Community Notes: An update on the WRRF, and other issues

By Dan Rimrod, Water Resources Recovery Facility Superintendent

Once again another year and another column to write. This year hasn’t had the excitement of construction of the Water Resources Recovery Facility (WRRF), but rather learning and adjustments for operations and maintenance.

With only four of us working at the plant, we definitely have stayed busy. Operating an activated sludge plant requires a lot more attention compared to the old trickling filter plant which basically did its own work. We have become growers in a sense.

Nowadays we control the system and basically farm microorganisms that take care of treating the waste stream. The organisms come from the waste stream and also the soil and we put them in the right environment to grow and reproduce so they can produce a clean effluent.

We get to choose the life span of the organisms based on certain criteria and tests and normally give them a life span of 16 days. If we didn’t remove a certain amount/day they would overpopulate, become old, and would end up having a septic foamy system.

We waste a daily amount of microorganisms to keep the system balanced using a Solids Retention Time Formula (SRT) that takes the total mass of the organisms in the Oxidation Ditch aerated section and divide that by the mg/L of RAS/Was that is converted to pounds and that’s how we can figure a life span. This might not be a good full description but gives you a little insight on the workings.

The microorganisms settle in the final clarifiers and are recycled back to the head of the plant where they can once again treat the incoming flow. When the organisms settle it leaves a clear water at the surface that continuously leaves the plant.

So now that we keep the micro-organisms for a certain time you need to know what we do with them when we take them out of the main treatment process. We used to waste about 9,000 gallons a day of a mud pie consistency from the old primary clarifiers to the digesters.

With the new system we now waste anywhere from 38,000 to 50,000 gallons a day that’s around 75% water from the final clarifiers which in treatment terms is called mixed liquor suspended solids.

To be able to re-use the solids for fertilizer we need to treat them in the digesters and get a volatile reduction. In order to get the reduction, we need to give them oxygen and periodically decant the clean water back to the main process in order give the organisms the right amount of time in the digester.

There you have it, in the end it’s a bug eat bug world.

Every year I like to end my Community Notes by asking for removal of sump pumps from sanitary sewer connections, which are illegal. Connection to storm sewer is assessable typically.

If I can slowly change the idea that it is fine for structures to be adding extra unwanted flow that all has to be pumped again at a lift station and again at the plant, and then unnecessarily treated, I will keep mentioning it.

Regulations require that we treat all flows, so if we can keep them down, the plant can operate more efficiently and without any violations and costly fines.

Chemicals such as gasohol, diesel, grease, paints, and any unnecessary materials are NOT to be put into the sewer. The digested treatment and secondary treatment systems operate biologically with living organisms and these substances kill the organisms vital to this treatment process.

“Flushable” wipes are not flushable, but have been seen more and more in the marketplace in recent years. There was a large campaign to include the word “flushable” on packaged items and it has been a big debate in the sewer industry.

The word “flushable” is used to encourage the purchase of these items, but please disregard the word, “flushable” on these products, as they often are NOT flushable.

Not only could city mains become clogged, but often private sewer lines become clogged first, creating unnecessary expense and mess to the homeowner.