Planning To Own A Digester?

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An open letter to new parents of anaerobic digesters:

No one knows a child better than the parents. If you’ve been in the business for a while, you know your plant and system like no one else. A bond forms between you and your plant, much like that of a parent for a child. You spend your days making sure it is fed properly, relieves itself properly, has enough air to breathe and is healthy in every way within your control.

Then the time arrives for an upgrade or process addition. Liken it to your child entering day care for the first time. You know that if little Flo is fed dairy, she will be up all night, and so will you. You know that if your plant is suddenly fed a new diet, it will have an upset system. In the case of anaerobic digestion, this means it will vomit, sometimes so much so that its lungs (gas piping) will fill with vomit (rising sludge) and it may experience Montezuma’s revenge, exuding solids from every orifice.

The entire system may become fouled (think perforated colon) or worse. It could blow the top right off — talk about spontaneous combustion! Waste will get into delicate filters and carbon beds. Gas will enter manholes and become a grenade waiting to detonate. Think about the worst gastric distress you’ve ever had, and that is how your digester feels.

Helpful folks (think grandparents — OK, engineers) will try to tell you the best way to calm your child’s symptoms. They will tell you that the child is resilient and will get over it. That perhaps you fed it too much or it could use some prune juice. Wanting to make things better as soon as possible, you listen to the experts and make the recommended changes, but you have a nagging feeling that these are not the correct things to do.

Deferring to folks who know they know better, you watch your child as it continuously vomits, gurgles and belches as if its stomach is a witch’s cauldron, all the while emitting noxious gases that no one should endure. Finally, you take the bull by the horns. You do what your gut tells you to do. You decrease the food and increase the quality. You make sure elimination is optimized, and the vomit and diarrhea begin to decrease slowly. 

Instead of alternating between flatulence and diarrhea, little Flo begins to sound more normal, and soon she is looking for more food. This is when you know her stomach has finally settled. You’ve mastered the art of feeding the perfect diet in perfect proportions, which results in a well-tuned digestive system, eliminating just the right amount of gas while maintaining the perfect amount of solids in the bowels.

And all is well — until the next problem arises. But using your knowledge of the child, you will be able to eliminate multiple possibilities and finally home in on the problem and solve it — again, until the next time.

The moral of the story is although any new system brings a learning curve, there is a correct-most-of-the-time formula for every system. While others can offer advice and textbook answers, no one knows the system more intimately than you, the operator. Don’t be afraid to challenge the experts and do what your gut tells you. Don’t be afraid to reach out to other operators who may have had similar issues, or to people who know the framework and can brainstorm with you to come up with more options.

Your state environmental department and the U.S. EPA can be your friends; even engineers can be your friends. But only fellow operators and folks who have this business coursing through their veins like you — people who are distressed when a system is upset and overjoyed when problems are resolved — can understand and help.

You may not be the most popular person in the world, but you are the one who will be up all night with the sick child, and you will be the one who will be driven to distraction until it is stable. There is nothing wrong with beginning with the textbook or trying to make the system meet a certain number or percentage or detention time, but ultimately each system is as unique as a child. And only by spending hours and hours nurturing your new child will you be the person who knows it best.

To keep that child happy and healthy, you will go to no end to make things right, and that is when you earn the title of operator/parent.

Linda Schick, Sewer/Wastewater Superintendent, Fairhaven (Massachusetts) Water Pollution Control Facility



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