Challenged with the need for expanded treatment facilities in the Lehigh area and also burdened with space limitations due to site constraints at the treatment facility, Florida Water Services (FWS) was seeking the latest and greatest in innovative treatment technology. The submerged membrane technology developed by Zenon Environmental was selected as the process to meet and exceed the challenge presented at the Lehigh wastewater treatment plant. The microfiltration system replaces the solids separation function of both the standard secondary settling basin and tertiary filters within a typical activated sludge process. The new process more than recover the treatment capacity lost by abandoned contact-stabilization tankage and also provides a cost-effective means to expand the facilities to provide additional capacity in the future.The results of a nine (9) month sampling program concludes that the effluent or permeate from the micro-filtration process has CBOD 5 and total suspended solids concentrations much lower than normal secondary treatment processes with filtration. The laboratory analyses of the microfiltration permeate consistently result in CBOD 5 concentrations below the 2 mg/L detection limits and consistently below the 0.20 mg/L detection limits for total suspended solids. The fecal coliform values are consistently less than 15 FCU prior to disinfection. In comparison, normal secondary effluent may have fecal values of over 100,000 FCU and over 100 FCU following normal filtration facilities. The results clearly indicate the successful replacement of normal secondary clarification and tertiary filtration for the solids separation function utilizing the submerged membrane technology, which has significant benefits for a treatment application producing reclaimed water.

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