Recovery and reuse of water from effluents of cooling tower

Abstract

Membrane technology is emerging as a viable and economical option in the reclamation of wastewater. The present study involves the feasibility of recycling and reusing the wastewater let out from a fertilizer unit. Cooling water blowdown from the waste stream has high salt concentration. An economically and technically viable reverse osmosis process has been employed to treat the wastewater. Feed water needs to be pretreated to apply reverse osmosis process.
Effluents from the cooling tower of the fertilizer unit studied contained about 50 mg/l of suspended solids and need to be removed prior to treatment with reverse osmosis unit to remove total dissolved solids (2500 mg/l). Pretreatment with a microfilter of sizes 5 and 1 um and carbon filter completely removed the suspended solids achieving a silt density index of 5. Pretreated water was sent to the reverse osmosis system, maintained at operating pressures of 275 X 10^3, 310 X 10^3, 344 X 10^3, 379 X 10^3 and 413 X 10^3 Pa, to reduce the level of the total dissolved solids. The best level of TDS (270 mg/l) was achieved at a maximum pressure of 413 X 10^3 Pa. The maximum amount of salt rejected by the membrane was 89.2% and the maximum recovery of 56.0% was obtained at a pressure of 413 X 10^3 Pa.