Application of Dynamic Simulations for Assessment of Urban Wastewater Systems Operation

The paper presents the results of a study aimed at the use of simple mathematical models of a sewer network, wastewater treatment plant (WWTP) and receiving water to control the discharge of diluted wastewater from combined sewer overflow system in order to protect water resources. The greatest burden on the receiving water usually occurs at the time of combined sewer system overflow, when diluted municipal wastewater is also discharged into the receiving water. Literature usually presents impact assessment results of either wastewater treatment plants or sewer system on the receiving water. In our work, we assess the impact of the integrated municipal wastewater system on the receiving water. The models for the sewer system, wastewater treatment plant, and receiving water under consideration were developed. Mathematical modelling of the subsystems of urban wastewater system was carried out using simulator SIMBA 6. Simulations were performed using real experimental data. Information about the sewer system overflow during the year (total amount of overflow, pollutant load of COD during overflow) was obtained by using dynamic simulations. The simulation results aimed at the impact assessment of the sewer system overflow and WWTP on the receiving water quality showed that the values of the monitored parameters in the river could exceed several times the environmental quality standards for receiving water

Degradation of Benzothiazole by Ozonation and Adsorptive Ozonation

The paper deals with the study of the use of ozonation for removal of benzothiazole rom model wastewater in order to perform chemical transformation and facilitate consecutive biological mineralization of ozonation products. Adsorption of benzothiazole on active carbon and integrated ozonation of benzothiazole with the addition of active carbon, were also studied. Lab-scale ozonation experiments were performed using ozone prepared from pure oxygen. Concentration values of benzothiazole as well as COD and TOC were measured during experiments. The oxidation intermediates of the processes were also studied. The best efficiency of benzothiazole degradation and transformation was observed when the combined ozonation/activated carbon process was applied. Respirometric measurements were carried out in order to evaluate the impact of ozonation products on the activated sludge microorganisms activity. Enhancement of biodegradability by ozonation was indicated by the increase in oxygen uptake rate with an increase in dosed volume of ozonated sample into respirometric cell

Removal of Selected Organochlorine Compounds by Ozone-based Processes

The paper is focused on the possibility of using ozonation process combined with iron nanoparticles (nZVI – nano zero-valent iron) to remove selected specific synthetic substances, such as hexachlorobutadiene, pentachlorobenzene, hexachlorobenzene, lindane and heptachlor. Experimental measurements were performed in order to evaluate the effectiveness of the removal of substances and their removal rates. Removal of pesticides was also monitored through calculated DOC (dissolved organic carbon) as cumulative wastewater quality indicator. We investigated the effectiveness of 5 mL L–1 nZVI suspension (equal to 1 g Fe0) for the optimization of micropollutants removal from model water. Applications of 5 mL L–1 nZVI suspension and combined O3/nZVI processes have been shown as the most effective. Increasing concentrations of nZVI had almost no impact on the efficiency of the degradation process. Higher degradation efficiencies of γ-HCH were measured in O3/nZVI compared to the ozonation process. Degradation of pesticides HCLB, HCLBD and PCLB in all tested processes achieved efficiencies above 88 %. This work is licensed under a Creative Commons Attribution 4.0 International License

Adsorptive Removal of Pentavalent Arsenic from Aqueous Solutions by Granular Ferric Oxide

Arsenic contamination of water resources, which is characterized by strong carcinogenic and toxic impacts, is a global problem. Therefore, the present study is focused on the isotherm and kinetic studies of pentavalent arsenic As(V) adsorption with initial concentration of 1 000 µg L−1 from aqueous solutions onto granular ferric oxide (GFO). Adsorption experiments were carried out by batch method, and the equilibrium and kinetic data were evaluated by the Langmuir, Freundlich, Dubinin-Radushkevich, Redlich-Peterson and Sips isotherm model, and pseudo-first and pseudo-second order kinetic model. The results obtained from this study imply that the adsorption of As(V) onto GFO was favourable, physical and multilayer process. The Sips and Redlich-Peterson isotherm and the pseudo-first order kinetic model gave the best fit to experimental data according to the values of correlation coefficient. The maximum theoretical adsorption capacity from Langmuir isotherm model was determined to be 1 900 µg g−1. In addition, the impact of different operating conditions such as As(V) initial concentration, adsorbent dose, agitation speed, pH, temperature, and presence of phosphates and silica on adsorption capacity of GFO was also investigated. As(V) was efficiently recovered from GFO by 0.1 M NaOH desorbing solution during the three adsorption-desorption cycles

Removal of Alkylphenols from Industrial and Municipal Wastewater

The results of the study of removal of nonylphenol, octylphenol and their ethoxylates from real industrial and municipal wastewater are presented. Industrial wastewater was pre-treated by coagulation with FeCl3 and adsorption on zeolite, before discharging into municipal sewer system. Their removal efficiencies in primary sedimentation tank of municipal WWTP were very low. From the practical point of view, the highest and the most significant removal efficiencies within the whole WWTP were observed for nonylphenol and nonylphenol ethoxylates. Dominancy of abiotic mechanisms of alkylphenols removal follows from adsorption measurements. Activated sludge cultivated in lab-scale extended aeration tank accounted for relatively high adsorption affinity to these substances. Activated sludge sampled from municipal wastewater treatment plant (MWWTP) receiving industrial wastewater containing alkylphenols accounted for very low adsorption affinity to these pollutants. Significantly higher removal efficiency of octylphenol ethoxylates was observed with the O3/granular active carbon (GAC) process compared to the ozonation process alone. Lower toxicity impact of intermediates and products of ozonation treatment on Vibrio fischeri was measured in comparison to the O3/GAC process. Actually, the municipal WWTP effluent discharge concentration values complies with EQS values, including nonylphenols. This work is licensed under a Creative Commons Attribution 4.0 International License

Kinetic Study of the Ozonation of Atrazine

The kinetic study of the ozonation of atrazine as a single contaminant characterized as COD was studied. A jet loop ejector reactor was used to improve the mixing and transfer of ozone in the reaction system. The results show a higher efficiency of atrazine degradation in alkaline pH during the first 45 minutes. At the same time, the dechlorination of atrazine is faster than in neutral pH. Respirometric measurements carried out with activated sludge were used to evaluate the effect of atrazine and the ozonation intermediates on microorganisms’ oxygen uptake rate. The results showed that ozonation performed at an alkaline pH resulted in the formation of substances that are more rapidly biodegradable compared to substances formed by ozonation at neutral pH, as well as compared to atrazine

Biological Nutrient Removal in an Intermittently Aerated Bioreactor

The extension of biological processes from carbonaceous impurities removal to nitrogen and phosphorus removal had an impact on the biological system configuration. The system must be well designed, optimized, and operated at its optimum in order to meet the ever more stringent effluent standards. An intermittently aerated completely mixed lab-scale activated sludge bioreactor (IACMB) has been used for modelling biological processes of nutrients removal. Concerning the nitrogen removal, the operating cycles 15–30 (15 minutes of aeration, 30 minutes of only mixing without aeration) and 30–30 were tested. For the experiments with luxury uptake processes, the operating cycles 15–45, 15–90, 30–60 and 15–75 were used. The cycle 15–75 was the most satisfactory with convenient lengths of aerobic, anoxic, and anaerobic period, high efficiency of the nitrification and denitrification processes, and significant decrease in phosphorus concentration. The results have shown that the intermittently aerated bioreactors are suitable for nitrogen removal as well as luxury uptake of phosphorus. The main advantage is high flexibility in maintenance and control of biochemical environments in the bioreactor. This work is licensed under a Creative Commons Attribution 4.0 International License

Dynamic simulations of waste water treatment plant operation

Activated Sludge Model No. 1 (ASM1) was used to model the biological stage of an actual waste water treatment plant (WWTP). Some possibilities for the utilisation of simulation programs for WWTP operation are presented. Simulation calculations were performed taking the conditions of WWTP in Nové Zámky, the Slovak Republic, into consideration, where measurements of the diurnal variations in waste water flow and composition at the inlet and outlet were carried out. A calibrated model predicting the influence of changes in the waste water composition and the operational parameters on the effluent waste water quality and related operational costs is available. Values of the operational parameters (solids retention time, internal recirculation flow, dissolved oxygen concentration) for effective operation (effluent concentration values, oxygen consumption, charges, i.e. charges for waste water discharge into the recipient water body) of the WWTP were obtained by simulations. The presented results are for illustration purposes only and are not intended as instructions for the operation of a waste water treatment plant. They correspond to the calibrated mathematical model ASM 1 based on the results of experimental measurements and operational data, as well as on the technical and monitoring level of the WWTP

Mathematical Modeling of an Oil Refinery WWTP

Activated Sludge Model No. 1 (ASM1) was used in the modeling of an activated sludge system treating effluents from an oil refinery. The measurements of the diurnal variation in wastewater flow and composition at the wastewater treatment plant inlet and outlet were carried out. The calibrated model predicting the influence of changes in the wastewater composition and the operational parameters on the effluent wastewater quality and the related operational costs is available. A calibration technique based on the heuristic method was applied. The model was used to analyze the influence of changes in wastewater flow and composition as well as different aeration systems on the process performance. The results of dynamic simulations indicate that the verified dynamic mathematical model is a useful supporting tool for optimizing operational parameter values and operational costs. The presented results are for illustration purposes only and are not intended as instructions for the operation of a wastewater treatment plant