Aeration Regimes Research Articles

Trends of N2O production during decentralized wastewater treatment: a critical review

Nitrous oxide (N2O) emissions have become a significant concern due to their potential high contribution to the carbon footprint of wastewater treatment plants. While their production pathways in centralized systems have been already deeply investigated, an analysis of N2O production trends from decentralized wastewater treatment plants, with a detailed description of the operating conditions affecting N2O generation in each technology, is missing. In this work, research on N2O emission from several decentralized technologies, including septic tanks and leach fields, soil infiltration systems, waste stabilization ponds, onsite activated sludge systems, Johkasou systems, onsite advanced technologies and constructed wetlands is reviewed. N2O emissions were found to depend on operating parameters, among which aeration regime, light exposure, influent carbon-to-nitrogen ratio, environmental temperature, nitrite concentration, plant species, and pH. It was not always possible to clearly understand the influence of a specific parameter on N2O emissions, given the complexity of the producing pathways, the temporal and spatial N2O variability, and the limited data. Research gaps, such as the lack of monitoring nitrification and denitrification intermediates, and the lack of long-term N2O monitoring campaigns, have also been identified. Considering the widespread diffusion of decentralized wastewater technologies and their need to meet more stringent requirements on sanitation, it will be more and more important in the future to understand their specific contribution to wastewater treatment carbon footprint. Standardized monitoring techniques, established estimation methods for emission factors, and a wider application of mathematical models could help in achieving a greater understanding of the complex N2O generation pathways.

Aeration regime modifies ligninolytic enzyme production and biodegradation of reactive black 5 by immobilized Trametes versicolor

Aeration regime modifies ligninolytic enzyme production and biodegradation of reactive black 5 by immobilized Trametes versicolor

Multi-stage aeration regime to regulate organic conversion toward gas alleviation and humification in food waste digestate composting

Aerobic composting has been considered as a pragmatic technique to convert food waste digestate into high-quality biofertiliser. Nevertheless, massive gaseous emission and immature product remain the primary challenges in food waste digestate composting. Thus, the performance of multi-stage aeration regimes to improve gaseous emissions and organic humification during food waste digestate composting was investigated in this study. In addition to continuous aeration with a constant intensity of 0.3 L kg·dry mass (DM)−1·min−1, two multi-stage decreased aeration regimes were designed as “0.3-0.2-0.1” and “0.3-0.1-0.1” L·kg·DM−1·min−1 from the thermophilic to cooling and then mature stages, respectively. Results showed that the decreased aeration regimes could alleviate nitrous oxide (N2O) and ammonia (NH3) emission and slightly enhance humification during composting. The alleviated N2O and NH3 emission were mainly contributed by abiotically reducing gaseous release potential as well as biotically inactivating denitrifers (Pusillimonas and Pseudidiomarina) and proliferating Atopobium to reduce nitrate availability under lower aeration supply. The “0.3-0.2-0.1 L kg·DM−1·min−1” regime exhibited a more excellent performance to alleviate N2O and NH3 emission by 27.5% and 16.3%, respectively. Moreover, the decreased aeration regimes also favored the enrichment of functional bacteria (Caldicoprobacter and Syntrophomonas) to accelerate lignocellulosic biodegradation and thus humic acid synthesis by 6.5%–11.2%. Given its better performance to improve gaseous emissions and humification, the aeration regime of “0.3-0.2-0.1 L kg·DM−1·min−1” are recommended in food waste digestate composting in practice.

Water quality evaluation of the Danube River basin in Bačka (northern Serbia) using multivariate statistical techniques

The study aimed to analyze changes in water quality based on ten physicochemical parameters for the Danube River in Bačka. Data from three profiles over a twenty-year interval were used and processed using multivariate statistics. An ANOVA indicated that the quality of surface water is mostly at a satisfactory level. Sufficient amounts of dissolved oxygen indicate a favorable aeration regime. The surpassing of the annual and monthly values of suspended solids was recorded for all profiles (especially in summer). The summary results show that most parameters, except for suspended solids, are within the allowed values for water quality Class II. A Pearson’s correlation test indicates a moderate to weak correlation of the analyzed parameters. A PCA analysis determined the influence of (a) eutrophication processes; (b) ecological factors; and (c) concentrated sources of pollution. Changes in the Danube’s water quality, primarily increased concentrations of suspended solids, can exert a limiting influence on some economic activities and their planning.

Exploring the potential of Bacillus subtilis as cell factory for food ingredients and special chemicals

BackgroundBacillus subtilis has been established as model microorganism for fundamental research in the laboratory on protein production/secretion and sporulation and as model bacterium for controlling spoilage in the food industry. It has also been used for production of (commercial) enzymes and several secondary metabolites such as vitamins. However, this doesn’t fully reflect the potential of B. subtilis as a cell-factory. Here, various strains of B. subtilis, including food-grade, spore-deficient strains and industrially used strains, were compared for their growth and metabolic potential. Industry-relevant parameters were analyzed for all strains under various aeration regimes, under anaerobic conditions, in various nutritious and nutrient-limited cultivation media, with and without organic nitrogen sources, and with and without sugar.ResultsPractical experiments were conducted to compare industrial relevant properties like growth rates, intracellular components and extracellular metabolite profile of different B. subtilis strains. Based on growth flexibility in different media, we found that some strains like NCIB3610 and DSM1092 are adapted to inorganic or organic nitrogen source utilization, which is highly relevant when considering a biorefinery approach using various cheap and abundant waste/sidestreams. Secondly, spore-deficient strains such as 3NA, 168 S and PY79S, showed advantages in microbial protein and acetolactate pathway expression, which is associated with applications in food industry for protein supplement and diacetyl production. Lastly, WB800 and PY79S exhibited potential for fermentative production of dipicolinic acid, 2,3-butanediol and lactic acid that could serve as precursors for biopolymers.ConclusionThis study demonstrates the broad potential for more extensive industrial use of Bacillus subtilis in the (bio-based) chemical industry for use of sidestreams, in the personal care industry, in the food industry for food additive production, and in the bio-sustainable industry for biofuel and bio-degradable plastic precursors production. In addition, selecting different B. subtilis strains for specific purposes makes full use of the diversity of this species and increases the potential of B. subtilis in its contribution to the bio-based economy.

Application of the fermented broiler chickens manure under different aeration regimes during vermiculture cultivation

The growth of poultry population in Ukraine and in the world leads to a number of environmental problems such as concentration and accumulation of large masses of manure without litter and manure mixed with organic litter. A rational way to dispose poultry manure, including broiler chickens’ manure, is to produce vermicompost from it by growing there a hybrid of local red worm or Eisenia fetida. Unfermented broiler manure contains a high concentration of nitrogen-containing compounds, including ammonia, which has a negative effect on worms. Even at low ammonia concentrations in the organic biomass, the worms die. Traditional methods can take more than 17 months to compost broiler manure. One of the ways to speed up composting is to apply bioprocessing devices and aeration of the manure. The effectiveness of growing vermiculture on the fermented broiler manure with a biodegrader and different aeration regimes remains insufficiently studied. For the experimental cultivation of worms, we used the broiler chicken manure fermented for 160 days, which was enriched with air once every 10 days by mechanical mixing (control), 15 minutes a day using a compressor (I experimental group) and twice a day for 15 minutes using a compressor (II experimental group). The study determined the number of adult and immature worms, their weight, the number of cocoons and their weight. It has been experimentally found that fermented broiler chicken manure under different aeration regimes with litter as part of the vermiculture substrate has an effect on the reproduction and weight of worms and their cocoons. Growing worms on a substrate from fermented broiler chickens' litter with a daily one-time air enrichment with a compressor increases the number of mature worms by 15.7 % compared to the control group. The largest mass of mature worms was recorded in the first experimental group. It was proved that the use of fermented broiler manure with active aeration (experimental group I) as a substrate increased the number and weight of immature worms by 10.3 and 33.3 %, respectively, compared to the control. The largest number of cocoons has been found in the first experimental group.

Ensuring the quality of atmospheric air on main streets and in residential buildings by means of planning and landscaping

Introduction. The level of concentration of toxic substances in the atmospheric air of main streets is largely determined by their aeration regime, established due to exposure to air flow of buildings and green spaces. Therefore, when developing master plans of cities and projects of detailed planning of residential formations to ensure hygienic standards for the expected content of emissions of motor transport in the air of transport communications and adjacent residential buildings, the influence of urban factors on wind speed and direction one should take into account.
 The aim of the study is the justification and selection of urban planning measures to reduce atmospheric air pollution from main roads and streets by exhaust gases of motor transport.
 Material and methods. Full-scale surveys of transport infrastructure facilities in large cities and modelling of the processes of dispersion of exhaust gases of cars in the air using models of residential buildings and green spaces.
 Results. The regularities of the formation of the aeration regime of city streets and the dispersion of car emissions behind the landscaping strips and in residential buildings have been established. Optimal variants of planning, development and landscaping of main streets have been determined, ensuring the reduction of gas contamination of pedestrian zones, public spaces and residential areas.
 Limitations. The choice of landscaping objects for urban roads and streets for field observations and modelling of car emissions dispersion processes is limited to strips of green spaces of a blown and dense construction, without taking into account the peculiarities of the transformation of the air flow and reducing gas pollution under the influence of landscaping strips of an openwork design.
 Conclusions. Reduction of gas pollution of main roads and streets is ensured by choosing the direction of the route and planning, and building techniques. At the same time, it is necessary to use environmental protection linear-strip landscaping facilities of optimal design. At the same time, it should be borne in mind that frontal multi-sectional buildings and strips of green spaces of windproof dense construction stimulate the appearance of stable vortices with a closed circulation of impurities in street canyons and on sections of highways. When choosing urban planning solutions to ensure the quality of atmospheric air of transport communications and adjacent residential buildings in various landscape and climatic conditions, it is necessary to take into account the specifics of the tasks arising in this case to regulate the aeration regime and reclamation of the microclimate as a whole.

Carbon Monoxide Production during Bio-Waste Composting under Different Temperature and Aeration Regimes.

Despite the development of biorefinery processes, the possibility of coupling the "conventional" composting process with the production of biochemicals is not taken into account. However, net carbon monoxide (CO) production has been observed during bio-waste composting. So far, O2 concentration and temperature have been identified as the main variables influencing CO formation. This study aimed to investigate CO net production during bio-waste composting under controlled laboratory conditions by varying aeration rates and temperatures. A series of composting processes was carried out in conditions ranging from mesophilic to thermophilic (T = 35, 45, 55, and 65 °C) and an aeration rate of 2.7, 3.4, 4.8, and 7.8 L·h-1. Based on the findings of this study, suggestions for the improvement of CO production throughout the composting process have been developed for the first time. The highest concentrations of CO in each thermal variant was achieved with an O2 deficit (aeration rate 2.7 L·h-1); additionally, CO levels increased with temperature, reaching ~300 ppm at 65 °C. The production of CO in mesophilic and thermophilic conditions draws attention to biological CO formation by microorganisms capable of producing the CODH enzyme. Further research on CO production efficiency in these thermal ranges is necessary with the characterization of the microbial community and analysis of the ability of the identified bacteria to produce the CODH enzyme and convert CO from CO2.

The effect of aeration on treatment efficiency and bioenergy generation of septic-tank effluent in constructed wetland-microbial fuel cell

This study examines the effect of different rates and modes of supplementary aeration on the treatment of synthetic septic tank effluent in a lab-scale unplanted constructed wetland-microbial fuel cell (CW-MFC) along with bioenergy generation. The experiment was conducted in 4 sequential phases; 1) the cell was operated with no aeration (NA), 2&3) the cathode layer was continuously aerated under different aeration rates (CA-I and CA-II), and 4) the cathode layer was intermittently aerated (IA). Results showed that the dissolved oxygen gradient caused by IA formed aerobic and anoxic zones in CW-MFC and promoted total nitrogen removal. The best performance was observed with intermittent aeration where the maximum removal efficiencies of COD (96.8 ± 3.3 %), TN (62.3 ± 2.1 %), TKN (68.3 ± 2.0 %), and NH3 (64.8 ± 2.3 %) were achieved. Furthermore, this treatment efficiency corresponded with enhanced bioenergy generation under the IA regime, achieving maximum power output (7.5 mW/m2), highest average voltage output (0.399 ± 0.02 V), Coulombic efficiency (1.94 %), and normalized energy recovery (1.4 Wh/m3). Continuous aeration, however, induced an adverse effect on energy generation due to excessive oxygen penetration into the anode region. Nitrate accumulation was also observed as a sign of an incomplete denitrification process under the continuous aeration regime. Overall, it can be concluded that the intermittently aerated CW-MFC not only lowers operational costs but improves effectiveness in terms of the nitrogen removal process in the treatment of septic tank effluent.

Intermittent aeration to reduce gaseous emission and advance humification in food waste digestate composting: Performance and mechanisms

This study investigated the performance and mechanisms of intermittent aeration to regulate gaseous emission and humification during food waste digestate composting. In addition to continuous aeration, three intermittent aeration regimes were conducted with the on–off interval ratio at 3:1, 2:1, and 1:1 within each 30 min, respectively. Results showed that intermittent aeration regimes reduced gaseous emission and enhanced humification during composting. In particular, intermittent aeration with the on/off ratio of 1:1 was more effective to reduce organic mineralization than other regimes, which alleviated the emission of nitrous oxide and ammonia by 63.1% and 75.7% in comparison with continuous aeration, respectively. In addition, this aeration regime also enhanced the content of humic acid by 24.1%. Further analysis demonstrated that prolonging aeration-off intervals could enrich facultative bacteria (e.g. Atopobium and Clostridium) from digestate and inhibit the proliferation of several aerobic bacteria (e.g. Caldicoprobacter and Marinimicrobium) to retard organic mineralization for humification.

TEMPERATURE AND MICROBIOLOGICAL PARAMETERS OF POULTRY MANURE UNDER DIFFERENT FERMENTATION MODES

To meet food needs both in Ukraine and globally, the production of affordable and relatively cheap poultry meat will increase. At the same time, the problem of increasing poultry waste accumulation, including manure with and without bedding, is becoming more acute. Large volumes of broiler manure in limited areas due to different storage conditions have a negative impact on the environment. The study of the conditions and modes of composting broiler manure as an effective way of its utilisation is of scientific and economic importance. The aim of the study is to determine the temperature and microbiological parameters of broiler manure composting using different modes of its aeration. To achieve this goal, fresh broiler manure was composted in the conditions of the scientific and educational research centre of the Bila Tserkva National Agrarian University using a mixture of biodestructors and different aeration regimes. In the control group, the piles were formed on a concrete platform without the use of a tubular frame of the barbital type, and aeration was carried out by mechanical mixing of broiler manure once every 10 days. In the experimental groups, piles of broiler manure were formed on tubular frames through which air was injected by a compressor. In the first experimental group, air injection was carried out for 15 minutes in the first half of the day. In the second experimental group, air was injected into the broiler manure twice for 15 minutes in the morning and in the evening. It was experimentally established that the composting temperature of broiler manure depended on the intensity of aeration of the latter. With daily aeration twice a day, the temperature of the manure biomass (6th day of composting) was the highest and exceeded the control values by 87.8 %. In experimental groups I and II, with one and two daily enrichment of broiler manure, the period of fermentation in the thermophilic mode was the same. Comparing the groups where poultry manure was enriched once and twice a day, it was found that double aeration did not lead to a statistically significant increase in the temperature of composted biomass. It was proved that active air enrichment of poultry manure (experimental group II) increased the QMAFAnM index and the number of Bacillus spp. bacteria by 7.6 and 24.0%, respectively, compared to the control group. The study of a number of chemical parameters of broiler chickens' manure composted by the accelerated method under different aeration regimes is promising.

Nutrient conservation achieved through mixing regime improves microalgal wastewater treatment and diminishes the net environmental impact

Operational mode of photobioreactor (PBR) play pivotal role in environmentally benign wastewater treatment. In this context, there is wider knowledge gap in decision making for sustainable microalgae PBR operation with least environmental impact. Therefore, the present work utilized two operational modes, aeration and mechanical mixing (non-aeration), for comparative evaluation of their impacts on nutrient removal, microalgae: bacteria (M:B) population dynamics, and performance along with environmental impact. The experiments initiated with dominant M:B inoculation ratio (60:40), demonstrated higher M:B ratio (78:21) with mixing regime, as essential nutrients (dissolved inorganic carbon and ammoniacal nitrogen) were conserved within the wastewater. On the other hand, lower M:B ratio (36:63) was obtained during aeration regime, as these nutrients were transformed into CO2 and NH3 and emitted to the environment. The nutrient conservation mechanism within mixing regime enhanced microalgal growth by 30 %, metal removal by 14–59 %, and exhibited carbon negative global warming potential (-0.0451 kgCO2 eqm−3), along with overall non-negative environmental impact. In contrast, aeration strategy showed net negative environmental impact with reduced contaminant removal potential. Overall, this study reveals a previously overlooked yet significant contribution of nutrient conservation achieved through mixing regime for holistic wastewater treatment.

Features of Assessment and Formation of the Aeration Regime of Residential Development on the Sloping Lands of the Russian Arctic

The urban development of areas in the Arctic zone of the Russian Federation is a relevant and important task to be tackled by contemporary urban planners. This focus is largely explained by the development of the Northern Sea Route (NSR) and its port cities. Last but not least, to develop these cities means to ensure a comfortable living environment for local residents and visiting specialists. However, given the harsh climate in the Arctic zone of the Russian Federation, this task requires a more elaborate approach. Current building techniques, designed for flatlands with relatively comfortable climates, cannot be applied to this territory without degrading the quality of the living environment. Environmental comfort is influenced by many factors, and one of them is the aeration regime. This study is aimed at researching the aeration regime of built-up areas on the sloping lands of the Arctic zone of the Russian Federation and identifying the features of its formation. The object of this study is a residential development on the sloping lands of the Arctic zone of the Russian Federation. The subject of the study is the external aeration regime at the level of 1.2 m from the ground level of the residential development on the sloping lands of the Arctic zone of the Russian Federation. These parameters were explored, and the aeration regime was assessed using such advanced software packages as QG for the GIS analysis of the area and ANSYS Fluent for the mathematical modeling of the aeration regime. The results of the research are presented in the form of graphs, dependency tables, and petal diagrams visually demonstrating the distribution of discomfortable zones for different morphotypes of development on various slopes most widely spread in the Arctic zone of the Russian Federation. The theoretical research was pilot-tested in the existing residential development area in Murmansk. The results of the study are usable in practice if respective land use documents are drafted for residential areas of settlements in the Arctic zone of the Russian Federation.

Effect of controlled aeration on COD and nitrogen removal in aerated constructed wetlands used for effluent polishing

Aerated wetland (AW) technology is typically used in high oxygen demand situations. This study however investigated its applicability for further polishing of effluents of both a municipal and an industrial wastewater treatment plant. Different aeration and pollutant removal strategies were tested, all under high hydraulic loading rate conditions (0.69 m3.m−2.d−1, 12h hydraulic retention time). The experiments were done on two 350 m² horizontal subsurface flow constructed wetlands (HSSF CW), filled with expanded clay aggregates (Argex™) and planted with common reed (Phragmites australis). Each CW was divided into three equal zones, each equipped with forced bed aeration (FBA™). For this study, continuous (100% on) and time-based (50%-time on/off) aeration were compared versus set dissolved oxygen levels controlled by oxygen sensors (3–4, 2–3 and 1–2 mgO2. L−1 in each zone, and 2–3 mgO2. L−1 in zone 1 and no aeration in zones 2 and 3, designated as 2–3/0/0). Results showed near 100% nitrification for all aeration regimes. Chemical oxygen demand (COD) removal was between 18% and 33% during high aeration (100%, 50%, 3–4 and 2–3 mgO2. L−1) but was reduced (1–15%) during the most limiting aeration modes (1–2 and 2–3/0/0 mgO2. L−1). Denitrification was limited for municipal effluent, however, reasonable NO3-N removal (31–72%) was noted for industrial effluent. The optimal balance between removal efficiency and energy consumption was found to be for the 2–3 mgO2. L−1 aeration setting, consuming 6.9–11.2 Wh.m−3. The outcomes of this study can be helpful for implementing aerated CWs as a tertiary treatment.

Aerobic Biostabilization of the Organic Fraction of Municipal Solid Waste-Monitoring Hot and Cold Spots in the Reactor as a Novel Tool for Process Optimization.

The process of aerobic biostabilization (AB) has been adopted for treatment of the organic fraction of municipal solid waste (OFMSW). However, thermal gradients and some side effects in the bioreactors present difficulties in optimization of AB. Forced aeration is more effective than natural ventilation of waste piles, but “hot and cold spots” exist due to inhomogeneous distribution of air and heat. This study identified the occurrence of hot and cold spots during the OFMSW biostabilization process at full technical scale. It was shown that the number of hot and cold spots depended on the size of the pile and aeration rate. When the mass of stabilized waste was significantly lower and the aeration rate was two-fold higher the number of anaerobic hot spots decreased, while cold spots increased. In addition, the results indicated that pile construction with sidewalls decreased the number of hot spots. However, channelizing the airflow under similar conditions increased the number of cold spots. Knowledge of the spatial and temporal distribution of process gases can enable optimization and adoption of the OFMSW flow aeration regime. Temperature monitoring within the waste pile enables the operator to eliminate undesirable “hot spots” by modifying the aeration regime and hence improve the overall treatment efficiency.

INFLUENCE OF BISPHENOL A AND PROBIOTIC-CONTAINING FEED CARASSIUS GIBELIO BLOCH INDICATES SEPARATELY

One of the most common pollutants of water bodies is bisphenol A (BPA), a plastic monomer used to synthesize polycarbonate plastics, epoxy resins and thermal paper (Barboza L. et. al., 2020). BPA enters freshwater and marine ecosystems as a result of leaching from BPA-based composites, as well as with water discharges from manufacturing plants, wastewater treatment plants and landfills. BPA is characterized by a low accumulation potential in freshwater environments, a short half-life under aerobic conditions, but due to the continuity of exposure, it is a serious problem (Wu N. C., Seebacher F., 2020). The ways BPA enters the fish body are diverse: through the digestive tract, gills, skin. Numerous studies have shown the adverse effects of BPA on the behavioral and morpho-physiological parameters of fish, including swimming patterns, coordination of movements, appetite, and dysfunction of many systems (endocrine, reproductive, nervous). It is possible to prevent the negative effects of hunting through the prophylactic use of agents that enhance the overall reactivity of the body. In this sense, our attention was drawn to probiotics - microorganisms that have a stimu-lating effect on the development of indigenous microflora, have a high antagonistic, synthetic, immunomodulatory, regulatory potential. We have studied the effect of bisphenol A and probiotic microorganisms Lactobacillus casei, introduced in the feed, on certain indicators of Carassius gibelio Bloch (general behavioral reactions, certain mor-pho-physiological parameters, qualitative and quantitative characteristics of erythrocytes and leukocytes). The study was carried out after 15-day acclimatization of fish in aquariums at a water temperature of 14°C, appropriate aera-tion regime and 16-hour photoperiod. It was found that 96-hour exposure to bisphenol A at a concentration of 1.5 mg/l causes darkening of the skin, in-creased mucus secretion, uncharacteristic motor activity, the appearance of unusual morphotypes of red blood cells, a slight increase in the number of leukocytes, and a decrease in the phagocytic activity of Carassius gibelio Bloch. Preventive introduction of probiotic cultures in the feed contributed to the correction of behavioral reactions and individual hematological parameters

Influence of aeration intermittency on nitrogen removal in a reactor with aerobic granular sludge treating wastewater

The process of aerobic granular sludge (AGS) has been considered an alternative of great interest for the tertiary wastewater treatment mainly due to the great capacity of granule densification, which makes the system very compact. The simultaneous nitrification and denitrification (SND) occurrence guarantees nitrogen removal at a high level of efficiency and biological phosphorus removal can be optimized in this arrangement with a single treatment stage in sequential batches. In this study, the general behavior of a sequential batch reactor (SBR)/AGS in wastewater treatment and the effect of the air supply regime on nitrogen removal were evaluated. A pilot scale system supplied by relatively high concentration wastewater in a warm climate region was set up over 525 days. The study was divided into three main phases. In Phase I, a cycle of 3 h of total duration and continuous aeration of the sludge was applied with high efficiency in the removal of soluble chemical oxygen demand (sCOD) from the wastewater, but excessive drag of total suspended solids (TSS) with the effluent persistently occurred throughout the cycle. Nitrification went well, but wastewater denitrification was only partial with a notorious and worrisome accumulation of nitrite. In Phase II, the total cycle duration was increased to 4 h, but this increase in the time available for the anoxic and aerobic reactions was not enough to control the problem and the nitrite and nitrate residuals remained high in the effluent. In Phase III, the implementation of an intermittent aeration regime led to the production of an effluent from the treatment system with ammoniacal nitrogen, nitrite and nitrate average concentrations of 4.3 mg N·L−1, 0.4 mg N·L−1 and 5.5 mg N·L−1, respectively. Surveys of concentration profiles were carried out over some batches and it was observed that denitrification occurs mostly simultaneously with nitrification during the aeration period. The general conclusion of this study is that the application of intermittency regime in the air supply of AGS is of great importance for the improvement of nitrogen removal in this process.

Тrophic structures and the specifcs of paleocoenosis of the Middle-Upper Carboniferous skeletal mounds on the Shchuger River (Northern Urals)

Research subject. Organogenic structures such as the Moscowian-Kasimovian skeletal mounds from the Verkhnie vorota section on the Shchuger River (Northern Urals). Materials and methods. The lithological-paleoecological analysis of biohermal limestones and the determination of their fauna in thin sections (60 samples) and polished slabs (10 samples) taken in outcrops 39 on the Shchuger River, 89 m thick. Results. It is revealed that the Middle-Upper Carboniferous skeletal mounds were characterized by a three-level food chain at three stages of their development. Cyanobacteria, calcimicrobes and green algae were the suppliers of organic matter. Their further consumers were bryozoans, brachiopods, fusulinids, small foraminifera and bacteria. Omnivores and predators were absent. It is found that, heterotrophs were the most common organisms at the stabilization stage, while autotrophs were typical of the colonization stage. The paleocenoses of the Kasimovian skeletal mound had a more extensive composition. Here, each developmental stage was represented by two types of paleocenosis, compared to the Moscowian mound. Conclusions. It is found that the main external abiotic factors that controlled the development of the biocenosis in the sites under study were the hydrodynamic regime and sea level fluctuations. An important internal factor was the development of bio-induced cement on the skeletons of organisms, which contributed to the formation of solid frameworks of buildings. Another internal factor was the widespread occurrence of Anchicodiaceae algae, which caused a decrease in the biodiversity of other groups of organisms. The data obtained allowed us to conclude that a shallow sea basin with a good aeration and low hydrodynamic regime existed in this area in the MiddleLate Carboniferous. A decrease in the basin area in the Late Carboniferous was manifested by a reduction in not only algal taxa, but also the biodiversity of the entire ecosystem.

Hydrodynamics and Free-Flow Characteristics of Piano Key Weirs with Different Plan Shapes

This paper focuses on Piano Key Weirs (PKWs) as an effective solution for improving the discharge capacity of spillway systems. The flow behavior in inlet and outlet keys is experimentally studied to analyze the discharge capacity of PKWs with different plan shapes (i.e., rectangular, trapezoidal, and triangular). The results show that in outlet keys, the flow aeration regimes extend to higher values of headwater ratios (Ho/P) by increasing the length magnification ratio (B/w) and apex width ratio (A/w). In addition, the local submergence length is a decreasing function of A/w, especially in high flow heads. While the total interference length enlarges by reducing A/w in lower Ho/P values (Ho/P < 0.5), a reverse trend is observed in higher headwater ratios. PKW performance may also be impacted by the flow contraction and recirculation zone in inlet keys, which intensify in higher values of Ho/P, B/w, and A/w. According to the obtained results, while the discharge coefficient is a decreasing function of A/w in Ho/P > 0.4, it may have a reverse trend in lower head conditions. In addition, a trapezoidal PKW has the highest discharge efficiency in a wide range of the studied domain (Ho/P > 0.25 and B/w ≥ 2). It can improve the discharge efficiency by around 5%, while its body volume is almost 7% smaller than the traditional rectangular PKW. However, for low-length and high-head conditions (B/w = 1 and Ho/P > 0.5), the efficiency a rectangular PKW exceeds that of the other shapes.

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.