Identification of micropollutants from graywater of different complexity and remediation using multilayered membranes

Simultaneous targeted and non-targeted analysis of plastic-related contaminants in e-waste impacted soil in Agbogbloshie, Ghana

An LC-MS based analytical method was developed and validated for the simultaneous targeted analysis and suspect screening of plastic-related contaminants in e-waste impacted soils. Satisfactory recoveries (97 ± 13 %) were achieved using ultrasound-assisted extraction for 14/15 of the targeted analytes (7 bisphenols and 8 plasticizers) in a range of agricultural and non-agricultural soils. The method was applied to 53 soil samples collected in May 2015 in the region of Agbogbloshie (Ghana) at e-waste facilities (incl. Dump, trade, and burn sites), neighboring non-agricultural (incl. upstream, downstream, and community) and agricultural fields, and at two control agricultural sites away from e-waste recycling facilities. Bisphenol A (BPA) and bis(2-ethylhexyl) phthalate (DEHP) were the two dominant contaminants in e-waste soil (with concentrations up to 48.7 and 184 μg g-1, respectively), especially at the trade site, where e-waste was sorted and dismantled. The non-targeted workflow was successfully applied to identify additional plastic-related contaminants previously unreported in e-waste impacted soils, including bis(2-propylheptyl) phthalate, diisononyl phthalate, trioctyl trimellitate, 4-dodecylbenzenesulfonic acid, perfluorooctanesulfonic acid, perfluorobutanesulfonic acid, diphenyl phosphate, and triethylene glycol monobutyl ether. The agricultural soils surrounding the e-waste sites were also contaminated by plastic-related chemicals (especially DEHP), highlighting the impact of e-waste activities on the surrounding agricultural system.

Identification of Membrane Fouling with Greywater Filtration by Porous Membranes: Combined Effect of Membrane Pore Size and Applied Pressure

Membrane fouling caused by complex greywater synthesized by personal care products and detergents commercially available for household applications was investigated using dead-end microfiltration (MF) and analyzed systematically by a multistage Hermia blocking model as a first attempt. The highest flux decline was associated with the smallest pore size of the membrane (0.03 μm). This effectiveness was more pronounced at higher applied pressures to the membrane. A cake layer was formed on the membrane consisting mainly of silica particles present as ingredients in greywater. Although organic rejection was low by the porous MF membrane, the organic compound contributed to membrane fouling in the filtration stage. With a 0.03 μm pore size of the membrane, dominant fouling mechanisms were classified into three stages as applied pressure increased, such as complete pore blocking, intermediate pore blocking, and cake layer formation. Specifically, during the early stage of membrane filtration at 1.5 bar, membrane fouling was determined by complete pore blocking in the 0.10 μm pore size of the membrane. However, the later stage of membrane fouling was controlled mainly by intermediate pore blocking. Regardless of the applied pressure, pore constriction or standard blocking played an important role in the fouling rate with a 0.45 μm pore size of the membrane. Our results also support that complex formation can occur due to the concentration of organic and inorganic species present in simulated greywater. Thus, strategic approaches such as periodic, chemically enhanced backwashing need to be developed and tailored to remove both organic and inorganic fouling from MF membranes treating greywater.

Organic micropollutant removal and phosphate recovery by polyelectrolyte multilayer membranes: Impact of buildup interactions

Polyelectrolyte multilayer (PEM) deposition conditions can favorably or adversely affect the membrane filtration performance of various pollutants. Although pH and ionic strength have been proven to alter the characteristics of PEM, their role in determining the buildup interactions that control filtration efficacy has not yet been conclusively proved. A PEM constructed using electrostatic or non-electrostatic interactions from controlled deposition of a weak polyelectrolyte could retain both charged and uncharged pollutants from water. The fundamental relationship between polyelectrolyte charge density, PEM buildup interaction, and filtration performance was explored using a weak-strong electrolyte pair consisting of branching poly (ethyleneimine) and poly (styrene sulfonate) (PSS) across pH ranges of 4-10 and NaCl concentrations of 0 M-0.5 M. PEI/PSS multilayers at acidic pH were dominated by electrostatic interactions, which favored the selective removal of a charged solute, phosphate over chloride, while at alkaline pH, non-electrostatic interactions dominated, which favored the removal of oxybenzone (OXY), a neutral hydrophobic solute. The key factor determining these interactions was the charge density of PEI, which is controlled by pH and ionic strength of the deposition solutions. These findings indicate that the control of buildup interactions can largely influence the physico-chemical and transport characteristics of PEM membranes.