California sanitation district provides regional biosolids management solution

By Anna Austin
Posted November 17, 2009, at 5:00 p.m. CST

The Ventura Regional Sanitation District in southern Ventura County, Calif., has officially commenced operations at its biosolids drying and electric generation facility in Santa Paula, a project which the utility hopes will serve as a model for other regional governments and municipalities.

It took about two years and $19 million to construct the facility, which is on three acres at the Toland Road Sanitary Landfill. The facility utilizes landfill gas to provide 100 percent of its required power (about 1 megawatt), and an extra 1.5 megawatts are sold to the local power grid, according to VRSD General Manger Mark Lawler. With some additional units, the facility could handle the biosolids from up to 700,000 people.

Within the 10-city county, VRSD is contracted to take biosolids from six cities that do wastewater treatment. "The remainders are special districts that don't have large volumes of biosolids, so they haven't contracted with us just yet, but we're working on those," Lawler said. "We needed these contracts with the cities in order to get the financing for the project-this project proceeded with no grants or special loans, so we went for conventional financing."

The land fill gas, after going through a process to remove excess liquids and filtration systems, is conveyed to the facility by a blower that supplies low-pressure gas to the biosolids dryer and a compressor that sends high-pressure gas to fuel nine microturbines for electricity generation.

Biosolids arrive at the facility via trucks, and are dried in two 80-ton batch dryers. Hot oil from process heaters circulates around the dryer shell and through a series of internal rotors that turn the biosolids to dry them evenly. Steam from the dryers is condensed to water, which is treated and then used for dust control at the landfill; exhaust air from the dryers is filtered to remove odors and particulates.

The dried biosolids are conveyed to trailers at the receiving station and hauled to the landfill. "The end product from the biosolids qualifies under California's Solid Waste Law, and we're using that as daily cover at the landfill right now," Lawler said. California's Solid Waste Law AB 939 requires each city or county to divert 50 percent of all solid waste from landfill or transformation facilities by Jan. 1, 2000, through source reduction, recycling and composting activities.

Several people have contacted VRSD and are interested in securing the end product for commercial use as a fuel source or fertilizer, Lawler said.

Since the electric generation and biosolids processing facility began initial start-up operations in August, the two dryers have been ramped up to handle about 120 tons of biosolids per day. "It's the first of its kind, so we've been doing things slowly to make sure everything's done properly," Lawler said. "To our knowledge, this is the first of its kind in California-where somebody is treating biosolids regionally rather than individually. We'd really like to show other regional governments and municipalities what we have, and help those who are interested try to duplicate it."