Thursday, December 29, 2005

Eleven Minutes

Bud is standing at the stainless steel filter console, smoking, cigarette clamped between leathery fingers stained burnt sienna. (He tells me, laughing, that his white cat licks the nicotine off his knuckles.) Through the break room window I watch his murky exhalations rise and get snapped into the swift, hot current from the make-up air units, imagine the smoke being trundled through the great open space like a leaf in manic rapids, out the louvered vents at the far end of the plant.

He stabs the glowing screen and an automatic valve hisses, sealing off the influent flume to the filter. The filter will draw down for sixteen minutes, allowing most of the water trapped in the basin to move through the filter media and escape to the chlorinated clearwell, ensuring the other three filters will gain in level so their flow can feed the starved filter.

Sixteen minutes, another hiss and Travis and I bolt for the door, wrestle over the captain’s chair in the control room. Neither of us really wants a shot of stress in front of the computer, but the scuffle has become routine. This time I win; he settles into a chair beneath the window, starts in on a story. On the screen numbers are flashing, plunging, the flow rolling over into the negative.

The five-minute multiwash stage begins when a horizontal red slash on the tidy diagram of pipes and valves and tanks changes to green and tips on its end, “valve open.” In the same instant there is a rumbling beneath our feet and the blowers in the concrete basement roar to life, forcing streams of air through the layers of sand and anthracite in the filter bed, releasing trapped impurities into the clean water flowing backwards through the filter from its three counterparts.

My job in all this is to monitor the negative flow and trick the console. When the operating capacity is at winter lows, the flow of water from three filters isn’t enough to maintain a high enough pressure through the fourth to remove the trapped matter from the filters. On the hill beside the plant is the backwash tank, filled with treated, disinfected water. Because its floor is higher than the surface of the filter no pumps are required; the simple opening and closing of a valve controlled by the computer allows gravity to feed the filter. The computerized console operates on the assumption that there is sufficient water from the three working filters. I am there to make sure the console never realizes there isn’t by opening the backwash valve just enough to maintain a certain flow. If the console detects that there isn’t enough water, it will stop the backwash process (this would be a crisis). Too much pressure will wash the permanent filter media out to the waste lagoons with the backwash water.

After five minutes the blowers slam off and the six-minute air purge stage begins. The flow continues to be erratic and I stop listening to Travis, focus on the numbers, peaking and diving like a roller coaster, unpredictable. The flow drops; open the valve 18%. The flow rises; close it to 14%, 12%, 10%. When six minutes is up the valve hisses and the influent flume spills half-filtered water from the sedimentation basins into the newly cleaned filter. The slash on the screen diagram goes back to red, horizontal, and I enter ‘0’ and close the valve, finally relax.

In the ancient leather logbook (on the brand new cherry-veneer desk) I enter an average flow for each stage, calculate and enter the total (Multiwash: 3,600 gallons per minute x 5 minutes, Air Purge: 3,200 gallons per minute x 6 minutes= 37,200 gallons). Add to that the filter-to-waste amount, the gallons flushed to the lagoons before the filter is put back online, because the filter doesn’t function well until it has a small amount of debris in it (Filter to Waste: 500 gallons), and write the final total in the report that goes to the County water master. (He determines how much water the City can pull from the Bear River, balances the water rights of all the communities and ranchers along the line. We deduct the wasted, non-treated water from our total use.)

Each filter is different. Eight is well behaved and hardly needs any help, Six is a maniac, all over the place, Five does fine during the multiwash but goes nuts during the air purge, Seven is a weakling and needs the valve open at least 20% all the time. (Filters One through Four sit empty in the old plant, waiting.) The air valve sticks on Six and takes about thirty seconds to open when it’s cold in the main basin. Five fills back up the fastest. Eight gets a slimy polymer scum built up on top that has to be hosed off the walls when it draws down. Seven would rather not be washed, retaliating for the disturbance by putting out slightly higher NTU water for the first twelve hours afterwards. How often the filters get washed depends on how much water is being treated. Right now it’s every six days, at 1.7 million gallons per day (MGD). In July and August it’s daily, at flows upwards of 8 MGD.

If you're not running the computer during a filter backwash, you're out watching the water get clearer and clearer. I'll never get tired of watching it. In 25 days I will have been at the plant for a whole year, and I can hardly believe it. It seems like I’ve always known the scents and sounds, the temperaments of the pumps and valves, the daily routines and monthly sampling rituals. It seems strange to think that I could be this charmed by a world of concrete and brass and multicolored wires and three silly men that treat me like a kid sister, but I’ll enjoy it while it lasts.


Blogger Shepcat said...

You had me at "influent flume." (I love these entries.)

This one made me think back to your first post-Katrina entry — which, more than anything else I read at that time, illustrated the far-reaching effects of the disaster in Louisiana — and until now I forgot to ask whether the Garyville plant ever got back up and running or you're getting your coagulant from someplace else these days.

You've turned me into such a geek.

December 29, 2005 at 11:12 PM  
Blogger A said...

Miraculously, the Garyville plant came through pretty much unscathed, and after a brief absense of employees whose homes were damaged and/or destroyed, production resumed.

I knew you'd like that. And did you notice all the purposeful indentions?

December 30, 2005 at 5:23 PM  
Blogger a572mike said...

Great stuff A! I feel like I am ready to ride shotgun on the next filter cleaning cycle after reading all of that. One thing that always bummed me out when I was a field engineer with Shurtleff & Andrews Corp. is that I never go to see any of the stuff I helped put together operate... None of the rotary kilns, none of the giant pumps or boilers, none of the giant conveyors, not even the Thermal Recompression Tripple Effect Malto-Dextrin Evaporator...

December 30, 2005 at 6:12 PM  
Blogger Shepcat said...

Thanks for that — stellar. Because if that had been a single paragraph, my head would have exploded somewhere around "backwash tank."

December 30, 2005 at 7:16 PM  

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