Comparative study of NF and RO membranes in the treatment of produced water II: Toxicity removal efficiency

This study compared the filtration of produced water using two new and highly hydrophilic NF and RO membranes to assess toxicity removal efficiency in pre- and post-filtration samples for reuse as indirect potable water. The toxicity test was conducted using marine luminescent bacterium Vibrio fischeri to monitor changes in the level of light emission during exposure to unknown toxic substances present in the tested pre- and post-filtration samples of produced water. The results show that the quality of water obtained using the NF membrane was toxic at an effective concentration of 13.65% (EC50). However, the performance of NF membrane in rejecting 48% of total organic carbon indicates that it has high potential for use as a pretreatment for the RO membrane in treating produced water because this configuration will decrease the rate of fouling by organics. Toxicity test analysis further revealed that the RO-treated produced water was free of toxicity, whereby 100% of the effective concentration (EC50) caused no effects when exposed to V. fischeri. Therefore, converting produced water from a pollution source into a new water resource has been conclusively shown to be readily achievable, especially through the use of a combined membrane system rather than a single membrane.

► The NF-treated produced water was found to be toxic at EC50 of 13.65%.
► The additive chemicals have potential to contribute toxicity to NF-treated water.
► The NF membrane removed 48% of TOC and shows potential to be used as a pretreatment.
► The RO-treated produced water was free of toxicity when exposed to Vibrio fischeri.
► The RO-treated produced water shows potential for reuse as indirect potable water.