February 2007, Vol. 19, No.2
Too Much of a Good Thing
Nutrients, by definition, are substances that provide nourishment. For humans and houseplants, it’s difficult to get enough of the right ones. That’s why we take multivitamins, throw balanced fertilizer on our garden, and order the kids to “Eat your spinach!” But for water quality professionals, less is more, nutrient-wise, and it’s far more complicated to remove nitrogen and phosphorus from wastewater than it is to add them to our flowerbeds. As states are implementing increasingly strict nutrient limits, utilities are reengineering their processes to come into compliance. In this issue, we examine nutrient removal from a variety of perspectives: researchers, small communities, states, and an individual wastewater treatment plant.
Grit is not necessarily a good thing, but too much of it certainly can be a problem for wastewater treatment plants. This month we take you to the Blue Plains Advanced Wastewater Treatment Plant (Washington, D.C.), which had grit in abundance, particularly after peak flows. After visiting treatment plants in the United States, Canada, and France, the Blue Plains project team opted for a heavy-duty, traveling-bridge grit removal system. This innovative system, which was implemented last summer, has shown promising results.
To meet challenges such as stricter nutrient limits and large grit loads, utilities need a fully staffed, highly skilled workforce. Too many vacant positions can spread manpower too thin. But the questions of how to recruit, train, and retain new employees — and ensure that key knowledge is transferred from more seasoned employees to the newcomers — still weigh heavily on the minds of many utility managers. We found some answers in our cover story on skill-based training and certification programs at public utilities.
We also found one instance where there is no such thing as “too much” right here at WE&T: We always welcome reader feedback. We would love to hear your comments on the stories in this issue, or on any other water quality topic that interests you.
Operations Forum Editor's Note
The Change Jar
I have a jar of change on my bedside table. Every evening I toss in whatever coins I accumulated during the day. It’s usually only a few coins. But about once a year I empty that jar into an automatic coin counting machine, and I’m always surprised at how much it adds up — usually about $85.
While $85 isn’t enough to make a huge difference, it’s enough to gas up my car three or four times or go out for a nice dinner. What pleases me most is that I am able to make something tangible out of, essentially, leftovers.
A New Hampshire facility used that same reasoning to make use of what was at hand to find a cost-effective solution to removing solids from its lagoons. Instead of draining and dredging the system at great hassle and expense, the facility put a pair of decommissioned rectangular primary basins into action as holders for geotextile bags. The other equipment bought for the project, pumps and hoses, can be used almost anywhere throughout the plant.
Change of a less tangible sort adds up in a similar fashion. For example, a Missouri utility found that a series of relatively small changes to its historically unreliable biosolids incinerator led to an operating process that finally enabled the 42-year-old stack to meet its original design load.
And a membrane bioreactor facility in Georgia employed several design modifications to reduce its power consumption by one-third . Moreover, further tweaks to its operation may reduce the power demand by 40%.
On the other hand, another Georgia plant is making a series of major changes to its digestion process and cogeneration system to get the most out of its digester gas. In this case, instead of building on what’s come before, the plant will use an entirely new digestion process and a type of engine never before used with digester gas.
While all of these projects operate on budgets much greater than nickels and dimes, the idea of making every bit count carries through.