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23 Cards in this Set
- Front
- Back
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Activated Sludge Process |
A biological process that utilizes microorganisms to convert organic and certain inorganic matter from wastewater into cell mass.The activated sludge is separated from the liquid by clarification. |
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Activated sludge is either returned RAS and or wasted WAS. |
Activated sludge is commonly used as a wastewater treatment process because it is an effective and versatile treatment process and capable of a high degree of treatment. |
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The roll of microorganisms have in the activated sludge process. |
Microorganisms convert dissolved and particulate organic matter, measured as biochemical oxygen demand (BOD), into cell mass. |
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Conventional activated sludge process, microorganisms: |
use oxygen to break down organic matter (food) for their growth and survival. |
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As wastewater moves through the aeration basin, |
Food (BOD) decreases with a resultant in crease in cell mass (mixed liquor suspended solids (MLSS concentration).
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Describe the environmental factors that influence the health and growth of microorganisms. |
The activated sludge wastewater process must operate under proper environmental conditions to support a healthy, growing population of microorganisms. |
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The operator must monitor the activated sludge process: |
To ensure the right environmental conditions are being provided for the microorganisms. Efficient wastewater treatment plant performance will then be achieved. |
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What seven factors influence activated growth process: |
Food, Flow, Oxygen, Temperature, pH, Nutrients, Toxitcity. |
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Food
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Incoming wastewater to a treatment plant provides the food that microorganisms need for their growth and reproduction.
Mostly organic material, themore soluble the material the easier the microorganism can use it. |
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Food: The amount and type of organic loading affects the growth of microorganisms: |
In fluent total BOD and soluble BOD are measurements an operator can make to determine the type of incoming food for microorganisms. |
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Flow |
Incoming wastewater must come through a plant at a rate that allows microorganisms sufficient time to consume the incoming food and to settle properly. |
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Flows: High flow can: ______ Extremely high flow can:____ |
Shorten the time necessary for the full treatment of wastewater. Wash microorganisms out of the plant through the final clarifier. |
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Oxygen |
Bacteria in the activated sludge process need free oxygen (O2) to convert food into energy for their growth. |
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Oxygen: Optimal performance |
Oxygen in the aeration tanks for the microorganisms (typically 1.0 to 3.0 mg/L). Aeration basin dissolved oxygen (DO) concentrations (mg/L) are measured continuously in many plants to ensure adequate oxygen is available. |
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Temperature |
All biological and chemical reactions are affected by temperature. Microorganisms' growth and reaction rates are slow at cold temps. and much faster at warmer temps. |
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Temperature: Microorganisms do best under: |
10 C to 25 C. Temperature and should routinely be measured & recorded. |
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pH |
biological & chemical reactions are affected by pH. Microorganisms do well in a pH environment between 6.0 and 9.0. Acidic (low pH) or alkaline (high pH) adversely affect microorganism growth and survival. Operators measure both influent and aeration basin pH to ensure proper conditions. |
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Toxicity |
Income wastewater to a treatment plant may at times contain materials or compounds that are toxic to microorganisms. Depending on the concentrations of toxic material, microorganisms could be destroyed or their metabolic rates affected, impairing the WW. treatment plant efficiency. |
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Protozoa |
Protozoa are single-celled microscopic organisms, several hundred times larger than bacteria. |
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Describe the types of protozoa and organisms commonly found in activated sludge and observable under a microscope.
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There are 4 types of protozoa commonly found in activated sludge, they are identified by their method of movement. Amoebae, ciliates (free swimming and stalked), flagellates, and suctoreans. Rotifers are multi-celled (metazoa) organisms also commonly found in activated sludge systems. The relative predominance of these protozoa is commonly associated with the age of activated sludge. |
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The growth of filamentous organisms occur due to the following conditions |
Low DO F/M ratio Low pH High sulfides Nutrient deficiency Excessive grease |
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Nitrifying bacteria convert ammonia to nitrate and work best under what conditions. |
DO greater than 1.0 mg/L pH between 7.0 to 8.5 Alkalinity greater than 50 mg/L Temp. between 50 F and 85 F (10 C to 30 C) |
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Environmental conditions necessary to support the growth of dentrifying bacteria. Dentrification converts nitrite and nitrate to nitrogen gas.
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Do less than 0.2 mg/L pH between 7.0 and 8.5 Adequate organic matter (BOD) Temp. between 50 F and 85 F (10 c to 30 C) |
