National Institute of Water and Atmospheric Research Ltd (NIWA), P. O. Box 11-115, Hamilton, New Zealand.
School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
Water Res. 2015 Dec 15;87:97-104. doi: 10.1016/j.watres.2015.09.013. Epub 2015 Sep 10.
Recycling a portion of gravity harvested algae (i.e. algae and associated bacteria biomass) has been shown to improve both algal biomass productivity and harvest efficiency by maintaining the dominance of a rapidly-settleable colonial alga, Pediastrum boryanum in both pilot-scale wastewater treatment High Rate Algal Ponds (HRAP) and outdoor mesocosms. While algal recycling did not change the relative proportions of algae and bacteria in the HRAP culture, the contribution of the wastewater bacteria to the improved algal biomass productivity and settleability with the recycling was not certain and still required investigation. P. boryanum was therefore isolated from the HRAP and grown in pure culture on synthetic wastewater growth media under laboratory conditions. The influence of recycling on the productivity and settleability of the pure P. boryanum culture was then determined without wastewater bacteria present. Six 1 L P. boryanum cultures were grown over 30 days in a laboratory growth chamber simulating New Zealand summer conditions either with (Pr) or without (Pc) recycling of 10% of gravity harvested algae. The cultures with recycling (Pr) had higher algal productivity than the controls (Pc) when the cultures were operated at both 4 and 3 d hydraulic retention times by 11% and 38% respectively. Furthermore, algal recycling also improved 1 h settleability from ∼60% to ∼85% by increasing the average P. boryanum colony size due to the extended mean cell residence time and promoted formation of large algal bio-flocs (>500 μm diameter). These results demonstrate that the presence of wastewater bacteria was not necessary to improve algal productivity and settleability with algal recycling.
回收一部分重力收获的藻类（即藻类和相关细菌生物量）已被证明可以通过维持快速沉降的群体藻类——蹄形藻（Pediastrum boryanum）在中试规模废水处理高速藻类池塘（HRAP）和户外中培养物中的优势地位，提高藻类生物量生产力和收获效率。虽然藻类回收并没有改变 HRAP 培养物中藻类和细菌的相对比例，但回收对提高藻类生物量生产力和沉降性的废水细菌的贡献尚不确定，仍需进一步研究。因此，将蹄形藻从 HRAP 中分离出来，并在实验室条件下，在合成废水生长培养基中进行纯培养。然后，在没有废水细菌的情况下，确定了回收对纯蹄形藻培养物生产力和沉降性的影响。在新西兰夏季条件下的实验室生长室中，用 1 L 的 6 个蹄形藻培养物在 30 天内生长，要么进行（Pr）要么不进行（Pc）回收 10%的重力收获的藻类。当在 4 和 3 d 水力停留时间下运行时，回收培养物（Pr）的藻类生产力比对照（Pc）高 11%和 38%。此外，通过延长平均细胞停留时间和促进大的藻类生物絮体（> 500 μm 直径）的形成，藻类回收还将 1 h 的沉降性从约 60%提高到约 85%。这些结果表明，在藻类回收中提高藻类生产力和沉降性并不需要废水细菌的存在。
