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ENCN347 > Week 6: Treatment Technologies > Flashcards

Week 6: Treatment Technologies Flashcards

1
Q

List all the SW treatment processes.
(Most important shown in bold)

A
  • Sedimentation
  • Flotation
  • Filtration
  • Adsorption and ion exchange
  • Flocculation or Precipitation
  • Microbial degradation and conversion
  • Bioaccumulation/uptake
  • Inactivation
  • UV degradation
  • Volatilisation
  • Chemical degradation/transformation
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2
Q

What pollutants might we remove by sedimentation?

A
  • Suspended solids
  • Metals
  • Pathogens
  • Anything bound to solids
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3
Q

What factors influence sedimentation?

A
  • Velocity
  • Energy
  • Turbulence
  • Particle Size
  • Density
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4
Q

What might we remove by flotation?

A
  • Hydrocarbons
  • Plastics and microplastics
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5
Q

What factors influence flotation (reverse process of sedimentation)?

A
  • Buoyancy (particle size and density)
  • Velocity
  • Energy
  • Turbulence
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6
Q

What might we remove by filtration?

A
  • Sediment/solids
  • Some pathogens
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7
Q

What factors influence filtration?

A
  • Size of filter pores/diameter of polllutants
  • Depth of filter
  • Angle of filter
  • Fluid velocity
  • Shape of particles
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8
Q

What might we remove by adsorption (binding to surface) + ion exchange?

A
  • Metals
  • Dissolved organics
  • Phosphate
  • Nitrogen species
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9
Q

What factors influence adsorption + ion exchange?

A
  • Adsorbent material
  • Chemical functional groups
  • pH
  • Contact time
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10
Q

What might we remove by flocculation & precipitation?

A
  • Metals
  • Colloidal particles (clays, organics)
  • Phosphate
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11
Q

What factors influence flocculation and precipitation?

A
  • pH
  • Salinity
  • Mixing
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12
Q

What might we move by microbial degradation?

A
  • Organics
  • Nitrogen
  • Phosphate
  • Metals
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13
Q

What factors influence microbial defgradation?

A
  • pH
  • Temperature
  • Concentration
  • Light
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14
Q

What might we remove by bioaccumulation/uptake?

A
  • Nitrogen
  • Phosphate
  • Metals
  • Organics
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15
Q

What factors influence bioaccumulation/uptake?

A
  • Temperature
  • Light
  • Growth stage
  • pH
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16
Q

What might we remove by inactivation?

A
  • Pathogens
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17
Q

What factors influence inactivation?

A
  • Time
  • Light (UV)
  • Temperature (colder is more effective)
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18
Q

What might we remove by UV degradation?

A
  • Certain organic compounds
  • Microplastics
  • Pathogens
  • Hydrocarbons may transform
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19
Q

What factors influence UV degradation?

A
  • Sunlight
  • Temperature
  • pH
  • Mixing/depth
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20
Q

What might we remove by volatilisation?

A
  • Volatile organic carbon
  • Ammonia
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21
Q

What factors influence volatilisation?

A
  • Temperature
  • Concentration
  • pH
  • Mixing depth
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22
Q

What might we remove with chemical degradation?

A
  • Organic compounds
  • Nitrogen species
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23
Q

What factors influence chemical degradation?

A
  • Temperature
  • Concetration
  • pH
  • Other chemicals
  • Time (it is a slow process)
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24
Q

What are some pretreatment systems?

A
  • Macro (or gross) pollutant traps
  • Propietary sediment devices
  • Swales
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25
Q

What are some soakage systems?

A
  • Swales (soakage)
  • Infiltration chambers
  • Rain garden/biofilter/soakage basin
  • Permeable pavement
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26
Q

What are some detention-type systems?

A
  • Detention basins (wet ponds or dry basins)
  • Retention basins (dry basins)
  • Household rain tanks
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27
Q

What are some constructed wetland systems?

A
  • Surface flow wetlands
  • Subsurface flow wetlands
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28
Q

What are some building integrated systems?

A
  • Green roofs
  • Living walls
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29
Q

What are some proprietary filters?

A

Package designs usually combining sedimentation and filtration
- Jellyfish
- Storminater
- …

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30
Q

What are some considerations for selecting a treatment device?

A
  • Cost
  • Amenity
  • Cultural and social alignment
  • Target pollutant removal
  • Robustness
  • Size/land area/excavation
  • Maintenance
  • Flow
  • Topography
  • WT, bedrock, other constraints
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31
Q

Describe Te Taiao (Mana Whenua alignment).

A

The environment that surroudns us, comprising whenua, wai, ahurangi (climate across time) and koiora (all living communities - people, plants, animals).

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32
Q

Describe Kaitiakitanga (Mana Whenua alignment).

A

Guardianship and protection of the natural environment by mana whenua based on the Maori world view.

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33
Q

Describe Mauri tu (Mana Whenua alignment).

A

Protection and awareness of the life force within all matter. The connection between spiritual, physical and temporal realms.

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34
Q

What are the 3 levels of a treatment system?

A

Primary
Secondary
Tertiary

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35
Q

Outline the processes, pollutants and examples of primary treatment.

A

Processes:
- Hydraulic, physical processes resulting in screening and rapid sedimentation

Pollutants:
- Litter, coarse sediments

Examples:
- Catch pit inserts, filter strips, litter traps, sediment ponds

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36
Q

Outline the processes, pollutants and examples of secondary treatment.

A

Processes:
- Filtration resulting in fine particle and sediment removal.

Pollutants:
- Fine sediment and attached pollutants.

Examples:
- Swales, infiltration trenches, pervious pavement, bioretention devices.

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37
Q

Outline the processes, pollutants and examples of tertiary treatment.

A

Processes:
- Biological, chemical, thermal processes.
- Provide removal through enhanced sedimentation, biological uptake, adsorption to sediments, UV inactivation.

Pollutants:
- Nutrients, dissolved heavy metals, temperature, pathogens.

Examples:
- Bioretention devices, wetlands

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38
Q

Descibe macro pollutant traps.

A

Debris collection upstream of other treatment devices to collect:
- plastic waste
- rocks
- sticks/branches
- leaves/organic debris.

Physical treatment processes:
- straining
- sedimentation
- flotation

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39
Q

Gross Pollutant Traps (GPT), sumps and propriety sedimentation devices have good removal capability for …

A
  • Sediment
  • Oil and grease
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40
Q

What are swales?

A

Broad channels to slow water runoff and direct it towards further treatment devices. Typically vegetated to improve filtration of sediment and other pollutants, and slow water movement.

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41
Q

How do swales align with Mana Whenua?

A
  • They are suitable for native grasses
  • Vegetated swales with minimal maintenance (avoids machine mowing)
  • Natural filtering of sediment is in line with principles of Taiao and kaitiakitanga
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42
Q

What are the advantages of swales?

A
  • Simple construction and well-understood maintenance
  • Can help to separate road traffic and pedestrians
  • With suitable subsoil, can provide area for infiltration
  • Use of rocks as check-dams can provide additional (minor) storage
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43
Q

What are the disadvantages of swales?

A
  • Can pose danger to traffic pulling off road
  • Occupies a signficant corridor of land
  • Not suitable on steep slopes exceeding 8% or on geotechnically unstable ground
  • Not suitable for extreme event management or volume control
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44
Q

What are the different types of swales?

A

Grass swale:
- Most simple
- Provides good sediment removal
- Vegetation can be more complex

Bio-swale:
- Some crossover with biofiltration device.
- Sandy or engineered media area for various chemical and biological processes including denitrification

Wet swale:
- Like an elongated wetland
- Constant standing water in the bottom

45
Q

Swales have good removal capability of:

A
  • Sediment
  • Temperature

Also, moderate removal of oil & grease, heavy metals. and pathogens.

46
Q

What treatment mechanisms do swales use?

A
  • Filtration
  • Sedimentation
  • Adsorption
47
Q

When is it desirable to select a swale?

A
  • Main goal is natural conveyance
  • Collection along large area (e.g. road length)
  • Low maintenance and cost
  • Small degree of detention
48
Q

When is it not desirable to select a swale?

A
  • Steep slope
  • Low structural-load bearing soil
  • Thermal load to water
  • High ground water table
  • high sediment load with no pretreatment
49
Q

What are bioretention/rain gardens?

A

Planted depressions/lowered gardens with deep engineered media base for storing and filtering water prior to infiltration to groundwater or passage downstream.

(Rain gardens, tree pits, stormwater planters, bioretention swales)

50
Q

What are some advantages of bioretention/rain gardens?

A
  • Provides retention, detention and treatment
  • High level of treatment comparative to other natural techniques
  • Provide enhanced aesthetic, ecological and amenity benefits
  • Easily incorporated into traditional landscaping
51
Q

What are some disadvantages of bioretention/rain gardens?

A
  • Specific construction and maintenance required
  • Plant establishment and replacement during startup
  • Not suitable for extreme event management or volume control
52
Q

How do bioretention/rain gardens align with Mana Whenua?

A
  • Provides treatment through soil and can eliminate mixing of waters through retention
  • Suitable for native plants. Could be harvestable
  • Typical locations are suitable for educational signage of cultural context and area history
  • Hand weeding aligns with principles of Taiao and kaitiakitanga
53
Q

What are the different types of bioretention devices?

A
  • Raingardens
  • Tree pits
  • Planter box
  • Bioretention swale
54
Q

Bioretention treatment devices have excellect removal capability of:

A
  • Sediment
  • Oil & grease
  • Pathogens
  • Temperature

Good removal of organics, nitrogen, heavy metals.

55
Q

What treatment mechanisms do bioretention devices use?

A

Uses filtration, sedimentation, adsorption, degradation through soil, volatization, denitrification, vegetation uptake, detention storage.

56
Q

When is it desirable to use bioretention devices?

A
  • Infiltration is desired
  • Treatment is necessary
  • Amenity / greenspace contribution
  • Localised small systems for upstream management
57
Q

When is it undesirable to use bioretention devices?

A
  • High groundwater table
  • Low permeability soils
  • Maintenance costs
58
Q

What is a dry retention pond (soakage basin)?

A

Basins that are designed to fill with water during a storm event, percolating it slowly into the gorund below. During dry periods, they can serve as spaces for other activities.

59
Q

How can dry retention ponds align with Mana Whenua?

A
  • Incorporate upstream treatment to ensure no mixing of clean and unclean water in the subsurface
  • Cultural monitoring during excavation
60
Q

Dry retention ponds have excellent removal capability of:

A

Sediment, oil & grease, pathogens, storm volume, temperature.

Good removal of organics, heavy metals.

Moderate removal of nitrogen and phosphorus.

61
Q

What treatment mechanisms do dry retention ponds use?

A

Uses filtration, sedimentation, adsorption, removal with sediment,

62
Q

When is it desirable to use dry retention basins?

A
  • Large-scale retention is required
  • Prefer public owned than private owned infiltration facilities
  • Downstream end of process
  • Amenity is important
  • Upstream treatment elements exist
63
Q

When is it not desirable to use dry retention basins?

A
  • Land area is critical
  • Shallow groundwater
  • Impermeable or too permeable soils
  • Sloped land
64
Q

What are pervious pavement?

A

Solid surfaces designed for pedestrians or traffic that also allows the infiltration and detention or percolation of water beneath the surface through a porous structure.

(Porous asphalt, permeable pavers, porous pavers, stabilised aggregate)

65
Q

What different characteristics do different types of pervious pavement have?

A
  • Hydraulic conductivity
  • Strength
  • Maintenance
  • Clogging
  • Appearance
  • Cost
66
Q

Pervious pavement has good treatment capability of:

A

Temperature.

Moderate removal of sediment.

Effectively no treatment.

67
Q

When is it desirable to use pervious pavement?

A
  • Infiltration is desired
  • No room for swales
  • Low maintenance
  • Avoid pooling and sheet flow on impervious surfaces
68
Q

Why might it not be desirable to use pervious pavement?

A
  • High sediment load
  • Installation cost
  • Heavy traffic area. High surface shear forces
  • Sloped areas
69
Q

What are dry detention ponds?

A

Basins that are designed to fill with water during a storm event, releasing it slowly to the downstream stormwater system. During dry periods they can serve as spaces for other activities.

70
Q

How do dry detention ponds align with Mana Whenua?

A
  • Planted with natives. Can be used for harvesting.
  • Incorporate educational signage
71
Q

What are some advantages of dry detention ponds?

A
  • Attenuate downstream flows to minimise flooding and erosion
  • Provide green space for amenity/activity between storm events
  • Aesthetically pleasing greenspace in urban and suburban areas
  • Easier maintenance than wet pond detention systems
72
Q

What are some disadvantages of dry detention ponds?

A
  • Temporary standing water can be a safety hazard
  • Creates a dammed water hazard
  • No retention or significant improvement in water quality
73
Q

Dry detention ponds have excellent removal capability of:

A

Storm volume (via detention)

74
Q

Why might it be desirable to use dry detention basins?

A
  • Large-scale detention is required (volume control is the goal)
  • Prefer public owned than privated owned facilities
  • Mid- to down-stream process
  • Upstream treatment elements exist
75
Q

Why might it not be desirable to use dry detention basins?

A
  • Land is restricted
  • Sensitive cold-water fish community downstream
  • Poor structural-quality soil
  • Sloped land
  • Treatment is necessary objective
76
Q

What is a wet detention pond?

A

Basins that permanently hold water and can provide additional live storage detention as flows increase, but releasing water more slowly from the outlet.

77
Q

How do wet detention ponds align with Mana Whenua?

A
  • NOT SUPPORTED? [Mixing of stormwater (dirty) with existing (clean) waterbody.
  • Native plants, amenity, biodiversity
78
Q

What are some advantages of wet detention ponds?

A
  • Attenuate downstream flows to minimise flooding and erosion
  • Aesthetically pleasing landscape in urban and suburban areas
  • Natural haven for avian and aquatic species
  • Enhanced green corridor for existing riparian environments
79
Q

What are some disadvantages of wet detention ponds?

A
  • Standing water can be safety hazard (drowning)
  • Can attract mosquitos and other pests/vectors
  • No retention or significant improvement in water quality
  • Can cause increase in water temperatures
80
Q

Wet detention ponds have excellent removal capability of:

A

Storm volume.

Good removal of sediment.
Moderate removal of oil & grease, organics, nitrogen, phosphorus, heavy metals.

81
Q

Why might it be desirable to use wet detention basins?

A
  • Large-scale detention required (volume control is primary goal)
  • Prefer public owned than private owned facilities
  • Mid- to down-stream process
  • Amenity and biodiversity aspects are important
  • Upstream treatment elements exist
82
Q

Why might it be undesirable to use wet detention basins?

A
  • Land is restricted
  • Sensitive cold-water fish community downstream
  • Poor structural-quality soil
  • Sloped land
  • Mana whenua alignment
83
Q

What are some advantages of rainwater tanks?

A
  • Allow water reuse (garden irrigation etc.)
  • Actively engage the public in stormwater management
  • Allow first flush capture to not leave the site
  • Do not require major earthworks
  • Can provide large portion of residential detention
  • Work well with downstream devices
  • Suitable for steep sloped areas
  • Good sediment removal
84
Q

What are some disadvantages of rainwater tanks?

A
  • Distributed maintenance responsibilities to public, with regular inspection and cleaning
  • Cost per tank owner
  • Poor aesthetics
  • First flush may get discharged with no treatment
85
Q

How do rainwater tanks align with Mana Whenua?

A

Reuse or recharge is in-line with kaitiakitanga, Mauri Tu and Taiao

86
Q

What are (constructed surface) wetlands?

A

Densely planted ponded areas utilizing submerged and riparian plants that mimic chemical and biological processes occurring in natural wetland systems.

87
Q

How can wetlands align with Mana Whenua?

A
  • Involvement in early design
  • Plant species selection, including harvestable species
  • Educational and cultural signage
  • Align closely with principles of kaitiakitanga, Taiao and Mauri Tu
88
Q

What are some advantages of wetlands?

A
  • Reduce downstream flood potential and erosion
  • Water quality improvement (treatment)
  • Aesthetics - increased amenity value for communities, including educational opportunities
  • Increased biodiversity
89
Q

What are some disadvantages of wetlands:?

A
  • Does not provide significant detention relative to size
  • Plant selection can be limited and plant maintenance is intensive
  • Can attract pests if not well maintained
  • Can potentially increase water temperature if insufficient shading from vegetation
90
Q

Wetlands have excellent removal capability of:

A

Sediment, oil & grease, organics, heavy metals.

Good removal of nitrogen, phosporus, storm volume.
Moderate removal of pathogens, temperature.

91
Q

Wetlands use the following treatment mechanisms:

A
  • Filtration
  • Sedimentation
  • Adsorption
  • Removal with sediment
  • Biodegradation
  • Denitrification
  • Degradation through soil
  • Vegetation uptake
  • Detention storage
92
Q

Why might constructed wetlands be desirable?

A
  • Treatment required
  • Flow attenuation desired
  • Downstream end of process
  • Amenity aspect important
  • Shallow groundwater
93
Q

Why might constructed wetlands not be desirable?

A
  • Land area is critical
  • Maintenance budget low
  • Receiving environment has sensitive cold-water fish
  • Sloped land
94
Q

What are some building-integrated systems?

A
  • Green/Living roofs
  • Green/Living wall
95
Q

What are green/living roofs?

A

Planted rooftops designed to filter and slow the runoff or precipitation on the urban structure, while providing other building amenities and utility.

96
Q

How can green/living roofs align with Mana Whenua?

A
  • Align with principles of Taiao (protection of environment)
  • Provide opportunity for native species introduction into urban environment
  • Depending on building type, can provide educational opportunities
97
Q

What are some advantages of green roofs?

A
  • Reduced visual impact of buildings (urban greening)
  • Pervious device
  • Improved building thermal efficiency
  • Improved noise abatement
  • Urban dust and particulates air filtering
  • Reduced urban heat island effect
98
Q

What are some disadvantages of green roofs?

A
  • High construction costs and increased structural requirements of building to support it
  • Intensive system startup
  • High maintenance costs
  • Not suitable for extreme event flow management
  • Potential for increase insect/pest presence around building
99
Q

Green roofs have excellent removal of ____ and moderate removal of _______.

A

Temperature

Sediment, oil & grease, organics, nitrogen, phosphorus, heavy metals, pathogens, storm volume

(Filtration, adsorption, microbial, uptake)

100
Q

Why might it be desirable to use green roofs?

A
  • Onsite retention is desired
  • Reduce onsite impervious area
  • Urban greening
  • Building envelope benefits
  • Shallow groundwater preventing other infiltration based techniques
  • Sloped land
101
Q

Why might it not be desirable to use green roofs?

A
  • Low budget system required
  • Structural reinforcement of building required or roof too sloped
  • Maintenance requirements
  • Climatic conditions (snow, frost, seasonality)
102
Q

What are green/living walls?

A

Planted walls designed to filter and slow the runoff of precipitation on the urban structure, while providing other building amenities and utility.

103
Q

How can green/living walls align with Mana Whenua?

A
  • Align with principles of Taiao (protection of environment)
  • Provide opportunity for native species introduction into urban environment
  • Depending on building type, can provide educational opportunities
104
Q

What are some advantages of green walls?

A
  • Reduced visual impact of buildings (urban greening)
  • Improved building thermal efficiency
  • Improved noise abatement
  • Urban dust and particulates air filtering
  • Reduced urban heat island effect
  • Not limited to buildings
105
Q

What are some disadvantages of green walls?

A
  • High construction costs and increased structural requirements of building to support it
  • Intensive system startup
  • High maintenance costs, especially taller installations
  • Not suitable for extreme event flow management
  • Potential for increase insect/pest presence around building
106
Q

Green walls have excellent removal capability of:

A

Organics.

Good removal of sediment, nitrogen, heavy metals, pathogens.

Moderate removal of phosphorus, storm volume, temperature.

107
Q

Why might it be desirable to have green walls?

A
  • Onsite retention is desired
  • Urban greening
  • Building envelope benefits (thermal, acoustic)
  • Shallow groundwater preventing other infiltration based techniques
  • Polluted roofs requiring good level of treatment
  • Sloped land
108
Q

Why might it not be desirable to have green walls?

A
  • Low budget system required
  • Structural reinforcement of building
  • Maintenance requirements
  • Humidity and pests
109
Q

How do you select a treatment system?

A
  • Impervious surfaces?
  • Pollutants?
  • Nearby surface water body to be protected? Water quality sensitivity?
  • Soil permeability and groundwater table? Infiltration feasible?
  • Space constraints?
  • Budget and maintenance requirements?
  • Stakeholder engagement?
  • Safety?

ENCN347 (10 decks)

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