Abstract
Several types of pretreatment system have been tested and investigated to treat salty lake water by reverse osmosis system. (1) A sludge blanket type clarifier followed by a sand filter and an activated carbon filter could not yield product water which complied with inlet water quality conditions for reverse osmosis systems. A precoated sand filter instead of the simple anthracite filter produced slightly better product water, but it could not satisfy the inlet water quality conditions. An additional injection of a small amount of coagulant ahead of the sand filter improved product water quality to the level where spiral wound type reverse osmosis system could be applicable. (2) An inline coagulation method using a dual media filter followed by an activated carbon filter gave an outstanding result comparing to the former processes producing very high quality water which covers the conditions of inlet water quality for spiral wound type and hollow fine fiber type reverse osmosis system as well. The tests suggested that an excessive long time retention of flocs in the process gave the worse product water quality. The PN value was used instead of SDI index to measure levels of very low suspended matter.
