How do you resolve floating sludge trouble in secondary clarifier?

How do you resolve floating sludge trouble in secondary clarifier?

If sludge is rising and clumping in the secondary clarifier, increase return sludge rates and or lower aeration rates a little. Lowering sludge age can also help, if it is a little too high. 4. Don’t forget that slow-settling sludge can be caused by both old and young sludge.

How do you prevent denitrification in secondary clarifier?

So what can you do to prevent denitrification in secondary clarifiers:

1. Control bed depths to between 2 – 3 feet by adjusting recycle rates.
2. Hydraulic residence time in clarifier 2 – 4 hours.
3. Warm temperatures increase denitrification (high metabolic activity) so problem is usually more pronounced in summer months.

How do I reduce SVI?

Raising the amount of MLSS (reducing waste rates) changes the density of the floc, creating a heavier sludge particle. The more dense the particle, the more likely it will settle faster. The higher milligram per liter MLSS reduces the SVI result.

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 rising sludge in secondary clarifier?

Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is compacted, and then starts to rise to the surface, usually as a result of denitrification, or anaerobic biological activity that produces carbon dioxide or methane.

What are major reasons for sludge bulking in the secondary clarifier?

Sludge bulking occurs when the sludge fails to separate out in the sedimentation tanks. The main cause of sludge bulking is the growth of filamentous bacteria. Filamentous microorganisms grow in long strands that have much greater volume and surface area than conventional floc and are very slow to settle.

What is a good SVI number?

SVI = 100 to 200 mL/g. Most activated sludge plants seem to produce a clear, good-quality effluent with an SVI in this range. SVI = 250 mL/g or higher. At this elevated SVI, the sludge settles very slowly and compacts poorly in the settleability test.

How do you read a Settleometer?

We collect the sample, pour it into the settleometer, set the timer for 30 minutes and walk away. When the 30-minute alarm sounds, we get the reading, write it down or log it in somewhere, and pour out the container. When we collect the readings every five minutes, we stay close to the test while it’s running.

What is good MLSS?

typical values are; Desirable range: MLSS around 3,000 and mg/l and SVI = 100 to 200 ml/g. SVI = 250 ml/g or higher (usually the system is still in startup phase) would cause poor selling and poor compaction of settled sludge (filamentous sludge bulking as well). MLSS would be around 1000 mg/L.

What kills activated sludge?

Effective chlorine dosages usually are in the range 1-10 pounds chlorine/1000 pounds MLVSS inventory/day (2-4 should work). Chlorine dosage should be started low and increased until effective. Sludge settleability usually improves within 1-3 days if the correct chlorine dosage is applied.

What happens secondary clarifier?

The secondary clarifier can be described as a circular basin where effluent from the activated sludge process is held. The biomass of microorganisms settles to the bottom in the form of activated sludge. After settling over a period of time, this biomass of microorganisms is returned to the first aeration tank.

How do I stop sludge when 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.

Which is the RAS rate of a clarifier?

RAS rate is the volume of settled sludge collected from the bottom of the secondary clarifier and returned to the influent of the upstream aeration basin(s). Equitable clarifier influent flow distribution is a critical clarifier operational performance parameter and often is overlooked.

How is RAS rate related to surface overflow rate?

settling characteristics allow the sludge particles to be pulled down faster than the upward surface overflow rate velocity, the particles eventually will end up in the sludge blanket. RAS rate is the volume of settled sludge collected from the bottom of the secondary clarifier and returned to the influent of the upstream aeration basin(s).

What does the secondary clarifier do in a WWTP?

The secondary or final clarifier is one of the most important unit processes and often determines the capacity of a WWTP. Clarification is a solids separation process, which results in the removal of 99 percent or more of the suspended solids (biological floc) received from the activated sludge system.