What are the steps of activated sludge process?
Treatment Steps
- Step 1: Screening and Pumping.
- Step 2: Grit Removal.
- Step 3: Primary Settling.
- Step 4: Aeration / Activated Sludge.
- Step 5: Secondary Settling.
- Step 8: Oxygen Uptake.
- Sludge Treatment.
How does an activated sludge plant work?
The activated sludge process in the treatment of wastewater involves blowing oxygen or air into raw, unsettled sewage. The sewage is bubbled, and sewage liquor is discharged into an activated sludge chamber. Live bacteria settle to the bottom of the tank and dead bacteria float to the top.
What is an activated sludge treatment plant?
The activated sludge process is a multi-chamber reactor unit that uses highly concentrated microorganisms to degrade organics and remove nutrients from wastewater, producing quality effluent. The goal is to maintain aerobic conditions and to keep the activated sludge suspended.
How is activated sludge calculated?
The activated sludge operational parameters calculated by the Excel formulas in the spreadsheet are: recycle activated sludge flow rate, Qr; waste activated sludge flow rate, Qw, and aeration tank food to microorganism ratio, F:M. The equations used are as follows: Qr = (X – Xo)/(Xw – X) Qw = (8.34*V*X)/(8.34*SRT*Xw)
Why activated sludge is called activated?
They aerated the waste-water continuously for about a month and were able to achieve a complete nitrification of the sample material. Believing that the sludge had been activated (in a similar manner to activated carbon) the process was named activated sludge.
Which bacteria play important role in activated sludge treatment?
Protozoa play a critical role in the treatment process by removing and digesting free swimming dispersed bacteria and other suspended particles. This improves the clarity of the wastewater effluent.
What is the F M ratio?
The term Food to Microorganism Ratio (F/M) is actually a measurement of the amount of incoming food ( Lbs of Influent CBOD) divided by the Lbs of Microorganisms in your system. If you have an activated sludge system, you should determine your F/M ratio regularly.
How do you calculate SVI and SDI?
A calculation used to indicate the settleability of sludge in a secondary clarifier or effluent that is related to the calculation for sludge volume index (SVI). The weight in grams of 100 milliliters of sludge after settling for 30 minutes. SDI = 100/SVI.
What happens to sludge from a sewage treatment plant?
Sewage sludge is a product of wastewater treatment. Once treated, sewage sludge is then dried and added to a landfill, applied to agricultural cropland as fertilizer, or bagged with other materials and marketed as “biosolid compost” for use in agriculture and landscaping.
How is activated sludge used in wastewater treatment?
Activated sludge is a biological process that utilizes microorganisms to convert organic and certain inorganic matter from wastewater into cell mass. The activated sludge is then separated from the liquid by clarification. The settled sludge is either returned (RAS) or wasted (WAS). Activated sludge is commonly used as a wastewater treatment
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.
What should be the settling value of sludge?
A good settling sludge (textbook value) is 100, but can commonly be between 80-150. Food to microorganism ratio (F:M or F/M) is the amount of food (BOD5) provided to the microorganisms (MLVSS or MLSS) in the aeration basins.
How does H2S reduce the pH of activated sludge?
One mg/L of H2S reduces the activated sludge OUR by 50% at pH 7, and the H2S dose to give a 50% OUR reduction increases to 100 mg/L at pH values above pH 8. It is advised to add lime or other alkaline agent to the aeration basin to raise the pH to 7.5 or above if sulfide toxicity is occurring.