Here’s How the Wastewater Treatment Process Works
Wastewater from homes and businesses is transported through the District’s sewer collection system, by gravity and through pump stations, to one of two Wastewater Treatment Plants.
Pre Treatment: At the Plant, wastewater flows through bar screens where rags, trash and debris are removed.
Wastewater then flows into a grit chamber where grit, mostly sand and eggshells, is removed. The grit is washed, dewatered and taken to a landfill for disposal.
Primary Treatment: The wastewater then flows to Primary Clarifiers where floating fats, oils, and vegetable matter, referred to as scum, is skimmed off the water surface and sludge, primarily organic material, is settled to the bottom. The sludge and scum removed in the primary sedimentation process are pumped to dewatering presses.
Secondary Treatment: From the primary process, the wastewater, which still contains dissolved solids and organic material, flows into Trickling Filters. The water is trickled over media which enables the formation of slimes or Biomass, which contains organisms that feed upon and remove wastes from the water.
The wastewater then flows to Secondary Clarifiers, where sloughed off biomass from the Trickling filters sinks to the bottom of the tank as Humus sludge, which is then pumped off to be mixed with primary sludge prior to dewatering. At this stage, the water coming off the top of the Secondary Clarifiers has had more than 95 percent of it’s impurities removed.
Denitrification: From the secondary clarifiers, the wastewater is pumped to denitrification filters, which are deep bed mono-media filters with methanol added to the filter influent as a carbon source, providing food for the denitrifying bacteria in the filters. This process is required to protect groundwater from Nitrogen contamination by percolation of the District’s treated wastewater.
Effluent Disposal: Following denitrification, wastewater is pumped through a 10 mile outfall pipeline to the District’s Effluent Management Site in Hesperia where the water flows into percolation ponds, recharging underground aquafers of the Mojave River basin.
Recycled Water: A portion of the treated wastewater that is not sent to the Hesperia site is sent the District’s Recycled Water Plant, where it is filtered and U.V. disinfected before being used for irrigation of the Lake Arrowhead County Club golf course.
Solids Handling and Disposal: The Primary and Humus sludges removed in Primary and Secondary treatment are thickened and then dewatered in rotary screw presses. The dewatered sludge, referred to as Bio Solids, is transported by hauling contractor and also by District dump truck and personnel to a Bio Solids composting site in Newberry Springs, Ca, where Bio Solids are combined with green waste to produce a fertilizer product.
To download an illustrated handout of the Wastewater Treatment Process, click here.
Grass Valley Treatment Plant
Grass Valley Treatment Plant
