Submerged membrane/adsorption hybrid process in water reclamation and concentrate management—a mini review

Abstract

Clean water shortage is a major global problem due to escalating demand resulting from increasing human population growth and industrial activities, decreasing freshwater resources and persistent droughts. Recycling and reuse of wastewater by adopting efficient reclamation techniques can help solve this problem. However, wastewater contains a wide range of pollutants, which require removal before it may be reused. Adsorption and membrane processes are two successful treatments used to remove most of these pollutants. Their efficiency increases when these processes are integrated as observed, for example in a submerged membrane adsorption hybrid system (SMAHS). It uses coarse air bubbling/sparging to produce local shear which minimises reversible membrane fouling, improves performance and extends the life of the membrane. Additionally, the adsorbent acts as a buoyant media that produces an extra shearing effect on the membrane surface, reduces membrane resistance and increases flux. In addition, it adsorbs the organics that would otherwise deposit on and cause fouling of the membrane. The use of activated carbon (AC) adsorbent in SMAHS is very effective in removing most pollutants including natural organic matter (NOM) and organic micropollutants (OMPs) from wastewaters and membrane concentrate wastes, the latter being a serious problem in practical applications of the reverse osmosis process. However, certain NOM fractions and OMPs (i.e. hydrophilic and negatively charged ones) are not efficiently removed by AC. Other adsorbents need to be explored for their effective removal. Graphical abstract

Removal of Organics with Ion-Exchange Resins (IEX) from Reverse Osmosis Concentrate

“…With the addition of resin, the TMP increased only to 250 mbar irrespective of the dosage. The addition of resin removed free organics from the wastewater before they could reach the membrane surface, thereby reducing membrane fouling by limiting the deposition of organics on the membrane surface [ 19 , 25 ]. This reduced the TMP by 100 mbar.…”

“…The hybrid system was found to be effective for two reasons. First, because the prior removal of organics/other charged compounds before they reach the membrane surface reduced fouling/scaling effects on the membrane surface, and second, because the airflow produces shear stress across the membrane surface, and its scouring effect further reduces the deposition of organics and reduces fouling [ 25 , 26 ].…”

Treatment Trends and Combined Methods in Removing Pharmaceuticals and Personal Care Products from Wastewater—A Review

“…A more efficient method than using membrane filtration and adsorption in the sequence is combining both processes together in a single tank containing the influent, where the membrane is submerged and adsorbent suspended. This process is called SMAHS, and its success is mainly due to the following [ 86 ]:…”

Membranes in Water Reclamation: Treatment, Reuse and Concentrate Management

“…As reported by Loganathan et al [ 27 ], there are different configurations of membrane systems: Pretreatment: Treatment prior to membrane filtration. Hybrid systems: Treatment with membrane filtrations.…”