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EEC2B > Wastewater Treatment (20b) > Flashcards

Wastewater Treatment (20b) Flashcards

1
Q

Components of domestic wastewater? (2)

A

• Blackwater.
• Greywater.

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2
Q

Blackwater consists of? (2)

A

• Urine.
• Faeces.

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3
Q

Greywater consists of? (3)

A

• Washing.
• Laundry.
• Kitchen.

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4
Q

Industrial wastewater components? (5)

A

• Pharmaceutical industry.
• Landfill leakage.
• Metal industry.
• Catering industry (Abattoir/slaughterhouse).
• Refinery (Oil refinery).

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5
Q

Stages of wastewater treatment? (5)

A

• Pre-treatment.
• Preliminary treatment.
• Primary treatment.
• Secondary treatment.
• Sludge disposal.

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6
Q

Pre-treatment occurrence?

A

Occurs in business/industry prior to discharge.

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7
Q

Pre-treatment purpose?

A

Prevention of toxic chemicals/excess nutrients being discharged in wastewater.

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8
Q

Sanitary sewers?

A

= where water discharged from homes, businesses, and industry enters.

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9
Q

Storm water sewers?

A

= where water from rainwater on streets enters.

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10
Q

Combined sewers?

A

= sewers that carry both sanitary wastes & storm water.

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11
Q

How does water move toward the wastewater plant?

A

Gravity flow.

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12
Q

Lift stations function?

A

Pump water from low-lying areas over hills.

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13
Q

Preliminary treatment purposes? (2)

A

• Removes large objects & non-degradable materials.

• Protects pumps & equipment from damage.

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14
Q

Preliminary treatment equipment? (3)

A

• Bar screen.
• Grit chamber.
• Mesh screen.

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15
Q

Bar screen purpose?

A

Catches large objects that have gotten into the sewer system like bricks, bottles, pieces of wood, etc.

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16
Q

Grit chamber purpose?

A

Removes rocks, gravel, broken glass, etc.

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17
Q

Mesh screen purpose?

A

Removes diapers, combs, towels, plastic bags, syringes, etc.

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18
Q

Primary treatment?

A

= physical process.

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19
Q

Primary treatment purpose?

A

Reduces the suspended solids & the BOD of the wastewater.

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20
Q

BOD stands for?

A

Biochemical Oxygen Demand.

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21
Q

COD stands for?

A

Chemical Oxygen Demand.

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22
Q

Primary treatment process? (5)

A

● Wastewater flow is slowed down & suspended solids settle to the bottom by gravity.

● The material that settles is sludge.

● Sludge from the primary sedimentation tanks is pumped to the sludge thickener.

● More settling occurs to concentrate the sludge prior to disposal.

● From primary treatment tanks water is pumped to the trickling filter for secondary treatment.

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23
Q

Secondary treatment?

A

= biological process.

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24
Q

Secondary treatment purpose?

A

Utilizes bacteria & algae to metabolize organic matter in the wastewater.

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25
Q

BOD?

A

= measure of the amount of oxygen needed to aerobically decompose organic matter in the water.

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26
Q

Suspended solids?

A

= the quantity of solid materials floating in the water column.

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27
Q

Flow meter?

A

= an instrument that continuously records the volume of water entering the treatment plant.

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28
Q

Eg of secondary treatment processes?

A

Aerobic processes.

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29
Q

Aerobic processes?

A

= presence of dissolved oxygen.

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30
Q

Egs of aerobic processes? (3)

A

• Biofilters.
• Trickling filters.
• Activated sludge.

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31
Q

Why are water samples taken in wastewater treatment?

A

Taken for determination of suspended solids & BOD.

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32
Q

What do measurements of suspended solids & BOD/COD indicate?

A

The effectiveness of treatment processes.

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33
Q

Relationship between suspended solids and BOD, & wastewater treatment processes?

A

As water moves through wastewater treatment processes, Less suspended solids & BOD.

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34
Q

Composition of wastewater? (2)

A

• Inorganics.
• Organics.

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35
Q

Inorganics include? (5)

A

• Ammonia.
• Phosphate.
• Nitrate.
• Carbonate.
• Minerals.

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36
Q

Egs of minerals found in Inorganics? (3)

A

• Calcium.
• Iron.
• Magnesium.

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37
Q

Organics include? (2)

A

• Biodegradable (BOD).
• Non-biodegradable (COD-BOD).

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38
Q

Egs of Biodegradable? (3)

A

• Carbohydrates.
• Proteins.
• FOG.

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39
Q

FOG stands for?

A

Fats, oils & grease.

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40
Q

Egs of Non-biodegradable? (5)

A

• Large particles.
• Complex polymers (plastics).
• Pesticides.
• Pharmaceuticals.
• Surfactants.

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41
Q

Requirements for the growth of microbes? (5)

A

• Temperature.
• pH.
• Water activity.
• Energy source.
• Nutrients.

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42
Q

Egs of nutrients? (5)

A

• C.
• N.
• P.
• Minerals.
• Vitamins.

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43
Q

Relationship between microbial growth & temperature?

A

Higher temperatures, More microbial growth.

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44
Q

Temperature range for microbial growth?

A

0°C – 55°C.

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45
Q

Results if temperature extremes? (2)

A

• Interfere with metabolic processes.
• Harm the organisms.

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46
Q

Kinds of organisms? (3)

A

• Psychrophilic.
• Mesophilic.
• Thermophilic.

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47
Q

Temperatures that Psychrophilics prefer?

A

<5°–35°C.

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48
Q

Temperatures that Mesophilics prefer?

A

20-45°C.

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49
Q

Temperatures that Thermophilics prefer?

A

45-60°C.

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50
Q

Eg of Temperature?

A

Yellowstone’s Grand Prismatic Spring.

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51
Q

4 features of Yellowstone’s Grand Prismatic Spring?

A

● Centre is the hottest (87°C).

● Very clear.

● Water creates concentric circles of varying temperatures.

● Very different environment inhabited by different bacteria types (prismatic colours).

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52
Q

Organism kinds associated with pH? (2)

A

• Acidophiles.
• Alkaliphiles.

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53
Q

pH range for Acidophiles?

A

0-6.

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54
Q

pH range for Alkaliphiles?

A

8-13.

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55
Q

pH range that most bacteria prefer?

A

6-8.

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56
Q

pH range that most fungi prefer?

A

4-7.

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57
Q

Importance of biological treatment? (3)

A

● Responsible for reduction of organic material in wastewater.

● Use organic material as a food supply to support the growth of biomass.

● Uses organic material to provide energy growth resulting in production of CO2 & other metabolic by-products.

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58
Q

Result of production of CO2 & other metabolic by-products by biological treatment?

A

Reduction of total BOD.

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59
Q

Types of microbial communities? (3)

A

• Aerobic.
• Anaerobic.
• Facultative.

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60
Q

Aerobic microbial communities?

A

= utilize oxygen.

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61
Q

Anaerobic microbial communities?

A

= grow in absence of oxygen.

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62
Q

Facultative microbial communities?

A

= can grow with or without oxygen.

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63
Q

Facultative microbial communities feature?

A

Metabolism changes as environment changes from aerobic to anaerobic.

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64
Q

Where do aerobic organisms thrive? (2)

A

Waters that:

• Are well aerated.
• Contain relative high concentrations of dissolved molecular oxygen.

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65
Q

Nutrients required for the growth of microorganisms? (7)

A

• Carbon.
• Notrogen.
• Phosphorus.
• Sulfur.
• Minerals.
• Trace elements.
• Vitamins/Growth factors.

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66
Q

Main nutrients required for growth of microorganisms? (4)

A

• Nitrogen.
• Carbon.
• Phosphorus.
• Sulfur.

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67
Q

Carbon nutrient sources? (2)

A

• Food source.
• CO2.

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68
Q

Nitrogen nutrient sources? (3)

A

• Ammonia.
• Nitrate.
• Simple organics (amino acids).

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69
Q

Phosphorus nutrient source?

A

Inorganic phosphate.

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70
Q

Sulfur nutrient source? (2)

A

• Inorganic sulfate.
• Sime organics.

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71
Q

Minerals include? (5)

A

• Ca.
• Mg.
• Na.
• K.
• Fe.

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72
Q

Trace elements include? (3)

A

• Zn.
• Cu.
• Ni.

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73
Q

Aerobic processes features? (3)

A

● Presence of O2.

● Rapid conversion.

● Release lots of energy.

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74
Q

Energy sources of aerobic processes? (2)

A

• Oxygen (aerobes) [autotrophs].
• Nitrate (facultative).

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75
Q

What do the aerobes produce? (3)

A

• Nitrifiers.
• Sulfur oxidizers.

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76
Q

What do facultative produce?

A

Denitrifiers.

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77
Q

Activated sludge?

A

= kind of biological treatment where the biofilm is in suspension.

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78
Q

What do aerobic organisms require?

A

High rates of oxygen supply for wastewater treatment processes.

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79
Q

Where do Anaerobic organisms thrive?

A

In conditions with little or no molecular oxygen.

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80
Q

How do anaerobic organisms obtain oxygen?

A

Obtain needed oxygen from molecules that contain oxygen.

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81
Q

The complex processes that occur in the absence of oxygen? (2)

A

• Acid-forming phase.
• Methanogenic phase.

82
Q

Acid-forming phase?

A

= where acid forming bacteria hydrolyze the complex organic molecules & convert them into organic acids.

83
Q

Result of Acid-forming phase?

A

Lowers the pH.

84
Q

Methanogenic phase process? (2)

A

● Methane forming bacteria metabolize the acids to CH4 & CO2.

● Amino acids are broken down to form NH4.

85
Q

Result of Methanogenic phase?

A

Raises the pH.

86
Q

Acid-forming phase is AKA?

A

Non-methanogenic phase.

87
Q

Product of Acid-forming phase?

A

Organic acids.

88
Q

Products of Methanogenic phase? (2)

A

• Fats = CH4 & CO2.

• Amino acids = NH4.

89
Q

Energy sources of anaerobic sources? (3)

A

• Sulfate (anaerobes).
• CO2 (anaerobes).
• Fermentation of glucose.

90
Q

Sulfate reducers?

A

= reduction of organic matter generates H2S and other foul-smelling compounds.

91
Q

What conditions do facultative organisms prefer?

A

Aerobic conditions.

92
Q

What conditions facultative organisms easily adapt to?

A

Low oxygen conditions.

93
Q

What do facultative organisms produce when growing anaerobically? (3)

A

• Alcohols.
• Organic acids.
• Other organic chemicals.

94
Q

When are most microbial organisms able to adapt changes in their environment?

A

If changes are gradual.

95
Q

Result of sudden changes / introduction of toxic materials to microbial organisms?

A

Cause harmful/lethal effects to the biological community.

96
Q

Microbial growth phases? (4)

A

• Lag phase.
• Exponential growth phase.
• Stationary phase.
• Death phase.

97
Q

Lag phase?

A

= period for cells to adapt to their new environment.

98
Q

Exponential growth phase?

A

= cells have abundant food & grow without limit during this phase.

99
Q

Stationary phase?

A

= food supply becomes limiting & some cells die while others continue to grow.

100
Q

Death phase?

A

= death processes dominate growth so the number of viable cells begins to decline.

101
Q

Describe microbial growth phase graph?

A

Resemble going up a hill (flat at top due Stationary phase) but decreases due to death phase.

102
Q

Lay out the typical upsets? (8)

A

Heavy Orgainc Load
|
Increased growth/respiration
|
Reduced DO & More sludge to clarify
|
Reduced growth/respiration
|
Inadequate removal (deflocculation of the biomass)
|
Poor settling
|
Worse effluent
|
Increased BOD/COD (high effluent suspended solids)

103
Q

Egs of Secondary treatment processes? (3)

A

• Activated sludge.
• Biofilter.
• Trickling filter.

104
Q

Common wastewater treatment process?

A

Activated sludge tank system.

105
Q

How do the biofilter & trickling filter differ?

A

They differ in the media/way of filter.

106
Q

Biofilter?

A

= where water is filtered by using porous media (LWA) of diameter 2.5mm.

107
Q

Trickling filter?

A

= where water runs over a plastic media and organisms clinging to the media remove organic matter from the water.

108
Q

Secondary treatment process? (2)

A

● After trickling filter water flows to the final clarifiers for further removal of sludge.

● The final clarifiers remove additional sludge and further reduce suspended solids & BOD.

109
Q

Final clarifiers?

A

= another set of primary sedimentation tanks.

110
Q

Primary treatment is AKA?

A

Primary sedimentation.

111
Q

What happens to the solids primary treatment?

A

Settle solids for 2-3 hours in a static, unmixed tank or basin.

112
Q

Result of primary treatment?

A

Primary sludge.

113
Q

Primary sludge?

A

= most sludge resulting from primary treatment.

114
Q

Primary sludge features? (2)

A

• Too toxic.
• Has most enteric microbes.

115
Q

Enteric microbes?

A

= rod-shaped Gram-negative bacteria.

116
Q

Where are enteric microbes found? (2)

A

• In human intestines.
• In animal intestines.

117
Q

Why is most enteric microbes found in primary sludge?

A

It’s because there’s little removal of enteric microbes (~50%) in the primary treatment.

118
Q

Secondary treatment is AKA?

A

Biological treatment.

119
Q

Why can’t primary sludge be used as a fertilizer?

A

It is too toxic and cause death of plants.

120
Q

Result of secondary treatment regarding enteric microbes?

A

Settle out 90-99% enteric microbes.

121
Q

What are enteric microbes broken down into? (2)

A

• Proteolytic enzymes.
• Other degradative enzymes/chemical.

122
Q

What are enteric microbes predated by?

A

Treatment microbes/plankton.

123
Q

Treatment microbes/plankton include? (3)

A

• Amoeba.
• Ciliates.
• Rotifiers.

124
Q

Sludge treatment?

A

= treatment of the settled solids from sewage treatment.

125
Q

Putpose of Sludge treatment?

A

Biological “digestion” to biologically stabilize the sludge solids.

126
Q

Methods for Sludge treatment?(4)

A

• Anaerobic digestion.
• Aerobic digestion.
• Mesophilic digestion.
• Thermophilic digestion.

127
Q

Aerobic digestion?

A

= aerobic biodegradation.

128
Q

Anaerobic digestion?

A

= anaerobic biodegradation.

129
Q

Mesophilic digestion duration?

A

3-6 weeks.

130
Q

Thermophilic digestion duration?

A

2-3 weeks.

131
Q

Aim of anaerobic digestion?

A

To reduce the amount of sludge that needs to be disposed.

132
Q

Common method for sludge treatment?

A

Anaerobic digestion.

133
Q

Process of anaerobic digestion? (2)

A

● A large fraction of the organic matter (cells) is broken down into CH4 & CO2.

● About half of the amount is converted into gases & the other half is dried into a residual soil-like material.

134
Q

Products of sludge treatment? (3)

A

• Digested sludge solids.
• Waste liquids.
• Waste gases.

135
Q

What happens to the digested sludge solids from sludge treatment?

A

Taken for further treatment or disposal.

136
Q

What happens to the waste liquids from sludge treatment?

A

Recycled through the sewage treatment plant.

137
Q

What happens to the waste gases from sludge treatment?

A

Released or burned if from anaerobic digestion.

138
Q

Why is the tank where sludge treatment occurs capped? (2)

A

• To prevent O2 from coming in.
• To capture the methane produced.

139
Q

In what is sludge treated?

A

A round digester made of asbestos.

140
Q

Why is the round digester made of asbestos?

A

To withstand very high temperatures when burning the sludge.

141
Q

Why is sludge burned in sludge treatment?

A

To kill the enteric microbes.

142
Q

Why can the sludge be used as a fertilizer?

A

It is rich in nitrates.

143
Q

What is Class A sludge?

A

= the perfect sludge that can be used as a fertilizer because it meets the standards to be used as a fertilizer.

144
Q

Class A sludge contains? (4)

A

• < 1 virus.
• < 1 viable helminth ovum.
• < 3 Salmonella.
• < 1000 focal coliforms.

145
Q

Class A sludge is AKA?

A

Biosolids.

146
Q

Class A sludge is disposed as?

A

Soil conditioner for use on non-edible plants.

147
Q

Processes for producing Class A sludge? (3)

A

● Thermal (high temperature) process.
● Lime (alkaline) stabilization.
● Composting.

148
Q

Thermal (high temperature) processes?

A

= where sludge is held at 50°C or more for specified times.

149
Q

Lime (alkaline) stabilization?

A

= where the pH is raised to 12 for 2 or more hours.

150
Q

Composting?

A

= where there’s additional aerobic treatment at elevated temperature.

151
Q

If sludge cannot be used as a fertilizer?

A

It’s taken to landfill sites.

152
Q

Purpose of thickening sludge?

A

To reduce the sludge’s volume, which can be several fold.

153
Q

Thickening methods? (4)

A

• Gravity thickening.
• Dissolved air flotation.
• Thickening centrifuge.
• Gravity belt thickening.

154
Q

Gravity thickening?

A

= achieves up to 10% solid fraction.

155
Q

Dissolved air flotation?

A

= achieve up to 6% solid fraction.

156
Q

Thickening centrifuge?

A

= achieve up to 8% solid fraction.

157
Q

Gravity belt thickening?

A

= achieves up to 6% solid fraction.

158
Q

What occurs in gravity belt thickening?

A

Uses a polymer to coagulate the solids, from which follows a rejection of water.

159
Q

What is wastewater reused for?

A

For beneficial, non-potable purposes in arid & water-short regions.

160
Q

Reclamation?

A

= the reuse of wastewater using advanced treatment processes.

161
Q

Physical-chemical processes used for drinking water? (4)

A

• Coagulation-flocculation & sedimentation.
• Filtration.
• Granular activated carbon.
• Disinfection.

162
Q

Filtration methods? (2)

A

• Granular medium filters.
• Membrane filters.

163
Q

Coagulation?

A

= a chemical reaction which occurs when a chemical/coagulant is added to the water.

164
Q

Purpose of coagulant?

A

Neutralizes the negative electrical charge on particles, which destabilizes the forces keeping colloids apart.

165
Q

Egs of coagulants? (3)

A

• Aluminum salts.
• Iron salts.
• Polyelectrolytes.

166
Q

Flocculation?

A

= a slow gentle mixing of the water to encourage the flocs to form & grow to a size that will easily settle out.

167
Q

Flocculants?

A

= low, medium & high molecular weight polymers.

168
Q

Clarification?

A

= the final part of the treatment process that allows the large flocks containing most of the suspended matter to sink to the bottom of a tank while the clear water overflows and is then further treated.

169
Q

Disinfection?

A

= any process to destroy or prevent the growth of microbes.

170
Q

How do Disinfection processes often inactivate microbes? (3)

A

• Physical processes.
• Chemical processes.
• Biological processes.

171
Q

How is inactivation of microbes achieved?

A

By altering or destroying the essential structures or functions within the microbe.

172
Q

Egs of inactivation processes? (3)

A

• Denaturation of proteins.
• Denaturation of nucleic acids.
• Denaturation of lipids.

173
Q

When is wastewater Disinfection is recommended or required? (5)

A

• Discharge to surface waters near water supply intakes.

• Discharge to surface waters used for irrigation of crops & greenspace.

• Discharge to surface waters used for primary contact recreation.

• Discharge to groundwaters used as a water supply source.

• Discharge to groundwaters used for irrigation of crops & greenspace.

174
Q

Purpose of disinfection of wastewater?

A

To reduce microbes in treated effluents.

175
Q

Disinfection methods? (3)

A

• Chlorination.
• UV Radiation.
• Ozone.

176
Q

In what forms is chlorine added? (2)

A

• Chlorine pellets.
• Chlorine gas.

177
Q

Why is chlorination the common disinfection method? (2)

A

• Cheapest.
• Easiest to use & apply.

178
Q

Why is UV Radiation not used as a disinfection method?

A

Expensive installation.

179
Q

Why is Ozone not used as a disinfection method?

A

Not safe for humans.

180
Q

Impact of Chlorination?

A

It and its by-products are toxic to aquatic life.

181
Q

Solution to impact of Chlorination?

A

Dechlorination.

182
Q

Dechlorination effects/features? (3)

A

• Less toxic chemical disinfectants.
• Alternative treatment processes to reduce enteric microbes.
• Granular medium filtration or membrane filtration.

183
Q

Eg of common disinfectants in water & wastewater treatment? (3)

A

• Chlorine dioxide.
• Free chlorine.
• Ozone.

184
Q

Properties of an ideal disinfectant? (5)

A

• Economical.
• Fast acting.
• Easy to generate & supply.
• Compatible with many materials/surfaces.
• Non-toxic.

185
Q

What do we mean when we say Fast acting?

A

= produces rapid inactivation.

186
Q

Non-toxic features? (3)

A

• Soluble.
• Non-flammable.
• Non-explosive.

187
Q

What do we mean by a Broad spectrum?

A

= active against all microbes.

188
Q

Red water includes? (2)

A

• Blood (from abattoir).
• Fabric dye (from textiles).

189
Q

Colour & texture of healthy sludge?

A

Hot chocolate, velvety texture.

190
Q

Smell of healthy sludge?

A

Earthy.

191
Q

Colour of toxic sludge?

A

Black.

192
Q

Why is toxic sludge black?

A

It lacks O2.

193
Q

Why does toxic sludge smell extremely bad?

A

Due to insects.

194
Q

Egs of substances that take up O2? (2)

A

• Oil.
• Heavy metals (Zn).

195
Q

Things to do after discovering black sludge/in a pollution scenario? (6)

A

• Take samples.
• Send for analysis.
• What is the cause of the sludge?
• Who discharged?
• Fix the plant (by trying to infuse O2 using the organisms left).
• If infusion fails, take out sludge & replace it with healthy sludge (expensive).

196
Q

Healthy treatment plant?

A

= Low BOD.

197
Q

First indicator of wastewater?

A

COD.

198
Q

How do you aerate/induce O2 in water?

A

Through mixing.

199
Q

How do wastewater treatment plants aerate/induce O2 in their water?

A

By having multiple mixers, i.e., surface mixers & below mixers.

200
Q

Why does wastewater smell?

A

It’s because of H2S and failure.

201
Q

Organic heavy load formula?

A

OL = BOD (or COD) × Flow reading

202
Q

Relationship between heavy organic load & respiration?

A

High OL, High respiration.

EEC2B (43 decks)

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