Lab-scale Evaluation of Spiral Vortex Artificial Circulation

摘要

When phosphorus and nitrogen concentrations are high in lakes and reservoirs, enough for algae to grow, algal bloom prevention needs to be approached by circulation of stagnant water. A new circulation technology 'Spiral vortex artificial circulation' was developed that transports water to the surface without any hose and also provides sufficient oxygen as the water circulates. Artificial thermal and dissolved oxygen stratification was created in a water tank, and thermometers and DO meters were placed at each layer to evaluate the technology's efficiency by comparing how fast the stratification broke. Two types of booster were used: a flow booster which promotes thorough mixing and a 12 cm flat round booster that protects the bottom of water column from disturbing, yet circulates the surface. Impeller speed was set at 60 rpm and 180 rpm to compare speed difference thus total of four experiments were conducted. The stratified water was completely mixed in two experiments with flow booster. However when 12 cm flat round booster was used at 60 rpm, even after 100 minutes of operation the stratification was not broken whereas it took 75 minutes at 180 rpm. The same or similar settings can be applied in situ without disturbing the benthic zone;; if not, nutrients could be released to water bodies which might lead serious eutrophication. The further technology evaluation is in progress for improving its algal bloom suppression and energy.