Organics and inorganics in flow back and produced water from shale gas operations: treatment and identification of glycols using gas chromatography–mass spectrometry

This study investigated the efficiency of different water treatment processes in reducing propylene glycol (PG), ethylene glycol (EG), ethylene glycol monobutyl ether (EGME), and other water quality parameters in flow back/produced water from a shale gas well operation. EG, PG, and EGME are the most widely used chemicals in hydraulic fracturing; however, limited investigations on these chemicals have been performed to date. Granular activated carbon (GAC) removed PG and EG to acceptable drinking water levels. Electrocoagulation was effective at decreasing turbidity (85%) as well as total petroleum hydrocarbons (TPH) (80%), while ultrafiltration removed 90% of the turbidity and TPH. GAC further removed approximately 95% of benzene, toluene, ethylbenzene, and xylene (BTEX), total organic carbon, dissolved organic carbon, and glycols but only removed 16% of total dissolved solids (TDS). Reverse osmosis removed approximately 90% of TDS (2,550 mg/L); however, this level remained high for certain purposes. Although some water quality parameters remained above the reusability threshold for most purposes, the treated water could be used on tolerant plants and permeable soils. In-depth knowledge and understanding of flow back/produced water quality characteristics, prior and post water treatment processes, can improve water treatment process strategies, reduce wastewater discharge, and improve treated water's reusability.