Submerged Membrane Bioreactor at Substrate‐Limited Conditions: Activity and Biomass Characteristics

Abstract

A pilot‐scale membrane bioreactor was operated for advanced treatment of secondary effluent from a wastewater treatment plant. The performance and biomass characteristics were evaluated under two different hydraulic retention time (HRT) values (7.5 and 15 hours). The system was operated successfully without biomass purge and, after an initial phase, evolved until reaching a constant mixed‐liquor volatile suspended solids (MLVSS) concentration, which resulted in the same value of carbon utilization rate (0.067 ± 0.004 kg COD kg−1 MLVSS d−1) for both HRTs. Respiration tests (maximum and endogenous oxygen uptake rates) confirmed a low microbial activity, which approached constant values (0.132 ± 0.001 and 0.064 ± 0.007 g O2 g−1 MLVSS d−1, respectively), regardless of the HRT. The sludge morphology and bound and supernatant extracellular polymeric substances also were assessed. Membrane performance was characterized by a stable behavior occurring simultaneously with a high level of biodegradation in the microcolloidal and soluble fraction.

Aerobic Membrane Bioreactor for Wastewater Treatment – Performance Under Substrate-Limited Conditions

“…Figure 5 shows the evolution of U with operation time where it can be observed that the system evolved until reaching a nearly constant value (0.083 ± 0.004 kg COD/kg MLVSS d). A symmetrical trend can also be observed for data obtained in a previously reported research (Delgado et al, 2010) in an MBR treating biological effluent from a WWTP. In that case, the MBR was inoculated and the initial biomass evolution was characterised by a lysis process.…”

Nanofiltration/Reverse Osmosis as Pretreatment Technique for Water Reuse: Ultrafiltration Versus Tertiary Membrane Reactor

“…Alternatively, tertiary submerged membrane bioreactors (tMBR) have also been proposed for old wastewater treatment plants (WWTP) with poor performance of secondary clarifiers [http://www.kochmembrane.com/PDFs/Case-Studies/KMS-Sao-Paulo-Brazil-Case-Study.aspx]. By operating at maintenance energy level ( i.e , minimal value for the carbon substrate utilization rate), tMBR significantly reduces sludge production and minimizes the concentration of organic soluble components . Despite advances in both technologies, experience gained over recent decades from operating membranes has demonstrated that membrane fouling continues to be the main limitation halting its widespread application .…”