The City of Pasco (City) treats and reuses the process wastewater produced by four food processors by applying it to agricultural crops grown on the City’s land treatment fields. The current capability of the system and desirability of the water for farming has been limited by organic and inorganic solids that plug sprinkler nozzles and accumulate in the storage pond. Excessive solids caused irrigation uniformity problems, nutrient loads from entrained solids, and significant costs to clean the storage pond. The system was operating near the capacity of the crops and soils to treat the applied process wastewater because of the solids. Limited capacity also limited the ability of the City to attract additional processors or allow expansion of the existing processing facilities.
With support from the food processors, the City applied engineering, agronomy, irrigation design, and operational changes to improve the system capacity through process wastewater pre-treatment and improved farm management techniques.
- Phase 1 improvements included fine screening to remove sand and food particles through the use of a large rotary screen. They also implemented of improved field monitoring and operations through use of a data management system.
- Phase 2 improvements included installation of a concrete rectangular clarifier (settling cell) to provide additional suspended sediment removal and surface (skim) removal of fats, oil, and grease (FOG) following the rotary screen..
- Phase 3 includes the construction of a covered anaerobic pond (CAP) for biochemical oxygen demand (BOD) reduction to allow additional low odor storage. This allows for expansion of one or more of the processors from seasonal to year-round operations..
- Further increases in system capacity will come from expanding the total land base, which is considered Phase 4..
The Process Water Treatment System Optimization and Capital Improvement Plan was completed in 2011. The engineering and design of Phases 1 and 2 was completed in January 2013. Construction of Phases 1 and 2 and design of Phase 3 is scheduled for completion by the end of 2013. Construction of Phase 3 and improved field monitoring through use of a Data Management System is scheduled for completion by the end of 2014. Phase 4 is being planned for the 2015 crop growing season.
The Process Water Treatment System Optimization and Capital Improvement Plan project cost will be covered through a debt service plan recently approved by the Food Processors who use the treatment system. The Food Processors have agreed to move the project forward.