Micropollutants and the Solution to All Wastewater Treatment Problems

by Peter Quince on 2017-12-13 12:54pm

We ask an awful lot of wastewater treatment plants. Time was, the goal was just to neutralize the worst bacteria and make our lives a bit better. Today, we expect sewage to be treated until it’s benign in every way – non-toxic and stripped of the nutrients that spur bacteria and algae growth, while leaving as small an environmental footprint as possible. These goals may defy biology, physics, and logic, but there are two things that are clear:

  1. It isn't getting done; and
  2. Communities don't want to pay what it would take to even try to get it done.

The wastewater infrastructure itself is partly to blame. It represents a huge investment, all designed to work one way. And it’s incredibly energy-intensive. Electricity powers almost every stage of the treatment process, with pumps, motors, and other equipment operating 24 hours a day, seven days a week, while UV, ozonation, aeration, and chemical and biochemical treatment are all energy pigs. So, it’s no surprise that wastewater plants are the largest municipally-funded energy users and greenhouse gas contributors. [Note: a 2013 joint study by the Water Research Foundation and Electric Power Research Institute found that wastewater facilities consumed 30 billion kwh of electricity annually, nearly 1% of total electricity usage in the U.S.]

Meanwhile, a threat to public health that was barely envisioned 20 years ago – micropollutants – is barely addressed by the existing infrastructure.

Micropollutants are tiny molecular compounds found in the residue of a host of pharmaceuticals, particularly birth control pills, HRT, steroids, antibiotics, and painkillers from Tylenol to Oxycodone, which pass through the medication user and are expelled into sanitary drainage. There’s more – some of the biggest sources of micropollutants are toothpaste, hair care products and cosmetics, hand sanitizer, pesticides and manufacturing processes (plastics, PVC, etc.), and even artificial sweeteners like aspartame and acesulfame (sold in little packets under a host of familiar names or added to diet soda). Households are responsible for over 70% of micropollutants, with the balance coming almost equally from hospitals and other medical facilities, agricultural runoff, and industrial processing. Because micropollutants are persistent and bioactive, (i.e., not completely biodegradable), they can pass through to rivers and streams without degradation. They also resist conventional water treatment methods and, as a result, the highest concentration is found at wastewater treatment plants, that may then send them back out after processing the sewage, to be drawn for drinking water by any downstream facilities.

Awareness of these itty-bitty troublemakers dates back less than 20 years. They’ve been around a lot longer, but not identified until testing equipment became sophisticated enough to see them. We now realize they’re everywhere, taken up from the rivers, streams, and water table by plants, animals, and (of course) people.

So, how harmful are they? The truth is, we don’t know. Since they’re molecular compounds, they can break into parts and recombine in the fertile soup of wastewater or work together with any of the hundreds of other micropollutants with unpredictable results. Some appear to have toxic or mutagenic effects. They may help create super bacteria or cause aggressive forms of cancer.

We think.

Since these little buggers are designed to interact with biological life forms like us, they can have powerful effects. Some have been labeled “Endocrine Disrupting Compounds” (EDCs), which means they mess with our hormones. The NIH writes: “The impact of most micropollutants on human health and environment is not well understood... For example, triclosan, an antibacterial and antifungal used in personal care products such as soap and toothpaste, is called an [EDC] because it interferes with natural hormonal functions, potentially altering metabolism, development, reproduction, and growth." The NIH doesn’t mention what EDCs can do to emotional stability – could it be partially responsible for increasing rates of autism and mental illness?

We just don’t know, because they’re small, so varied, and so prone to interact with each other and with bacteria, determining their impact is nearly impossible and, in many cases, we’d rather not know. Why not? Because, even if there ARE ways to greatly lower the concentration of micropollutants in wastewater, it’s way expensive. The treatments developed so far are massive energy hogs, far beyond what treatment plants already use. At a time when we’re trying reduce costs and environmental impact, it’s hard to justify big INCREASES in energy demand to fight these itty-bitty thingies whose impact remains unclear.

Here’s how these challenges become one of the greatest opportunities ever. Removing micropollutants takes lots of energy. Where will we find it? Ironically enough, the organic matter in wastewater contains up to five times as much energy as treatment plants use. Bacteria that works in oxygenated tanks to break down solids, can then be put to work again (but this time without oxygen) to generate methane that’s then captured and burned in a biogas engine to produce electricity or upgraded to natural gas quality and put into a pipeline. About 35 percent of U.S. plants already generate some electricity from biogas and the rest burn it off instead, believing harnessing the electricity generated isn’t worth the cost. With rapid advances in battery storage capacity and lower costs, this may no longer be as great as you think.

Clearly generating electricity from bio-waste is virtuous, which is rarely enough to move a community into a large investment, even one that eventually pays for itself. But, what if our survival and health and the health of our kids ALSO depended on it? If politicians can claim to be virtuous AND defeat the micropollutants that could (maybe, potentially) be at the heart of every mysterious and terrible developments over the past 50 years, would they be moved to act?

Clearly, we need to know more and improve ways to remove micropollutants. Researchers are at this moment developing advanced oxidation and nanotreatments such as carbon nanotubes show promise and may be more effective and require less (although still lots of) energy.

But now may also be the moment to scare the hell out of your friends and neighbors about how micropollutants must be defeated and that we can do it all AND Save the Planet by capturing and burning enough methane right there at the wastewater facility to Win the War on Micropollutants. At a time of budget cuts and environmental worries, this could be an opportunity to finally upgrade the wastewater infrastructure to face the challenges of today and tomorrow.

Who knew such little bitty micropollutants could do so much?

Peter Quince has been making his living as a professional writer since 1978, most recently as a contributor with At Your Pace Online, an innovative online education company that offers pre-license and continuing education for Water Operators, as well as for professionals in real estate, insurance, plumbing, electrical, HVAC, mortgage loan origination, and tax preparer fields.