Dear Colleagues,

In order to satisfy the growing demand for water in a framework defined by the global climate change, increasing urbanization, and population growth, it has been necessary to use membrane technologies, which enable the treatment of poor-quality water sources such as wastewater, seawater, brackish, or contaminated natural waters.

The application of reverse osmosis, electrodialysis, or nanofiltration membranes in sea and brackish water desalination, effluents remediation, and pollution removal are clear examples of the continuous and progressive innovation exhibited during membrane technologies evolution. The remarkable development experienced by membrane bioreactors in the last 15 years, due to its high competitiveness and versatility, has gone hand-in-hand with the increasingly demanding regulations regarding the quality of recycled or reused water. The incorporation of membranes in processes of recovery of resources such as nutrients and organic matter present in wastewater, in harmony with the principles of the circular economy that will guide future wastewater treatment facilities, is an example of the possibilities of the future development of membrane technologies in the water sector.

One of the great challenges that the development and expansion of membrane technologies must address is to seek their sustainability through the design of materials with less tendency to fouling; to improve their capacity to retain emerging contaminants; and to develop strategies to control fouling and prolong the life of the membranes minimizing chemicals and energy, while considering life-cycle assessment focused on minimizing environmental impacts.

This "Membrane Technologies and Water Treatment" Special Issue will bring together articles on new developments in the manufacture and application of membranes in water treatment processes. The Special Issue is requesting articles on all aspects of membranes, including manuscripts on membrane fouling and control strategies, new materials, sustainable designs, on-line monitoring, fouling characterization and modeling, and new membrane processes oriented towards global sustainable developments and membrane applications.

Dr. Luisa Vera
Dr. Luis E. Rodríguez-Gómez
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• water reclamation
• water reuse
• water recycling
• membrane fouling
• nutrients recovery
• membrane photobioreactor
• membrane bioreactor
• shear stress
• sustainability

Antonio Monteoliva-García ^a; Juan Carlos Leyva-Díaz ^b;*; Cristina López-López ^a; José Manuel Poyatos ^a; María del Mar Muñío c; Jaime Martín-Pascual ^a

^a Department of Civil Engineering, University of Granada, Granada, Spain; Institute of Water Research, University of Granada, Granada, Spain.

^b Department of Chemical and Environmental Engineering, University of Oviedo, Oviedo, Spain.

^c Department of Chemical Engineering, University of Granada, Granada, Spain.

Corresponding author: Juan Carlos Leyva-Díaz, Email: [email protected]

Abstract: Numerous studies have analyzed the viability of the biodegradation and removal of different compounds of emerging concern in biological systems for wastewater treatment; however, the effect on the heterotrophic biomass for organic matter removal is missed sometimes. The aim of the present research was to study the effect caused by the addition of a mix of three pharmaceuticals (carbamazepine, ciprofloxacin and ibuprofen) on the behavior of the biomass in a membrane bioreactor (MBR) system treating urban wastewater. This work studied a membrane bioreactor pilot plant operating at a similar condition of mixed liquor suspended solids (about 5.5 g/L) with and without combination with moving bed biofilm reactor (MBBR-MBR and MBR, respectively) to treat real urban wastewater at 6 and 10 h of hydraulic retention time (HRT) under three different shocks of pharmaceuticals (carbamazepine, ciprofloxacin and ibuprofen) with increasing concentrations. Although in all cases, the organic matter removal was higher than 92.08 % of BOD₅, 79.06 % of COD and 85.03 % of TOC, in average terms the removal was higher in MBBR-MBR technology under the same HRT and similar MLSS. Moreover, this removal increased during the shock of pharmaceuticals compounds especially in MBR technology due to the fact in MBBR-MBR technology these were higher. From a kinetic perspective, MBBR-MBR is more suitable for low HRT (6 h) and MBR is more effective for high HRT (10 h). This could be based on the fact that biofilm systems are less sensitive to more unfavorable operation conditions than the MBR systems. In relation to the removal of N-NH₄, this decreased considerably when the pharmaceutical compounds mix was introduced in the system, until that no removal was detected in cycle 1 even when biofilm was present (MBBR-MBR).

Keywords: membrane bioreactor; pharmaceutical shock; nitrogen; heterotrophic kinetics.

2. Techno-economic assessment of membrane distillation: application to cruise ships and acid mine drainage water treatment.

David Amaya-Vías; Juan A. López-Ramírez^*

Departamento de Tecnologías del Medio Ambiente, Faculty of Marine and Environmental Sciences. Instituto Universitario de Investigación Marina (INMAR). Campus de Excelencia Internacional del Mar (CEIMAR). University of Cadiz, Av. República Saharaui, Puerto Real, 11510 Cádiz. Spain

Corresponding author: Juan A. López-Ramírez, E-mail: [email protected]

Abstract: Membrane distillation (MD) shows a great potential that it is being explored by scientific community. This paper shows a techno-economic assessment, using experimental data for two MD applications: desalination on-board of cruise ships and acid mine drainage water treatment, using air gap and water gap MD configurations. Both waters are studied under several scenarios, performing a sensitivity analysis and cost analysis (CAPEX and OPEX). For this, heat sources and scale factors are considered to simulate from the least favourable to the most desirable conditions. In the most favorable, results show that MD is a technology as competitive as conventional ones.

Keywords: membrane distillation, air gap membrane distillation, water gap membrane distillation, techno-economic assessment, cruise ship desalination, acid mine drainage treatment.

3. Identification of foulants on polyethersulfone (PES) membranes used to remove colloids and dissolved matter from a paper mill treated effluent

Mayko Rannany S. Sousa*, Jaime Lora-Garcia*, Maria-Fernanda López-Pérez*, Marc Heran**

*Instituto de Seguridad Industrial, Radiofísica y Medioambiental (ISIRYM) Universitat Politècnica de València (UPV), Plaza Ferrándiz y Carbonell, s/n 03801, Alcoy, Spain

** IEM, Univ Montpellier, CNRS, ENSCM, Montpellier, France

Abstract: In this study, membrane fouling caused by paperboard mill treated effluent (PMTE) was investigated, based on a dead-end ultrafiltration pilot-scale study. The membranes employed were commercial hydrophobic ultrafiltration (UF) membranes made of polyethersulfone (PES) with a molecular weight cut-off of 10 kDa, 50 kDa and 100 kDa.

Membrane fouling mechanism during dead-end filtration, chemical analysis, scanning electron microscopy (FESEM), SEM-energy-dispersive spectrophotometry (EDS), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and 3D fluorescence excitation–emission matrix (3DEEM) analysis were applied to understand which fraction of the dissolved and colloidal substances (DCS) caused the membrane fouling.

The results indicated that the phenomenon controlling fouling mechanism tended to be cake layer formation (R2 ≥0.98) for all membranes tested. The 3DEEM results indicate that the majority of the organic foulants with fluorescence characteristics on the membrane were colloidal proteins (protein-like substances I+II) and macromolecular proteins (SMP-like substances). In addition, polysaccharide (cellulosic species), fatty and resin acid substances were identified on the fouled membrane by the ATR–FTIR analysis and they play an important role in membrane fouling. In addition, the FESEM and EDS analyses indicate that the presence of inorganic foulants on the membrane surfaces, such as metal ions and especially Ca2+, can accelerate membrane fouling.