Water-lifting Aerator Research Articles

Analysis of Water-Lifting Aerator Performance Based on the Volume of Fluid Method

Water quality deterioration is a major problem faced by reservoirs globally, owing to the inflow of pollution from industrial and municipal activities. Water-lifting aeration is an in situ water quality improvement technology that mixes and oxygenates deep water bodies in reservoirs to improve pollution control efficiency and water quality. While previous studies have mainly focused on the mixing process in the reservoir outside the water-lifting aerator (WLA), knowledge of the internal flow remains limited. In this study, a two-phase flow within a WLA system was numerically studied using the volume of fluid (VOF) method to comprehensively analyze the internal two-phase flow characteristics and the influence on the water-lifting and oxygenation performance of the system. The statistical analysis results showed that increasing the aeration chamber volume enhanced the bottom oxygenation performance by 27% because of the prolonged time of the deflector plate outlet outflow. Additionally, increasing the air release rate enhanced the water-lifting performance by 47%, which was induced by the shortened air piston release period. This study demonstrates the internal flow mechanism of the WLA and provides technical support for parameter optimization design, which has significant scientific research and engineering application value.

Constraining release of pollutants from anoxic bottom sediment via water-lifting aeration in a source water reservoir, East China

Seasonal hypoxia in water bodies can increase levels of reduced chemical species in the hypolimnion as they are released from anoxic bottom sediments. Water-lifting aeration (WLA) is a technology known to solve this problem by elevating near-sediment dissolved oxygen (DO) and increasing mixing in the water column in a canyon reservoir with deep water (>20 m). The influence of WLA in reservoirs with large surface area and small water depth has not been adequately evaluated. For this purpose, the efficiency of an innovative WLA system was reviewed in Zhoucun Reservoir (ZCR), a mildly eutrophic reservoir with a mean depth of 15 m. Three years of field experiment was performed in ZCR. Water and sediment samples were collected before and after the operation of the WLA system to explore the causes for the deterioration of water quality in ZCR, and the efficiency of the innovative WLA system installed in 2015. With the use of a microporous aerator and a kinetic energy dissipator, the new-style WLA system is different from WLA studied before. As a result of thermal stratification and the long duration of anaerobic environment in the hypolimnion, the sediment oxygen consumption rate in ZCR was calculated to be 16.14 mg m−2 h−1, which was much higher than other reservoirs, and the main pollutants in ZCR were ammonia, phosphorus, manganese and sulphide. After the operation of the new WLA system, the anaerobic environment in the bottom water was completely reversed and the DO concentration in the hypolimnion water has been maintained at more than 6 mg L−1. The release of pollutants from sediments, such as ammonia, phosphorus, manganese and sulphide, was inhibited significantly. Ammonia, phosphorus, manganese and sulphide in water decreased by 89%, 84%, 97% and 87%, respectively. The results of this study demonstrate that employing WLA systems to oxygenate and mix stagnant water bodies is a viable and potentially favourable management strategy for reservoirs with large surface area and relatively small water depth.

Water-lifting aerator reduces algal growth in stratified drinking water reservoir: Novel insights into algal metabolic profiling and engineering applications

Water-lifting aerator (WLA) which was developed by Professor Tinglin Huang at Xi’an University of Architecture and Technology, China has multi-functional water quality improvement that significantly inhibits the occurrence of harmful algal blooms (HABs) in deep drinking water reservoirs. However, the biological mechanism of WLA to the suppress algal growth has not been comprehensively understood. Here, the cellular mechanism that allows WLA to control HABs was explored based on the combination of both laboratory simulation and field investigation. Under simulated hydrodynamic conditions, the results showed that the cell density, chlorophyll a content, chlorophyll fluorescence parameters, and dehydrogenase activity in Microcystis aeruginosa all peaked under light conditions at 25 °C. The metabolic activity of M. aeruginosa varied significantly under low temperature at 6 °C and light conditions when cultured for 48 h. The extracellular organic matter (EOM) and intracellular organic matter (IOM) contents of M. aeruginosa were both resolved into three components. Moreover, the total fluorescence intensities from EOM and IOM both peaked under light conditions at 25 °C. The field investigation showed that the growth of algae was decreased significantly in Lijiahe drinking water reservoir with WLA application. The chlorophyll fluorescence parameters decreased significantly after vertical mixing, thereby indicating that the WLA weakened the photosynthetic ability and reduced the biological activity of algae in situ. In addition, the WLA significantly affected the vertical distribution of the phytoplankton community composition. Altogether, these results shed new lights on understanding the control of algal blooms by WLA in stratified drinking water reservoirs. WLA has broad prospect of engineering applications, which can control algal blooms of water supply resources in situ, therefore, reduce the content of disinfection by-products in drinking water treatment plants.

Field Research on Mixing Aeration in a Drinking Water Reservoir: Performance and Microbial Community Structure.

Field research on the performance of pollutant removal and the structure of the microbial community was carried out on a drinking water reservoir. After one month of operation of a water-lifting aeration system, the water temperature difference between the bottom and the surface decreased from 9.9 to 3.1 °C, and the concentration of the dissolved oxygen (DO) in the bottom layer increased from 0 to 4.2 mg/L. The existing stratification in the reservoir was successfully eliminated. Total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) concentrations were reduced by 47.8%, 66.7%, and 22.9%, respectively. High-throughput sequencing showed that Proteobacteria, Bacteroides, and Actinomycetes accounted for 67.52% to 78.74% of the total bacterial population. Differences in the bacterial changes were observed between the enhanced area and the control area. With the operation of the water-lifting aeration system, the populations of bacteria of the main genera varied temporally and spatially. Principal component analysis pointed out a clear evolution in the vertical distribution of the microbial structure controlled by the operation of the aeration system. Permutational analysis of variance showed a significant difference in the microbial community (p < 0.01). Redundancy analysis showed that physical (water temperature, DO) and chemical environmental factors (Chl-a, TOC, TN) were the key factors affecting the changes in the microbial communities in the reservoir water. In addition, a hierarchical partitioning analysis indicated that T, Chl-a, ORP, TOC, pH, and DO accounted for 24.1%, 8.7%, 6.7%, 6.2%, 5.8%, and 5.1% of such changes, respectively. These results are consistent with the ABT (aggregated boosted tree) analysis for the variations in the functional bacterial community, and provide a theoretical basis for the development and application of biotechnology.

Seasonal variation of potential denitrification rate and enhanced denitrification performance via water-lifting aeration technology in a stratified reservoir—A case study of Zhoucun reservoir

Zhoucun reservoir is one of the major water resources in Zao Zhuang city, northern China. The seasonal distribution of surface sediment denitrification rate and enhanced performance of denitrification via water-lifting aeration technology were explored using the acetylene-inhibition technique. Surface sediment denitrification rates ranged from 2.57 ± 1.32 to 923.90 ± 86.81 nmol N2/(g dw·h), with the highest rates in November (ANOVA, p < 0.05) and significantly low rates in June, July, and August (ANOVA, p < 0.05), mainly because of the seasonal differences in nitrate concentration, water temperature, and sediment total nitrogen (STN). Meanwhile, the N2/(N2+N2O) ratio (83.44–91.70% for the highest sediment denitrification period) indicated that N2 accounted for a majority of denitrification. Correlation analysis between various environmental factors and denitrification was conducted, and nitrate concentration, STN, low molecular weight organic carbon, the number of aerobic denitrifying bacteria, and the environmental parameters of oxidation-reduction potential (ORP), pH, electrical conductivity (EC), and chlorophyll a (Chl-a) presented significant relationships during the entire study period. On the basis of the multiple regression model, nitrate and low molecular weight organic carbon concentration were the most influential factors on denitrification variability. Moreover, the denitrification rates of the surface sediment clearly increased, from 5.28 to 13.22 nmol N2/(g dw·h) to 1117.02–3129.47 nmol N2/(g dw·h), which were higher than those in the non-operating year. This suggests that the denitrification in the sediment system could be enhanced in situ by water-lifting and aeration technology in the reservoir ecosystem.

Destratification and oxygenation efficiency of a water-lifting aerator system in a deep reservoir: Implications for optimal operation

Thermal stratification is a common phenomenon in lakes and reservoirs and has a significant influence on water quality dynamics. Heihe Reservoir is a canyon-shaped reservoir in Shaanxi Province with strong thermal stratification. Therefore, eight water-lifting aerators (WLAs) were installed in this reservoir, which could overcome thermal stratification and increase oxygenation with gas flows between 20 and 50m3/hr, and oxygenate the hypolimnion with gas flows less than 20m3/hr. To examine the destratification efficiency of the WLA system, we used a three-dimensional hydrodynamic module based on MIKE 3 to simulate the thermal structure of Heihe Reservoir and compared the simulations with measured data. Results showed that operation of the WLA system promoted water mixing and effectively oxygenated the hypolimnion. Through the established energy utilization assessment method, the energy utilization efficiency of the WLA system was between 5.36% and 7.30%, indicating the capability of the technique for destratification in such a large reservoir. When the surface water temperature dropped to the theoretical mixed water temperature calculated by the energy utilization assessment method, reducing gas flow could save energy. This would prevent anaerobic conditions from occurring in the bottom water and maintain good water quality in Heihe Reservoir.

Sediment pollution characteristics and in situ control in a deep drinking water reservoir

Sediment pollution characteristics, in situ sediment release potential, and in situ inhibition of sediment release were investigated in a drinking water reservoir. Results showed that organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) in sediments increased from the reservoir mouth to the main reservoir. Fraction analysis indicated that nitrogen in ion exchangeable form and NaOH-extractable P (Fe/Al-P) accounted for 43% and 26% of TN and TP in sediments of the main reservoir. The Risk Assessment Code for metal elements showed that Fe and Mn posed high to very high risk. The results of the in situ reactor experiment in the main reservoir showed the same trends as those observed in the natural state of the reservoir in 2011 and 2012; the maximum concentrations of total OC, TN, TP, Fe, and Mn reached 4.42mg/L, 3.33mg/L, 0.22mg/L, 2.56mg/L, and 0.61mg/L, respectively. An in situ sediment release inhibition technology, the water-lifting aerator, was utilized in the reservoir. The results of operating the water-lifting aerator indicated that sediment release was successfully inhibited and that OC, TN, TP, Fe, and Mn in surface sediment could be reduced by 13.25%, 15.23%, 14.10%, 5.32%, and 3.94%, respectively.

The Variation Characteristic of Sulfides and VOSc in a Source Water Reservoir and Its Control Using a Water-Lifting Aerator.

Sulfides and volatile organic sulfur compounds (VOSc) in water are not only malodorous but also toxic to humans and aquatic organisms. They cause serious deterioration in the ecological environment and pollute drinking water sources. In the present study, a source water reservoir—Zhoucun Reservoir in East China—was selected as the study site. Through a combination of field monitoring and in situ release experiments of sulfides, the characteristics of seasonal variation and distribution of sulfides and VOSc in the reservoir were studied, and the cause of the sulfide pollution was explained. The results show that sulfide pollution was quite severe in August and September 2014 in the Zhoucun Reservoir, with up to 1.59 mg·L−1 of sulfides in the lower layer water. The main source of sulfides is endogenous pollution. VOSc concentration correlates very well with that of sulfides during the summer, with a peak VOSc concentration of 44.37 μg·L−1. An installed water-lifting aeration system was shown to directly oxygenate the lower layer water, as well as mix water from the lower and the upper layers. Finally, the principle and results of controlling sulfides and VOSc in reservoirs using water-lifting aerators are clarified. Information about sulfides and VOSc fluctuation and control gained in this study may be applicable to similar reservoirs, and useful in practical water quality improvement and pollution prevention.

Characteristics of seasonal variation and water-lifting aerator improvement of water quality in a steady stratified reservoir

为了解深水型水库水体的热分层结构、水质特征及扬水曝气系统对水质的改善情况,对水温、溶解氧、pH、叶绿素a、营养盐、溶解性有机碳浓度等水质指标进行为期一年的监测,探讨各项指标的季节性变化规律.结果表明,黑河水库水体呈单循环混合模式,在3-10月形成自然热分层,水体的热分层导致相应水库水质明显分层.黑河水库为偏碱性水体,叶绿素a、总磷、总氮、铵态氮和溶解性有机碳浓度平均值分别为2.21 μg/L、0.022 mg/L、1.32 mg/L、0.20 mg/L和2.93 mg/L,表明黑河水库处于中-富营养状态.热分层期底部水体溶解氧浓度在0～7.9 mg/L之间,平均值为2.9 mg/L,氮磷质量比在41～100之间,表明黑河水库是一个底部季节性缺氧、高营养盐型水库.在水库自然热分层末期,应用扬水曝气技术,不仅改善了底部水体的厌氧/缺氧环境,抑制了厌氧/缺氧条件下内源污染物的释放和藻类的增殖,而且还使得水库水体提前混合,实现了强制混合与水体自然混合过程的有机衔接,延长了水质持续改善的作用时效,有效地改善了水环境,保障了安全供水.;In order to understand the thermal stratification, the characteristics of the water quality and the application of water-lifting aerator system in the deep reservoir, water temperature, dissolved oxygen, pH, chlorophyll-a, nutrient and dissolved organic carbon(DOC) were monitored in a whole year. The results showed that Heihe Reservoir belonged to single hybrid mode, and the natural thermal stratification period was from March to October. The thermal stratification led water quality stratifications. The chlorophyll-a, total phosphorus, total nitrogen, ammonium nitrogen and DOC average concentrations were 2.21 μg/L, 0.022 mg/L, 1.32 mg/L, 0.20 mg/L and 2.93 mg/L, respectively, which showed that Heihe Reservoir was mesotrophic. In the thermal stratification period, the dissolved oxygen in the underlying water ranged from 0 mg/L to 7.9 mg/L, with an average of 2.9 mg/L, and the ratio of N/P was between 41 and 100, which showed that Heihe Reservoir had a seasonal hypoxia, with high nutrient concentrations. In the end of natural thermal stratification period, the application of water-lifting aerator technology can not only improve the bottom anaerobic/anoxic environment, and reduce the release of endogenous pollutants and the proliferation of algae, but also enhance the water mixture.

Comparison of water-lifting aerator type for algae inhibition in stratified source water reservoirs

Abstract Non-submerged and submerged water-lifting aerators have been recently developed to improve the water quality of source water reservoirs, but the non-submerged aerator has the drawbacks of higher initial investment and being more difficult to operate and maintain compared with the submerged aerator. To explore whether the submerged water-lifting aerator also has better performance on in-situ algae inhibition in source water reservoirs, the effects of submerged and non-submerged water-lifting aerators on algae inhibition were numerically investigated under different hydrological and operational conditions. Taking Jinpen Reservoir as a study case, under different conditions of water depth, temperature gradient and inlet velocity period, the flow outside the aerators, core algae inhibition zones and mixing of algae were numerically analyzed, and the simulated results were validated against the measured data. Simulated results showed that the flow outside any water-lifting aerator was characterized as one large clockwise circulation under a stable state, but the circulated flow was developed further for the submerged case. When the water depths were 77.25 m, 87.25 m and 97.25 m, the percentages of the core algae inhibition zone to the whole flow domain were 39.71%, 41.14% and 42.73% respectively, which were 5.88%, 3.68% and 1.15% larger than those for the non-submerged case; the periods required for complete mixing of algae were 10 days, 12 days and 14 days respectively for the submerged case, which were 8 days, 7 days and 6 days shorter than those for the respective non-submerged cases. Algae were transported from the surface layer to the bottom layer mainly by advection generated from the circulated flow arising from water-lifting aeration. Under similar hydrological and operational conditions, the core algae inhibition zones were larger and the mixing of algae was quicker for the submerged case. Submerged water-lifting aerators have advantages over the non-submerged aerators in the investment required and the operation and performance of algae inhibition and are recommended for in-situ algae inhibition in stratified source water reservoirs.

Application of the technology of water lifting and aeration on improving water quality in a Deep Canyon Reservoir – a case study from northern China

ABSTRACTThe technology of water-lifting and aeration can be widely applied in water aeration, algal inhibition, and endogenous pollution control. The Jin-Pen reservoir has been undergoing increasing water pollution in the past few years. To solve this problem, the water-lifting aerator system was installed here in the summer of 2010, and its improving effect on water quality was investigated. The results showed that under the mixing and aeration conditions, the thermal stratification structure was disturbed but not destroyed. The vertical water temperature difference was reduced by 3–5°C, and the surface temperature fell at 2.1–3.6°C. The seasonal aerobic state was withheld at the bottom of the reservoir, and the concentration of DO was maintained above 2 mg/L at the sediment surface. The decay rate of DO in the hypolimnion decreased by 51.2 and 49.6%, respectively, compared to the same period in 2008 and 2009. The concentrations of TP and NH3-N in the overlying water on the sediment surface decreased to ...

Comparison of Water-Lifting Aerator Type for Algae Inhibition in Deep Reservoirs

Water-lifting aeration technology is one of the effective in-situ algae control technologies in deep reservoirs. Effects of water-lifting aerator type on the in-situ algae inhibition using water-lifting aeration technology was numerically analyzed with the help of FLUENT software. Under stable state, one large clockwise circulation flow was generated outside non-submerged and submerged water-lifting aerators, but the core algae inhibition zone was farther away from the non-submerged aerator under each water depth. When the water depth was increased from 77.25 m to 97.25 m, the percentage of the core algae inhibition zone to the whole flow domain was decreased from 56.01% to 47.34% for the submerged water-lifting aerator case, while that was decreased from 55.48% to 40.15% for the non-submerged water-lifting aerator case.

Effects of Temperature Gradient on Algae Inhibition Zone in Source Water Reservoirs Using &lt;i&gt;In Situ&lt;/i&gt; Water-Lifting Aeration Technology

Flow outside the water-lifting aerator was simulated with FLUENT software, and the effects of temperature gradient on the in-situ algae inhibition zone were numerically analyzed. Flow characteristics directly influence the effect of algal inhibition using water-lifting aeration technology. Under quasi-steady state of flow outside the water-lifting aerator, the clockwise flow near the inlet and counter-clockwise flow in other domains coexisted, zone and strength of inlet circulation weakened as the water temperature gradient increased, flow velocity decreased as the distance from the water-lifting aerator increased. When the temperature gradient within the depth of 30 m increased from 0.17 °C/m to 0.73 °C/m, the radius of the core algal growth inhibition zone increased from 100 m to 150 m, and the ratio of the algal growth inhibition zone to the whole flow domain increased from 25.16% to 28.60%. The proper design intervals of water-lifting aerators in reservoirs were proposed as 100m-150m.

Effects of Water Depth on Algae Control in Stratified Reservoirs Using&lt;i&gt; In Situ&lt;/i&gt; Water-Lifting Aeration Technology

Flow outside the water-lifting aerator was simulated with FLUENT software, and the effects of water depth on the in-situ algal growth control using water-lifting aeration technology was numerically analyzed. Under stable state of flow outside the water-lifting aerator, the clockwise flow near the inlet and counter-clockwise flow in other domains coexisted, flow velocity decreased as the distance from the water-lifting aerator increased. When the water depth was increased from 50 m to 110 m, the radius of the core algal growth control zone increased from 60 m to 175 m, and the ratio of the algal growth control zone to the whole flow domain increased from 12.5% to 30.6%. The proper design intervals of water-lifting aerators in reservoirs were proposed as 1.2-1.6 times of water depth.

Sensitivity Analysis and Parameter Optimization of a Hydrodynamic Model for the Aeration Chamber in a Water-Lifting Aerator

A one-dimensional hydrodynamic model for the aeration chamber in the water-lifting aerator was developed on the basis of the total force balance between the driving force and flow resistance acting on the gas-liquid two-phase flow. Water velocity in the aeration chamber was predicted under different combinations of flow resistance coefficients at the top (KT) and the entrance and exit (KE), the results of sensitivity analysis showed that both KT and KE have significant effect on the predicted water velocity and gas holdup in the riser of the aeration chamber. Taking the water velocity as the main objective, flow resistance coefficients of KT and KE were optimized as and , where Ulr is the superficial water velocity. Using optimized model parameters, the water velocities were well predicted within ±7% of the measured ones respectively.

A new method of inhibiting pollutant release from source water reservoir sediment by adding chemical stabilization agents combined with water-lifting aerator

Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more effectively, a new method, which combined chemical stabilization with water lifting aerator (WLA) technology, was proposed and its efficiency in inhibiting pollutant release was studied by controlled sediment-water interface experiments. The results showed that this new method can inhibit pollutant release from sediment effectively. The values of mean efficiency ( E) in different reactors 2#–5# (1# with no agent, 2# 10 mg/L polymeric aluminum chloride (PAC) was added, 3# 20 mg/L PAC was added, 4# 30 mg/L PAC was added, 5# 20 mg/L PAC and 0.2 mg/L palyacrylamide (PAM) were added) for PO 4 3− were 35.0%, 43.9%, 50.4% and 63.6%, respectively. This showed that the higher the PAC concentration was, the better the inhibiting efficiency was, and PAM addition strengthened the inhibiting efficiency significantly. For Fe 2+, the corresponding values of E for the reactors 2#–5# were 22.9%, 47.2%, 34.3% and 46.2%, respectively. The inhibiting effect of PAC and PAM on Mn release remained positive for a relatively short time, about 10 days, and was not so effective as for PO 4 3− and Fe 2+. The average efficiencies in inhibiting the release of UV 254 were 35.3%, 25.9%, 35.5%, 38.9% and 39.5% for reactors 2#–5#, respectively. The inhibiting mechanisms of the agents for different pollutants varied among the conditions and should be studied further

Research on applying a water-lifting aerator to inhibit the growth of algae in a source-water reservoir

A new hydraulic, water-lifting aerator was developed for ameliorating water quality. It aims at mixing lower and upper water bodies, controlling algae growth, increasing dissolved oxygen concentration in water and inhibiting the release of pollutants from sediments. This new device was applied to control the algae growth in surface water of the water source of Tianjin. It was found that the content of agrology chlorophyll-a was reduced by 13.96%, and the growth of algae was inhibited. In this paper, the theory and application conditions of this new device for controlling algae are discussed.

A new mixing–oxygenating technology for water quality improvement of urban water source and its implication in a reservoir

The Water-lifting Aerator, which is a retrofit of the hydraulic gun, was developed to oxygenate lower-layer water and mix the water on the upper and lower layers in stratified reservoirs where pollutants increase from sediments because of anoxic condition in the lower-layer water. The Fenhe reservoir began to supply raw water to the drinking water treatment plant of the City of Taiyuan, China in 2004. The surface of the reservoir froze in winter, and the lower-layer water above the reservoir bed became anoxic because of oxygen consumption by the sediments. Hence, ammonia–nitrogen released from the sediments and trapped in the lower-layer water. After the ice surface thawed in spring, the ammonia–nitrogen in the deepwater was brought up owing to the wind–wave mixing processes. Thus the concentration of ammonia–nitrogen in the outlet water exceeded the permitted level, and the water supply from the Fenhe reservoir had to be cut off. To solve the problem, the Water-lifting Aerator system was installed in the reservoir in the winter of 2005, the dissolved oxygen concentration in the lower-layer water has been maintained at more than 3 mg/L and the ammonia–nitrogen concentration has been reduced to less than 0.1 mg/L. The ammonia–nitrogen concentration in the outlet water is a 95% reduction compared to the same period of last year before the system installation. Since then the water supply from the Fenhe reservoir has no longer been interrupted. Compared with traditional water treatment technology to remove ammonia–nitrogen, the new technology saves energy for 77%.