June 2008, Vol. 20, No.6
Melissa H. Jackson
According to the U.S. Greenhouse Gas Emissions Inventory, generation of electricity represents the largest source of carbon dioxide emissions in the United States. Rising energy prices and growing concern about climate change have prompted utilities to investigate producing power and heat onsite, if they aren’t doing so already.
In this issue we feature the County Sanitation Districts of Los Angeles County (CSD), which for years has been harnessing the power of “waste gas” from its digesters and landfills. A leader in the industry, CSD has implemented a number of power-generating projects, including gas turbines, internal combustion engines, microturbines, and fuel cells. To find out more about these facilities, see our story “The Power of Digester Gas.”
Melissa H. Jackson, editor
Operations Forum Editor’s Note
Keep It Flowing
Collection systems are the veins of our society. Without them in place to carry wastewater away from our homes and to the treatment facilities, life as we know it would be drastically different.
It’s a hassle when drinking water supplies are disrupted by a power outage or line break. It would be a nightmare if the drains stopped working. Keeping our veins running swiftly and clear of blockages is essential to good health, and paying the same attention to our collection systems is essential to public health.
Eating healthily and exercising regularly prevent problems from arising in our veins and keep operations smooth. But while jogging 4 hours a day might be good for our hearts and veins, we need to temper what’s best with what’s reasonable. Likewise, “Saving for a Rainy Day” weighs in on the importance of considering operations and maintenance (O&M) costs when designing and building a stormwater treatment system. Skip this step in the constriction process, and the “least-cost” capital alternative may lead to higher overall expenses when the O&M costs are factored in.
Even with the best planning, sometimes veins and collection systems alike develop blockages. The options for removal, in both cases, are mechanical or chemical. For veins — but more commonly arteries — this means using a special tool to remove the built-up material or prescribing drugs to slowly disintegrate the blockage. Procedures for collection systems are similar if a little more aggressive.
"Rooting Out SSOs" looks at how fast roots can fill a lateral pipe and what tools are best for removing the blockage and preventing root regrowth. The researcher built a pilot-scale collection system, planted trees throughout, and tested mechanical and chemical root reduction and prevention methods. A better understanding of how popular root-control methods work can help lead to optimal root-removal and pipe-maintenance practices.
By designing effective and affordable collections systems and maintaining them properly, the wastewater industry keeps the hearts of our cities pumping along.
In the article “No Space? No Problem!” from the March issue, the figure on p. 66 lists incorrect flow data under the heading Plants 1 and 2. The figure should state that the annual average daily flow, mean daily flow, and peak hourly flow for Plants 1 and 2 are 1.25 mgd, 1.88 mgd, and 2.5 mgd, respectively. We regret the error.
Steve Spicer, editor