What is the standard volume of activated sludge used to conduct an SVI test?

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 is the best range of SVI for proper operations of STP ETP?

SVI = 100 to 200 mL/g. Most activated sludge plants seem to produce a clear, good-quality effluent with an SVI in this range.

How is SVI calculated?

determine the suspended solids concentration for a sample of the same mixed liquor; calculate SVI by dividing the measured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in grams/L.

How do you increase sludge age?

Normally, a bright white foam will occur on the aeration section of the plant, looking similar to soap suds. All of the sludge from the clarifier should be returned to the aeration section of the plant to raise the sludge age as soon as possible.

What methods are used to treat sludge?

Many sludges are treated using a variety of digestion techniques, the purpose of which is to reduce the amount of organic matter and the number of disease-causing microorganisms present in the solids. The most common treatment options include anaerobic digestion, aerobic digestion, and composting.

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.

How do I increase MLSS in aeration tank?

Fill the aeration tank with 50% primary treated wastewater + 50 % water and add some bacterial seed material (say 500 litre mixed liquor from an operating ASP plant or 100 kg cattle dung) aerate for 12 hours (as a batch reactor) to acclimatize and develop more biomass.

How do I control my 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.

What is a good SVI?

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.

What should the SVI be for activated sludge?

SVI is expressed as the ratio of the volume in milliliters of activated sludge settled from a 1,000-mL sample in 30 minutes divided by the concentration of mixed liquor in milligrams per liter multiplied by 1,000. A good settling sludge (textbook value) is 100, but can commonly be between 80-150.

How does an operator increase the sludge volume index?

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.

What should the SVI be for a treatment plant?

The SVI is 133. This might be a good SVI for a plant providing a good-settling sludge that first forms a blanket, and then traps fine particles as it slowly settles and compacts.

What causes the SVI of a sludge plant to change?

The SVI of any activated sludge plant will change in response to the operating conditions of the plant. In particular, under feeding or over feeding the plant can cause a huge effect on the SVI. Note COD is not a good control in itself.