Effect of periodic backwash in the submerged membrane adsorption hybrid system

The submerged membrane adsorption hybrid system (SMAHS) is an attractive solution in treating wastewater; however it faces membrane fouling although to a less extent. In this study, different adsorbents and resins were investigated in order to find a substitute to the powdered activated carbon (PAC); The effect of new backflush was also studied in further reducing the membrane fouling. The SMAHS led to 72–86% dissolved organic carbon (DOC) removal. A detailed study on the transmembrane pressure development led to a conclusion that there is a critical flux and this value is around 16 l/h.m2 for the wastewater studied

Couplage de procédés physico-chimiques et séparation par membranes pour la rétention de matières organiques dans les eaux.

Les eaux naturelles comme les effluents secondaires produits par les stations d’épuration contiennent des matières organiques qui constituent actuellement l’une des cibles prioritaires des filières de production d’eau potable ou de réutilisation des eaux usées. Les membranes de Microfiltration et d’Ultrafiltration ne retiennent que très partiellement ces composés organiques de faible masse moléculaire qui sont par ailleurs responsables de phénomènes importants de colmatage. Un réacteur à membranes immergées analogue dans son principe aux bio réacteurs à membrane semble constituer un outil adapté pour réaliser simultanément dans le même équipement la réaction physico-chimique et la séparation membranaire. Les résultats présentés concernent les deux aspects : ils ont été obtenus sur des effluents secondaires ou des solutions de matières humiques : · Recherche d’un adsorbant ou d’une résine échangeuse d’ions susceptible de constituer une alternative au charbon actif en poudre utilisé jusqu’ici, en permettant notamment une régénération plus facile. · Essais à l’échelle pilote sur un réacteur à membranes immergées

Effect of Periodic Backwash in the Submerged Membrane Adsorption Hybrid system (SMAHS) for wastewater treatment

The Submerged Membrane Adsorption Hybrid system (SMAHS) is an attractive solution in treating wastewater; however it faces membrane fouling although to a less extent. In this study, different adsorbents and resins were investigated in order to find a substitute to the Powdered Activated Carbon (PAC); The effect of new backflush was also studied in further reducing the membrane fouling. The SMAHS led to 72 to 86% dissolved organic carbon (DOC) removal. A detailed study on the transmembrane pressure development led to a conclusion that there is a critical flux and this value is around 16l/h.m2 for the wastewater studied

Metals Recovery from Seawater Desalination Brines: Technologies, Opportunities, and Challenges

The urgent need for environmental sustainability has increasingly prompted policy makers to emphasize resource recovery from desalination brine streams. Recent research on resource recovery from waste streams has shown rising momentum with near term viability for several new technologies. In this perspective, we focus on new opportunities for metal resource recovery from seawater desalination brine, while outlining associated sustainability challenges and opportunities. The potential of metals recovery is discussed

Readily Wash-Off Road Dust and Associated Heavy Metals on Motorways

Road dust contains a wide range of potentially health-hazardous pollutant sources. In this study, road dust samples were collected from nine locations along the Sydney orbital motorway during wet weather events and analysed for their mineralogy and heavy metal contents. The aim of this study was to examine for the specific particle size fractions in road dust samples that can be associated with anthropogenic pollutant sources, mainly on the prevalence of heavy metals. Surface morphological and elemental composition of the road dust particles was analysed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The heavy metal contents and degree of contamination were also investigated including in the two specific particle size fractions of <75 and 75–150 μm. It was found that the particle size fraction of <75 μm made up between 6 and 16% of the entire particle size distributions and contributed to more than 90% of the heavy metal contents. In addition, a moderate to high degree of heavy metal contamination was measured in the collected road dust samples, and this was correlated well with the local traffic volumes. The good correlation between heavy metals and traffic volumes in the finer road dust particle size fraction of <75 μm indicated that the finer road dust particles were not only important in terms of heavy metal attachment, accumulation and mobilisation during wet weather events but they could also provide evidence of potential anthropogenic pollution sources. These findings will facilitate our scientific understanding on the specific role and importance of particle size fractions on the mobilisation of pollutant sources, particularly heavy metals during wet weather events. It is anticipated that this study will assist in the development of best management practices for pollution prevention and control strategies on the frequency of road sweeping and retention pond design to trap fine road dust particles

Metals Recovery from Seawater Desalination Brines: Technologies, Opportunities, and Challenges

The urgent need for environmental sustainability has increasingly prompted policy makers to emphasize resource recovery from desalination brine streams. Recent research on resource recovery from waste streams has shown rising momentum with near term viability for several new technologies. In this perspective, we focus on new opportunities for metal resource recovery from seawater desalination brine, while outlining associated sustainability challenges and opportunities. The potential of metals recovery is discussed

Advances and challenges in metal ion separation from water

Technologies for selective metal ion separation from water and wastewater are currently attracting strong research interest as a pathway to greater sustainability. The chemistry of metal ion separation processes is critical for understanding the mechanisms of selectivity and making the technologies viable. This paper discusses current advances and challenges in metal ion separation technologies from chemical points of view and proposes how they should be approached in the future

Deposition of submicron particles in deep bed filtration under unfavorable conditions

Deterioration in the filter removal efficiency of submicron particles (λ/λo) under unfavorable surface conditions is affected by the number of deposited particles per filter grain. In the case of above micron particles, the deterioration of filter removal efficiency has been mainly due to the blocking effect of deposited particles and not by the number of deposited particles. Deposition of large number of submicron particles changed the surface characteristics of collectors (filter grain associated with deposited particles) and enhanced unfavorable surface conditions. Filtration experiments were conducted with monodispersed suspensions of known sizes of submicron latex particles at different ionic strengths, using glass beads as filter grains. The filtration performance was predicted by using a mathematical model, assuming a linear relationship between λ/ λo and Σ (i.e. λ/λo=1 − kΣ). For both particles, k was found to decrease andλ o was found to increase with the increase in the ionic strength. A comparison was made of the importance of blocking effect for the filtration of submicron particles