Filamentous foaming is a major cause of problems in wastewater treatment plants all over the world. Nocardioform and Microthrix parvicella foams are often controlled by lowering the sludge age. Chlorination of the RAS line is sometimes successful as well. Type 1863 grows at very young sludge ages (3-4 days or less). Denitrification Scum/Foam
Why are filaments bad for wastewater treatment?
Early is needed in the wastewater treatment market. MICROCAT‑XF is formulated to reduce filamentous microbe populations, improve sludge settling and reduce effluent suspended solids. When used on a preventive maintenance basis, this product can enhance overall system performance while reducing operating costs.
What is filamentous foaming in wastewater treatment plants?
According to the results, a range of 3–39% of the total quantity of viable foaming filamentous bacteria present in biological wastewater treatment stage of …
How to control type 0092 filament in wastewater treatment?
· Problem #1: Floc is too small. Check for proper chemical dosage with jar testing. Look for low chemical metering by checking your drawdown and metering (pump settling). Your chemical feed pump could be adjusted too low. Increase your feed pump or drawdown rate if needed. Check your pH and control calibration, and make adjustments if needed.
How do you fix filamentous bulking in aeration basin?
· Filamentous foaming bacteria: the nuisance of many biological nutrient removal (BNR) wastewater treatment plants. Although filamentous microorganisms are a natural part of the biomass in plants and are the backbone of floc formation and settling, the overproliferation of filamentous microorganisms causes the sludge to float (foaming) and causes ...
What are the causes of filamentous bulking?
Filamentous bulking is caused by the proliferation of bacteria filaments that outcompete floc forming bacteria for food and occurs due to bad settling and thickening of the solids.
What are filaments in wastewater treatment?
Under adverse conditions however, bacteria that grow in filaments begin to form longer chains called filamentous bacteria or “filaments”. Filaments can dominate in the wastewater treatment system under a variety of conditions.
How can you improve settling in activated sludge?
Excess organic load can be remedied by reducing the waste-activated sludge rate by an amount less than 10 percent per day, to return to proper loading parameters and increase the returned activated sludge rates. About a 30 percent level of settled solids in the clarifier should be established and maintained.
How can I improve SVI?
To increase the SVI, an operator would increase the waste sludge rate, effectively creating a less dense particle that settles slightly slower. This same particle might also trap more fine suspended solids as it settles, clarifying the effluent even more. The lower MLSS mg/L results in a higher SVI calculation.
How can filamentous bacteria be reduced?
Filamentous bacteria can be controlled by treating the return sludge with chlorine or hydrogen peroxide to selectively kill filamentous microorganisms. Chlorine concentration should be 10-20 mg/L (concentrations greater than 20 mg/L may cause deflocculation and formation of pin-point flocs).
How are filamentous bacteria isolated?
Narrow and short filaments or filaments scarce in the activated sludge may be concentrated by centrifugation. Another method for selective isolation of filamentous bacteria is micromanipulation with special microtools under a microscope (Kämpfer, 1997).
How do I stop sludge bulking?
To avoid sludge bulking some of the flow that enters the reactor can be bypassed, recycle ratio can be increased, lime or soda can be added to the reactor or the re-aeration rate increased.
How can you avoid or minimize sticky sludge?
Agitation avoids the formation of sticky sludge by efficiently mixing the sludge during the problematic sticky phase in order to maintain its movement throughout. This ensures that the lumps quickly disintegrate before they can become sticky.
How do you reduce sludge age?
The easiest and most practical way to control sludge age is with hydraulic control by wasting a defined proportion of the reactor volume daily. In AS plants with reactor concentration control, nitrification fails first.
What is a good SVI range?
Generally, a good quality sludge has an SVI in the range of 50-150 mL/gram.
What is a good SVI number?
How to control the SVI? The typical sludge volume index for a sludge wastewater system that is operating as it should will be between 50 and 150 mL/g. If your SVI is outside of this range, you may need to take steps to control the sludge levels in your system.
What happens if MLSS is high?
If the MLSS becomes too high you may have problems with solids separation from too-low a settling velocity / too high a small solids size fraction (this will depend upon your separator - sedimentation / membrane) and design details. Treat the MLSS ranges as guidelines to avoid separation issues.
What are filamentous microorganisms?
These are microorganisms that grow in long strands and are, among other things, characterized by a much larger volume and surface area compared to the usual activated sludge flocs.
What bacteria are in activated sludge?
There are more than 30 filamentous bacteria known that can be present in activated sludge. One of them is the filament Nostocoida limicola, which showed up in the activated sludge in a Monsanto WWTP (Figure 2). This bacterial population thrived as a result of insufficient phosphorus nutrient in the feed stream to our biodegradation basins, and an insufficient feed-to-biomass (so-called F/M) ratio. Under substrate- and P-nutrient-limiting conditions, these filaments benefit from their inherently high surface area and are able to gain access to scarce essential materials, and this allows them to maximize their growth at the expense of the development of conventional floc-forming bacteria [ 2–3 ].
Can activated sludge be controlled?
Excessive growth of filaments and biopolymers in activated sludge should be controlled in CPI wastewater-treatment plants, as both lead to sludge that is hard to handle. The sticky behavior of such sludge can be minimized by the addition of polyaluminum chloride
What are the problems with filamentous bulking?
These problems can lead to violations in effluent limits and less efficient treatment. Bulking problems cause extra sludge hauling expenses and the addition of polymers to control filamentous bulking is often expensive due to the high cost ...
What is 0092 in wastewater?
Type 0092. Type 0092 can cause bulking problems in aerobic wastewater systems but is an important precursor to foaming caused by M. parvicella . Type 0092 thrives in conditions with very similar food sources to M. parvicella but in warmer weather conditions. This filament’s cells individual cells are difficult to see as they are normally contained ...
How to identify nocardia in wastewater?
Nocardioforms, or “Nocardia”, are typically easy to identify in wastewater because of their true branching, Gram positive staining, and Neisser positive granules. True branching means one filament continues to grow in multiple directions, like the growth of an oak tree. Nocardiforms, like M. parvicella produce a low density fatty cell wall which causes them to float on the surface of water. This in combination with their generation of surfactants during growth, and their formation of a thick mat due to branching causes them to typically form very stable foam that can be several feet thick. It is important to note, that while Nocardiforms are known to produce a very thick stable foam, they also can form thin layers of scum which means you cannot definitively identify “Nocardia foaming” without microscopic observations to identify the filament in the foam. Nocardioforms can be controlled with the addition of Qwik-Zyme L, and Foam Buster to favor floc forming bacteria over filaments, and through increased wasting to reduce sludge age. VitaStim Low F:M can be used to rebuild bacterial populations after increased wasting.
Why is foaming important?
Foaming leads to extra labor controlling foam by spraying water or adding defoamer, and often leads to the unpleasant task of cleaning up filamentous foam to maintain sanitary conditions and to avoid operational problems. It is important to note that there are many more filaments that can appear in wastewater than are included in this guide.
What is M. parvicella?
M. parvicella is usually a very distinctive filament in wastewater treatment. This is due to its spaghetti-like appearance under Gram stain. It stains strongly Gram positive and contains Neisser positive granules. M. parvicella tends to thrive in cold temperatures with high fats, oils, and greases (FOG). M. parivciella floats in water due to the high concentration of low density fats present in its cell wall. These filaments form a tangled mat on the surface of aeration systems which effectively traps air from air diffusers leading to foam formation. While M. parvicella is known for forming a thick layer of dark brown scum up to around 6 inches, M. parvicella can lead to foaming of a variety of colors and consistency’s and therefore must be identified microscopically before an effective treatment can take place. M. parvicella foaming can be controlled effectively through the addition of Foam Buster and Qwik-Zyme L while increasing sludge wasting. Foam Buster provides a blend of proteins, amino acids and micronutrients which allows wastewater floc forming bacteria to better outcompete filamentous bacteria in conditions with high levels of incoming FOG. Qwik-Zyme L catalyzes and degrades fats, oils and greases to allow floc forming bacteria to more easily out-compete filamentous bacteria such as M. parvicella.
What is foam buster?
Foam Buster provides a blend of proteins, amino acids and micronutrients which allows wastewater floc forming bacteria to better outcompete filamentous bacteria in conditions with high levels of incoming FOG.
What is a 1701 filament?
These filaments are likely the same filamentous species responding to slightly different environmental selectors. These filaments are typically distinguished due to false branching characteristics in the case of S. natans and the presence of attached growths in Type 1701. Both filaments have a thick sheath and sausage shaped cells. Interestingly, it is not uncommon to observe attached growth and false branching at the same time in these filaments making the distinguishing feature between these filaments not very helpful. Fortunately, these filaments thrive in nearly identical conditions with high flow rate, low DO, and septic compounds. These filaments most often grow upstream from a wastewater system in a sewer line or lift station. These filaments are effective at anchoring themselves to the side of a sewer line but will occasionally break off due to changes in flow rate, very high populations, or routine sewer line/lift station cleanings. When these filaments enter a wastewater plant, they can cause long term bulking problems in plants even in conditions that are unfavorable to their growth due to the strength of their sheath. In fact, the sheath of S. natans and Type 1701 can remain in a wastewater system long after the filament itself dies, continuing to cause bulking problems. Due to these characteristics, the only effective way to prevent the presence of S. natans in a wastewater system is to prevent its growth upstream. This can be done by more frequent sewer cleans, nano-bubble diffusion upstream, or by metering in OxyFresh, particularly in weeks prior to sewer cleanings or conditions that could increase flow rate such as snow melt, or heavy rain.
What is a filamentous algae?
Filamentous algae are colonies of microscopic plants that link together to form threads or mesh-like filaments. These primitive plants normally grow on the surface of hard objects or other substrates under the water but they can break loose and form floating mats.
Why are filamentous algae important?
Filamentous algae are important because they produce oxygen and food for ...
Why do algae grow in ponds?
The algae are growing in response to nutrients that have washed into the pond, so excessive growth of algae may indicate that there are other pollutants that also have washed into the water. If the source of nutrients is pet or animal waste, it is likely that bacteria and other pathogens are living on the algae mats.
How much of a pond is covered by algae?
On the other hand, ponds that have algae covering more than 20% of the surface area are more likely to develop stagnancy, noxious odors and fish kills, so it is recommended that filamentous algae be controlled to prevent it from covering more than 20% of the pond surface.
What is a floating wetlands?
Floating wetlands use native wetland plants contained in a synthetic matrix that floats to pump nutrients out of the water. Diffusion circulators can assist with managing nutrients in the water and prevent stagnancy, and they do not clog like fountains and irrigation pumps.
Why are algae important to ponds?
Filamentous algae are colonies of microscopic plants that link together to form threads or mesh-like filaments. These primitive plants normally grow on the surface of hard objects or other substrates under the water but they can break loose and form floating mats. Filamentous algae are important because they produce oxygen and food for the animals that live in the pond, but they also can cause problems such as clogs and stagnancy. Filamentous algae do not have roots; rather they get their nutrients directly from the water, meaning that their growth and reproduction are entirely dependent on the amount of nutrients (i.e. fertilizer) in the water. Because stormwater ponds collect water flowing from yards and roads in the community, they often grow an abundance of algae as a result of the many sources of nutrients in residential and commercial developments. It is not uncommon for stormwater ponds to develop large floating mats of algae during the warm months of the year in response to fertilization of lawns and animal wastes in the watershed.
What causes foaming in wastewater?
Filamentous Foaming. There are three filaments that are known to cause foaming and these grow due to high amounts of fats, oils, and grease present in the wastewater. Septicity helps convert fats, oils, and grease to unsaturated forms, which are easier for these organisms to assimilate.
What causes denitrification foam?
Denitrification is caused by anoxic conditions (no free dissolved oxygen), the presence of nitrate, and a carbon source (readily available BOD). Denitrification foams are common in the final clarifier and a major cause of effluent TSS violations.
What is control method for filamentous bulking?
Control methods for filamentous bulking are based on, first, confirmation that the problem is indeed caused by filaments (some are not) and, second, identification of the causative filament (s). This information leads to specific remedies that can be used, appropriate for the filament (s) involved.
What is the most commonly used chemical to control filaments?
Two toxicants, chlorine and hydrogen peroxide, have been used successfully to control filaments. Chlorine is the most widely used as it is relatively inexpensive and available on-site at most plants, and only this will be discussed here. Chlorination for bulking control is widespread, used by more than 50% of plants.
What pH should be used for aeration?
The aeration basin pH should be maintained in the range 6.5 to 8.5. Low pH, <6.5, may cause the growth of fungi and fungal bulking. The aeration basin pH can be adjusted using caustic, lime or magnesium hydroxide.
What causes activated sludge foaming?
Activated sludge foaming is caused mostly by two filaments: Nocardia spp. and Microthrix parvicella (there are other non-filament causes of foaming). Both of these filaments have three causes in combination: (1) high grease and oil; (2) longer sludge age; and (3) low oxygen conditions or septicity.
What is the BOD5:N:P weight ratio in wastewater?
In general, a BOD5:N:P weight ratio in the wastewater of 100:5:1 is needed for complete BOD removal.
Filamentous Bacteria Are to Blame
Understanding The Challenges
- There are more than 30 filamentous bacteria known that can be present in activated sludge. One of them is the filament Nostocoida limicola,which showed up in the activated sludge in a Monsanto WWTP (Figure 2). This bacterial population thrived as a result of insufficient phosphorus nutrient in the feed stream to our biodegradation basins, and an insufficient feed-to …
Impacting Settleability
- The settling ability of a sludge is measured by means of the sludge-volume index (SVI), which expresses the volume (in mL) that 1 g of activated sludge (referring to dry solid matter) occupies after 30 min of settling. The SVI is determined using an easily performed sedimentation test in the laboratory, in accordance with the Dutch norm NEN 6624 [ 4].