You turn on the tap; you flush the toilet. Stuff goes down the drain. It’s gone. Vanished. Out of sight, out of mind.
Of course, stuff doesn’t actually just disappear, as many mid-nineteenth century Londoners were painfully aware. Without the infrastructure that we take for granted today, they were taken to piling up their solid wastes in their basements!
Before I became a W.P.C.A. Commission member, I took a closer look at the operations at Suffield’s wastewater treatment plant. Happily, plant superintendent Jamie Kreller made time to give me a lengthy tour.
If you’ve never given much thought to how our waste water is treated, let me tell you – this is no small or simple operation. It is in fact a complicated endeavor involving chemistry, microbiology, and engineering. The complex of pumps and pipes, tanks and filters, chemicals and microorganisms produce a stream of clean water safe enough to return to the Connecticut River.
I was first escorted into a building that began the Preliminary Treatment of the incoming wastewater. Here, devices screen out large debris such as wipes, rags, plastics, sanitary products, and other trash. Next, sand, grit, and all remaining solids are allowed to settle out and are removed mechanically.
Wastewater is then passed to other tanks for Secondary Treatment. Here, microorganisms – mostly bacteria and protozoans – consume dissolved organic matter. This is referred to as “Biochemical Oxygen Demand” (BOD), because these little helpers, being “aerobic,” use up dissolved oxygen when digesting the organics. Care must be taken, therefore, to keep the water at this stage sufficiently aerated, or else the wastes would not be sufficiently broken down. Pumps are often used to bubble in air, but the Suffield plant uses surface aerators. Also, to keep the microorganisms working at peak efficiency, they are suspended and moved around in a circular motion.
The processes I’ve described so far can remove up to 90% of the waste. Microscopic particles, called “Total Suspended Solids” (TSS), must be filtered out. Our permit requires us to remove at least 85% of TSS and BOD, because high levels can cause severe harm to aquatic organisms, wildlife, and even be dangerous to human health. The Suffield Treatment Plant removes an average of 99% of TSS and BOD.
It’s also necessary to remove “nutrients” such as phosphates and nitrogen compounds. These are bad for rivers, lakes and streams because they promote algal blooms, which reduce the dissolved oxygen in the water and kill the fish.
You may be thinking that wastewater at this stage would still be pretty germy, and you’d be right. Plenty of bacteria and viruses have escaped the processes I’ve described so far. It’s important to disinfect the water in the final stage because some of these microorganisms are pathogenic.
Suffield’s wastewater treatment plant doesn’t use the traditional chlorine solution for disinfection. The chlorine can be carried into the river and harm aquatic organisms. Some plants use ozone instead, but our Suffield plant uses ultraviolet light.
You may also be wondering what happens to all the solid waste that had settled to the bottom of the sedimentation tanks. This is removed periodically, and much of its water content is extracted. The de-watered sludge, now called “biosolids”, can be buried in landfills, incinerated, or treated for agricultural use. In Suffield, we press and dry it, then ship it to Hartford where it is incinerated.
Furthermore, such systems can be overtaxed by improper activities and behaviors. Throwing wipes or sanitary products down the toilet is a definite no-no, as all such materials must first be separated out in the Preliminary Treatment stage, if they haven’t first clogged a pump station somewhere. Ditto for paper towels, towelettes, diapers, condoms, Q-Tips, cotton balls, dental floss, toothpicks, Band-Aids, kitty litter, or anything plastic.
Cooking oils and bacon grease should not go down the drain! The treatment plant has to skim these from their holding tanks, assuming they don’t clog your own pipes first! And if your basement sump pump’s outflow pipe is connected to your house drain pipes, you’re breaking the law.
My tour of this essential town facility was both enjoyable and fascinating. We can be proud of our wastewater treatment plant. It is so well run that it produces one of the highest quality effluents in Connecticut. You may want to consider taking such a tour yourself!