A Method for WWTP Sludge Valorization through Hygienization by Electron Beam Treatment

Pilot-scale investigation of performance and microbial community in a novel system combining fixed and suspended activated sludge

The conventional activated sludge (CAS) process is a widely used method for wastewater treatment due to its effectiveness and affordability. However, it can be prone to sludge abnormalities such as sludge bulking/foaming and sludge loss, which can lead to a decrease in treatment efficiency. To address these issues, a novel bag-based fixed activated sludge (BBFAS) system utilizing mesh bags to contain the sludge was developed for low carbon/nitrogen ratio wastewater treatment. Pilot-scale experiments demonstrated that the BBFAS system could successfully avoid the sludge abnormalities. Moreover, it was not affected by mass transfer resistance and exhibited significantly higher nitrogen removal efficiency, surpassing that of the CAS system by up to 78%. Additionally, the BBFAS system demonstrated comparable organic matter removal efficiency to CAS system. 16S rRNA gene high-throughput sequencing revealed that the bacterial community structure within the BBFAS system was significantly different from that of the CAS system. The bacteria associated with ammonium removal were more abundant in the BBFAS system than in the CAS system. The abundance of Nitrospira in the BBFAS could reach up to 6% and significantly higher than that in the CAS system, and they were likely responsible for both ammonia-oxidizing and nitrite-oxidizing functions. Clear stratification of microbial communities was observed from the outer to inner layers of the bag components due to the gradients of dissolved oxygen and other substrates. Overall, this study presents a promising approach for avoiding activated sludge abnormalities while maintaining high pollutant removal performance.

Recent Trends in Biogenic Gas, Waste and Wastewater Fermentation

In recent years, the optimization of bioprocesses for the removal of pollutants from industrial biogenic gas emissions, waste and wastewater has been the focus of intensive research. Recently developed technologies not only aim to remove such pollutants, but also to valorize them, whenever possible, through their bioconversion into useful added-value products. In this domain of progressive research, lab-, pilot-, and demonstration-scale studies are dealing with the fermentation of biogenic gases (e.g., CO2, CO, and CH4), waste or wastewater to produce a range of biofuels and valuable products, based on the activity of pure or mixed cultures of native or recombinant aerobic and anaerobic bacteria, algae, or yeasts as biocatalysts. Waste can also be converted to syngas, which can subsequently be fermented as well. A broad range of bioproducts can be obtained, e.g., biofuels and several other platform chemicals and products. This environmentally-friendly biorefinery approach addresses the need to build modern societies according to the concept of a circular economy, and yields products of commercial interest. Different examples of such approaches are described in this collection of scientific reports.