Custom Engineered Systems –
Ion Exchange with Reverse Osmosis

Reverse Osmosis Retrofit of Ion Exchange provides cost and performance advantages compared to legacy Ion Exchange. Providing high purity water usually requires an Ion Exchange (IX) system. For feed water with relatively low levels of dissolved solids, ion exchange is perhaps all that is necessary. At high solid levels, however, or if particulate or organics removal is important, using Reverse Osmosis (RO) membranes ahead of IX beds can provide greater overall efficiency.

The technology selection is based on capital and Operating & Maintenance (O & M) costs, and the environmental impact of each technology. RO will add to the capital costs, but will reduce the O & M costs with regard to regeneration, resin replacement and chemical discharges.

Above a certain solids level, the total cost of a combined RO/IX system is less than the cost of ion exchange alone. As rule of thumb, the current breakpoint is about 100 ppm TDS; a level that is at our below most fresh water sources.

Solution

AVANTech provides complete treatment solutions that can be easily and cost effectively integrated into custom facilities. RO systems, such as Hi-PRO™, act as a demineralizer similar to the two bed cation/anion system shown in the original system. This compact, skid mounted system was provided retrofitted into the facility in an area adjacent to the original cation/anion system.

Pipe connections from the facilities pretreatment system and the Degasifier were easily completed. The Control System consists of a Process Controller, a Local Control Panel and a Supervisory Control Station networked together. The RO can be operated from either station. Graphical displays communicate the status of the RO. Taking process control a step further, the system alerts the operator of conditions that could cause equipment problems and/or out-of-specification product output. Alerted to the changing conditions, the operator has ample time to adjust the equipment to maintain peak operation efficiency.

The combined effects of escalating chemical prices (sodium hydroxide and acid) and the offsetting lower energy requirements of low pressure RO membranes have created a dramatic shift in the economics of high purity water treatment technology. Thus, compared with straight IX systems, the combined RO/IX operation can provide economic advantages that merit retrofits. In existing IX systems, a retrofit of RO ahead of the demineralizers can be justifiable at a feed water TDS as low as 100 ppm. Further, low pressure membranes allow the user to optimize the operating parameters, taking into account such variables as feed water temperature, TDS, energy, raw materials, and membrane expense to minimize capital and O&M.