Fouling of membranes in membrane bioreactors for wastewater treatment: Planktonic bacteria can have a significant contribution

Abstract

Membrane bioreactors (MBRs) for wastewater treatment show great potentials in the sustainable development of urban environments. However, fouling of membranes remains the largest challenge of MBR technology. Dissolved extracellular polymeric substances (EPS) are often assumed be the main foulant in MBRs. However, single bacterial cells are often erroneously measured as EPS in traditional spectrophotometric analysis of EPS in activated sludge, so we hypothesized that single cells in many cases could be the true foulants in MBRs for wastewater treatment. To study this, raw MBR sludge and sludge supernatant with varying concentrations of planktonic cells were filtered on microfiltration (MF) membranes, and we found a direct correlation between the cell count and rate of flux decline. Addition of planktonic cells to fresh MBR sludge dramatically increased the flux decline. The identity of the most abundant planktonic cells in a full‐scale MBR water resource recovery facility was determined by DNA fingerprinting. Many of these genera are known to be abundant in influent wastewater suggesting that the influent bacterial cells may have a direct effect on the fouling propensity in MBR systems. This new knowledge may lead to new anti‐fouling strategies targeting incoming planktonic bacteria from the wastewater feed. Practitioner points Planktonic cells constituted up to 60% of the total protein content of “soluble extracellular polymeric substances” in membrane bioreactor sludge. Planktonic cells are hidden under a surrogate concentration of extracellular polymeric substances which is often associated with fouling. Membrane fouling rate is directly proportional to amount of free planktonic cells suspended in sludge. Several influent bacterial genera are enriched in the water phase of membrane bioreactor sludge. Removing these may mitigate fouling.

Microbial Electrochemical Systems and Membrane Bioreactor Technology for Wastewater Treatment

“…However, MBRs and MESs have problems that limit their overall performance. For example, membrane fouling is a major issue in MBR systems [16,17], which affects the overall performance and lifetime of the membranes and increases the operation costs and maintenance costs of the system [18,19]. Microorganisms, cell debris, colloids, solutes, and sludge flocs in wastewater are the main causes of membrane fouling in MBR.…”

Aminophosphonic Acid Functionalized Cellulose Nanofibers for Efficient Extraction of Trace Metal Ions

“…However, many of them have severe limitations, such as the chemical precipitation method, which generates a large amount of toxic residue and leads to secondary pollution, while the electrochemical process is of high cost with low efficiency. Membrane separation is better and restricts the pollutants to pass into the mainstream; however, faces fouling after a particular time period [ 19 , 20 ]. The solid-phase extraction (SPE) technique has been considered a promising method due to its simple preparation, relatively low cost, ability to use both in batch and column procedures, faster kinetics, and high possibility to reuse the adsorbent [ 21 , 22 , 23 ].…”