Typically, a short pilot trial on site or in the supplier’s laboratory, using a sample of the process stream, will help narrow down the choice of membranes.
Next, a test rig or pilot plant is set up at the plant site. This will test the effectiveness of the chosen membrane system on a larger scale, utilizing up to 15 m2 (160 ft2) of total membrane area, and generate data useful in the development of final design parameters. These initial trials typically last for 2-3 weeks but can take longer if the waste stream varies in composition or volume over time. A well-designed testing procedure will save time and effort later.
With the test rig, engineers can take realistic measurements, including the degree of membrane fouling, the permeation rate (“flux”), the pressure drop, the retention levels as concentration increases, the effectiveness of the cleaning regime, and the quality of the end product.
From these data, the final system design is developed. In cases where a standard membrane is not suitable for the application in question, a new configuration of the membrane system may be needed. Also at this pilot stage, engineers can estimate the probable membrane life span, and this can be taken into account when considering the total lifetime costs of the system.