Petaluma's wastewater plant is running at close to 75 percent capacity, largely because dairies and breweries are pumping in more waste than anticipated when the plant was being designed a decade ago. More waste is good, in a way.

In means production is up and increased sales revenues for the city. But because companies are charged for every pound of wastewater they discharge into the city's sewer, many have long been pushing the city to reevaluate its fee structure while upping the capacity of Ellis Creek Wastewater Treatment Plant.

High-density waste is typically things like fat, grease, oil and beer byproduct that can clog the city's sewer lines unless it's pre-treated first. On Monday, Petaluma Public Works Director Dan St. John gave a detailed presentation about ways to tackle the problem, but made clear that it would take another six months before any improvements are implemented.

Among his ideas:

Change the rate structure for industrial users instead of fining companies that discharge more than their allotted share,

Increase how many pounds of high-density waste the plant can take,

Upgrade and optimize the equipment that processes waste solids and look into reusing solids (Currently, some is already utilized as fertilizer, while more "toxic" solid waste goes into landfills.)

Install methane digesters that would convert solid waste into energy, then sell it. St. John said the amount of high-density waste jumped significantly last September and has remained high, although he did not know why.

"It's something we are investigating," he said. He reiterated that no matter what option was selected, it would first have to be studied, which could take another half a year.