Define Flashcards
(24 cards)
Define SVI
The volume in milliliter (mL) occupied by one gram (g) of activated sludge mixed liquor after 30 minutes of settling.
For an Activated sludge plant to be considered operating well. It will have an SVI range of?
80-120mL/g
What happens when the SVI goes gown?
Settling too fast and get pin flock which can go through the filters.
What happens when the SVI is too high. ?
The sludge isn’t settling well
This chemical is frequently used to raise the pH of either wastewater or provide alkalinity for “sour” anaerobic digester.
Lime
Hydrated Lime
Calcium hydroxide
Chemical used as a flocculent to improve suspended solids removal in a primary clarifier.
Ferric chloride.
Chemical added to anaerobic digesters to control the concentration of sulfur (Hydrogen Sulfide) in the digester gas.
Ferrous chloride.
Chemical used primarily as a coagulant in CEPT and to precipitate phosphorous in primary, secondary or tertiary treatment.
Aluminum sulfate
Also known as “Bioxide”. Commonly added in collection systems or at the influent structure in order to reduce or eliminate the production of hydrogen sulfide.
Calcium Nitrate
This chemical is an alkaline liquid solution commonly called “bleach”. 14% chlorine.
Sodium hypochlorite
White crystalline material which contains approximately 70% available chlorine. Used in small scales. Due to high costs.
Calcium Hypochlorite.
DAFT operational controls
Air/solids ratio - provides enough air to float the solids influent to the unit.
Range: .03-.05 lb air/lb TS
Solids loading. 3-5 lb TSS/hr•ft2
Typical range. 1-2 lb TSS/ he •ft2
Sludge Conditioning. - polymer added. 5-15 lb dry polymer/ton of TSS
Flight speed.
Belt Filter Press (BFP) operational controls
Belt speed: 2-5 feet/min.
Ideal is slowest possible without causing “washout”.
Hydraulic Loading: flow rate applied to the belt per foot of belt width.
Recommended: 10-25 gal/min •ft
Sludge conditioning. : polymer necessary.
Feed sludge: primary only.
Belt tension: increased tension = more water being squeezed from the cake. (Higher TSS%).
Belt porosity: proper cleaning and tension.
BFP solid washout problem. What’s the cause and the corrective steps. ?
Cause: insufficient polymer
Hydraulic loading too high
Belt speed too low
Belt binding.
Solutions : Increase polymer Lower fees rate Increase belt speed Increase washwater flow.
BFP Poor filtrate problem.
Cause: solids washout
High Belt Porosity
Solutions decrease belt tension. Properly wash belt Increase belt speed. Lower fees rate Increase polymer
BFP wet cake problem.
Cause and solution.
Cause
Belt speed too high
Belt tension too low
Solution.
Rescue belt speed.
Increase belt tension.
Centrifuge operational controls.
Bowl speed:
Typically bowl turns 800-2,800 rpm producing 500-3,000 “Gs”
The higher the speed the dryer the cake.
Differential Scroll Speed.
Controls how fast cake is moved out of the bowl.
Higher differential = wetter cake
Pool Depth.
Greater pool depth reduces the time solids spend in the beach resulting in wetter cake.
Sludge Conditioning
Add appropriate amount of polymer.
Feed sludge:
Gravity Thickener operational controls:
Sludge blanket thickness :
5-8 feet thick.
SVR - Sludge Volume Ratio
The detention time of solids in the thickener
Feed sludge: separated primary with secondary.
Temperature: cooler temps
Sludge age: with high-MCRT
Hydraulics loading.
Primary - 400-800 gal/d •ft2
Solids loading:
Primary sludge: 20-30 lbTS(S)/d•ft2
Trickling filter: 8-10 lbTS(S)/d•ft2
WAS. : 5-8 lbTS(S)/d•ft2
Primary sludge+trickling filter humus:
10-20 lbTS(S)/d•ft2
Primary sludge + WAS :
6-12 lbTS(S)/d•ft2
Types of ponds
Stabilization
Oxidation
Polishing
Waste treated in a stabilization pond?
Raw
Waste water treated in an Oxidation pond?
Primary effluent
What type of wastewater is treated in a polishing pond?
Secondary effluent.
Pond that has an aerobic and anaerobic layer.
Stabilization. Or called facultative.
