Optimization of the chemolithotrophic denitrification of ion exchange concentrate using hydrogen-based membrane biofilm reactors

Abstract

A H₂-based membrane biofilm reactor (MBfR) was used to remove nitrate from a synthetic ion-exchange brine made up of 23.8 g L^-1 NaCl. To aid the selection of the best nitrate management strategy, our research was based on the integrated analysis of ionic exchange and MBfR processes, including a detailed cost analysis. The nitrate removal flux was not affected if key nutrients were present in the feed solution including potassium and sodium bicarbonate. Operating pH was maintained between 7 and 8. By using a H₂ pressure of 15 psi, a hydraulic retention time (HRT) of 4 h, and a surface loading rate of 13.6 ± 0.2 g N m^-2 d^-1, the average nitrate removal flux was 3.3 ± 0.6 g N m^-2 d^-1. At HRTs of up to 24 h, the system was able to maintain a removal flux of 1.6 ± 0.2 g N m^-2 d^-1. Microbial diversity analysis showed that the consortium was dominated by the genera Sulfurimonas and Marinobacter. The estimated cost for a 200 m³/h capacity, coupled ion exchange (IX) + MBfR treatment plant is 0.43 USD/m³. This is a sustainable and competitive alternative to an IX-only plant for the same flowrate. The proposed treatment option allows for brine recycling and reduces costs by 55% by avoiding brine disposal expenses.

Keywords: H(2)-based membrane biofilm reactor; Ion exchange brine; Nitrate reducing bacteria; Nitrate removal.