Note: August Rudisell, of Lawrence, recently toured Lawrence’s wastewater treatment plants. He submitted this piece to The Lawrence Times in acknowledgement of Earth Day 2021.
Today we commemorate the 51st annual Earth Day celebration, the largest secular holiday observed around the globe.
This year’s theme is “Restore Our Earth” — a call on humanity to create new and innovative ways to rehabilitate the planet’s ecosystem. Typically, we take this opportunity to join fellow Lawrencians and plant trees, participate in beach or riverbank cleanups, learn about climate change, and most commonly, recycle.
Although Earth Day is a yearly reminder for us to be good stewards of our planet’s finite resources, locally, the community as a whole makes a substantial impact on our surrounding ecology everyday.
Recently I was able to tour the city’s two wastewater treatment plants: the Kansas River Wastewater Treatment Plant at 1400 E. Eighth St. and the Wakarusa River Treatment Plant in the 1600 block of North 1175 Road. These facilities, managed under the umbrella of the City of Lawrence Municipal Services and Operations (MSO), receive, process, and release on average 10 million gallons of stormwater and sewer water every day.
MSO Treatment Manager Jay Lovett and his team of around a dozen trained treatment operators work tirelessly 24 hours a day to process “influent” water. Influent water is anything that enters through a storm drain, is poured down a sink, or what most of us picture when you say wastewater: flush down our toilets. From here, the sewage travels along 400 miles of pipes and under 15,000 manhole covers to one of our treatment plants.
The first step is what’s called pretreatment. Every single drop of water passes through a “bar screen” in order to pull out all the inorganic items. Picture a giant screen that stops larger material from passing through.
In 2019, Lawrence experienced a heavy rainfall event that caused stormwater to enter our treatment plants at more than double their capacity, and the bar screens were overwhelmed with material. This forced utility operations to temporarily reroute the untreated wastewater directly into the Kansas River.
Since then, the city has made major upgrades to the head houses and the screens have no trouble keeping up. It’s at this point Lovett likes to stop and remind his tours of the Big No’s of what’s OK to flush down the commode: no condoms, menstruation products, Q-tips, hair or dental floss, and most importantly, no baby wipes.
“They may say they’re flushable, but they’re not!” Lovett said. It’s important to remove these items in pretreatment because they are frequently the cause of clogs, and they damage the treatment lines.
Next in the process are grit chambers. Since sand and rock cannot be broken down by chemicals or bacteria, a centrifuge is used to remove the grit so our effluent can become more homogeneous. The removed material is simply taken to the landfill for disposal.
Up next, the water moves into primary clarifiers — likely the most recognizable features of treatment plants. Clarifiers are large circular tanks with conical bottoms that use the natural tendency of heavier solids to settle out of liquid and concentrate into a solid. This solid material is scraped out from the middle, while the supernatant (clear water) is moved on to the next step. At this point, it’s free of all solid matter larger than 10 microns, or .00039 inches. For comparison, a human hair is about 75 microns thick.
Going forward from here, it’s helpful to think of water treatment plants as giant chemistry sets, or more aptly, biochemistry sets. The waste in our sewer pipes carries a variety of naturally occurring elements and microorganisms that we can use to aid in the breakdown of organic matter; others, we have to introduce.
Oxidizers are crucial because they break down organic compounds, especially hydrogen sulfide, or what we would know from its rotten egg smell. Flocculants absorb many solutions, such as pesticides, solvents, fuel, and other street runoff. We use coagulants to reduce suspended solids and organic loads from primary clarifiers.
In 2020, the city’s budget was around $2.1 million for the chemicals necessary to treat our waste. This is because all municipalities in the country must meet the wastewater treatment requirements outlined in the EPA Title 40 of the Code of Federal Regulations Part 503 — a result of the Clean Water Act of 1987.
From here, we begin secondary treatment, where the goal is to encourage the breakdown process of the remaining biological content. Aeration basins accomplish this by using giant “blowers” to create millions upon millions of bubbles from the bottom of the basins.
Now, here is where it will get interesting if you’re a home brewer. Much like breweries will reuse a portion of the yeast from the completed fermentation process in the next batch of beer, treatment plants reincorporate what’s known as return activated sludge to the basin. This “yeast” of bacteria from further down the treatment line works along with the billions of oxygen bubbles in the aeration basin to create an aerobic zone, or a buffet line of food for the millions of bacteria present. Nitrates and nitrites are consumed and removed from the effluent water. At this point, 85% of all organic matter should be removed. You could actually drink the water at this stage if you so chose to.
Next comes disinfection. In Lawrence, we use two methods for disinfection: chlorine and ultraviolet light. At the Kansas River plant, the most widely used method is employed due to being very cost-effective. Sodium hypochlorite is used to destroy target organisms by oxidizing the cellular material. This disinfected water is then treated with sodium bisulfate to remove the chlorine residual and our process is complete. At the newer Wakarusa plant, ultraviolet bulbs are used to disinfect the effluent water. This process does not kill the bacteria but instead sterilizes them so they are unable to reproduce and die off.
This is the end of the treatment line for our wastewater. All requirements of the National Pollutant Discharge Elimination System (NPDES) have been met, and we are permitted to discharge into the Kansas and Wakarusa Rivers. In this way, by restoring wastewater to a pristine condition and putting it back into our watershed, we are recycling our drinking water back to its source.
To ensure the water discharged from the Wakarusa Plant has no harmful effects on our river systems, the city has arranged for Debra Baker of the Central Plains Center for Bioassessment to conduct a follow-up study to her initial 2015 assessment. Baker takes water samples and forwards them to her lab at the Kansas Biological Survey for testing. Testing will continue through 2021, and reports should be available for city staff next spring.
There is a second way we recycle each day. Carolyn Woodhead is an MSO program manager who oversees the city’s biosolids land application program. Every year since 1994, 90-95% of the leftover treated biosolids are applied to local agriculture fields as fertilizer and new organic matter. It’s also available for local gardeners at the 11th Street compost facility to use in their home gardens.
Woodhead’s team applies 3 million gallons of liquid biosolids and 8,000 cubic yards of dewatered biosolids. This recycling process has several highly beneficial aspects. It increases the vegetation’s drought tolerance by improving the soil’s ability to retain water, which in turn encourages root growth. It also acts as an alternative to expensive, inorganic chemical fertilizers, offering essential nutrients such as nitrogen, phosphorus, nickel, and zinc. The nutrients in biosolids are less water-soluble and so they will see less runoff into surface or groundwater. They are also released slowly into the growing plants as opposed to all at once.
So if you miss out on the opportunity to participate in the global Earth Day celebration today, don’t stress yourself out. Simply remember the Big No’s of flushable material and thank the unsung heroes of wastewater management!
