Volume reduction of produced water generated from natural gas production process using membrane technology

This paper presents a case study of a natural gas production site covering various technical issues related to selection of an appropriate Reverse Osm osis (RO) system. The long-term field experience indicates the necessity of the selection of appropriate pretreatment systems for fouling-free RO oper ational conditions. The produced water has a variety of impurities such as oil and grease, process chemicals used for corrosion and scaling control, a nd dehydration of natural gas, etc. This situation leads to a complicated a nd extremely difficult task for a membrane specialist to design RO systems, especially the pre-treatment section. Here as part of the pretreatment selection, two types of UF membrane module s viz. spiral wound and hollow fibre, with MWCO of 8000 and 50,000 Dalton r espectively, were tested in parallel with NF membranes of the spiral wound type with MWCO 200 Dalton. The UF permeate is used as feed for RO compatibi lity testing. Both configurations of UF failed to be compatible, due to irr eversible fouling of the RO membrane. The NF membrane, however, showed inte resting results, due to membrane stability in terms of cleaning and fouling . The NF plant with 50% capacity gave a recovery of 75% and the RO plant ga ve a recovery of 60% versus the expected 92-95%. The long-term tests have i ndicated that the reminder of the membranes could be installed to achieve f ull capacity of the plant. This study also demonstrates the importance of s election of proper pre-treatment set-up for the RO system design.