Supervisors extend restrictions on using sewage sludge as fertilizer

dsneed@thetribunenews.comMay 7, 2014 

Temporary restrictions that have all but banned the use of sewage sludge as fertilizer in San Luis Obispo County will continue four more years.

County supervisors Tuesday approved the extension, which gives county environmental health officials more time to develop a permanent ordinance. This is an issue the county has been grappling with since 1998.

The interim ordinance currently in place was originally approved in 2004. “This may be the longest interim ordinance ever,” quipped Rich Lichtenfels, supervising environmental health officer.

Sludge or biosolids is the mulch-like solid material left over from sewage treatment that can be used as crop fertilizer. The land application of sludge is controversial because it can contain harmful metals such as zinc, cadmium, selenium and copper that are not removed by the sewage treatment process and can accumulate in soils with repeated applications.

The ordinance limits the use of sludge to historic levels and is so restrictive that it has essentially eliminated its use in the county. Only 1,500 cubic yards of sludge a year can be applied in the county.

A major stumbling block in developing a permanent ordinance is the cost of an environmental impact report, which is expected to be $200,000 and take two years to complete due to the complexity and controversy of the issue.

County officials also are waiting for a report from the federal Environmental Protection Agency expected next year that will examine the environmental effects of pollutants and other compounds commonly found in sludge.

Continuing the interim ordinance received unanimous support from the public at Tuesday’s hearing including the wastewater treatment managers from San Luis Obispo and Morro Bay. Both cities dispose of their sludge outside the county.

They urged the county to look at ways to use sludge inside the county other than as fertilizer. For example, it can be burned as cogeneration fuel. It can also be disposed of in landfills, used as cover material in landfills, and used to stabilize burned areas.

The county’s 17 wastewater treatment plants generate approximately 11,500 tons of biosolids a year, Lichtenfels said. About a quarter of that amount is disposed of in landfills and another quarter is trucked to the San Joaquin Valley to be used as compost. The other half of the sludge is trucked to a composting facility in Santa Maria.

Sludge can be mixed with green waste and sold as composting material without regulatory oversight. Composted biosolids sold in 40-pound bags are available at most retail nurseries and home improvement stores.

“We want options,” said Bruce Keogh, Morro Bay’s sewage treatment plant manager. “We want as many options considered as possible.”

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