The Heavy Burden of Abundance

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Those involved with wastewater treatment are aware of the challenges faced through ever-tightening regulations regarding nutrient discharge to waterways. The Chesapeake Bay and Lake Erie are two examples of waterbodies having received media attention for issues such as hypoxia (low oxygen levels) which is related to nutrients.  Even though experts agree that 60-75% of the nutrients come from agriculture, wastewater treatment has been identified as the solution provider to this sizable problem. In some cases, limits imposed on municipal wastewater treatment plants are lower than what the available amelioration technology can achieve. And it’s not uncommon to expect virtually unlimited investment in the search for solutions.

But most lay people are unaware of nutrient issues, also known as eutrophication, let alone the efforts underway to address them, such as water quality trading and adaptive management. Fewer people, including wastewater treatment professionals are unaware, as I shared three years ago, using disposers can reduce nutrients discharged from treatment plants.

Water quality trading and adaptive management

What is water quality trading and adaptive management? Both are strategies instituted by regulators to help municipalities meet compliance with low nutrient discharge limits. According to the Wisconsin DNR, water quality trading is used to offset treatment plant discharges, to comply with permit limits.  It pertains to reducing nutrients from other sources in the watershed instead of reducing the effluent discharge.  Adaptive management, on the other hand, focuses on achieving water quality criterion (acceptable background levels) and emphasizes overall reduction. How much success either offers depends on the measurement used to gauge them.

Both are being forced on municipal treatment plants in an effort to reduce nutrients coming from agriculture.  In fact, most of the water quality trading and adaptive management strategies are specifically employed in the agriculture sector and yet – they are paid for by municipalities.


Image: World Resources Institute



Food production thanks to fertilizer

U.S. farmers are tremendously successful at food production largely due to fertilizer use (nutrients) which, by the way is a limited resource (see Phantastic Phosphorus). This overproduction via fertilizer ends up polluting waterways. Then the wastewater sector has to pay for remediation.  We all need to understand the price for the luxurious grocery store selection we expect. This abundance is one of the reasons rates are increased by the treatment plant. Unfortunately, we live in a society that largely takes food availability and its consequences for granted.  So what is to be done? It’s a big problem requiring big solutions, right?  Maybe not.

Starting small instead of big

Some argue that small-scale steps taken by small agriculture can be more productive than grand initiatives and costly treatment plant investments. This makes sense, especially when the cost of remediation at the treatment plant using the “best available technology” is much more expensive and yields a much lesser reduction – a concept explained by Maria Laukkanen and Anni Huhtala in their paper, “Optimal Control of Nutrient Pollution in a Coastal Ecosystem:  Agricultural Abatement vs. Investment by Wastewater Treatment Capacity.” However, I still struggle with placing the burden of managing the reduction of nutrients on one industry, when a majority of the problem comes from another.


Easy Peasy

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Sharing my passion for disposer usage to divert food waste from landfills invariably generates questions about what can and can’t put down a disposer – even in the professional settings where I make presentations.  Last week the questions were about onion skins from one person, and cantaloupe rinds from another.  Of course both can go down a disposer – easy as can be, I told them.  As long as you use it in the right way.

But over time I’ve learned that people do not use their disposer as much or as effortlessly as they could. They mainly use the appliance to clean up, and anxiety over potential plumbing problems leads them to follow the old adage, “better safe than sorry.”

I believe this is either from experiencing problems firsthand or from hearing about them after an episode of improper disposer use.  All too often, people use one in a way that is completely opposite to instructions. 

Some people fill up the disposer chamber with food scraps, start the unit, and then turn on the water. This sends a “slug” of food into the plumbing trap all at once.  Others don’t use any water at all.  Either way is using the appliance improperly and invites issues.

The steps to proper use are few — turning the water on, then the disposer, and then gradually adding food scraps into the disposer, grinding them until nothing is left in the chamber. You can tell by the sound when grinding is complete. Then make sure to keep the water on for a few additional seconds to carry the food waste through the trap and internal plumbing.  Simple.

Using a Disposer is Easy

But many people are even more expert at ignoring or dismissing instructions.

During a recent series of tests in five cities we provided pretty extensive education and use instructions to participants getting them accustomed to using their new appliances in the right way.  Through direct contact we learned that about 30% of household food waste gets processed in disposers. While this is substantial, there is potential for disposers to keep much more out of landfills. And it’s easy to do successfully when following directions.

I Assembled My Cat Without Instructions

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Significant Relevance

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American Food Load

How much do you use your food waste disposer (garbage disposal)? Said another way – how much food waste is put down your disposer? The answer to this question is elusive. Think about it. Once the food waste goes down the drain into the plumbing and on to the water resource recovery facility (wastewater treatment plant) it is gone. It cannot be measured.

DisposerFor our five city food waste evaluation we applied out of the box thinking to quantify how much people use their disposer by comparing the amount of food waste in people’s garbage before and after installing a disposer. It was important for the results to be statistically significant, so the sample size for the number of households included in the study was relatively high.                                       

We set the goal of 90 households, and a minimum of 70, but these homes also needed to be in the same neighborhood where one garbage truck would collect the waste. We had two separate weeks’ worth of garbage evaluated in the neighborhood before disposers were installed, and then two times after the disposers were installed.

In the U.S. 50% of all homes already have a disposer, so an added challenge to our study criteria was finding 90 homes without one. Indeed in some neighborhoods selected (with input from key individuals in each city), many people already owned a disposer and we were unsuccessful in finding enough participants. Interestingly, some residents suspicious of “free stuff” from the government study resulted in reluctance to participate. “There ain’t no such thing as a free lunch.”

While it was frustrating to not be able to recruit sufficient participation in every city, in the end we did get statistically significant results in 4 out 5…and that’s significant relevance!