Nano-Fe mediated treatment of real hydraulic fracturing flowback and its practical implication on membrane fouling in tandem anaerobic-oxic membrane bioreactor

The rising water-use intensity, and lack of cost-effective treatment strategy and reuse of hydraulic fracturing flowback (HFF) has become an increasing cause of concern. The present work evaluates the integration of parallel sets of tandem anaerobic-oxic membrane bioreactor (AMBR) with and without nano-Fe for treatment and reuse of real HFF obtained from Ordos Basin, China. Treatment efficiencies in terms of organic conversions, micro-pollutants degradation, resource recovery, and effects of nano-Fe release on membrane fouling were evaluated. Nano-Fe mediated AMBR (FAMBR) system effectively reduce target micro-pollutants (such as Acenaphthylene) at 94.4 % compared to the parallel AMBR system (17.1 % without nano-Fe). Moreover, recovery of potential economic chemicals like Al and P (1.0 and 0.6 mg/g spent nano-Fe) availed using FAMBR system. However, colonization of FAMBR membrane surface by Fe-protein/peptide hydroxocomplexes initiated by Fe-catalyzed microbial extrusions present a huge fouling challenge relative to the AMBR system. Additional evidences from microscopic/spectroscopic analysis of the FAMBR membrane system revealed that despite having a promising outlook, mediation of nano-Fe with AMBR system might result in a major fouling event during HFF treatment. Engineered design of nano-Fe to reduced leached nano-Fe ions in pre-treatment step prior to AMBR treatment system may be of potential research consideration.