Grease can accumulate in sewer lines restricting flow and eventually blocking the pipe. The blockage can cause untreated sewage to discharge into the surrounding area in an event called a "sanitary sewer overflow (SSO)." A major number of these SSO events are caused by grease released into the sewer system from houses, restaurants, and local businesses. Small quantities of grease come out of solution in the sewers and begin to coat pipes and begin a buildup that starts to restrict flow. Most cities utilize camera inspection and physical cleaning to remove grease in troublesome sections of the sewer lines. In many cities, increased population density and older sewer lines have created a need for frequent cleaning and educational programs to keep people from dumping grease into the sewers.
Since the 1980s, people have been using microbial cultures to initiate grease degradation in the sewers. This process relies on the ability of select microbes to convert the grease into ever smaller particles that do not buildup in the sewer system. At Aster Bio we have several options to keep the grease from causing blockages while preventing free grease from entering the sewage treatment plant where it is more difficult to treat than other components of wastewater. Over the next three blog posts, we will discuss the treatment options that exist for grease control, odor control, and lower loadings hitting the treatment plant. The next topics are going to be:
Restaurant Grease Control - Treating lines in the restaurant helps prevent plumber emergencies caused by grease in drain lines. It also helps keep the grease trap from producing substantial foul odors and helps lower the amount of grease entering into the sewer system. Additional benefits include the reduction in "drain flies" that rapidly breed on grease found in floor drains.
Gravity Sewer Lines - Treatment can be established that allows for a beneficial grease degrading biofilm to establish on the pipe walls. This reduces grease accumulation and associated odors/corrosion caused by hydrogen sulfide (H2S).
Lift Stations/Force Mains - Lift stations often have grease accumulating on walls, pumps and floats. This grease causes damage to equipment and causes odors that can create complaints from local residents. Aster Bio can use a combination of microbes and equipment to convert the station into a working biological treatment system node that does not accumulate grease or produce odors.
For the past twenty years, I have worked in the field of biological waste treatment and have often used bioaugmentation as an operational tool. Similar to adding select yeasts in producing wine or bread, waste treatment professionals can add a "seed" culture to water or soils to supplement the indigenous microbes with beneficial microbes. These beneficial microbes are selected for a number of reasons including:
By adding select cultures to a working waste treatment system, operators can adjust the biomass to meet target treatment goals without the time delay or unexpected results often seen as the indigenous microbes adjust to the environment or changing waste stream.
The bioaugmentation seed culture is developed after laboratory testing and must meet criteria for stabilty, biosafety, and ability to adapt to changing conditions. After selecting the cultures, the individual microbes are grown and stabilized using techniques similar to those used to produce antibiotics and other pharmaceutical compounds. The pure microbes are then stabilized on various carriers for preservation until applied by operators.
Often waste professionals faced with difficult treatment criteria, cost concerns, or a new waste stream find themselves pressured to purchase strange additives. Today I will address one of the most common that I see being marketed to industrial and municipal wastewater professionals.
What I offer is like a "Bug Steroid" - natural extracts and vitamins that make bugs grow faster, degrade more compounds, reduce odors, and produce less sludge. Of course it sounds great, but I am of the curious/scientific type and always ask.... "well how does it actually work?" In this case the answer is almost a uniform... "We don't know the exact mechanisms, but it does what we say it does.... Can I have your purchase order."
I am not suggesting that vitamins and micronutrients cannot increase microbial growth rates and in some cases be necessary for proper function. The most common use of micronutrient additives is in operating anaerobic systems where methane production is often increased by adding rare elements such as Co, Ni, & Mo. Again; before adding micronutrients the system should be examined to see if the additives are needed based on influent characterization.
In addition to anaerobic systems, I have seen adding some micronutrient/vitamin formulations make slight improvements to floc formation and microbial activity in systems with some lacking micronutrients. The most cost effective way to get these micronutrients is not some expensive additive. In my lab tests on pulp mill wastewater, I have found that adding glacial rock powder provides an excellent supply of minerals that can be used by the microbes when needed. With glacial rock powder readily available in 50 lb bags - it is used by organic farmers - you can often solve issues with lacking micronutrients by adding glacial rock at a rate of 5 - 10 pounds per million gallons flow ~ 0.7 - 1.2 parts per million (PPM).
To conclude - There is no such thing as a bug steroid. If you are found lacking micronutrients, add the lowest cost source of these minerals which is often glacial rock or even a metal salt (example magnesium sulfate).
Of course, if someone has a bug steriod and can tell me how it works on a cellular basis, I am willing to evaluate how it can help improve waste treatment.
Industrial facilities often discharge wastewater into municipal treatment systems and pay a surcharge based on loadings (pollutants) sent to the municipal facility. Often target components are BOD/COD, TSS, & ammonia. Surcharges are often high enough that the industrial facility will consider pretreatment to lower pollutants being transferred. The problem is most pretreatment systems tend to have either a high upfront equipment costs or have expensive chemical requirements.
Aster Bio has recently worked with an customer with high strength BOD (highly degradable organic acids majority of BOD) average of 3,500 - 4,800 mg/L with a flow of 20,000 gallons per day. Proposed pre-treatment systems were all priced $250,000 - 750,000 which was too high for the facility. Given a budget of $70,000, Aster Bio and the facility designed a pretreatment system using existing tanks with a total volume of 100,000 gallons. Adding a coarse bubble diffuser and eductor aeration/mixing system and associated piping resulted the facility meeting budgeted costs with room to spare. Since the system is simply an aerated series of tanks with no biosolids recycle, Aster Bio developed a microbial blend to inoculate active cultures at the front of the system. Testing runs resulted in 5 day decreases in influent BOD to <200 mg/L with a low of 75 mg/L. The ongoing Aster biological seed cultures used are a minor cost for the facility and run approximately $15 - 20/day depending upon charge and waste strength.
Recent cold weather has caused some bioremediation and water treatment facilities to have less efficient treatment. Most of our microbes in waste treatment are mesophilic organisms, meaning they grow best in temperature ranges from 12 - 38oC. When we go outside these ranges "strange things" start to happen as the population dynamics begin to favor organisms more suited for either low or high temperatures. It is this population shift that causes issues in both spring and fall.
By now our systems have drifted to a lower temperature biomass, but even with this biomass a drop in temperature does lower activity rates of the microbes and their enzymes. A rule-of-thumb is that for every 10 oC drop in temperature we lose 50% of microbial activity. You can combat this efficiency loss by running higher MLVSS (more bacteria) and by adding exogenous cultures (bioaugmentation) to supplement your active population of microbes.
Indicator protozoa are easily observed under low magnification (100x) under a light microscope. These wastewater protozoa are actually single celled, eukaryotic organisms that "feed" on bacteria cells in the water. As they are larger and more complex organisms than their prey (bacteria), protozoa are often used to judge the "health" of your bacteria (bugs).
Under times of high loadings, low dissolved oxygen, and general stress; we tend to see more primitive protozoa (flagellates). As the amount of soluble BOD/COD decreases and dissolved oxygen becomes more available the protozoa population becomes more complex with free-swiming ciliates, crawling ciliates, and stalk ciliates becoming increasingly common.
I have included a picture from a refinery activated sludge plant with a stalk ciliate attacted to the bacterial floc. When you see stalked ciliates in a wastewater system you generally have good floc formation, sufficient dissolved oxygen (DO), and efficient BOD/COD removal.
Biofilms develop as microbial growth slows and the cells begin to excrete polymers that act like a glue between cells. The cells and other solids in the water begin to form a biofilm on surfaces (also called floc in suspended growth systems). Biofilms contain a relatively low percentage of "active" living microbes usually between 5 - 12% in wastewater with the remainder being dead cells, biopolymers, particulates, and other debris found in the water. When exposed to harsh conditions such as pH changes, toxic chemicals, or adverse temperatures; the biofilm acts to protect the microbes from harm. Only the top layers are killed in the by chemicals such as disinfectants. Wastewater treatment requires the effective formation of biofilms as they indicate proper BOD/COD removal and provide a means to remove suspended solids from the water flow. Loss of biofilm consistency and seeing free cells in the water column are the first indications of upset condition.
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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