Laura Borea

Combination of Electrochemical Processes with Membrane Bioreactors for Wastewater Treatment and Fouling Control: A Review

This paper provides a critical review about the integration of electrochemical processes into membrane bioreactors (MBR) in order to understand the influence of these processes on wastewater treatment performance and membrane fouling control. The integration can be realized either in an internal or an external configuration. Electrically enhanced membrane bioreactors or electro membrane bioreactors (eMBRs) combine biodegradation, electrochemical and membrane filtration processes into one system providing higher effluent quality as compared to conventional MBRs and activated sludge plants. Furthermore, electrochemical processes, such as electrocoagulation, electrophoresis and electroosmosis, help to mitigate deposition of foulants into the membrane and enhance sludge dewaterability by controlling the morphological properties and mobility of the colloidal particles and bulk liquid. Intermittent application of minute electric field has proven to reduce energy consumption and operational cost as well as minimize the negative effect of direct current field on microbial activity which are some of the main concerns in eMBR technology. The present review discusses important design considerations of eMBR, its advantages as well as its applications to different types of wastewater. It also presents several challenges that need to be addressed for future development of this hybrid technology which include treatment of high strength industrial wastewater and removal of emerging contaminants, optimization study, cost benefit analysis and the possible combination with microbial electrolysis cell for biohydrogen production.

Wastewater treatment by membrane ultrafiltration enhanced with ultrasound: effect of membrane flux and ultrasonic frequency

HighlightsUltrasonic enhanced membrane ultrafiltration at two fluxes and two US frequencies.Enhancement of the treatment performance at the lowest US frequency of 35 kHz.US are more effective in fouling rate reduction at higher membrane flux (150 L/m2 h).Higher OM and turbidity removals were obtained at 130 kHz. ABSTRACT Membrane ultrafiltration is increasingly applied for wastewater treatment and reuse, even though membrane fouling still represents one of the main drawbacks of this technology. In the last years, innovative strategies for membrane fouling control have been developed, such as the combination of membrane processes with ultrasound (US). In present work, the application of membrane ultrafiltration and its combination with US were studied, evaluating the influence on the performance of the treatment and membrane fouling formation of two membrane fluxes, 75 and 150 L/m2 h, along with two US frequencies, 35 and 150 kHz. The results observed showed that the combination of membrane ultrafiltration with US, respect to the filtration process alone, reduced membrane fouling rates to a greater extent at the higher membrane flux and lower US frequency applied, reaching a reduction of 57.33% at 150 L/m2 h and 35 kHz. Furthermore, higher organic matter and turbidity removals were observed at higher frequency (130 kHz). The results obtained highlights the applicability of this combined process for the upgrading of membrane ultrafiltration and as an alternative option to conventional tertiary wastewater treatments.

Control of fouling formation in membrane ultrafiltration by ultrasound irradiation

The increasing application of membrane filtration in water and wastewater treatment necessitates techniques to improve performance, especially in fouling control. Ultrasound is one promising technology for this purpose as cavitational effects facilitate continuous cleaning of the membrane. This research studied the ultrafiltration of lake water in systems with constant permeate flux under medium frequency (45 kHz) ultrasound irradiation. Fouling was investigated by monitoring transmembrane pressure (TMP) using continuous or intermittent ultrasound irradiation and dead-end or crossflow operation. Best performance was observed with continuous ultrasound irradiation in crossflow mode. Intermittent irradiation reduced the rate of TMP build-up but nevertheless allowed irreversible fouling to develop.

An Electro Moving Bed Membrane Bioreactor (eMB-MBR) as a Novel Technology for Wastewater Treatment and Reuse

Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reuse. However, since membrane fouling and energy consumption still remain operational obstacles and challenges for the widespread application of the MBR technology, research studies for fouling control are still underway. Recently, among different integrated approaches for membrane fouling mitigation, the combinations of MBRs with electrochemical processes (eMBR/electro MBR) or with moving bed biofilm reactor (MBBR) have been adopted as alternative technological methods. In the present study, the performance of an electro moving bed membrane bioreactor (eMB-MBR), in terms of treatment efficiency and fouling formation, was investigated as a novel integrated process which combines an electro MBR with a moving bed membrane bioreactor (MB-MBR). An intermittent voltage gradient of 3 V/cm was applied between two electrodes immersed around a membrane module inside the bioreactor filled with carriers at 30% filling ratio. A MB-MBR was operated as a control test. The integration of electrochemical processes into the MB-MBR improved the treatment performance especially in terms of nutrient removal, with an enhancement of orthophosphate (PO4-P) and ammonia nitrogen (NH4-N) removal efficiencies up to 55.0% and 98.7%. The filtration cycles were extended in the eMB-MBR with a reduction of membrane fouling rate of around 60% and of membrane fouling precursors respect to the control test. The results obtained showed the synergic effect of the combined process. Hence, the eMB-MBR process represents a novel exciting technology which is deemed possible for wastewater treatment.

Applicability of the electrocoagulation process in treating real municipal wastewater containing pharmaceutical active compounds

In this study, the viability of using electrocoagulation process as a method for pharmaceuticals removal from real municipal wastewater was demonstrated. Batch experimental runs were performed using a simple laboratory scale electrochemical reactor with aluminium and stainless steel as anode and cathode, respectively. Diclofenac (DCF), carbamazepine (CBZ) and amoxicillin (AMX) were selected as representative of pharmaceuticals frequently detected in the aquatic environment. The effects of varying experimental parameters namely current density (0.3, 0.5 1.15 and 1.8 mA cm-2), initial pharmaceutical concentration (0.01, 4 and 10 mg L-1), electrolysis duration (3, 6 and 19 h) and application mode (continuous vs. intermittent) on pharmaceutical removal efficiencies were evaluated. High pharmaceutical abatement was recorded at elevated current density and prolonged electrolysis duration due to additional electro-generated coagulant species in solution.

Control of quorum sensing signals and emerging contaminants in electrochemical membrane bioreactors

The present study investigated the influence of electric field on the removal of quorum sensing (QS) and emerging contaminants using an electrochemical membrane bioreactor (eMBR). A significant reduction of N-octanoyl-L-homoserine lactone signal molecules (∼76%) was achieved in the eMBR, with respect to the level observed in the conventional MBR as the control. Furthermore, the intermittent electric current supply (0.5 mA/cm2) was found to be effective for the removal of atrazine and estrone. The degradation of key pharmaceutical compounds, such as diclofenac, carbamazepine, and amoxicillin, was also possible, confirming the applicability of the eMBR system for removing the priority chemical compounds of public health concern.

Wastewater Treatment and Energy Production Through Electro Membrane Bioreactors

Membrane bioreactors (MBRs) are a well established and mature technology with many full-scale plants around the world treating municipal and industrial wastewater (Krzeminski et al. in J. Membr. Sci. 527:207–227, 2017).