Emerging water regulations and fresh water scarcity are driving the natural gas processing industries in Qatar towards implementing Zero Liquid Discharge (ZLD) systems. ZLD implies that all wastewater produced in the plant is contained within the plant fence and treated industrial and process water (TIPW) is not discharged into the environment.
This paper presents an evaluation of technologies, their potential effectiveness and challenges in achieving ZLD. Pre-treatment facilities for TIPW re-use generally consist of neutralisation and filtration packages, Hydrogen Sulfide (H2S) strippers and Dissolved Air Floatation (DAF) and Membrane Bioreactor (MBR) units. A combination of technologies such as Brine Concentrators, Ultrafiltration (UF), Reverse Osmosis (RO), evaporation-crystallisation unit, and other emerging technologies, are considered as viable solutions for ZLD. However, space limitations, capital expenditure, and concentrate management (brine disposal minimisation) are being recognised as significant obstacles for the existing plants. Deep well injections, evaporation ponds (and landfill disposal options) and discharge to the marine environment (with proper mixing) are the only feasible options for disposal of concentrated brine. With restrictive environmental permits and requirements for these disposal methods, industrial facilities find it difficult to economically justify a ZLD system. A combination of re-concentration techniques and a comprehensive utilisation of concentrated brine, with supportive governmental policies, would be one of the most effective ways to fulfill ZLD.