Demo case: Petrochemical industry
REPSOL
Main challenges of the demo case: The petrochemical complex in Puertollano in Spain faces two main challenges: The first one is to maximise water reclamation to minimise the freshwater intake. The production process is a major consumer of fresh water in the local area and Puertollano in the south of Spain has a high risk of water stress due to its geographical location, with occasional moments of water scarcity. The second challenge is compliance with strict limits on compounds at discharge, with the most critical ones being chemical oxygen demand (COD), nutrients, suspended solids (SS), and metals. Although the wastewater treatment plant currently complies with the relevant discharge limits, they are expected to become more restrictive in the future. Therefore, the zero-liquid-discharge (ZLD) strategy is pursued.
Approach to overcome the challenges: The following treatment scheme has been defined for the site and will be adapted during the project. It focuses on achieving more than 90% of high-quality reclaimed water reuse using Reverse Osmosis (RO) and an efficient pre-treatment focused on the rejection of challenging organic matter (through granular activated carbon (GAC) and ultrafiltration UF), and divalent salts and ammonia (through nanofiltration (NF) and Zeolites). The concentrate stream of the RO, free of main scaling agents and organics, will be concentrated up to 10 times using ceramic membrane distillation (MD) – operated in direct contact membrane distillation mode – and derived to the bipolar electrodialysis (BPED) stage in which Hydrochloric Acid (HCl) and sodium hydroxide (NaOH) will be recovered. At the second step, the zeolites will be regenerated with the onsite produced NaOH, and a rich ammonia stream will be derived to a second ceramic MD module (operated in vacuum membrane distillation (VDM) mode) to recover an ammonia (NH3) condensate stream. The rejections generated in the pre-treatment (rich in divalents and solids) are managed through a physicochemical system in which a chemical sludge is generated to be managed as a solid, while the water free of divalents and solids is sent back to the first treatment.
