Here’s a frightening story for Halloween.
In September of 2018, the Macomb County Public Works Office in Michigan cleared out an obstruction from a sewer line.
It was 100-feet long, 11-feet wide, and six-feet tall.
Underground monster? No.
Scary Blob? Kinda.
The blockage was what’s now been commonly known as a fatberg — a collection of oils, grease, fat, and solid items like baby wipes, hair, and makeup pads.
According to Asha Srinivasan, a Research Associate in the Department of Civil Engineering at the University of British Columbia (UBC), this sewer mountain is a “huge nuisance.”
The term “nuisance” is perhaps a gentler, more generous description of the sewer monstrosity. Aside from being annoying to municipalities, fatbergs are also…pretty gross.
Fatbergs are essentially made of what is called “FOG,” or fats, oils, and grease, along with a variety of items that should not be flushed down a toilet. The collection forms a huge mass that can clog sewer lines, like the one in Macomb County.
FOG-heavy fatbergs are becoming increasingly common. In October of last year, divers in South Carolina had to swim through raw sewage to unclog pipes blocked by "flushable" wipes.
On September 12 of 2017, workers in London discovered one of the largest fatbergs ever seen: 800 feet long and 130 metric tons, according to the London utility provider Thames Water.
The Museum of London even decided to display a piece of the record-breaking berg.
“It would have been nice if people had come to look at it,” Srinivasan told Tech Briefs, referring to the museum presentation. “It would've created some sort of awareness as to what not to be flushed.”
Srinivasan and her team at the University of British Columbia are testing out ways to turn the “nuisance” into a product far more helpful: methane. The clean fuel, when burned, releases water and low levels of carbon dioxide.
The process developed at the University of British Columbia breaks down the fatberg’s fats, oils, and grease. A tank known as a biodigester houses the anaerobic bacteria that digest the organic material and produce the greater amounts of methane.
The UBC study was recently published in the journal Water, Air & Soil Pollution.
By hitting the FOG with microwaves and adding hydrogen peroxide, the team was able to decrease the number of unusable solids, like antimicrobial compounds, in the samples by up to 80 percent.
"Effective source separation techniques like grease traps at the source can help to divert FOG from being discharged into the sewer lines,” said Srinivasan in a recent article published by Inverse.
The new process is in the pilot scale testing stage, and demonstration tests are underway at municipal sewage treatment plants and dairy farms. A full-scale system is expected to be in place in a year or two, according to the researchers.
Srinivasan spoke to Tech Briefs about how her team is hoping to fight the fatberg blobs and turn the sewer blockages into a valuable energy resource.
Tech Briefs: What led you to sustainable waste management?
Srinivasan: I was born and raised in India. I started my undergraduate education in Chemical Engineering, but even before that, I was a Girl Guide. As a Girl Guide, I worked with a lot of factory teams. I had a proficiency badge in world conservation, so I was always interested in Environmental Sciences.
At UBC, my research focus was mainly on developing a process for wastewater or sewage sludge treatment, which goes by the term Microwave Enhanced Advanced Oxidation. This is a process that was developed by Doctor Victor Lo's research group in 2002. I joined the group in 2012, and I've been working with this group commercializing this process.
Tech Briefs: What are fatbergs, and how do they occur?
Srinivasan: A fatberg is a huge mass or clump mainly made of what is called fat, oil, and grease, abbreviated as FOG. A fatberg also contains other kind of materials such as wet wipes, hair, makeup pads, or inorganic material that is not supposed to be flushed down the toilet. All this, in the presence of FOG, creates a huge mass, and they essentially clog those sewer lines or sewer pipes. Fatbergs are a huge nuisance.
Tech Briefs: Why are fatbergs such a big problem?
Srinivasan: In the past 10 years or so, fatbergs have increasingly become more and more of a problem, because they mainly clog the sewer lines and cause sewer overflows; this leads to discharge of untreated sewage into the environment.
Tech Briefs: What can the average person do to help prevent fatbergs?
Srinivasan: From my perspective, prevention at the source could be the best approach. We should really not be disposing cooking oils or waste oils down the drain. Of course, it goes without saying that no one should be flushing wet wipes or anything that's not supposed to be flushed down the drain.
Tech Briefs: What's a worse fatberg contributor: Wet wipes or cooking oil in the sink?
Srinivasan: Cooking oil; it can form a clump with other, larger things. It can really clog the pipes, or it can start building up layers in the sewer lines. FOG is generally made of different kinds of cooking oils collected from kitchen sewers or restaurant waste waters. It is not worth flushing down the drain, because FOG is an energy rich resource. That is where my research come into picture where we are trying to treat FOG using a microwave oxidation process.
Tech Briefs: How does your treatment of FOG work?
Srinivasan: The process involves microwave heating up to 110 °C or 120 °C maximum, with the addition of hydrogen peroxide as an oxidant. The process is called microwave enhanced oxidation process. What that means is it's an advanced oxidation process involving a chemical hydrogen peroxide, with a process enhanced by microwave heating.
Tech Briefs: Why is FOG such a challenging substance to treat?
Srinivasan: FOG is complex in nature, and generally microorganisms find it difficult to break down. Our solution to this is to treat FOG with a pretreatment technology. Our microwave oxidation-based process involves heating with microwaves and adding hydrogen peroxide, which is a green oxidant chemical.
Fats are made of long chain fatty acids. Our microwave oxidation process breaks them into simpler, smaller chain compounds.
The process helps to break down FOG, or any other organic substances in the waste, into simpler forms. If you take this pretreated FOG, or pretreated organic waste, into a biodigester, it will be easy for the microorganisms to eat up the already broken-down organics.
Tech Briefs: Why is methane such a desirable byproduct?
Srinivasan: First of all, these biodigesters produce biogas. Biogas is a renewable natural gas that contains approximately anywhere between 60-70% methane. A lot of agricultural feedstock or manure could be a good source for biogas production.
It will also be a good idea to combine FOG with manure, or FOG with municipal sewage sludge, to produce biogas. This biogas is being produced from a renewable source, so it's good for the environment. FOG or any other kind of renewable source or agricultural waste or sewage sludge would be a rich resource that could be used to produce renewable energy to form biogas or renewable biogas.
Tech Briefs: What makes your process so innovative?
Srinivasan: There have been different treatments available to treat FOG, such as simple mechanical, physical, or chemical methods. But our process is unique in the way that it's tailor-made to pretreat FOG to efficiently recover resources. It could be used to just recover energy, or could be used for recovering a nutrient such as phosphate. This process can also produce more energy efficiently in the form of biogas or if it could be combined with other waste streams such as manure or sewage sludge.
Tech Briefs: Is there anything to be done about wet wipes and the other things that get flushed down the toilet? Is there any hope for breaking those down?
Srinivasan: I'm sure there will be other processes that can help to break down these kind of waste streams, but that has not been our focus at the moment. We focus mainly on organic studies like for sludge that can be taken in a microwave and heated.
Tech Briefs: Are you actively testing the treatment process in the field?
Srinivasan: Before we started this project on FOG last year, we had been focusing mainly on treating municipal sewage sludge and animal manure. We have large-scale systems being demonstrated in waste water treatment plants and in an animal/dairy farm in BC around Vancouver, around Fraser Valley, BC. Our aim is to move this technology forward for a full-scale commercialization.
Our published paper focused primarily on treatment of pure FOG and seeing the effect of microwave oxidation treatment on these pure FOG materials. We are now proceeding with treating a mixture of FOG with dairy manure and sewage sludge under different ratios. We want to see how good the process can break down FOG and manure together. If a farm or a municipal waste water treatment plant is interested in, let's say, co-digesting FOG with their bio digester, there is a limitation to which they can unload FOG into their digester. They cannot load over 25% of FOG as dry bait, because FOG again could be inhibiting the microorganisms.
We hope that the microwave oxidation pretreatment will be able to break down these long chain complex molecules into simpler forms so that the pretreated mixture of FOG and manure or FOG in sewage sludge will be easy on the microorganisms, and they will be able to break down this mixture easily. What that means is we can load more FOG, not just a limit of 25%, and that will help to produce more methane or more biogas.
Tech Briefs: What outcomes are you hoping to see and what results have you seen so far?
Srinivasan: We believe from our preliminary result, in terms of treating FOG manure or FOG sewage sludge mixtures, that we can pretreat a mixture with the ratio of 70% FOG to 30% manure (or 30% sewage sludge). We believe anywhere from a ratio of 50/50 to 70/30 could be used in the digesters.
Tech Briefs: Regarding commercialization, would this be for restaurants? Households?
Srinivasan: This is actually a very modular system. The footprint is typically what could be housed inside a standard 20-foot shipping container. Usually, we aim for large municipal waste or treatment plants or large dairy farms that have huge amounts of waste materials to handle. If you're talking about, let's say, a big restaurant or a mall, this could be used at their own site where they could pretreat FOG and then discharge them or then they could send them off for processing. We would have to look at the economics. In terms of municipal wastewater treatment plant or a dairy farm, we know for sure that the economics really work well.
Tech Briefs: Do you see fatbergs as an increasing problem?
Srinivasan: With aging infrastructure, I believe it's going to be a problem in the future. You're going to hear more and more of these stories, like what happened in London.
Tech Briefs: Fatbergs have been kind of trending in the news. Do you find the publicity helpful at all? Is it benefiting your research?
Srinivasan: This is primarily university-based research at this point. But, any publicity is good publicity. It does encourage the research group and especially the students involved. I hope this will bring in some interested parties and stakeholders who could help us move forward.
What do you think? Have you heard of "fatbergs?" Share your questions and comments below.