A critical review of artificial destratification systems for mitigating water stratification

Reservoir stratification impacts reservoir and downstream water quality, creating complex management challenges driven by interactions between hydrodynamics, weather patterns, and nutrient dynamics. Artificial destratification is one technique used to ameliorate the impacts of stratified reservoirs, with bubble plumes or mechanical mixers being the primary methods employed. This global review assessed 138 bubble plume and mechanical mixer artificial destratification systems installed in 114 reservoirs to evaluate the comparative effectiveness of each method. Destratification systems were assessed in terms of their effectiveness in breaking thermal stratification and consequently mitigating cold water pollution, increasing dissolved oxygen concentrations throughout the water column, reducing the concentration of soluble metals, and reducing (potentially toxic) cyanobacteria populations. Bubble plume destratification was found to be more effective than mechanical mixing at mitigating the impacts of thermal stratification. Successful thermal destratification was closely linked to subsequent increases in dissolved oxygen concentrations and decreases in manganese and iron concentrations. Mixed results were observed for the reduction of cyanobacteria populations from artificial destratification; however, a correlation was observed between cyanobacteria control and successful thermal destratification in deeper reservoirs. Achieving thermal destratification was closely linked to the ratio of the reservoir capacity to the air flowrate used for destratification (the "volumetric destratification coefficient"). Failed thermal destratification was observed in reservoirs where the volumetric destratification coefficient was less than approximately 0.005L/s/ML. This review identified the potential for scalability of bubble plume destratification across different reservoirs, but future research needs to provide more quantitative data that can be used to develop holistic design guidelines for bubble plume destratification systems for a wide range of reservoirs and operational conditions.

Inducing an extended naturally complete mixing period in a stratified reservoir via artificial destratification

Applications of artificial intelligence algorithms in artificial lift systems: A critical review

In this study, a one-dimensional model called DYRESM was used to simulate the thermal structure and artificial destratification of 15-Khordad Reservoir over a period of one year. The simulation showed that the reservoir is warm monomictic and is stratified during 210 days of the simulation year. The model reproduced the temperature of the meta- and hypolimnion very close to the observed data, but the temperature of the epilimnion was overestimated. As the meteorological data used for the simulation was collected in a nearby weather station, a sensitivity analysis was conducted to evaluate the effect of meteorological data bias on the simulation results. Air temperature, shortwave solar radiation, wind speed and vapour pressure were found to be, respectively, the most effective parameters. Furthermore, applications of two artificial destratification systems: bubble plume diffuser and surface mechanical mixer, were modelled. The sensitivity of the model outputs to the specifications of each system was investigated and the two systems were compared considering their efficiencies. It was revealed that the air diffusers were much more efficient than the mechanical mixers. This study showed that the DYRESM can accurately describe physical processes in this reservoir if the forcings are accurately given and the application of bubble is recommended for artificial destratification in this reservoir

The objective of the present study was to assess the effectiveness of artificial destratification by air‐bubble plumes in reducing evaporation from reservoirs. The model DYRESM was used to model the evaporation rates and thermodynamic behaviour of a temperate reservoir in Australia under a number of combinations of destratification designs and operating conditions, comprising various numbers of ports and air‐flow rates per port. The operating conditions involved continuous operation and various intermittent operating strategies. Three reservoir depths were considered, characterizing “shallow,” “medium” and “deep” reservoirs, respectively. The present study results indicated that, assuming thermal stratification develops in a reservoir (the case for the “medium” and “deep” reservoirs), artificial destratification is able to reduce surface temperatures and evaporation rates. As a result of the larger volume of cold water at the lake bottom, deeper reservoirs can derive greater benefit from the use of these systems. Being raised to the water surface by the air injected through the destratification system, the cold water from the bottom will help reduce surface temperatures. Conversely, because of their typical homothermous regime, shallow lakes are unlikely to benefit from these systems, since these reservoirs lack an abundant cold water source at the bottom. Even so, however, the reductions in evaporation from deep reservoirs are only modest, with the maximum reduction being only 2.9% for a deep lake (16.5 m) using an energy‐intensive destratification system. Based on the present study, it was concluded that using destratification systems for reducing reservoir evaporation was not warranted because of the modest water savings achieved.

Modelling of lake mixing induced by air-bubble plumes and the effects on evaporation

The structure of the turbulent wake and the random internal wave field generated by a moving sphere in a stratified fluid

Prolonged periods of thermal stratification in a lake suppress convective motions capable of vertical transport of dissolved oxygen and other dissolved and suspended matter. When this leads to anoxia in the hypolimnion, it can give rise to profound water quality implications. Artificial destratification is one means whereby low oxygen levels in the hypolimnion may be averted. The operating principles of bubble plume destratification and its effect on the physical transport and mixing that occurs in a lake are described. Monitoring of temperature and dissolved oxygen was conducted at Lake Nepean, Australia, prior to the destratification, and then continued for two summers while the destratification system was operating. The results showed that artificial destratification had an immediate effect on lake motions across a range of scales. The actual process of destratification occurred by the erosion of the base of the thermocline. Deep‐water temperatures were elevated well above historical values, the heat storage in the lake increased, and the time of turnover was brought forward 2.5 months. An integral plume model coupled with a one‐dimensional lake model is shown to predict the effect of the bubble plume entrainment and the subsequent redistribution of the entrained water throughout the lake.

Thermal stratification during summer may result in lowered dissolved‐oxygen levels below the thermocline of lakes and reservoirs. To avoid further deterioration of water quality, artificial destratification has long been practiced. This paper presents a totally new design methodology for the design of bubble‐plume destratification systems. It is based on the interaction that occurs between a buoyant bubble plume and the density stratified water column through which it rises. Two dimensionless parameters, M and C, universally describe the behavior of such plumes. M represents the bubble source strength compared to the total pressure head, and C represents the effect of the stratification compared to the bubble source strength. By selecting appropriate values for these parameters, the individual bubble plumes can be designed to operate within high‐efficiency bands. The number of such plumes that are required to destratify the lake can then be calculated by a simple energy balance. The method is validated using a combination of a dynamic reservoir simulation model (DYRESM) and a bubble‐plume model. Comparison of the design recommendations with those produced from conventional practice suggest that large cost savings may be realized.

Book Review

To determine the influence of artificial destratification on nutrient variations in a small eutrophic impoundment, field monitoring and laboratory analyses were conducted in three consecutive summers (2010, 2011, and 2012). The impact of aeration among sampling locations and across the water column of nutrient concentrations, including total and dissolved inorganic nitrogen (N) and phosphorus (P) and water temperature and dissolved oxygen (DO) was evaluated under aerated and non-aerated conditions. Aeration eliminated thermal stratification and DO concentrations of bottom waters increased. Nutrients including soluble reactive phosphorus (SRP), total phosphorus (TP), and total nitrogen (TN) concentrations across the water column did not change significantly during aeration. Nevertheless, under aerated conditions, dissolved inorganic nutrients, TN, TP, and temperature were homogenously distributed throughout the water column as an effect of aeration. Results indicated that artificial destratification resuspended nutrients throughout the water column; however, it did not have a significant effect on nutrient concentrations in the water column, but SRP, TN, and TP concentrations did not reach to the recommended limit as needed by the North Dakota Department of Health requirements. Therefore, alternative aeration methods, for instance, hypolimnetic oxygenation or hypolimnetic aeration are recommended to control nutrient redistribution and/or further releases by existing aeration system.

Summary1. The response of phytoplankton to the installation of an artificial destratification system in North Pine Dam, Brisbane (Australia) was investigated over an 18 year period (1984–2002); 11 years before and 7 years after installation.2. An overall increase in phytoplankton abundance was revealed for some groups (in particular, diatoms, cyanobacteria and chlorophytes), but not for others (chlorophytes). Changes in the abundance of chlorophyte functional groups was attributed to eutrophication.3. A strong spatial gradient in phytoplankton abundance and chlorophyllawas observed, with low abundance in the downstream regions affected by the destratification system which was likely because of light limitation induced by vertical mixing. The upstream region acted as a surrogate for the unaltered state of the reservoir, particularly as an indicator of eutrophication without direct influence from the destratification system. Despite the continuous trend in eutrophication of the reservoir, there has been a definite decrease in the rate of eutrophication (approximately 30%) since the installation of the destratification system at the downstream locations.4. Correlations of the dominant cyanobacteriaCylindrospermopsis raciborskiiwith other genera changed after destratification, indicating that prior to destratification the dominance ofCylindrospermopsiswas because of its ability to compete for phosphorus, whereas after destratification its dominance was because of its ability to compete for light.

A longstanding ambiguity surrounds the operationalization of consciousness in artificial systems, complicated by the philosophical and cultural weight of subjective experience. This work examines whether cognitive architectures may be designed to support a functionally explicit form of artificial consciousness, focusing not on the replication of phenomenology, but rather on measurable, technically realizable introspective mechanisms. Drawing on a critical review of foundational and contemporary literature, this study articulates a conceptual and methodological shift: from investigating the experiential perspective of agents (“what it is like to be a bat”) to analyzing the informational, self-regulatory, and adaptive structures that enable purposive behavior. The approach combines theoretical analysis with a comparative review of major cognitive architectures, evaluating their capacity to implement access consciousness and internal monitoring. Findings indicate that several state-of-the-art systems already display core features associated with functional consciousness—such as self-explanation, context-sensitive adaptation, and performance evaluation—without invoking subjective states. These results support the thesis that cognitive engineering may progress more effectively by focusing on operational definitions of consciousness that are amenable to implementation and empirical validation. In conclusion, this perspective enables the development of artificial agents capable of autonomous reasoning and self-assessment, grounded in technical clarity rather than speculative constructs.

Artificial intelligence systems for tool condition monitoring in machining: analysis and critical review

Membrane fusion has an overarching influence on living organisms. The fusion of sperm and egg membranes initiates the life of a sexually reproducing organism. Intracellular membrane fusion facilitates molecular trafficking within every cell of the organism during its entire lifetime, and virus-cell membrane fusion may signal the end of the organism's life. Considering its importance, surprisingly little is known about the molecular-level mechanism of membrane fusion. Due to the complexity of a living cell, observations often leave room for ambiguity in interpretation. Therefore artificial model systems composed of only a few components are being used to further our understanding of controlled fusion processes. In this critical review we first give an overview of the hypothesized mechanism of membrane fusion and the techniques that are used to investigate it, and then present a selection of non-targeted and targeted model systems, finishing with current applications and predictions on future developments (85 references).