The design, equipment selection, and implementation were geared towards reducing the pathogenic content of the overall system effluent to safe levels for irrigation use. A UV disinfection system was installed (by others) at the back end of the process to accomplish this task. Our challenge was to provide the high quality influent required by UV disinfection systems utilizing cost-effective technologies. The challenges were to:
- Provide a complete mix aerated cell at the front end to meet Alberta Environment's (ANEV) requirements.
- Sufficiently aerate the treatment cells to reduce effluent TSS and cBOD5 to less than 20 mg/L and to digest settled solids.
- Implement a Poly aluminum Chloride (PAC) dosing system prior to sand filters to form removable flocs containing absorbed suspended pollutants.
- Implement a continuous backwash up-flow gravity sand filtration system to remove flocs of absorbed suspended solids.
NEI's optAER fine-bubble aeration system was used to replace an outdated coarse bubble system.
An impermeable geomembrane floating baffle curtain was installed in the first cell to split it into two. The aeration in the first cell was designed to keep all solids in suspension to provide completely mixed conditions, and the second was designed as a partial mix aerated cell. Two continuous backwash up-flow gravity sand filters were fitted following the aerated ponds. A chemical injection pump to supply PAC was installed up stream of the sand filters. Chemical addition was necessary to achieve an effluent quality of 5 mg/L TSS during the algae growth season.
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