Effect of backwash and powder activated carbon (PAC) addition on performance of side stream membrane filtration system (SSMFS) on treatment of biological treatment effluent

In this study, a pilot scale Side Stream Membrane Filtration System (SSMFS) was used to demonstrate the need for optimization of backwash conditions and the addition of PAC. Through an investigation of the amount of fouling each cycle that can be restored through backwashing over a short-term, a good operating point for long-term operation was developed. Periodic removal of 1.5% of the PAC slurry mixture (7.5 L out of 500 L) and PAC replacement (15 g/d) was found to have a positive impact on the reduction of membrane fouling. © 2009 Desalination Publications

Submerged membrane coagulation hybrid system as pretreatment to organic matter removal from seawater

In this study, a commonly used ferric chloride was utilised as coagulant for removing organic compounds from seawater. More than 57% of dissolved organic carbon (DOC) was removed at optimum dosage of 3 mg Fe+3/L. The coagulation by FeCl3 at optimum dosage could remove a majority (95%) of hydrophobic compounds. The results from Liquid Chromatography - Organic Carbon Detector showed that only <0.02 mg/L of hydrophobic compounds was found after coagulation. In addition, the modified fouling index decreased considerably from 15,848 s/L2 with raw seawater to 3,025 s/L 2 with seawater after coagulation. In-line coagulation coupled with submerged membrane system (ICSMS) was also trialled. It is observed that critical flux was increased from 20 L/m2·h in the conventional submerged membrane system to 55 L/m2 h in ICSMS. The ICSMS could remain the high DOC removal efficiency (more than 70%) at filtration rate of 20 L/m2 h when keeping the development of trans-membrane pressure was significant lower than that of conventional submerged membrane system. © IWA Publishing 2011

Effect of Photocatalysis on the Membrane Hybrid System for wastewater treatment

An integrated photocatalysismembrane hybrid system was investigated for wastewater treatment with the main focus on improving the cross flow microfiltration (MF) permeate flux. Photocatalysis with TiO2 (P25 Degussa) suspension as photocatalyst was applied both as pre-treatment and as inline treatment with MF. The TiO2 slurry was found to have significant effect in permeate flux for wastewater with lower dissolved organic carbon concentration. The MF flux decline due to TiO2 slurry cake on the membrane surface was minimized by allowing the TiO2 slurry to settle and by using only the supernatant for further treatment using the hybrid system. The investigation also included the study on the effect of photocatalytic reaction time and the slurry settling times on the MF permeate flux. The irradiation of ultraviolet on the MF surface in presence of TiO2 catalyst in suspension yielded in an increase in permeate flux

Effluent organic matter (EfOM) in wastewater: Constituents, effects, and treatment

Wastewater reuse is being increasingly emphasized as a strategy for conservation of limited resources of freshwater and as a mean of safeguarding the aquatic environment due to contaminants present in wastewater. Although secondary and tertiary treated wastewater is often discharged into surface waters, it cannot be reused without further treatment. One of the parameters of concern for human and environmental health is components of organic matter originating from wastewater treatment plant (WWTP) effluents. This effluent organic matter (EfOM) should be carefully characterized in order to find an optimum treatment method for water reuse. This review presents the components of EfOM present in WWTP effluents and various treatment methods that may be employed for reduction of EfOM. These processes include flocculation, adsorption, biofiltration, ion exchange, advanced oxidation process, and membrane technology. The removal efficiency is discussed in terms of removal of total organic carbon, endocrine-disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs), different polarity fractions (such as hydrophobic and hydrophilic), and molecular weight distribution of organic matter. Copyright © Taylor & Francis Group, LLC

Mining valuable minerals from seawater: A critical review

©2017 The Royal Society of Chemistry. Seawater contains large quantities of valuable minerals, some of which are very scarce and expensive in their land-based form. However, only a few minerals, the ones in high concentrations, are currently mined from the sea. Due to recent problems associated with land-based mining industries as a result of depletion of high-grade ores, sustainable water and energy demand and environmental issues, seawater mining is becoming an attractive option. This paper presents a comprehensive and critical review of the current methods of extracting valuable minerals from seawater and seawater brines generated in desalination plants, and suggests ways to overcome some of the limitations and challenges associated with the extraction process. The extraction methods discussed are solar evaporation, electrodialysis (ED), membrane distillation crystallisation (MDC), and adsorption/desorption

Simultaneous removal of particles and dissolved organic matter in floating media filter for surface water treatment

This research investigated the performance of floating media filter in removing particles and dissolved organic matter from surface water. Pilot-scale study consists of floating plastic media pre-filter connected with either granular activated carbon (GAC) or sponge biological filter (BF) bed. In the floating plastic media filter, coagulation and flocculation processes using poly-aluminum chloride (PACl) as coagulant at an optimum dose of 8 mg/L helped removing particles from raw water. The floating media filter was operated a filtration rate of 11 m3/m2.h whereas those in GAC and BF units were maintained at 2 m3/m2.h. Continuous operation for over 120 days gave 98% and 99% average removal efficiencies of turbidity and UV254 in floating media filter in combination with GAC unit whereas and 78% and 52% removal efficiencies of turbidity and UV254 removal were obtained in floating media filter in combination with BF. The removal of dissolved organic carbon in GAC and BF units reduced chlorine demand for disinfection by 29% and 14%. It could also reduce the sum of trihalomethane (THMs) ratio from 1.1 to 0.1 and 0.5 respectively. © 2009 Desalination Publications

Simultaneous removal of polycyclic aromatic hydrocarbons and heavy metals from water using granular activated carbon

© 2019 Elsevier Ltd Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are dangerous pollutants that commonly co-occur in water. An adsorption study conducted on the simultaneous removal of PAHs (acenaphthylene, phenanthrene) and heavy metals (Cd, Cu, Zn) by granular activated carbon (GAC) showed that, when these pollutants are present together, their adsorption was less than when they were present individually. The adsorptive removal percentage of PAHs (initial concentration 1 mg/L) was much higher than that of heavy metals (initial concentration (20 mg/L). The reduction in adsorption of PAHs by heavy metals followed the heavy metals' adsorption capacity and reduction in the negative zeta potential of GAC order (Cu > Zn > Cd). In contrast, PAHs had little effect on the zeta potential of GAC. The Langmuir adsorption capacities of acenaphthylene (0.31–2.63 mg/g) and phenanthrene (0.74–7.36 mg/g) on GAC decreased with increased metals' concentration with the reduction following the order of the metals’ adsorption capacity. The kinetic adsorption data fitted to Weber and Morris plots, indicating intra-particle diffusion of both PAHs and heavy metals into the mesopores and micropores in GAC with the diffusion rates. This depended on the type of PAH and metal and whether the pollutants were present alone or together

Effect of flocculation and/or adsorption as pretreatment on the critical flux of crossflow microfiltration

This study aims at identifying the effect of pretreatment such as flocculation and/or adsorption on the performance of crossflow microfiltration (CFMF). CFMF performance was studied in terms of critical flux. The results indicated that: (1) flocculation alone as a pretreatment could effectively remove the large molecular weight organic matter from 30,000 to 60,000 Daltons; (2) flocculation, together with adsorption as a pretreatment to CFMF, could remove both large and small molecular weight organics; (3) flocculation as a pretreatment was significantly better than adsorption in improving the critical flux; (4) critical flux increased from 100 L/m2.h to 520 L/m2.h when flocculation-adsorption was applied. The critical flux in long-term experiments was the same as that of the short-term experiments. However, the critical flux slightly decreased (5%) in long-term experiments compared to short-term operation with flocculation and adsorption as a pretreatment. © 2005 Elsevier B.V. All rights reserved