A Novel Membrane Biofilm Reactor for Microalgae Cultivation and Harvest and Wastewater Treatment

藻类产业是全球经济的重要组成部分。除生物产品外，藻类在生物能源和废物管理部门（从废水中去除营养物质和减少温室气体（CO2））中的用途日益得到认可。然而，悬浮微藻培养物的细胞浓度非常稀，通常小于0.5- 2g/L。因此，在开放式池塘或封闭式光生物反应器中生长的微藻需要大量的水和大量的能量输入用于培养、收获和脱水。据估计，20-30%的微藻生产成本和约90%的设备成本分别与藻类生物质的收获和脱水有关。因此，非常需要用于微藻培养、收获和脱水的新技术来提高微藻生产的经济性。藻类生物膜系统作为开放式池塘和封闭式光生物反应器的替代方案，因其生物量密度高、易于收获、生物量生产率高等特点，近年来引起了人们的广泛关注。微藻生物膜（MB）的主要优势在于更高的细胞浓度（高达悬浮细胞浓度的100倍），这大大减少了收获工作，因为MB可以简单地从表面刮下或真空吸走，并且可以使用而无需进一步浓缩。然而，MB中的高细胞密度需要更大量和更快的CO2转移速率用于生物膜生长。传统的将CO2气体直接鼓泡到光生物反应器或微藻池中的策略具有较低的转移和利用效率，50%至90%的CO2返回大气。因此，新的二氧化碳输送技术对于提高二氧化碳转移和利用效率以及降低能源成本至关重要，特别是对于甲基溴系统而言。该研究计划的重点是开发一种用于微藻培养、收获和废水处理的新型膜碳化微藻生物膜生物反应器（MCMBR）。这种新型系统利用疏水性气体渗透膜将分子CO2输送到生长在膜外表面上的MB中，而营养物质（N和P）和光子从相反方向输送到MB中。这种新型生物反应器系统结合了高细胞密度生物膜系统和通过膜的高CO2转移和利用效率（通过协同效应）的优点，并且具有低能耗，因此可以实现用当前微藻技术无法实现的高得多的工艺效率。本研究的成果是开发一种新型的MCMBR系统，用于微藻培养、收获、废水处理和温室气体（CO2）减排。这项研究将有利于加拿大的环境和能源行业，并培养高素质的人才（HQP），

The algae industry is an important part of the global economy. In addition to bioproducts, algae are increasingly recognized for their use in the bioenergy and waste management sectors (nutrients removal from wastewater and abatement of greenhouse gas (CO2)). However, the cell concentration of suspended microalgae culture is very dilute and usually less than 0.5-2 g/L. Consequently, microalgae grown in open ponds or closed photobioreactors require large volumes of water and a significant amount of energy input for cultivation, harvest, and dewatering. It is estimated that 20-30% microalgae production cost and about 90% of the equipment cost are associated with the harvest and dewatering of algal biomass, respectively. Thus, novel technologies for microalgae cultivation, harvest, and dewatering are highly desirable to improve the economy of microalgae production.******As an alternative to open ponds and closed photobioreactors, algal biofilm systems have drawn great attention in recent years, due to their unique features, such as high biomass density, easy biomass harvest, and increased biomass productivity. The key advantage of microalgal biofilm (MB) lies in the higher cell concentration (up to 100 times of suspended cell concentrations), which greatly reduces harvesting effort as the MB can simply be scraped or vacuumed off the surface and can be used without the need for further concentration. However, the high cell density in MB requires a larger amount and faster transfer rate of CO2 for biofilm growth. The traditional strategies of directly bubbling CO2 gas into photobioreactors or microalgae ponds have a low transfer and utilization efficiency with 50% to 90% CO2 existing back to atmosphere. Thus, novel CO2 delivery technologies are vital to increase CO2 transfer and utilization efficiencies and reduce energy cost, particularly for MB systems.******The proposed research program focuses on the development of a novel membrane carbonated microalgal biofilm bioreactor (MCMBR) for microalgae cultivation, harvest, and wastewater treatment. This novel system utilizes hydrophobic gas permeable membranes to deliver molecular CO2 into MB grown on outside surfaces of the membrane, while nutrients (N and P) and photons are transported into the MB from an opposite direction. This novel bioreactor system combines the advantages of high cell density biofilm systems and a high CO2 transfer and utilization efficiency through membranes (via a synergistic effect) and has a low energy consumption and thus can achieve a much higher process efficiency that is not achievable with current microalgal technologies. The outcome of this research is the development of a novel MCMBR system for microalgae cultivation, harvest, wastewater treatment, and greenhouse gas (CO2) abatement. This research will benefit the Canadian environmental and energy industries and train highly qualified personnel (HQP) i