Environmental Engineering Chapter 4: Microbiology Applications

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Questions and Answers

What is the primary goal of denitrification in wastewater treatment?

To convert nitrate to nitrogen gas (correct)

To increase oxygen levels in the treatment system

To reduce the pH of the wastewater

To increase the growth of aerobic bacteria

What is required to promote denitrification in a wastewater treatment system?

Higher pH levels

Higher temperatures

An external carbon source (correct)

Increased oxygen supply

What is the result of intermittent aeration in a wastewater treatment system?

Increased growth of aerobic bacteria

Increased oxygen supply

Creation of an anoxic environment (correct)

Reduced nitrate removal

What is the purpose of modifying the activated sludge process in wastewater treatment?

To improve nitrate removal Signup and view all the answers

What is the end product of denitrification?

Nitrogen gas Signup and view all the answers

What is the condition required for denitrification to occur?

Anoxic conditions Signup and view all the answers

What is the role of denitrifying bacteria in wastewater treatment?

To convert nitrate to nitrogen gas Signup and view all the answers

What is the benefit of adding an additional treatment tank or zone for denitrification?

To improve nitrate removal Signup and view all the answers

What is the key principle of Enhanced Biological Phosphate Removal (EBPR)?

To create an environment that promotes the growth of specific bacteria known as polyphosphate-accumulating organisms (PAOs). Signup and view all the answers

In the EBPR process, what happens in the Anaerobic Zone?

The phosphorus is released from the biomass in the form of orthophosphate. Signup and view all the answers

What is the purpose of the Aerobic Zone in the EBPR process?

To support the growth of aerobic bacteria responsible for organic matter removal. Signup and view all the answers

What happens to the PAOs in the Aerobic Zone?

They assimilate phosphorus and store it as intracellular polyphosphate. Signup and view all the answers

What is the purpose of the Settling and Sludge Separation step in the EBPR process?

To separate the clarified effluent from the biomass. Signup and view all the answers

What happens to the settled biomass in the EBPR process?

It is recycled back to the anaerobic zone. Signup and view all the answers

What is the benefit of the EBPR process?

It facilitates the removal of phosphorus from the wastewater. Signup and view all the answers

How does the energy production compare between anaerobic and aerobic conditions in the EBPR process?

More energy is produced under aerobic conditions. Signup and view all the answers

What is the primary purpose of regeneration adsorption?

To restore the adsorption capacity of saturated adsorbent materials Signup and view all the answers

What is the cryocondensation process used for?

Collecting and condensing gases or vapors at low temperatures Signup and view all the answers

How do bio-scrubbers remove pollutants from industrial exhaust gases?

By using microorganisms to metabolize pollutants Signup and view all the answers

What is the key feature of bio-scrubbers?

The recirculation of water laden with microorganisms Signup and view all the answers

What happens to the pollutants in a bio-scrubber system?

They are metabolized by microorganisms Signup and view all the answers

What is the main difference between bio-scrubbers and bio-trickling filters?

Whether water is recirculated Signup and view all the answers

How do bio-trickling filters remove pollutants from industrial exhaust gases?

By using microorganisms to metabolize pollutants Signup and view all the answers

Where do microorganisms grow in a bio-trickling filter system?

Within the media Signup and view all the answers

What is the purpose of periodically removing excess sludge from the system?

To maintain the proper sludge balance Signup and view all the answers

What is the primary function of Nitrosomonas bacteria in the nitrification process?

To convert ammonia to nitrite Signup and view all the answers

Why is aeration often provided in the treatment system during nitrification?

To maintain the necessary oxygen levels for bacterial metabolism Signup and view all the answers

What is the purpose of filtration after nitrification in drinking water production?

To enhance the quality of the treated water by reducing turbidity and removing remaining impurities Signup and view all the answers

Why are iron and manganese challenging in water treatment?

Because they can pose challenges due to their presence as dissolved or particulate forms Signup and view all the answers

What is the purpose of pre-oxidation before the water enters the rapid sand filters?

To convert the dissolved forms of iron and manganese into their insoluble forms Signup and view all the answers

What is one method of achieving the oxidation step in pre-oxidation?

Adding oxidizing agents like chlorine Signup and view all the answers

What is the overall goal of the treatment process in drinking water production?

To enhance the quality of the treated water by reducing turbidity and removing impurities Signup and view all the answers

What is the primary purpose of rapid sand filters?

To remove insoluble iron and manganese particles Signup and view all the answers

What is the typical depth of the sand bed in a slow sand filter?

0.6 to 1.5 meters Signup and view all the answers

What is the biological layer on the top surface of the sand bed called?

Schmutzdecke Signup and view all the answers

What is the primary mechanism of slow sand filtration?

Combination of physical, biological, and chemical processes Signup and view all the answers

What is the purpose of the gravel layer in rapid sand filters?

To support the fine sand layer Signup and view all the answers

What is non-regeneration adsorption?

A process that captures and removes contaminants from a fluid or gas stream Signup and view all the answers

How do slow sand filters operate?

At a low flow rate Signup and view all the answers

What is the primary difference between rapid sand filters and slow sand filters?

The mechanism of filtration Signup and view all the answers

Study Notes

Application of Microbiology in Environmental Engineering

Environmental microbiology plays a crucial role in environmental engineering, particularly in the degradation of pollutants, solid waste management, water and wastewater treatment, drinking water production, and air pollution control.

Water and Wastewater Treatment

Nitrate removal can be achieved by modifying the activated sludge process through the addition of specific treatment steps or altering operational parameters.
Denitrification is a biological process that converts nitrate (NO3-) to nitrogen gas (N2) under anoxic conditions, requiring an external carbon source and an additional treatment tank or zone.
Intermittent aeration can promote nitrate removal by periodically reducing or stopping the aeration, creating an anoxic environment.

Enhanced Biological Phosphate Removal (EBPR)

EBPR is a process that creates an environment within the activated sludge process that promotes the growth of polyphosphate-accumulating organisms (PAOs), which take up and store phosphorus within their cells.
The EBPR process involves anaerobic and aerobic zones, where PAOs release and store phosphorus, and then settle and separate in the sludge separation stage.
The process also involves sludge return and wasting, where a portion of the settled biomass is recycled back to the anaerobic zone.

Drinking Water Production

Oxidation of ammonia (nitrification) followed by filtration is an important process in drinking water production to remove ammonia and convert it to nitrate.
During nitrification, ammonia is first oxidized to nitrite (NO2-) by Nitrosomonas bacteria, and then further oxidized to nitrate (NO3-) by Nitrobacter bacteria.
Filtration involves passing the water through a bed of granular media (such as sand and gravel), which enhances the quality of the treated water by reducing turbidity and removing remaining impurities.

Iron and Manganese Removal

Iron and manganese are commonly found in groundwater sources and can pose challenges in water treatment due to their presence as dissolved or particulate forms.
Pre-oxidation is often employed to convert the dissolved forms of iron and manganese into their insoluble forms before the water enters the rapid sand filters.
Rapid sand filters consist of layers of different-sized media, which effectively trap and remove the insoluble iron and manganese particles.

Slow Sand Filters

Slow sand filters are a type of water treatment technology that uses a bed of fine sand to remove impurities and improve water quality.
The filters operate at a low flow rate and rely on biological, physical, and chemical processes to purify the water.
A biological layer, called the "schmutzdecke," forms on the top surface of the sand bed, playing a crucial role in the filtration process.

Air Pollution Control

Non-regeneration adsorption refers to a process in which adsorbent materials are used to capture and remove contaminants from a fluid or gas stream without regenerating or reactivating the adsorbent material.
Regeneration adsorption refers to a process in which adsorbent materials are treated or regenerated to restore their adsorption capacity after they have become saturated with contaminants.
Cryocondensation is a process that involves the condensation and collection of gases or vapors by cooling them to very low temperatures.

Bio-scrubber and Bio-trickling Filter

A bio-scrubber is an air pollution control device that utilizes microorganisms to remove pollutants from industrial exhaust gases or other contaminated air streams.
The device relies on microorganisms present in the water that's recirculated through the treatment vessel, which metabolize the offending compounds, leaving clean air to be released.
A bio-trickling filter is an air pollution control technology that combines the principles of both biological treatment and gas scrubbing to remove pollutants from industrial exhaust gases or other contaminated air streams.
The key differentiator of biotrickling filters is that they do not recirculate water.

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Description

Learn about the role of microbiology in environmental engineering, including pollutant degradation, waste management, water treatment, and air pollution control.