Algal bioproductivity in turbulent water: An experimental study
San, Lei, Tianyu Long, and Clark C.K. Liu
Water 9(5), 304, https://doi.org/10.3390/w9050304 (2017)
Excessive growth of biomass causes eutrophication and other related water quality problems. For the past several decades, these problems have been managed based on the principle of limiting nutrient, which is to reduce the loading of essential nutrients—either nitrogen or phosphorus—through point and non-point waste source control. More recent research efforts indicated that eutrophication of a natural water body such as a lake or a reservoir can be controlled alternatively by altering its turbulent intensity. The success of this alternative approach depends on more knowledge on the intimate relationship between turbulent intensity and the bioproductivity of a water body. In this experimental study, an oscillating grid turbulence (OGT) reactor was constructed to evaluate the effect of turbulent pulsation strength in terms of vibration frequency on algae bioproductivity under adequate nutrient, light, and temperature conditions. Experimental results showed that moderate turbulent intensity with vibration frequency of 0.5 Hz or less increased algal growth; with a vibration frequency of 1.0 Hz, the observed peak chlorophyll a (Chl-a) concentration in the reactor was 0.112 mg/L. The experimental results also showed that strong turbulent intensity with vibration frequency of 1.5 Hz or more reduced algal growth; with vibration frequency of 1.5 Hz, the observed peak Chl-a concentration in the reactor was only 0.06 mg/L, which was even lower than the observed peak Chl-a concentration in the reactor with stationary water. In this study, the effect of water turbulence on algal bioproductivity was further verified with experimental data on the variations of other relevant water quality parameters in the OGT reactor including total nitrogen (TN), total phosphorus (TP), pH, and dissolved oxygen (DO).