Management of Marcellus Shale Produced Water in Pennsylvania: A Review of Current Strategies and Perspectives

The reuse of produced water generated by natural gas extraction from Marcellus Shale for hydraulic fracturing is the dominant management option in Pennsylvania (PA), USA. The advantages and disadvantages of this management approach are reviewed and discussed together with long-term concerns and technology development needs. Abandoned mine drainage is a promising alternative make-up water, but high sulfate concentrations will lead to barite precipitation once it is mixed with the produced water. Bench-scale studies were conducted to optimize barite separation from this mixture that meets the finished water quality criteria for sulfate. Conventional separation processes are very effective in removing these solids but radium (Ra) co-precipitation may be a concern for their disposal in municipal landfills. If the produced water volume exceeds the reuse capacity for hydraulic fracturing, lime-soda ash softening can be used to remove divalent cations, including radium, to enable the production of pure salts using subsequent thermal processes.