Q&A | HOW NANOBUBBLES SOLVE TOUGH PROBLEMS AT WATER RESOURCE RECOVERY FACILITIES
Moleaer Inc.
Leader in nanobubble technology with over 2,500 installations in over 55 countries, improving how industries use water
Moleaer and Malvern Panalytical cohosted three webinars on the science behind nanobubbles and how they are studied, measured and viewed. We’ve compiled all the questions that were asked during the webinars to provide you with a comprehensive overview.?
If you’d like to access the recordings of these webinars, please visit them below:
Q&A | HOW NANOBUBBLES SOLVE TOUGH PROBLEMS AT WATER RESOURCE RECOVERY FACILITIES
Q1: What products do you have related to nanobubble generation within sewer collection systems (i.e., Wet wells and force mains to control odor and corrosion)???
A1: At this time, Moleaer's nanobubble generators require the wastewater to be screened to protect the pump and nanobubble generator internals. We do have installations in wet wells and lift stations where either the wastewater is screened or free of large debris and fibrous materials. However, Moleaer is actively working on a collection system solution and does have a product under development for the collection system.
Q2: When nanobubbles navigate do all the attached surfactants get removed?
A2:?? The extent of surfactants removed is a function of water quality, nanobubble dose, reaction time, and surfactant concentration. Moleaer has observed the complete conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD with sufficient doses of nanobubbles injected into flowing wastewater.
Q3: Do surfactants make the nanobubble unstable?
A3: Higher nanobubble concentrations are measured in the presence of surfactants, salts, and other common water contaminants. Such contaminants serve as nucleation points for nanobubbles to form and also stabilize the nanobubbles. However, the fate and longevity of the nanobubble are a function of many variables including water quality. It is the interaction/reaction of nanobubbles with contaminants, dissolved gases, energies, and other surfaces/interfaces in the wet environment that destabilizes the nanobubble.
Q4: Briefly clarify how the nanobubbles scavenge the surfactants.
A4: The surfactants are attracted by the hydrophobic surface of the nanobubbles. The pressure and temperature released and the possible hydroxyl radical generated during nanobubble collapse break down the surfactants, likely breaking the hydrophobic tail from the hydrophilic head which changes the molecular structure of the compound by making it non-polar and more readily biodegradable.
Q5: Can nanobubble concentration be determined in partially treated wastewater?
A5: Nanobubble concentration can only be measured in clean water samples. There is too much interference from nano- and larger particles to measure nanobubble concentration in wastewater.
Q6: How would this system be applied to a below-grade collection tank/lift station that has manhole access and is located below a road/parking lot? I.e. - there is limited availability at the ground level to station equipment.
A6: At this time, Moleaer's nanobubble generators require the wastewater to be screened to protect the pump and nanobubble generator internals. We do have installations in wet wells and lift stations where either the wastewater is screened or free of large debris and fibrous materials. However, Moleaer is actively working on a collection system solution and does have a product under development for the collection system.
Q7: Can you please talk more about the end products of surfactant removal/destruction by nanobubbles (what remains from surfactant after NBs treatment)?
A7: Roughly 2% to 10% of the total COD is removed during nanobubble pretreatment of raw, screened municipal wastewater suggesting that some surfactants may be degraded all the way to water and CO2. The byproducts of the remaining surfactants that are not completely degraded will depend on the surfactant type and the degradation step that the reaction stopped at. Moleaer has observed the complete conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD with sufficient doses of nanobubbles injected into flowing wastewater.
Q8: Where do the surfactants go after interacting with NB if not into the sludge? How/where are they disposed of?
A8: The surfactants are removed/partially degraded during nanobubble treatment. Roughly 2% to 10% of the total COD is removed during nanobubble pretreatment of raw, screened municipal wastewater suggesting that some surfactants may be degraded all the way to water and CO2. The byproducts of the remaining surfactants that are not completely degraded will depend on the surfactant type and the degradation step that the reaction stopped at. Moleaer has observed the complete conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD with sufficient doses of nanobubbles injected into flowing wastewater.
Q9: Hello, were you able to achieve readings repeatability of the nanobubble concentration and size?
A9: Yes, you can get repeatability with good experimental controls and training.
Q10: Can we measure Zeta potential with particle size with Nanosight Pro?
A10: If you are interested in Zeta Potential, please consider our Zetasizer. The NanoSight NS300 and NanoSight Pro can measure size, concentration and fluorescence.
Q11: What kind of gas did you use for surfactants mitigation, do you have any idea about other gases?
A11: The gas supply recommended for nanobubble pretreatment of wastewater is compressed air because it is affordable and widely available. However, pure oxygen and high-purity oxygen gas supplies have also been used.
Q12: Is there any specific reason why nanobubbles were not added in the secondary treatment?
A12: The surfactants need to be pretreated upstream of the biological process to prevent the surfactants from binding to the biosolids. Also, the dose of nanobubbles required to treat mixed liquor is much higher than the dose required to treat raw wastewater due to the interaction of nanobubbles with biomass. Treating the mixed liquor requires significantly more nanobubble treatment resulting in much larger pumps and nanobubble generators compared to treating raw wastewater. The interaction with NB and surfactants is found to have a better contact time for a reaction to occur. Extra Organic matter in secondary treatment competes with the NB. We have done it, but the best efficiency is achieved when NBs are injected prior to physical separation processes (such as clarifiers, DAFs, etc.). This allows for higher surfactant removal and provides higher efficacy.
Q13: How is the foaming property of different surfactants in the presence of different nanobubbles?
A13: Since there are many different types of surfactants in wastewater, the effect of NBs on individual surfactants is unknown. However, foaming in municipal wastewater is significantly reduced as a result of nanobubble pretreatment.
Q14: How do you see this playing a role in the larger decarbonization and ESG strategies?
A14: Pretreating raw wastewater with nanobubbles has the potential to dramatically shift the energy balance by preventing solids from solubilizing and reducing the soluble organic and nutrient load to the secondary treatment process. Further, removing surfactants from wastewater makes wastewater easier to treat; thereby generating more biogas and reducing the amount of infrastructure, chemicals, and energy required to maintain effluent water quality.
Q15: If NB are so effective, why are they not more widely used - can NB be naturally formed?
A15: Yes, nanobubbles occur in nature. They were first discovered in crashing ocean waves. Nanobubbles are a relatively new field of study because it has only been within the last decade or so that the analytical equipment required to measure and quantify nanobubbles has been available. Further, Moleaer's patented shear method for producing nanobubbles is one of the few if not only methods of generating nanobubbles at scale in flowing wastewater. Moleaer was formed in 2016 and started selling large-scale nanobubble generators in 2021. One issue is awareness, which we are trying to improve. We are seeing increasing adoption in yield and energy-intensive industries.
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Q16: Have you introduced this into the more conventional CHP (combined heat & power) central plants and/or microgrids?
A16: This is an area we are investigating for possible implementation.
Q17: What is the longevity of NBs in wastewater? Any idea?
A17: The longevity of nanobubbles in wastewater depends on water quality, surface interaction, and dissolved oxygen levels. As such, nanobubble reactions and interactions are dynamic and dependent on many variables. Also, there are no known analytical methods for directly measuring nanobubbles in wastewater due to the interference of other nano- and larger particles. When injecting air nanobubbles into raw, screened municipal wastewater, the conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD generally takes around 15 to 30 minutes so it may be fair to assume that nanobubble longevity in wastewater is about the same as the COD reaction time.
Q18: Can you please talk more about the end products of surfactant removal/destruction by nanobubbles (what remains from surfactant after NBs treatment)?
A18: Roughly 2% to 10% of the total COD is removed during nanobubble pretreatment of raw, screened municipal wastewater suggesting that some surfactants may be degraded all the way to water and CO2. The byproducts of the remaining surfactants that are not completely degraded will depend on the surfactant type and the degradation step that the reaction stopped at. Moleaer has observed the complete conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD with sufficient doses of nanobubbles injected into flowing wastewater.
Q19: How were nanobubbles generated? Was there the issue of quick temperature rise?
A19: The nanobubbles were generated using a Moleaer nanobubble generator. Moleaer's nanobubble generators use the shear method to produce nanobubbles. During nanobubble production, the only heat that is measurably added to the system by Moleaer's nanobubble generator is from heat loss from the pump motor to the water and the heat loss from the compressed air gas supply to the water. Nanobubble concentration can only be measured in clean water samples. There is too much interference by nano- and larger particles to measure nanobubble concentration in wastewater. In tap water, Moleaer's nanobubble generator generates hundreds of millions of nanobubbles per milliliter. Higher nanobubble concentrations are achieved in the presence of surfactants, salts, and other common water contaminants.
Q20: How do nanobubbles affect foam fractionation?
A20: This is unknown, but an area of interest that should be evaluated as part of a future study.
Q21: How is the surfactant removed after treatment?
A21: The surfactants are removed/partially degraded during nanobubble treatment. The pressure and temperature released and probably also the hydroxyl radical generated during nanobubble collapse and break down the surfactants, likely breaking the hydrophobic tail from the hydrophilic head which changes the molecular structure of the compound by making it non-polar and more readily biodegradable. Surfactants break down, removing their dual property of Hydrophilic and hydrophobic, and are no longer detected as surfactants, organic parts would be degraded further in secondary treatment.
Q22: When nanobubbles cavitate do all attached surfactants get removed?
A22: The extent of surfactants removed is a function of water quality, nanobubble dose, reaction time, and surfactant concentration. Moleaer has observed the complete conversion of slowly biodegradable soluble COD to readily biodegradable soluble COD with sufficient doses of nanobubbles injected into flowing wastewater.
Q23: Can you provide us with a range, minimum size, and price for the largest project and price?
A23: Moleaer's nanobubble generators generally range in hydraulic capacity from 10 to over 4500 gpm. Price varies widely based on the nanobubble solution package requirements and installation geography. Please contact Moleaer with project location and application specifics for pricing range.
Q24: How long does NB stay active? Are they more effective with hydrogen?
A24: It depends on water chemistry.
Q25: Were you able to achieve repeatability when measuring the NB concentration and size? And may you comment on the NB stability?
A25: Yes, you can get repeatability with good experimental controls and training. In clean water at room temperature without any disturbance, stability has been reported to be months.
Q26: Is this a sale or a multi-year service agreement contract?
A26: The contract agreement will depend on the geographic location of the installation and the treatment capacity of the nanobubble generator. Generally, low-flow equipment is available for lease or sale and larger equipment is available for lease with an option to purchase it at a significantly discounted price after 3 years.
Q27: Does temperature increase due to bubble generator affect bubble size and concentration?
A27: Moleaer's nanobubble generator uses the shear method to produce nanobubbles. During nanobubble production, the only heat that is measurably added to the system by Moleaer's nanobubble generator is from heat loss from the pump motor to the water and the heat loss from the compressed air gas supply to the water. If recirculated for a long time the temp could increase. With Moleaer equipment we don't see any significant increase.
Q28: Will adding Ozone to Oxygen increase the performance?
A28: The gas supply recommended for nanobubble pretreatment of wastewater is compressed air because it is affordable and widely available. However, pure oxygen and high-purity oxygen gas supplies have also been used. Ozone at a sufficient dose would degrade the surfactants, but Moleaer has not tested ozone nanobubbles for surfactant removal since degradation occurs using safer, less corrosive, and more affordable gases like air or oxygen. Pretreatment NB of WW uses air, not require other gas sizes the interaction is with NB regardless of the gas source. Ozone can be used for other applications like disinfection for example.
Q29: Can you provide us with different sizes and prices?
A29: Moleaer's nanobubble generators generally range in hydraulic capacity from 10 to over 4500 gpm. Price varies widely based on the nanobubble solution package requirements and installation geography. Please contact Moleaer with project location and application specifics for pricing range.
Read more Moleaer articles on our website:?https://www.moleaer.com/blog
Other Resources:
Moleaer also has a large database of case studies for a variety of nanobubble applications.
Malvern Panalytical Resources: