Purification of firefighting water containing a fluorinated surfactant by reverse osmosis coupled to electrocoagulation–filtration

Abstract

Extinguishments of large scale solvent res produce large amounts of water that may contain various uorinated surfactants depending on the type of re ghting foam used. Due to their chemical nature, uorinated parts of uorinated compounds are highly resistant to biochemical and advanced oxidation processes. Therefore the current treatment for the degradation of uorinated surfactant from water used in re extinguishment is high temperature incineration of the water in halogen resistant incinerators. This paper aims to propose a process for purifying re ghting water containing uorinated surfactants.Pilot re ghting waters resulting from heptane re extinguishment with reghting foam containing a uorinated surfactant were produced. Suspended matter was estimated on the basis of turbidity measurement and uorinated not suitable for direct membrane processes because of high fouling, hence electrocoagulation and ltration were required. Electrocoagulation with aluminium electrodes at a charge loading of 600 C L −1 followed by ltration were found su cient to remove turbidity from pilot re ghting waters. Fluorinated surfactant removal was 71 77% and was not signi cantly increased by higher charge loading. Floc separation in bulk solution was achieved by ltration. Reverse osmosis of pretreated pilot re ghting water and concentrated model solutions of pretreated re ghting water were studied and though ux decline was observed, measured retention rates were 99.94 99.97%, with permeate concentrations down to 10 16 µg L −1 of uorinated surfactant at the laboratory scale. The concentrate from reverse osmosis could be recycled in electrocoagulation-ltration. Experimental results indicated that electrocoagulation and ltration followed by reverse osmosis e ciently treated the water from re extinguishment, which enables a further scale-up work.

Influence of bulk concentration on the organisation of molecules at a membrane surface and flux decline during reverse osmosis of an anionic surfactant

“…For sufficiently low monomer concentrations, most of the molecules in the solution are isolated. Once the concentration reaches the CMC, addition of surfactant molecules results in the formation of micelles, leaving monomer concentrations largely unchanged at the CMC value [4]. The CMC values are influenced by the nature of the hydrophobic tail and hydrophilic head, pH, ionic strength, temperature, etc.…”

“…Various approaches have shown that membrane filtration, such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), is an effective technique to remove surfactants from effluents [3,4]. Membrane technology stands out as being environment-friendly and easy to operate, and requiring no added chemicals.…”

“…Membrane technology stands out as being environment-friendly and easy to operate, and requiring no added chemicals. The best retention of surfactants has been achieved by the RO process [4,5], although surfactant adsorption on the active layer of the membranes led to folding and thus penetration (i.e. partitions) inside the membrane of this, as other trace organics, and some weak leakage [6].…”

“…partitions) inside the membrane of this, as other trace organics, and some weak leakage [6]. However, accumulation of matter may occur during membrane filtration of surfactants, resulting in severe flux decline [4,[7][8][9][10][11][12]. Classic modelling of RO membrane fouling can take into account the following phenomena: adsorption (accumulation of solutes on the external and internal surfaces, changing membrane hydrophobicity), cake formation (accumulation of particles on the membrane forming a second porous media) and concentration polarisation (rise of solute concentration in the layer near the membrane surface).…”

Treatment of Post-Hydrothermal Liquefaction Wastewater (PHWW) for Heavy Metals, Nutrients, and Indicator Pathogens

“…However, as sand with granulated activated carbon had lower concentrations than sand alone, sand with granulated activated carbon may be an effective filter media for PHWW or other wastewaters with higher heavy metal concentrations. Reverse osmosis was used in this study as a benchmark, as it is one of the most effective filtering methods available [16,40,41]. Reverse osmosis proved to be quite effective in removing metals from the PHWW mixtures, achieving percent removals ranging from 82.77% for cadmium in the nitrified 2.5% PHWW mixture to complete removal of cadmium and mercury in the 1% and 2.5% PHWW mixtures before nitrification.…”