What causes straggler floc

In the summer time, biological activity increases and lower sludge ages normally produce a higher quality effluent. … A low sludge age tends to produce a light, fluffy, buoyant type of sludge particle commonly referred to as straggler floc, which settles slowly in a final clarifier.

What causes pin floc in wastewater?

Pin floc occurs most commonly at starvation conditions — a very low F/M and long sludge age. Chronic toxicity can also cause a pin floc condition. Free floating filaments can, at times, cause a dispersed growth problem. Here, the cause is filament-specific and is the same as for filamentous bulking (discussed below).

How do I reduce pin floc?

Pin floc leads to a more turbid effluent. It is most commonly the result of exceedingly high sludge age. Reducing sludge age often minimizes the occurrences of pin floc. Algae growth within secondary clarifiers is common for uncovered secondary clarifiers.

What causes pinpoint floc?

Pin-floc also occurs in systems where solids are unintentionally being returned from solids processing. Excessive solids in anaerobic or aerobic digester supernatant or improper solids capture from sludge dewatering systems can all cause excessive loads of tiny sludge particles that will show up as pin-floc.

What causes filamentous bacteria in wastewater?

Shifts in the activated sludge environment, such as changes in pH, dissolved oxygen, nutrients, etc. will often cause a change in the behavior of the bacteria. Instead of single cells, small chains or clumps, the bacteria will begin to form longer “chains” which develop into filamentous bacteria.

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.

What is floc in activated sludge?

Activated sludge flocs are a flocculated mass of microorganisms, extracellular polymeric substances (EPS) and adsorbed organic and inorganic material. … The results indicate that the EPS, both in terms of quantity and quality, are very important for the floc properties of the activated sludge.

What causes high pH in wastewater effluent?

A low or decreasing pH is often caused by low dissolved oxygen (DO) or organic overloading. Algal activity is responsible for most of the variation in the lagoon; in fact, high effluent pH is almost always attributed to algae.

How do you get rid of filamentous bacteria in wastewater?

Ingenuity To The Rescue Chlorine and hydrogen peroxide have been used success- fully to selectively kill filamentous bacteria. 3 Chlorine is the most widely used toxicant, as it is relatively inexpensive and readily available. A highly concentrated chlorine solution (0.5 to 1.0 percent) has been shown to be successful.

How do I raise my MLSS in aeration tank?

The biofilm is retained in the aeration tank and thus one can achieve higher biomass density. MLSS can be increased by adding part of cow dung slurry. Macro nutrients ,Micronutrients which supports the microbial growth may be added.

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What causes high TSS?

Soil erosion can be caused by Building and Road Construction, Forest Fires, Logging, and Mining. The eroded soil particles can be carried by stormwater to surface water. This will increase the TSS of the water body.

What is a good sludge age?

Optimum MLSS concentrations should be determined experimentally for each plant. – A sludge volume index of about 100 and a sludge age of three to fifteen days are normal for most plants.

What causes sludge bulking?

Sludge bulking is the most common solids settling problem in wastewater treatment plants, which is caused by the excessive growth of filamentous bacteria extending outside the flocs, resulting in decreasing the wastewater treatment efficiency and deteriorating the water quality in the effluent.

Where does filamentous bacteria come from?

Segmented filamentous bacteria or Candidatus Savagella are members of the gut microbiota of rodents, fish and chickens, and have been shown to potently induce immune responses in mice. They form a distinct lineage within the Clostridiaceae and the name Candidatus Savagella has been proposed for this lineage.

What causes filamentous growth?

The possible causes of filamentous growth are identified, including long retention times of solids, low substrate concentration in the liquid phase, high substrate gradient within the granule, dissolved oxygen deficiency in the granule, nutrient deficiency inside granule, temperature shift and flow patterns.

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 does aeration tank work?

Aeration in an activated sludge process is based on pumping air into a tank, which promotes the microbial growth in the wastewater. The microbes feed on the organic material, forming flocks which can easily settle out.

What is the percentage of aerobically digested sludge?

What is the percentage of aerobically digested sludge? Explanation: The solids concentration in thickened, aerobically digested sludge is generally in the range 1.0% – 2.0% as determined by digester design and operation.

How does activated sludge get produced during sewage treatment?

The activated sludge process in the treatment of wastewater involves blowing oxygen or air into raw, unsettled sewage. This process smashes the solids. The sewage is bubbled, and sewage liquor is discharged into an activated sludge chamber.

Which gas is produced during sludge digestion?

Biogas is generated during anaerobic digestion when microorganisms break down (eat) organic materials in the absence of air (or oxygen). Biogas is mostly methane (CH4) and carbon dioxide (CO2), with very small amounts of water vapor and other gases.

What is slime bulking?

Polysaccharide bulking, also known as “slime bulking,” happens when activated sludge bacteria produce too much polysaccharide. This may occur when the mix is low in nutrients or oxygen, or when the food to microorganism (F/M) ratio is too high. … This can happen when the F/M ratio is too high or in low oxygen conditions.

What is sewage sickness?

Explanation: Sewage sickness: When sewage is applied continuously on a piece of land, the soil pores or voids may get filled up and clogged with sewage matter retained in them. This phenomenon of soil getting clogged is known as sewage sickness of the land.

How is filamentous treated?

Physical/Mechanical Control Mechanical control of filamentous algae usually involves netting or raking the algae mats from the pond surface. If this method is used, it is important to dispose of the algae mats away from the pond edge to prevent nutrients from reentering the pond as the algae decays.

How do you control filamentous bacteria in aeration tanks?

Current approaches for controlling foam includes operational adjustments, additional structures, controlling dissolved oxygen levels, water sprays, steam application, polymer addition, chlorination and a novel and ecofriendly approach that is treatment of filamentous bacteria with the specific phages.

How do I stop my aeration tank from foaming?

Dissolved oxygen (DO) parvicella was eliminated by increasing DO to 2-3 mg/L[4]. As an effective control for sludge bulking and foaming, aerobic selectors with high DO (>2mg/L) are often placed before aeration tank to inhibit the growth of filamentous bacteria[3].

How do you lower the pH of effluent?

Wastewater with a low pH is generally neutralized using sodium hydroxide (NaOH), lime (CaO), magnesium hydroxide (Mg(OH)2), or calcium hydroxide (Ca(OH)2). Wastewater with a high pH is generally neutralized with sulfuric acid (H2SO4), hydrochloric acid (HC1), or carbon dioxide (CO2).

How do you increase the pH of effluent?

1. Calcium oxide or calcium hydroxide (as lime slurry)
2. Sodium hydroxide (caustic soda)
3. Sodium carbonate (soda ash) or sodium bicarbonate.
4. Magnesium hydroxide or magnesium bicarbonate.

What does a pH of 5 in urine mean?

According to the American Association for Clinical Chemistry, the average value for urine pH is 6.0, but it can range from 4.5 to 8.0. Urine under 5.0 is acidic, and urine higher than 8.0 is alkaline, or basic.

How much MLSS maintain in aeration tank?

suspended solids (MLSS) is maintained in the aeration tank of the order of 3000 to 6000 mg/L and mean cell residence time of 5 to 15 days is maintained.

Why is MLSS low in aeration tank?

For any conventional activated-sludge process, the probable causes of cloudy effluent include that mixed-liquor suspended solid (MLSS) in the aeration tank is low due to process start-up, organic-loading increase, toxic-shock loading or over-aeration, causing mixed liquor floc to shear or improper DO levels maintained …

What should be the MLSS in aeration tank?

The typical optimum MLVSS-to-MLSS ratio in activated sludge plants is between 0.7 and 0.8. Mixed Liquor Suspended Solids (MLSS) is the suspended solids in the mixed liquor of an aeration tank. Well designed and operated primary clarifiers should remove from 20 to 40 percent of BOD.