Continuous acidogenic fermentation: Narrowing the gap between laboratory testing and industrial application.

This study explored the potential of acidogenic fermentation of sewage sludge (SS) in an 80 L automatized pilot scale platform. A high-rate VFA production was obtained at HRT 5 d and pH 9, with a volatile fatty acid (VFA) yield of 336 mg VFA g-1 VS and a VFA productivity of 2.15 kg VFA m-3 d-1. During co-fermentation of SS with OFMSW, a reversible pH shift from pH 9 to pH 6, evidenced a higher acidogenic activity which promoted the butyrate metabolic pathway, with 13.97 g COD L-1 of butyric acid and a VFA peak 23.2 g COD L-1. The results show the degree of flexibility of mixed culture fermentation systems, where other pH control methods other than steady control could be used to enhance the fermentation process. Ultrafiltration was a feasible technology to obtain a VFA rich permeate where 12.3-26.6 g COD L-1 could be recovered.

Model-based design of a software sensor for real-time diagnosis of the stability conditions in high-rate anaerobic reactors - Full-scale application to Internal Circulation technology.

Internal Circulation (IC) anaerobic systems are especially suitable when plant designs that involve both small footprints and high organic loading rates (>25 kg COD m-3 d-1) are required. However, given that operating anaerobic processes at high organic loads increases their vulnerability to external disturbances, real-time indicators of the stability conditions become particularly pertinent for IC reactors. This paper addresses the design and full-scale validation of a software sensor that uses only feeding flow-rate and biogas flow-rate measurements to classify the operating conditions of the reactor as "strongly", "moderately" or "weakly" stable. A simulation-based procedure was used to design the software sensor and configure its parameters. Then, the performance of the software sensor was tested under real conditions in a full-scale IC reactor of 1679 m3 installed in a recycled paper mill (RPM).