I often get this question. If you believe that a microbe is a microbe - then it should work perfectly. You could truck in sludge from a municipal plant and it would work perfectly for building biomass in a refinery. Of course we all know it is not that simple. To answer the title question, adding sludge can help but it all depends on your expectations and treatment needs.
To more fully answer the question, we need to look at wastewater microbiology and the nature of Mixed Liquor Suspended Solids (MLSS). As I like bullet points, here it is:
Bioaugmentation includes adding cultures screened for growth in the system. The resulting product is highly concentrated with respect to active microbial fraction. How we use it with adding MLSS from nearby plants is based on evaluation and experience. Here are the situations:
National Geographic has recently run an article on intersex fish being found in wildlife refuge waters. While this can occur sporadically in nature, a trend for higher numbers of intersexed fish, amphibians, and reptiles has been identified over the past 30 years. While we may have anticipated this happening in highly polluted streams near industrialized areas, it is now being found in agricultural and non-industrialized areas.
What are hormone mimics? In general a number of compounds including some naturally-occurring chemicals have the ability to mimic natural hormones in animals & humans. Most of the research has been on estrogen mimics causing males to become hermaphrodites. Early indicator species include small mouth bass - but early research also found a huge impact in alligators in Florida in the 1990s.
What is important is the concentration of hormone mimics in waters causing disruption in indicator species. We do not know the long run impact on higher trophic level organisms including humans. So, the next generation of wastewater permits will start to also include reduction of hormone mimics and pharmaceuticals that are currently passing through conventional wastewater treatment systems. The issue is how to remove these compounds without excessive costs or other environmental impacts.
I am including a link the National Geographic story. A online search will also give further references on hormone mimics and regulators efforts to remove problematic chemicals from waters.
Extracellular polymeric substances (EPS) is literally the glue that hold bacteria in a biofilm or floc. This glue also allows the floc to act like a sponge - adsorbing organic and inorganic insoluble compounds and forming the matrix that we call biofilm or floc (depending upon your system).
What exactly is the EPS composition? Well it has been found to be:
A recent study on houses in Peru and Brazil led by Maria Gloria Dominguez-Bello of New York University, examined microbial communities on walls in houses from remote areas of Peru (both totally rural and in small villages) and compared the diversity and type of microbes to those found in urban Brazil housing.
We may not realize it, but our immediate environment is full of microbial communities. And, our houses have differences in microbes found on walls in various rooms. In this study, they found you could identify room use by the microbes on walls.
Another finding, was the more we seal off our houses with walls, windows, and insulation - the less microbial diversity on the walls (especially soil microbes). Instead, our walls tend to keep our human associated bacteria (E. coli, Steptococcus mutans, and on) in higher concentrations than found in rural, more open air houses.
So what does this mean? Well right now we just know there are differences in the microbial communities in urban versus rural houses. The next phase of research needs to look at how this impacts our personal microbiome on our skin and digestive tract. We may find that the urban environment has an impact on our digestive tract health.
At Aster Bio we have been bench testing several new organisms with the goal of converting sulfides and H2S into harmless oxidized forms at non-acidic pH. While many Thiobacillus cultures exist that oxidize reduced sulfur, they tend to thrive at pH levels below 5 which is outside the range of many other organisms. So, we started looking for other sulfur oxidizing cultures that worked at higher pH.
After screening a number of candidates, we found some unique microbes with excellent applicability to waste treatment. The first is a Paracoccus denitrificans. This unusual bacterium has a number of key metabolic pathways that are useful in control of both sulfides and malodorous short-chain volatile fatty acids. An additional benefit, is the P. denitrificans can utilize nitrate/nitrate when growing on the short-chain volatile fatty acids. So what does all this mean for waste treatment?
We all like quick and easy tests to screen for potential problems in the biological treatment unit. The problem is that many of these tests require specialized equipment, reagents, or are just expensive.
Today, I want to talk about using the oxygen uptake test done daily in most facilities as a way to estimate influent toxicity. Does it work in all places, all the time..... no. But, It can prove useful in many systems that have periodic "suspicious" influent conditions.
The spiked DOUR simply consists of a set amount of MLSS from the aeration tank to which you add a set amount of influent or waste stream to be tested. You can allow to react with the biomass for 2 - 4 hours using an aquarium air stone or you can do the test immediately. Then, you saturate the sample with oxygen as in a typical DOUR by shaking. Once saturated with oxygen, you use a BOD bottle & DO probe to record oxygen uptake by the biomass + sample. Once the DO is depleted to <1.0 mg/L, you convert the uptake rate to mg O2/L/hour.
An increase in DOUR in the spiked versus the normal MLSS and is expected. The red flag here is if the spiked DOUR pulls down the O2 extremely fast - due to chemical oxygen demand. Or, if the respiration is reduced significantly which indicates toxicity.
Key to the spiked DOUR being an effective operational tool is running the test frequently to get a correlation between the spiked DOUR to system operational numbers. Another important issue is whether to allow the sample to aerate for a time period before running the DOUR tests.
I have used spiked DOUR to test equalized waste streams in industrial pretreatment and pulp & paper wastewater. With frequently tested samples, it proved useful in predicting high strength or toxic influent which allowed for operators to slow the influent flow and prevent system wide upset.
Can you duplicate civet cat processed coffee without the civet cat? (most expensive coffee in the world if you were wondering)
Sometimes I find a bit of biology outside the environmental realm too good to ignore.
Indonesia produces the most expensive coffee in the world, Kopi Luwak. What makes this coffee so unusual is that the beans are processed in the digestive tract of civet cats. In theory, the cats eat only the best beans detected by their sense of smell. Once consumed, the digestive acids, enzymes and intestinal bacteria all work in concert to process the bean making the resulting coffee bean have exceptional smoothness once roasted. The beans had to be collected from the civet poop for washing and eventual roasting. With demand for the coffee increasing and producers wanting to cash in on the $200+ per pound coffee, they have been experimenting with civet cat houses where they force feed coffee beans at a higher rate than would naturally happen. Besides being cruel to the animals, it is costly and inefficient. So, in steps some enterprising scientists....
At a company called, Afineur, researchers have attempted to duplicate the civet cat treatment process in a controlled, bioreactor environment. This way special enzymes and microbes can work to reduce the bitterness and create a similar experience to the best Kopi Luwak coffee. After appearing in an issue of Wired Magazine in 2014, it appears that the company is starting to sell the coffee.
What is interesting to me is the use of natural microbes and enzymes to simulate the animal digestive tract. This type of simulation is aided by ongoing research into digestive tract microbes, enzymes, and biochemical interactions in both animals and humans. As we learn more about this process, even more unusual applications of food processing by fermentation will probably be mentioned in the press.
Lag phase is where the biomass grows slowly with low respiration rates as they adjust to new environmental conditions or influent makeup. While we often think of this as an individual organisms that turns on or off various biochemical pathways, it is more often a general shift in microbial population makeup. Adding new waste streams, operating at different temperatures, D.O., or pH can be similar to starting up a system. The more change from existing operations, the greater the shift. How fast will a system return to stable or steady-state condition? It all depends on the changes and waste type.
Can the lag phase time be reduced? Yes. You can truck in sludge from a compatible plant with the same waste or in many cases it is easier to inoculate with a bioaugmentation product suited to the waste/system. By adding adapted cultures to the existing microbes, the adjustment time can be significantly reduced which can reduce holding back influent, adding extra polymers/antifoams, or having effluent permit issues.
Can you predict if adjustment will be an issue? Once again yes. You can do bench testing with oxygen uptake rates and various toxicity testing to determine if the new waste will be an issue. I have discussed both heterotrophic and nitrifier toxicity testing in previous posts.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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