Table of Contents
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).
How do you calculate sludge?
Sludge volume index ( SVI ) is calculated by dividing the settleability by the MLSS concentration. The SVI is always expressed in mL/g.
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 I activate sludge?
Process description Aeration tank where air (or oxygen) is injected in the mixed liquor. Settling tank (usually referred to as “final clarifier” or “secondary settling tank”) to allow the biological flocs (the sludge blanket) to settle, thus separating the biological sludge from the clear treated water.
What causes sludge to float?
And more importantly, what can be done to control it. First floating sludge is most often caused by: Denitrification – small nitrogen gas bubbles float the sludge in the clarifier creating floating sludge chunks with small bubbles entrapped. Fats, Oils & Grease – simply put, FOG floats on water.
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.
How do you calculate sludge retention time?
The solids retention time (SRT) is the time the solid fraction of the wastewater spends in a treatment unit. It is the quantity of solids maintained in the reactor divided by the quantity of solids coming out of the reactor each day: SRT = V *Cd / Qout* Cout.
How do you calculate sludge in STP?
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 would happen if no sludge is wasted in the activated sludge process?
Wasting removes solids buildup in the activated-sludge system, formed when solids amounts in the aeration-tank influent are greater than the solids amounts in the secondary-clarifier effluent. If sludge is not wasted, the secondary clarifier eventually fills up with solids.
What is the range of MLSS?
MLSS/MLVSS The mixed liquor suspended solids (MLSS) concentration is a measure of the total concentration of solids in the aeration tank and includes both inert and organic solids. Typical MLSS concentrations for conventional activated sludge plants range from 2,000 to 4,000 mg/L.
How many types of sludge are there?
In the present paper an alternative approach has been followed. A mathematical model was proposed and identified on a set of six different types of sludge (primary, secondary and mixed sludge from both urban and industrial WWTP).
What is return activated sludge?
Return Activated Sludge (RAS) – The settled activated sludge (biomass) that is collected in a secondary clarifier and returned to the secondary treatment process to mix with incoming wastewater. This returns a concentrated population of microorganisms back into the aeration basin.
DO level of aeration tank?
and Dissolved oxygen (DO). Dissolved oxygen levels in the aeration tank must be maintained at 1-3 mg/L for effective treatment. Low levels of DO will result in the death of the microbial biomass, which is timely and expensive to reestablish.
What is treated sludge used for?
Overview. Sewage sludge is a mud-like residue resulting from wastewater treatment. Sewage sludge contains heavy metals and pathogens such as viruses and bacteria. It also contains valuable organic matter and nutrients such as nitrogen and phosphorus, and can therefore be very useful as a fertilizer or soil improver.
What happens when activated sludge?
The activated sludge process is a means of treating both municipal and industrial wastewater. The flocs can be removed in the secondary clarifier by gravity settling and some of this sludge is recycled from the clarifier back to the reactor. The effluent can then be discharged to final polishing.
What are sources of sludge?
Primary sludge is generated from chemical precipitation, sedimentation, and other primary processes, whereas secondary sludge is the activated waste biomass resulting from biological treatments. Some sewage plants also receive septage or septic tank solids from household on-site wastewater treatment systems.
What is MLSS test?
MLSS testing measures the total concentration of mixed liquor suspended (non-soluble) solids in the aeration basin of an activated sludge system. In order to test the mixed liquor suspended solids (MLSS) a well-mixed sample should be filtered through a weighed standard glass-fiber filter.
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.
How much sludge is produced each day?
Specific sludge production in wastewater treatment varies widely from 35 to 85 g dry solids per population equivalent per day (gTS PE-1 d-1).
How does the chemical sludge appear?
How does the chemical sludge appear? Explanation: In case the sludge contains iron it is red in colour. In case it is lime sludge, it is grayish brown in colour. This sludge also has an objectionable odour.
What is sludge made up of?
Sewage sludge is composed of both inorganic and organic materials, large concentrations of some plant nutrients, much smaller concentrations of numerous trace elements¹ and organic chemicals, and some pathogens.
What is the difference between primary and secondary sludge?
It is sludge formed during primary sewage treatment. It is sludge formed during secondary sewage treatment. A lot of decomposition occurs during the formation of primary sludge. Very little decomposition occurs during the formation of activated sludge.
How is MLSS measured?
MLSS is measured by filtering a known volume of the mixed liquor sample, which is the same way that suspended solids are measured in wastewater. These measurements allow engineers to adjust the flow rate of return sludge from the secondary clarifier into the secondary treatment reactor.
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 many types of sludge are present?
Explanation: There are two types of sludge present, primary and secondary sludge.
