Rancho Las Virgenes Composting Facility

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Rancho Las Virgenes Composting Facility provides for the beneficial reuse of biosolids removed during wastewater treatment at the Tapia Water Reclamation Facility, converting them to nutrient-rich soil amendment.

Traditionally, options for biosolids disposal included landfills or trucking to agricultural areas to spread on land – both of which have become costly and limited due to public opposition and new regulations.

In service since 1994, Rancho Las Virgenes uses a composting process to transform biosolids into a useful, rich soil amendment. The biosolids are transported to Rancho from Tapia through four miles of underground pipelines.

Processing begins in two anaerobic digesters that provide a warm oxygen-free environment in which the natural decay process is accelerated, some of the harmful bacteria are neutralized, and odors are reduced. This process takes 20 to 30 days to complete.

The next step is to dewater the solids. As much as 75 percent of the remaining water is removed. Called “centrate”, this liquid is returned to Tapia to again be run through the treatment process. The remaining solids form a dense “cake”, which is mixed with ground wood chips or sawdust. The added texture helps air flow through the product and allows the composting process to take place.

Using in-vessel composting, the mixture is mechanically “churned” and moved along bays. During this period, helpful microbes feed on organic materials in the mix, raising the temperature to about 130oF. The heat stabilizes the material and further neutralizes potentially harmful bacteria which remain, while maintaining the right temperature for beneficial, “composting” microbes to do their work. Air is blown through the mixture to keep it from overheating and to provide oxygen to the microbes.

It takes 21 days for the mixture to travel the length of the processing bays. Automated equipment stirs the mixture and moves it along. By the time it reaches the end, it has become a light and consistently textured compost. The mixture is allowed to “cure” for about 15 more days, at which time it is ready for distribution.

State and federal safety tests are conducted throughout the process and again on the finished compost, to assure it is ready for use and that it meets the stringent standards for Class A garden compost, meeting all requirements for use on lawns and gardens, including vegetables grown for human consumption.

Free supplies of Rancho Las Virgenes Compost are available for pickup. Bulk supplies can be arranged. For more details, visit Community Compost.

Awards received by Rancho include:
L.A. area EPA Plant of the Year awards - 1995, 2003
Excellence in Community Outreach for Compost and Biosolids processing
US EPA Clean Water Act Recognition Award 
    Exemplary Biosolids Management
    Public Acceptance Activities

QUICK FACTS

Purpose
Transform biosolid waste into exceptional quality compost.
Provide long-term, environmentally benefi ial disposal for biosolids removed from wastewater during treatment at Tapia.

Location
Las Virgenes Road / Lost Hills Road in Calabasas, CA.

History
Began operation in November 1994, as the first in-vessel composting facility in Los Angeles County.

Capacity
Each year the compost facility saves enough landfill space to fill a football field to a height of one story.
Processes about 120,000 gallons of biosolids per day.
Produces about 11,000 cubic yards of compost annually.
Disposes of nearly all solids separated from wastewater at the Tapia Water Reclamation Facility.

Features
One of the most advanced, automated biosolids composting facilities in the world.
Enclosed processing for efficient odor control.
Two anaerobic digesters; each 80 feet in diameter and 50 feet high, with a combined capacity of 2.3 million gallons.
Two centrifuges, each with a 250 gallon-per-minute capacity for dewatering.
1/2-acre biofi lter, which uses natural processes to control odors.

Tapia Water Reclamation is operated under a Joint Powers Authority between LVMWD (located in western L. A. County) and Triunfo Sanitation District (located in eastern Ventura County).

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