Assessment of Microalgal-Bacterial Granular Sludge Process for Environmentally Sustainable Municipal Wastewater Treatment

The conventional municipal wastewater treatment processes are facing increasing pressures due to their huge energy consumption, significant emissions of greenhouse gases, and low resource recovery potential. As such, the microalgal-bacterial granular sludge (MBGS) process has recently been explored with the aim for concurrent high-efficiency water, energy, and resource recovery from municipal wastewater in an environmentally sustainable manner. This review attempts to offer a holistic view of the state of the art techniques of MBGS process for municipal wastewater treatment. It was shown that mutualism and symbiosis between microalgae and bacteria could determine the physical structure and microbial community of MBGS. Microbial assimilation instead of dissimilation was identified to be the main mechanisms for removing soluble organics, ammonia, and phosphate in municipal wastewater under both light and dark conditions. Different from the conventional biological nutrients removal processes, wastewater nutrients were effectively fixed into MBGS which could be regarded as a potential source for further energy and resource recovery. Compared to the conventional activated sludge process, the energy consumption and carbon emissions would be reduced, respectively, by 100% and 63% by adopting MBGS. It is apparent that MBGS could offer an alternative toward energy-and carbon-neutral municipal wastewater treatment.

传统的城市污水处理工艺由于能耗巨大、温室气体排放显著以及资源回收潜力低，正面临着越来越大的压力。因此，近年来人们对微藻 - 细菌颗粒污泥（MBGS）工艺进行了探索，旨在以环境可持续的方式从城市污水中同时实现高效的水、能源和资源回收。本综述试图全面介绍用于城市污水处理的MBGS工艺的最新技术状况。研究表明，微藻和细菌之间的共生关系能够决定MBGS的物理结构和微生物群落。在光照和黑暗条件下，微生物同化作用而非异化作用被确定为去除城市污水中可溶性有机物、氨和磷酸盐的主要机制。与传统的生物脱氮除磷工艺不同，污水中的营养物质被有效地固定在MBGS中，这可被视为进一步能源和资源回收的潜在来源。与传统的活性污泥工艺相比，采用MBGS可使能耗和碳排放分别降低100%和63%。显然，MBGS可为实现能源和碳中性的城市污水处理提供一种替代方案。