Item A-MWMC Facilities Plan - Laserfiche WebLink

Home Browse Search

MWMC FACILITIES PLAN limited to primary effluent diversion, which typically occurs only I or 2 weeks per year. The alternatives have nearly equal non-monetary ratings. Based on the analysis presented above, it is recommended that the WPCF p'r6ceed with Alternative 1, conversion of the existing gaseous chlorine system to sodium hypochlorite chlorination for both SE and PE diversion flows. Future Considerations and Recommendations At some future time the WPCF will want to implement Level IV reuse water on a relatively large scale and this will drive the expansion of the disinfection system. Regulatory requirements for Level IV reuse water require either the construction of a new UV system or the addition of chlorine contact basins providing a 90 minute modal contact time. The requirement for a 90 minute modal contact time using an industry accepted dispersion coefficient of 0.7 would require a total detention time of 128 minutes, resulting in extremely large chlorine contact basins. This will make the construction of a new UV facility much more cost-competitive with a new chlorine disinfection system. The recommended approach for disinfection of future reuse effluent is to construct UV facilities as reuse is implemented over the 20-year project life. The UV facilities would provide a reuse effluent with a 2.2 Mean Probable Number (MPN)/100 mL Total Coliform effluent on a 7-day median basis. A UV facility designed with this criteria would provide substantially more secondary effluent disinfection capacity at the lower disinfection requirement of 406 MPN/100 mL (this is for a single sample and is the criteria that would control secondary effluent disinfection design). Thus, a disinfection facility initially designed to provide reuse quality effluent could be used to provide disinfection of a much larger quantity of secondary effluent. In addition, the existing chlorine contact basins could easily provide the 90 minutes modal contact time required for Level IV reuse water using sodium hypochlorite disinfection. The recommended future approach to disinfection will be extremely flexible. 6.4 Effluent Disposal Alternatives Effluent reuse alternatives evaluated are based on application of Level II (secondary effluent) and Level IV (filtered) process water from the WPCF. Effluent quality influences the alternatives available for disposal. In general, effluent reuse alternatives were based on application of reuse to poplar trees, grass for hay, pasture, green spaces, and golf courses. Because of regional climate conditions, reuse alternatives are focused primarily on application during the dry season months of June through September. Regional crops uptake the greatest amount of liquid during these months. Drivers for MWMC effluent reuse include: · Develop public awareness and preference for reuse · Regulatory requirements related to temperature of effluent discharge to receiving waters · Increasing biosolids (liquid and dewatered) loading rates to land application sites Fill-ration improvements identified in this Facilities Plan (see Section 6.2.6) will provide 30 mgd of filtration capacity through the design period (2025). These improvements along with 6-26 MWMC_6.0_REV11.DOC