REUSE OF TREATED SEWAGE EFFLUENT FOR COOLING WATER MAKE-UP - A FEASIBILITY STUDY AND A PILOT-PLANT STUDY

This investigation was aimed at developing an acceptable technology fo r using secondary effluent as cooling water makeup for inland manufact uring industry in Australia, Approximate economic evaluations were mad e for a number of pretreatment alternatives and for internal treatment with chemical conditioning agents. Internal treatment with biocide do sing appeared to be the most promising option. A portable pilot plant scale cooling tower/heat exchanger unit was constructed. The unit inco rporated an on-line, differential pressure biofilm monitor together wi th automated control and data acquisition systems. The pilot plant was installed on site at a sewage treatment plant near Sydney. It was dem onstrated that the use of TSE for cooling water makeup is technically feasible. The rate of biofilm growth observed using chlorinated second ary effluent directly from the sewage treatment plant as makeup water was similar to the rate of biofilm growth observed when potable water was used and supplementary chemical treatment was not introduced in ei ther case. Excellent control of biofilm growth was observed in subsequ ent experiments when supplementary additions of simple chlorine or bro mine chloride treatment systems were carried out. The pilot plant was operated successfully at 5 cycles of concentration without any other s upplementary treatment being required. Copyright (C) 1996 IAWQ. Publis hed by Elsevier Science Ltd.