Recovery Facility, AS WRRF

Metcalf & Eddy´s formula that gives the mixed liquor volatile suspended solids, MLVSS= Xv, produced in the aeration tank, from hereon called Reactor, will be used giving it the parameters for AS WRRFs shown in Table 10-5 of its 3rd Edition placing values of hydraulic retention time, HRT, in the first column and values of solids retention time, SRT, in the first row. Many solutions are found that solve the formula. Some will be studied, using the flux graph, to check if they comply with other requirements as moderate volume, V, of Reactor, small surface, S, of Clarifier, ample range of return flow percentages, R, and admissible relation F/M. A solution will then be chosen.

Chloride and Sulphate Removal by Using N-GET System with Additional Filters

Groundwater is an alternative source of water for human consumption. Groundwater at Research Centre of Soft Soil (RECESS), Universiti Tun Hussein Onn Malaysia (UTHM) is one of the water sources that available to be used. Unfortunately, it has a high content of chloride and sulphate concentration in which originated from the mineral content in the ground. This research was conducted to identify the effectiveness of the Nature Groundwater Eco-Treatment (N-GET) system that has been designed at RECESS in removing sulphate and chloride concentration as well as pH and turbidity parameter. N-GET system is a natural treatment process without mixing any substances intended to improve the quality of groundwater can give benefits to users. N-GET system in this study uses two treatment tanks in the treatment of groundwater which are aeration tanks, sedimentation tanks, and three sets of filters which were activated carbon filter, Do-It-Yourself (DIY) filter, and ceramic filter. The chloride and sulphate parameters were tested with 12 numbers of the sample while pH and turbidity were tested with 63 numbers of the sample. Using combination with sedimentation and aeration, ceramic filtration were performing better by reducing the pH of the samples by 3.9% towards neutrality and removed 32.6 % of sulphate, 13.1 % turbidity, and 33.0 % of chloride concentration from RECESS groundwater in comparison to an activated carbon filter, Do-It-Yourself (DIY) filter. Then, the effectiveness of each filter based on design flow and types of particle size in the filter. Therefore, the capability of each filter able to remove the specific contaminant as designed need.

RESEARCH ON IMPROVEMENT OF THE METHOD OF PERIODIC AERATION OF WASTEWATER

The aeration process is a key part of biological wastewater treatment technology. But, paradoxically, during the existence of this technology, it has not changed significantly. The process of aeration of wastewater remains the largest consumer of electricity in the entire complex of treatment facilities. The possibility of adjusting the duration of the aeration cycle depending on the "explosive" change in the amount of contaminants was stated. In this case, the system must respond to this "perturbation" and adjust the duration of the aeration cycle to provide the necessary oxygen regime of biological oxidation of contaminants. The research data on the method of periodic aeration based on a comparison of the concentration of oxygen in the liquid to be cleaned and in the gases leaving after aeration are presented. The basic principle is that the aeration system continues to supply oxygen, which is no longer able to diffuse into the aerated liquid, and comes to the surface, bypassing the process of mass transfer. The experimentally established method of adjusting the duration of aeration periods for implementation in one aeration tank can be applied to a whole group of aeration tanks. Using the method in the optimal mode for each of the specified number of aeration tanks is impossible without the use of a microprocessor. Therefore, a control method was developed that allows the application of a fundamentally new algorithm for periodic aeration. This algorithm allows to increase the growth of activated sludge and to increase the efficiency of wastewater treatment. To assess the possibility of stabilizing the operation of certain aeration tanks, in the implementation of intermittent aeration by the concentration of oxygen in the liquid, a model example was considered, from which follows the differential equation of oxygen balance in the liquid. The study of this equation for stability and behavior in the phase plane makes it possible to choose the conditions under which the periodic aeration algorithm will be the most efficient in terms of purification and energy consumption. Theoretical calculation gave a mathematical justification for the experimental data. Based on numerical calculations, the condition of optimal operation of the aeration system for a group of aeration tanks is derived. Thus, it was found that the optimal concentration of oxygen in the liquid at which to start aeration is 0.06-0.12 mg / dm3. Periodic aeration with a period of 30 minutes makes it possible to maintain a stable gradient of oxygen concentrations in the liquid. The productivity of treatment plants according to the developed algorithm of controlled aeration, in accordance with the concentration of oxygen in the liquid to be cleaned, ensures the rational use of electricity.

Compressor Scheduling and Pressure Control for an Alternating Aeration Activated Sludge Process—A Simulation Study Validated on Plant Data

Aiming at reducing their emissions, wastewater treatment plants (WWTP) seek to reduce their energy consumption, where a large amount is used for the aeration. The case plant, Grindsted WWTP uses an alternating aeration strategy, with a common air supply system facilitating the process in four aeration tanks and thus making optimisation challenging. In this work, a nonlinear model of the air supply system is designed, in which multiple key parameters are estimated by data-driven optimization. Subsequently, a model-based control strategy for scheduling of compressors and desired airflow is proposed, to save energy without compromising the aeration performance. The strategy is based upon partly static- partly dynamic models of the compressors, describing their efficiency in terms of system head and volumetric airflow rate. The simulation study uses real plant data and shows great potential for improvement of energy efficiency, regardless of the aeration pattern in any of the four process tanks, and furthermore contributes to a reduction in compressor restarts per day. The proposed method is applicable to other WWTP with multiple compressors in the air supply system, as this study is conducted using first principle models validated on data from the daily operation.

3D MODELING OF BIOLOGICAL WASTEWATER TREATMENT IN AERATION TANK

Purpose. The main purpose of the article is to develop a 3D CFD model for modeling the process of biological wastewater treatment in an aeration tank. Methodology. For mathematical modeling of the process of biological wastewater treatment in the reactor, taking into account the flow hydrodynamics, geometric shape of the aeration tank, convective-diffusion transfer of the substrate and activated sludge, a 3D CFD model was built. The model is based on the three-dimensional equation of motion of an ideal liquid and the equation of mass conservation for the substrate, activated sludge. The field of sewage flow rate in the aeration tank is calculated based on the velocity potential equation. The process of biological transformation of the substrate is calculated on the basis of the Monod model. The splitting scheme was used for numerical integration of the equations of convective-diffusion transfer of activated sludge and substrate. The splitting is carried out in such a way to take into account the transfer of substrate (activated sludge) in only one direction at each step of splitting. The calculation of the unknown value of the substrate (activated sludge) concentration is carried out according to an explicit scheme. The Richardson method is used to numerically integrate the three-dimensional equation for the velocity potential, and the unknown value of the velocity potential is calculated by an explicit formula. Euler's method is used for numerical integration of equations describing the process of substrate transformation and change in activated sludge concentration (Monod model). Findings. The software implementation of the constructed 3D CFD model is carried out. A description of the structure of the developed software package is provided. The results of a computer experiment to study the process of wastewater treatment in an aeration tank with additional elements are presented. Originality. A new multifactor 3D CFD model has been developed, which allows quick assessing the efficiency of biological treatment in an aeration tank. Practical value. The constructed 3D CFD model can be used to analyze the efficiency of the aeration tank under different operating conditions at the stage of sketch design of wastewater treatment systems.

Application of synthetic and grafted polymeric flocculants in agricultural wastewater treatment

Due to the large amounts of freshwater consumed in Egypt by the agricultural sector that is more than 85% of Egypt share of freshwater in addition to the high concentrations of salts, chemicals and nutrients produced from fertilizers. Reduction of these pollutants concentrations to an acceptable level and breaking the sedimentation stability of colloidal substances and organic particles for reuse for irrigation purposes was associated with the application of biological treatment with coagulants addition. The flocculation process was performed by using polydiallyldimethylammonium chloride (polyDADMAC) and polyacrylamide grafted oatmeal (OAT-g-PAM). The scale-pilot consists of an aeration tank equipped with an air blower, sedimentation tank followed by a filtration stage through 20 cm of pottery scrubs media. To study the performance of synthetic and grafted polymeric flocculants, 3 trials were performed. Activated sludge process without adding any polymeric flocculants was the control trial. In the second trial, polyDADMAC was added with a dose of 5 mg/l. Finally, OAT-g-PAM with a dose of 1.25 mg/l was used in the third trial. The physicochemical properties of agricultural wastewater were measured at the national research center in Cairo. It was found that OAT-g-PAM incorporated with activated sludge process was the most effective in treating agricultural wastewater as it achieved COD, BOD,TKN, TP, and TSS removal efficiency up to 92.29%, 93.13%, 90.64%, 90.46%, and 92.5%, respectively which made it suitable to reuse for agricultural purposes, in addition to its ability to biodegrade, environmentally friendly, and low dosage required compared to polyDADMAC.

Secondary wastewater treatment processes optimization

Introduction. The level of water pollution in Ukraine continues to grow, despite the strengthening of requirements for the treated water, so the existing approaches to the water treatment processes control need to be revised and improved.&#x0D; Materials and methods. Mathematical Programming methods for formalization and solving the optimization problem are used. Computer simulation research using the program developed by the authors are applied to verify the compliance of the obtained results with the normative values and data of normal operation.&#x0D; Results and discussion. The optimization of processes control was performed on the example of a typical process of secondary wastewater treatment, which is used for wastewater treatment in Kyiv and nearby settlements. The secondary treatment unit consists of an aeration tank, into which air is forcibly supplied and evenly distributed, and a secondary settling tank with recycling. The problem of optimization of biological wastewater treatment control process is formalized: minimization of pollutant concentration in treated water is chosen as the main aim of optimization, air flow to aeration tank is chosen as control parameter, quadratic deviation of current concentration values from normative ones is chosen for target function. To solve the optimization task, a software module in JavaScript was developed using a client-server architecture that works in real time and allows to obtain such values of oxygen consumption in the aeration tank, which provide a minimum deviation of the concentration of pollutants from the normative values. The simulations showed that the calculated control values provide a reduction in the concentration of pollutants to the normative values within 6-10 hours, which corresponds to the data of normal operation, and the difference between the calculated and actual data does not exceed 5%.&#x0D; Conclusions. The obtained results allow to find a set of technological influences to ensure optimal control according to the selected criterion, and are also the basis for calculating the control system. The results of calculations can be used for short-term - up to 8 hours - forecasting of water quality indicators.

TEMPERATURE PREDICT OF AERATION TANK WALLS FOR BIOLOGICAL WASTEWATER TREATMENT SUBSYSTEM OF HAMDAN STATION

A heat transfer modeled for predicting the wall temperature of aeration tank in a biological wastewater treatment subsystem of Hamden station is presented. The method to treatment employed depending upon the pollutants in wastewater and extent to which it is desired to eliminate them in order to congregate required standards of water quality. Several heat gain and loss mechanisms concerned to develop of the model of temperature computer includes heat gains through conduction and radiation. While the heat losses referred to convection and radiation. It classified radiation heat transfer and biological reaction as a gained heat, while classifying the rate of evaporation, aerator, and wind velocity as lost heat.&#x0D; This study relied on a previous study, and based on the assumptions that have been identified so that a model development can be obtained to calculate the surface temperature of the wall of the aeration tank in a biological treatment system. The operational, weather and temperature data were to be registered from Iraqi weather forecast- Basra Airport. To obtain reliable results, the model was simulated using the STELLA software v.9.02, which gave accurate results in determining the parameters that affect the tank wall temperature changes. The STELLA software is Model calibration and considers as a dynamics language because of STELLA is software for graphic and dynamic simulation for the wall temperature of aeration tank. The results have shown a good accuracy and increment between the production walls temperatures with average ranged about (0.2 %) of present work. The model shows the sensitivity through set of precious five parameters like organic removal rate, ambient air temperature, wind velocity, air relative humidity, and the wall effective area of the aeration tank