Table of Contents
The sludge age is the amount of time, in days, that solids or bacteria are under aeration. Sludge age is used to maintain the proper amount of activated sludge in the aeration tanks.
What is a good sludge age?
The common range for sludge age for a conventional activated sludge plant is between 3 and 15 days. For extended aeration activated sludge plants the range is between about 15 and 30 days. Generally during the winter months, higher sludge ages are required to maintain a sufficient biological mass.
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 activated sludge made of?
Activated sludge is also known as waste activated biosolids or waste activated solids. The sludge consists of a mixed blend of microorganisms, 95% of which are a variety of mostly aerobic species of bacteria, according to Science Direct.
How do I increase sludge in my aeration tank?
If the influent solids are primarily organic and result in increased Biochemical Oxygen Demand (BOD) loading, then you may need to increase the amount of microorganisms (MLVSS) in the aeration tank. This is commonly accomplished by reducing the sludge wasting rate.
How do you get rid of floating sludge?
Floating Sludge
- Increase dissolved oxygen prior to the clarifier.
- Improve treatment to reduce residual soluble BOD.
- Reduce sludge retention time in the clarifier.
- Optimizing denitrification in its desired location.
- Limit nitrification which forms nitrate (only possible if there is no ammonia limit on the effluent).
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 is the formula for sludge age?
The sludge age of an activated sludge process can be calculated by dividing the pounds of suspended solids or MLSS in the aeration tanks by the pounds of suspended solids that enter the aeration tanks (Equation I. 10).
What is required to keep the activated sludge suspended?
To maintain aerobic conditions and to keep the activated sludge suspended, a continuous and well-timed supply of oxygen is required. It consists of flocs of bacteria, which are suspended and mixed with wastewater in an aerated tank.
What causes sludge to float?
When entrapped in floc, excessive grease or oil can cause floating biomass. This appears as a scum blanket that can cover the entire clarifier. Viscous bulking or billowing sludge – viscous bulking can sometimes create floating sludge (more often it is just billowing over the weir versus floating).
Where is activated sludge used?
In a sewage (or industrial wastewater) treatment plant, the activated sludge process can be used for one or several of the following purposes: oxidizing carbonaceous matter: biological matter. oxidizing nitrogeneous matter: mainly ammonium and nitrogen in biological materials. removing phosphate.
What is the difference between sludge and activated sludge?
This sediment is called activated sludge.
| Primary sludge | Activated sludge | |
|---|---|---|
| (iii) | It does not require aeration | Formation of activated sludge requires aeration |
| (iv) | A lot of decomposition occurs during the formation of primary sludge | Very little decomposition occurs during the formation of activated sludge |
How do I control bulk sludge?
Control of low F/M bulking is by reducing the aeration basin MLSS concentration and increasing the F/M (manipulating the “M” component). Lowering the MLSS concentration may not be suitable for many plants as this may cause the loss of nitrification and increase waste sludge production.
How do you control sludge?
To control activated sludge, you need to “have a handle” either on aeration, sludge-wasting or return-sludge flow.Control sludge wasting
- Bacteria growth rate.
- Oxygen consumption.
- Mixed liquor settle-ability.
- Occurrence of foaming/frothing.
- The possibility of nitrifying.
- Nutrient quantities needed.
- Final effluent quality.
Why foaming occurs in aeration tank?
Air in the aeration unit, nitrogen gas that is produced during denitrification in anaerobic conditions, methane and carbon dioxide that is produced in anaerobic digesters may cause foaming in units (Hug 2006).
What causes bulking sludge?
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. Under certain growing conditions, filamentous organisms predominate.
How do you measure sludge concentration?
How to calculate the SVI?
- Take a sample from the aeration tank.
- Let the sample settle for 30 minutes before analysis begins.
- Analyze the sample and find out the concentration of suspended solids.
- Divide the wet volume of the settled sludge (represented in mL/L) by the MLSS value from the last step.
What is return activated sludge?
Settled activated sludge that is collected in the secondary clarifier or the membrane basin and returned to the aeration basin to mix with incoming raw or primary settled wastewater.
How do I activate sludge?
The process involves air or oxygen being introduced into a mixture of screened, and primary treated sewage or industrial wastewater (wastewater) combined with organisms to develop a biological floc which reduces the organic content of the sewage.
What is the purpose of sludge return in activated sludge treatment process?
The purpose of Return Activated Sludge (RAS) is to prevent loss of microorganisms from the aeration tank and maintain an adequate population for treatment of the wastewater. As microbes metabolize their substrate, they grow and multiply in number.
How does the activated sludge appear in Colour?
Dark brown/earthy odor indicates old sludge with high solids (increase wasting). Black color/rotten-egg odor indicates septic conditions, low dissolved oxygen concentration, and too low of an airflow rate (increase aeration). A light chocolate brown mixed liquor color indicates a well-operated activated sludge process.
What is sludge concentration?
Sludge concentration may be defined. as the reduction in moisture content. of the sludge in order to decrease. significantly sludge volume while still. maintaining its fluid properties.
How is sludge calculated?
Calculation : The daily sludge mass produced = ( 100,000 ) ( 0.080 ) = 8,000 kg dry SS / day. Since 97 % MC is 3 % SC or approximately 30 kg dry SS / m 3 sludge, the daily volume produced is 8,000 / 30 = 267 m 3 .
What sludge means?
Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. Sludge can consist of a variety of particles, such as animal manure.
