Typically open-sea water intake structures are constructed in the shallow areas where sea water depth is in the range of 3m up to 10m. Due to this SWRO plant with open intake will have source water with high debris, suspended solids and aquatic organisms requiring a very elaborate pretreatment system. Thus Pretreatment design becomes an important part for a long term operation of the seawater desalination plants.
Pretreatment system depending on the source water characteristics may include one or more of the following:
- Intake screens
- Conventional or enhanced sedimentation
- Granular media filtration
- Membrane pretreatment filtration
Pretreatment evolves around the following objectives:
- Better filtered quality
- More consistent quality
- Less fouling of RO membranes
- Lesser quantity and number of process chemicals
- Less foot print area
- Lower operating and capital cost.
Key design criteria for the pretreatment facilities are as tabulated in Table 1.