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wastewater > Wastewater > Flashcards

Wastewater Flashcards

1
Q

Total Solids

A

all matter remains after evaporation by oven 105 deg C for 24h

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2
Q

Volatile Solids

A

Amount that of total solids that evaporates after being put in the muffle for 4h at 550 deg C

Organic Solids

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3
Q

Fixed solid

A

amount of total solid that remains after being put in the muffle for 4h at 550 deg c. INORGANIC

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4
Q

Total Suspended Solids

A

Solids that don’t pass through 0.45 microm filter (measured after drying)

60% of them are settleable

75% are organics

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5
Q

Total Dissolved Solids

A

Amount that pass through a filter of 0.01-1micro (measured after drying)

40% are organics

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6
Q

Settleable Solids

A

Solids that settles in a 1L imhoff cone after 30 min - 1 hr due to gravity. unit is mL/L

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7
Q

Odors

A

from gasses produced during degradation process

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8
Q

Temperature

A

Optimal for microbial activity is 25-20 deg C

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9
Q

Electrical Conductivity

A

Measures ability of water to conduct electrical current due to the presence of ion.

Indirect measure of TDS

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10
Q

Colors

A

From organic and inorganic compounds

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11
Q

Turbidity

A

Measure of light scattering properties due to the presence of suspended and colloidal particles. It is proportional to TSS Concentration

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12
Q

Total Organic Carbon

A

The total amount of carbon in organic compounds in a water sample.

Mw C x mole C

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13
Q

Theoretical Oxygen Demand

A

Indirect measurement of organics. How much O2 needed to oxidize to CO2

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14
Q

COD

A

O2 equivalent of organic (bio and non bio) that can be chemically oxidized

measurement usually using dichromate

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15
Q

TOC/COD Ratio

A

Oxidation state, the higher the ratio, the higher the oxidation state, the less O2 needed to oxidize compound

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16
Q

Theoretical COD

A

ThCOD=ThOD

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17
Q

COD Classification factsz

A
  1. Check particulate of soluble: Filtration
  2. Check if Organic or not: BOD
  3. Check if inert or not: SRT, if longer than SRT to degrade than it is inert
  4. Soluble Inert COD go in go out WW as is
  5. Particulate inert COD go out as sludge
  6. bCOD= biodegradable particulate (xs) + biodegradable soluble (Ss)
  7. Xs need more time to degrade because it needs to be hydrolyse to Ss first, and the time to hydrolyse is SRT or Sludge Age
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18
Q

BOD

A

Oxygen equivalent of organic that can be oxidized by M/O

Indirect measurement of biodegradable organic (bioCOD estimate)

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19
Q

BOD measurement conditions

A

must add O2, sufficient m/o, sufficient nutrients, no toxic compounds, no nitrification

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20
Q

What is the meaning of BOD5/BODtot ratio

A

BOD5: amount of dissolved oxygen consumed by microorganisms while decomposing organic matter over a 5-day period.

UBOD: total amount of oxygen required to completely decompose all the biodegradable organic matter

BOD5/UBOD Ratio: A high BOD5/BODtot ratio (closer to 1) indicates that most of the organic matter is readily biodegradable.

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21
Q

BOD effects of Nitrification

A

Nitrification normally starts after 8-10 days. If initial presence is high, need to inhibit. Or else the BOD inflates. Because nitrification also needs oxygen so higher o2 consumption –> BOD inflates

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22
Q

BOD Limitation

A
  1. Takes 5 days
  2. Result varies due to inocculum acclimitazation
  3. Does not include Non-biodegradable organics
    4.
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23
Q

BOD/COD ratio?

A

How much COD is actually biodegradable.
Usually, 0.5
If very low meaning not ideal to use biological units.

24
Q

Alkalinity

A

Capacity of a buffer to resist pH changes
Mainly come from OH-, CO32-,HCO3-, Ammonia, Phosphates

25
Q

Mass Equivalent of CaCO3

A

50 g CaCO3/ eq

26
Q

What is typical value of alkalinity in Domestic WW

A

3-7 eq/m3 or 150-350 mgcaco3/l

27
Q

What is Organic and Inorganic Nitrogen?

A

Organic: Mainly proteins
Inorganic: Ammonia (from hydrolysis of org matter), Ammonia oxide –> Nitrate (NO3-) and NItrite (NO2-)

28
Q

What is TKN

A

Total reduced form of N
Organic Nitrogen + Ammonia

Estimation of Total Nitrogen at incoming WW because not yet oxidized and change form to nitrite and nitrate (Ammonia oxide)

29
Q

What is Ammonia Nitrogen?

A

NH3 (Volatile Gas) + NH4+ (Ion)

usually 50-80% in WW
Concentration depends on pH higher pH usually more Ammonia Gas portion. but at pH 9.25 the % is the same

30
Q

Total Nitrogen

A

TKN+Ammonia oxide

Ammonia N + N org, Nitrate + Nitrite

31
Q

Pseudomonas role

A

Reduce NO3 to N, biological nitrate removal

32
Q

Acinetobacter Role

A

store large amount of phosphate under aerobic and release under anaerobic conditions

33
Q

nitrosomonas

A

transform NH4 to NO2-

34
Q

Nitrobacter

A

Transform NO2- to NO3-

35
Q

Coliform Bacteria Role

A

E-coli indicator for pathogens

36
Q

Hydraulic and BOD PE

A

Hydraulic PE: 200 L/cap/day
BOD PE: 60g BOD/cap/day

37
Q

QAverage and Q Peak

A

QAve: Consumption/cap/day x population x WW generation coefficient (0.7-0.9)

Q Peak: Qave x K
K= peaking factor

38
Q

Why is below contaminants of concerns?
Suspended Solids, Biodegradable org, pathogens, Nutrients, Heavy Metals

A

Suspended Solids: Sludge deposits and anaerobic conditions
Biodegradable org: O2 depletion –> Septic
Pathogens: Health disease
Nutrients: Groeth of indesirable aquatic life
Heavy Metals: Toxicity, Bioaccumulation

39
Q

Scheme of WWT General

A

Screening
Grit Sed. or Floatation
Eq. Tank
Primary Settling
Aerobic treatment
Secondary Settling
Filtration
Disinfection

Additional units: Nitrification, denitrification, phosphorus removal, Filtration, coagulation and flocculation, adsorption

40
Q

Role of Preliminary Treatment and which are removed by screenings, grit sedimentation, and floatation

A

Removal of coarse solids that may cause operational & maintenance Problems

Screening: Remove coarse solids and avoid damages

Grit Sedimentation: eliminate sand, gravel, cinders, and other heavy solid particles

Floatation: remove particles that are too light to settle by gravity, such as oils, grease, and fine suspended solids. By gas bubbles, remove suspended matters.

41
Q

Role of Secondary Treatment

A

Remove biodegradable organic compounds (particulate and soluble COD) by bacterial growth and conversion into CO2 energy and biomass

High org content should choose Anaerobic

42
Q

Role of Tertiary Treatment

A

Chemical & Physical process to enhance WW Quality.

Removal of residual solids, Nutrients, pathogens

e.g: Filtration, precipitation, membrane treatment, disinfection, adsorption

43
Q

Sludge Management

A

Stabilize sludge, thickening & dewatering, Anerobic or aerobic digestion, drying, composting

44
Q

What does steady state mean

A

Rate of accumulation is zero

Mass flow in - Mass flow out +- Reaction = 0

45
Q

What is HRT & SRT

A

HRT (Hydraulic Retention Time): The average time wastewater remains in a treatment tank or system. It ensures adequate contact time for treatment processes.

SRT (Solids Retention Time): The average time biological solids remain in the treatment system. It ensures the maintenance of an effective microbial population for treatment processes.

SRT=total mass of solids in the system/flow of solids leaving the system= Vx/QwXr

46
Q

Types of screens

A

Coarse screen for >6 mm
could be manually and mechanically cleaned (e.g: belt screen, vertical bar screen, arch screen)

Fine Screen 0.5 mm to 6 mm
possible substitute for primary sedimentation (catch COD)

47
Q

Grit chamber types

A

Horizontal Flow Grit Chamber (oldest)
Aerated Grit Chamber (done properly 100% grit removal)
Vortex Type Grit Chamber (small size) use a turbine

48
Q

Types of Floatation

A

Dispersed-Air Floatation or Induced air Floatation (IAF)
Air is directly sparged into tank, usually for high vol industrial WW.
Pros: Compact size, low capital cost
Cons: High power req, strict hydraulic control, less flocculation flexibility

Dissolved Air floatation (DAF)
Air is pressurised instead of injected, thus very fine bubbles, main design parameter is Air to Solid Ratio, have higher removal efficiency than sedimentation but more high capital cost.

49
Q

Whar are the 3 types of settling, and where it used

A

Discrete particle settling: settle as individual, no interaction, Grit and Sand removal

Flocculent Settling: floc together and settle, primary sedimentation

Hindered or zone settling: fixed position particles and settle as unit (secondary sedimentation)

50
Q

A/S design in DAF is based on what

A

TSS in effluent goals NOT TSS Removed

51
Q

Equalisation Tank

A

Dampen fluctuations in Flow, concentration or both and avoid shock loading

52
Q

Pros and Cons of Equalisation Tank

A

Pros: Overcome potential problems caused by flowrate fluctuations (shock loadings), improve downstream performance (constant loading, better feed control), Reduce size and cost of downstream facilities

Cons: large areas needed

53
Q

what are the 2 arrangements of equalisation tank

A

Inline: All flow pass through after grit removal

Offline: only flow above specified flow limit is diverted to the tank

54
Q

What is the principle settling of primary sedimentation?

A

Gravity settling: type 2 –> flocculent sedimentation

55
Q

What are the shape of primary sedimentation tank?

A

rectangular and circular

56
Q

Can we add chemicals during primary sedimentation? if yes what?

A

yes to increase efficiency thus reducing surface area

57
Q
A

wastewater (4 decks)

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