Control of severe membrane silica scaling: investigation and trouble shooting

Abstract

Reverse osmosis (RO) continues to develop into an important means for water purification. The increase in RO applications has forced many projects to contend with water sources containing higher levels of sparingly soluble minerals. In many parts of the world, membrane silica scaling is becoming a limiting parameter for the design and operation of RO systems using brackish feed water. Located in the northeast of China and established since 2009, the LiaoNing Panjing power company is the only energy supplier of the Panjing Lioabin economic zone (400 km2). The power generation requires demineralized water coming from the power plant water treatment facility, which consists of a primary filtration step followed by RO trains and ion exchange resins. At the end of 2011, the RO plant performance severely dropped—normalized flux declined by 50%—indicating an occurrence of fouling or scaling on the membranes. Membrane autopsies have shown evidence of silica scales resulting from high levels of silica (50 ppm) in the feed water. This paper describes the investigation and troubleshooting processes used to restore membrane performance. The process utilized thorough scientific analysis, deposit removal via very efficient proprietary membrane cleaners, and dosing a novel antiscalant developed specifically to reduce silica deposition on RO membranes. To date, the chemical-based solution used to curb scaling has been effective in ensuring smooth operation of the membranes in the power plant water treatment facility.