Recovery of Extracellular Polymeric Substances from Excess Sludge Using High-Flux Electrospun Nanofiber Membranes

Abstract

The recycling of extracellular polymeric substances (EPSs) from excess sludge in wastewater treatment plants has received increasing attention in recent years. Although membrane separation has great potential for use in EPS concentration and recovery, conventional membranes tend to exhibit low water flux and high energy consumption. Herein, electrospun nanofiber membranes (ENMs) were fabricated using polyvinylidene fluoride (PVDF) and used for the recovery of EPSs extracted from the excess sludge using the cation exchange resin (CER) method. The fabricated ENM containing 14 wt.% PVDF showed excellent properties, with a high average water flux (376.8 L/(m2·h)) and an excellent EPS recovery rate (94.1%) in the dead-end filtration of a 1.0 g/L EPS solution at 20 kPa. The ENMs displayed excellent mechanical strength, antifouling properties, and high reusability after five recycles. The filtration pressure had a negligible effect on the average EPS recovery rate and water flux. The novel dead-end filtration with an EPS filter cake on the ENM surface was effective in removing heavy-metal ions, with the removal rates of Pb2+, Cu2+, and Cr6+ being 89.5%, 73.5%, and 74.6%, respectively. These results indicate the potential of nanofiber membranes for use in effective concentration and recycling of EPSs via membrane separation.

Calcium Alginate Production through Forward Osmosis with Reverse Solute Diffusion and Mechanism Analysis

“…However, the conventional commercial FO membranes are manufactured to avoid a trade-off between membrane permeability and selectivity [ 35 ], in which the FO membranes are designed to minimize RSF. The nanofiber structure resulting from electrostatic spinning has many excellent characteristics, such as high porosity and permeability, large specific surface area per unit mass, and small inter-fiber pores [ 36 ]. A porous nanofiber support layer can reduce the inner concentration polarization and increase water flux by 7- to 8-fold.…”

Separation Techniques and Circular Economy

“…Additionally, the highest possible value added of the separated products is obtained to enhance the economy. This current Special Issue titled “Separation Techniques and Circular Economy” in Membranes presents the novel separation technologies involving the recovery of extracellular polymeric substances (EPSs) [ 1 ], calcium alginate (Ca-Alg) [ 2 ] in wastewater treatment, plasmid DNA in gene therapy [ 3 ], lactose in dairy industry [ 4 ], lactic acid (LA) in the fermented broth of kitchen waste [ 5 , 6 ], phenylalanine losses in neutralization dialysis (ND) [ 7 ], the removal of secondary effluent organic matter (EfOM) [ 8 ], and acetaldehyde (CH 3 CHO) in the atmosphere [ 9 ].…”

“…For the recycling of EPSs from excess sludge in wastewater treatment plants (WWTPs), the potential of nanofiber membranes for use in effective concentration and the recycling of EPSs via membrane separation was indicated [ 1 ]. Electrospun nanofiber membranes (ENMs) were fabricated using polyvinylidene fluoride (PVDF) and used for the recovery of EPSs extracted from the excess sludge using the cation exchange resin (CER) method.…”