National Institute of Water and Atmospheric Research Ltd. (NIWA), PO Box 8602, Christchurch, New Zealand; School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
Water Res. 2014 Sep 15;61:130-40. doi: 10.1016/j.watres.2014.05.011. Epub 2014 May 24.
Laminar flows are a common problem in high rate algal ponds (HRAP) due to their long channels and gentle mixing by a single paddlewheel. Sustained laminar flows may modify the amount of light microalgal cells are exposed to, increase the boundary layer between the cell and the environment and increase settling out of cells onto the pond bottom. To date, there has been little focus on the effects of the time between mixing events (frequency of mixing) on the performance of microalgae in wastewater treatment HRAPs. This paper investigates the performance of three morphologically distinct microalgae in wastewater treatment high rate algal mesocosms operated at four different mixing frequencies (continuous, mixed every 45 min, mixed every 90 min and no mixing). Microalgal performance was measured in terms of biomass concentration, nutrient removal efficiency, light utilisation and photosynthetic performance. Microalgal biomass increased significantly with increasing mixing frequency for the two colonial species but did not differ for the single celled species. All three species were more efficient at NH4-N uptake as the frequency of mixing increased. Increased frequency of mixing supported larger colonies with improved harvest-ability by gravity but at the expense of efficient light absorption and maximum rate of photosynthesis. However, maximum quantum yield was highest in the continuously mixed cultures due to higher efficiency of photosynthesis under light limited conditions. Based on these results, higher microalgal productivity, improved wastewater treatment and better gravity based harvest-ability can be achieved with the inclusion of more mixing points and reduced laminar flows in full-scale HRAP.
层流是高速藻类塘 (HRAP) 中的一个常见问题，因为它们的通道较长，并且只有一个桨轮进行温和的混合。持续的层流可能会改变微藻细胞暴露的光量，增加细胞与环境之间的边界层，并增加细胞沉淀到池塘底部的量。迄今为止，人们很少关注混合事件之间的时间（混合频率）对废水处理 HRAP 中微藻性能的影响。本文研究了三种形态不同的微藻在四个不同混合频率（连续、每 45 分钟混合一次、每 90 分钟混合一次和不混合）下在废水处理高光生物反应器中的性能。微藻性能根据生物量浓度、养分去除效率、光利用和光合性能进行测量。对于两种群体物种，微藻生物量随着混合频率的增加而显著增加，但对于单细胞物种则没有差异。随着混合频率的增加，所有三种物种对 NH4-N 的吸收效率都有所提高。增加混合频率支持更大的群体，通过重力提高了收获效率，但牺牲了有效的光吸收和最大光合速率。然而，由于在光限制条件下光合作用效率更高，连续混合培养中的最大量子产量最高。基于这些结果，在全规模 HRAP 中增加更多的混合点并减少层流，可以实现更高的微藻生产力、改善废水处理和更好的重力收获能力。
