Impacts of shale gas production wastewater on disinfection byproduct formation: An investigation from a non-bromide perspective

The rapid rise of shale gas development has triggered environmental and human health concerns due to its impacts on water resources, especially on disinfection byproduct (DBP) formation upon chlorination. Despite the recently reported results on bromide, the effects of non-bromide ions in production wastewater at extremely high levels are vaguely defined. In this study, we investigated the effects of production wastewater, with bromide and non-bromide species, on the formation of DBPs when production wastewater was spiked into surface waters at various percentages. Results showed that the introduction of debrominated production wastewater led to increased formation of some chlorinated DBP species in selected surface water and wastewater. As the spiking percentage of debrominated production wastewater increased, the chlorinated DBP species increased. The contributions of individual cations to DBP formation followed a sequence of magnesium > calcium > barium at 0.10% spiking percentage due to the different catalytic effects of their chelates with organic precursors. The study of anions suggested that the discharge of treated production wastewater containing elevated sulfate may further enhance DBP formation. The significance of this study lies in the fact that in addition to bromide concerns from production wastewater, non-bromide species also contributed to DBP formation. The gas production wastewater management decision should consider the negative impacts from both bromide and non-bromide species to better protect the receiving water resources.