Successive Conditioning in Complex Artificial Wastewater Increases the Performance of Electrochemically Active Biofilms Treating Real Wastewater

Abstract

This study focuses on improving the treatment capacity and current output of electrochemically active microorganisms (EAM) during real wastewater treatment. A multi‐carbon‐source artificial wastewater consisting of several carbon sources, which represent typical fermentation and hydrolysis products derived from the otherwise myriad wastewater constituents, was developed as a more realistic simulation thereof. An electrochemically preselected inoculum was obtained by means of re‐suspension of a well‐established EAM biofilm, which was subsequently used to inoculate sterile electrodes. Repeating this procedure yielded increasingly enriched and conditioned biofilms with improved performance. After cultivation in the complex artificial medium, highly efficient fourth generation EAM biofilms were fed real wastewater (i. e. effluent after primary settling) and outperformed those cultivated using a single substrate (i. e. acetate) in terms of current output and chemical oxygen demand (COD) degradation rates.

Cultivating Electrochemically Active Biofilms at Continuously Changing Electrode Potentials

“…To ensure anaerobic conditions, the cultivation medium was purged with nitrogen for at least 20 minutes before inoculation. The inoculation procedure was adapted from the methods used previously: For primary or first generation biofilm cultivation, 50 mL of inoculum (real wastewater, i. e. effluent after primary settling (EAPS) from wastewater treatment plant (WWTP – Steinhof, Braunschweig, Germany) was added to 950 mL artificial wastewater. For second generation or secondary biofilm cultivation, well‐established primary biofilms served as the inoculation source.…”

“…two weeks). 100 mL of this stock solution was diluted with carbonate buffer and, after addition of trace metal and vitamin solutions, filled up to 1 L, leading to a COD theo of 800 mg COD L −1 (see).…”

“…WW 2.1). The resulting electrochemically active biofilms were capable of more efficiently treating real municipal wastewater with higher current densities and COD removal efficiencies than those grown only on acetate . The performance of these systems was further improved by applying a consecutive cultivation procedure, in which established biofilms were used as the inocula for forthcoming biofilm generations …”

“…This method of cultivation and operation is applicable to both microbial fuel cells and microbial electrolysis cells. The biofilms were cultivated in several consecutive selection and conditioning steps in a multi‐carbon‐source artificial wastewater, as described previously, tertiary EAB biofilms were fed both with artificial and real, domestic, wastewater. The composition of the microbiomes of these tertiary biofilms was characterized in addition to model‐based investigations of the electron transfer kinetics.…”

Investigating Community Dynamics and Performance During Microbial Electrochemical Degradation of Whey

“…If the rate of fermentation greatly exceeds the rate of utilization of the generated acids by EAB, the drop in pH (especially in low‐buffer capacity or non‐buffered media) may inhibit the entire system. Keeping in mind that EAB in biofilms at the bioanode are also subjected to lower pH values than the pH values of the bulk medium, because there is a pH gradient within the biofilm.…”