Application of Circular Bubble Plume Diffusers to Restore Water Quality in a Sub-Deep Reservoir

Abstract

Circular bubble plume diffusers have been confirmed as an effective technology for the restoration of the deep water system, but have never been applied in sub-deep water system. In this study, circular bubble plume diffusers were used, for the first time, to restore water quality in the Aha Reservoir, a typical sub-deep reservoir in Southwest China. Axisymmetric intrusive gravity currents were formed with a horizontal radius of 250 m at the equilibrium depth and the intrusion of oxygen-enriched water occurred within the depth of 10–14 m, while thermal stratification remained intact. A total of 95% of the imported oxygen was dissolved, but most was consumed by organic matter and other reduced substances within the hypolimnion. The oxygen consumption of organic matter, NH4+ and remaining reduced materials, accounted for 41.4–52.5%, 25% and 13.3–24.4% of the total imported oxygen, respectively. Compared with the control sites, dissolved oxygen level in the hypolimnion increased 3–4 times, and concentrations of NH4+, total Fe and total Mn were reduced by 15.5%, 45.5% and 48.9%, respectively. A significant decrease in total phosphorus and nitrogen concentrations was observed in the experimental zone (0.04–0.02 mg/L and 1.9–1.7 mg/L, respectively). This indicates that circular bubble plumes have great potential for oxygenation of the hypolimnion and improving water quality in the sub-deep water system. Nevertheless, further efforts are needed to improve the discrete bubble model to elaborate the oxygen transmission dynamics and the plume formation processes in sub-deep water systems, incorporating oxygen consumption processes.

Unveiling the ecological significance of phosphorus fractions in shaping bacterial and archaeal beta diversity in mesotrophic lakes

“…Aha Lake is a P-limited and deep plateau lake (Liu et al, 2019), with total P concentrations ranging from 0.022 to 0.205 mg L −1 and an average of 0.046 mg L −1 (Wang et al, 2021b). Owing to the aggravation of anoxia in the hypolimnion, large amounts of pollutants like phosphorus have been released from the sediments (Lan et al, 2017). Such phosphorus can broadly induce algal blooms and thereby endanger the water quality of this lake (Han et al, 2018).…”

In-Lake Mechanisms for Manganese Control—A Systematic Literature Review

“…A widely used Mn control measure to minimize anoxia in the hypolimnion is direct oxygenation of this water column layer. Previous research has reviewed the impacts of Hypolimnetic Oxygenation (HO) on the chemical conditions of the bottom layers of the water column and found it as an effective method to decrease soluble Mn concentration even though did not eliminate the formation of reduced Mn [33]. Rather, it pushed the oxicanoxic boundary out of the water column into the sediments, lowering the Mn concentration in the water column with the risks of influxes of Mn in the water column due to sediment release [32].…”

“…The mechanism involves compressed air to be driven through a diffuser located near the bottom of the lake to prevent Mn accumulation in the hypolimnion. The rising columns of bubbles are supplemented with water to form a combined bubble and water plume [36] and have the ability to improve water quality in the sub-deep water system through hypolimnion oxygenation [33]. For instance, a study in Arha Reservoir, China, observed that placing circular bubble plume diffusers at the drinking water outlet area resulted in reductions of 48.9% in Mn concentration [35].…”

“…It breaks the thermal stratification layers by mixing and changing the deoxidized water layer at the bottom of a lake into an oxidized status. Previous research has found it to effectively decrease the Mn concentration in the water column [33,37]. This process involves lifting the anoxic bottom waters to the surface for destratification, while the oxygenated waters in the aerated region are pushed toward the bottom sediments [38].…”

The buffering of a riverine carbonate system under the input of acid mine drainage: Example from a small karst watershed, southwest China

“…The mining of medium-to high-sulfur coal has caused serious surface water acidification issues, which in turn has complicated the evolution of DIC in surface freshwater systems in karst areas (Han and Liu, 2004;Li et al, 2008;Huang et al, 2017;Li et al, 2018;Jin et al, 2020). Compared to the marine system, more complex influencing factors may affect the buffer capacity of carbonate systems in freshwater systems in karst areas, and the pH fluctuation is much wider than that found in marine systems (Lueker et al, 2000;Sunda and Cai, 2012;Hagens and Middelburg, 2016b;Lan et al, 2017;Lauvset et al, 2020).…”