2 OXYGEN DEMANDING WASTES

2 OXYGEN DEMANDING WASTES T.K. Liu 1 Marine Pollution Dissolved oxygen and oxygen demand High in surface due to photosynthesis; Decrease under phot...
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2 OXYGEN DEMANDING WASTES T.K. Liu

1

Marine Pollution

Dissolved oxygen and oxygen demand High in surface due to photosynthesis; Decrease under photic zone due to respiration; Increase in the bottom due to sinking oxygen rich polar water.

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Dissolved oxygen in the ocean Gas

Percent of gas in atmosphere by volume

Percent of dissolved gas in seawater by volume

Conc. in seawater in ppm, by mass

N2

78.08%

48%

10-18 ppm

O2

20.95%

36%

0-13 ppm

CO2

0.03%

15%

64-107 ppm

Garrison, 2005

3

Oxygen solubility in ocean

(Metcalf & Eddy, 1991)

DO =fn(T,S,P) T: Temperature S: Salinity P: Pressure

4

Oxygen demand 

Aerobic bacteria make use of O2 C6(H2O)6 + 6O2 → 6H2O + 6CO2 When DO >1~1.5 mg/L



organics + O2 → H2O + CO2 + stable end products (SO42-, PO43-, NO3-) 

Anaerobic bacteria oxidize organics without O2 

When DO < 1~1.5 mg/L Fe3+

Fe2+

organics + SO42- → HSNO3

-

CO2 

+ unstable end products

NO2

FeS (black)

CH4

H2S (odor)

-

Inorganic wastes deplete O2 when get oxidized 5

Measurement of BOD 

Biological oxygen demand (BOD): parameter of organic pollutants

Five-day BOD test (BOD5): Total O2 consumed by microorganisms during the first 5 days. 

Measure DO @ t=0:

initial DO0



Put in dark room @ 20℃ for 5 days



Typically, background seawater BOD < 2 mg/L domestic wastewater BOD ≒ 200~300 mg/L



DO = 7.4 mg/L @ 20 ℃ & s a l i ni t y35‰ , us ua l l yne e dsdi l ut i on during BOD test. BOD = (DO0-DOf )/df

df=Vsample/(Vsample+Vdilution water)

6

Measurement of BOD Seeded BOD test (BOD5): To assure adequate bacteria population to carry out the biodegradation. Typically add 2 mL of wastewater to 1L of dilution water BODSVS + BODDVD =BODMVM

t=0

df = VS/VM

BODS = BODM (VM/VS) –BODD (VD/VS) = BODM/df –BODD (1-df)/df

M

D

DOi

Bi

t = 5 days

= [(DOi –DOf ) –(Bi –Bf )(1 - df)] / df S: sample; D: dilution; M: mixture

M

D

DOf

Bf 7

Ultimate BOD Ultimate BOD∞ (=L0) dLt/dt = - k Lt (assme 1st order decay) Lt = L0 e-kt (organics left after time t) L0 = BODt + Lt

L0 Organics as mgO2/L

BODt = L0 –Lt = L0(1-e-kt)

BODt

Lt t

BOD∞ BOD5

k @ 20℃ BODt

5

t

BOD5

Time

Ex. Domestic wastewater BOD5=200 mg/L assume k = 0.4 d-1 BOD∞= 200/(1-e-0.4*5) = 230

5

Time

day-1

Raw wastewater

0.35-0.7

Polluted river

0.10-0.25

Reaction constant is Temp dependent kT = k20 * (1.047) T-20 k5 (winter) = k20 * 0.5 8

Nitrogenous BOD Nitrification: typically observed from 5~8 days in BOD test Wastes (organic-N) → NH3 → (e.g., protein, urea)

NO2- → NO3-

Nitrification(硝化)



N2

Denitrification(脫硝)

BOD∞ Nitrogenous BOD

Nitrosonomas sp. (亞硝酸菌) 2NH3 + 3O2 →2NO2- + 2H+ + 2H2O

Carbonaceous BOD

Nitrobacter sp. (硝酸菌)

BOD5

2NO2- + O2 →2 NO35

Time

2NH3 + 4O2 →2NO3- + 2 H+ + 2H2O 1 mole NH3 oxidation need 2 mole O2 2*32 g O2/ 14g NH3-N ≒ 4.6 gO2/gNH3-N Ultimate NBOD = 4.6 TKN (Total Kjeldahl Nitrogen = Organic-N + NH3-N) 9

Other measures of oxygen demand Chemical oxygen demand (COD)  Organics (CaHbOc) + Cr2O72- + H+ Cr 3+ + CO2 + H2O  COD test only takes 3 hours (BOD needs 5 days)  COD>BOD, some compounds only can be chemically oxidized  COD usually correlate with BOD e.g., for domestic wastewater, COD/BOD = 1.25 ~2.5 Theoretical demand (ThOD)  Completed oxidation (C → CO2; N → NO3-)  Ex. ThOD of glycine (C2H5O2N) (1) C2H5O2N + 1.5 O2 → 2CO2 + NH3 + H2O (2) NH3 + 2O2 → H+ + NO3-+H2O ThOD = (1.5+2)*32 = 112 gO2/mole glycine 10

Dilution factor :

2

The solution to pollution is dilution 





Saturated DO

freshwater

seawater

5℃

12.76

10.13

20 ℃

9.08

7.38

BOD of organic effluent is typically greater, dilution is needed . Current ocean outfall standards (mg/L)

BOD

COD

甲類海域

100

200

乙類海域

150

300

11

Dilution example Ex.

A 4day

Plant I

Plant II

B’ B

C’C

3day, k=0.15

k=0.2

BOD

Flow (cms)

k (d-1)

A

2

10

0.1

I

30

0.5

0.2

II

10

2

0.3

(1) Lo,A= 2/(1-e-0.1*4) = 5.08 Lo,B’= 5.08 e-0.1*4 = 3.41 BOD5,B’= 3.41(1-e-0.1*5) = 1.34 Lo,I = 30/(1-e-0.2*5) = 47.46 L0,B=(Q0L0,B’+ QIL0,I)/(Q0+QI) = 5.51 BOD5 BOD5,B = 5.51(1-e-0.15*5) = 2.91 3 (2) L0,C’= 5.51 e-0.15*3 = 3.51 2 BOD5,C’= 3.51 (1-e-0.15*5) = 1.85 1 Lo,II = 10/(1-e-0.3*5) = 12.87 L0,C={(Q0+QI) L0,C’+ QIIL0,II}/(Q0+QI +QII) = 5.01 A BOD5,C = 5.01(1-e-0.2*5) = 3.17

B

C 12

Oxygen budget

3



Source  Incoming water  Reaeration from atmosphere  Photosynthsis



Sink  Bacteria activity  Respiration (aquatic organisms/algae)  Reduced materials  Release to atmosphere  Sediments 13

Oxygen sag curve in river 

Rate of deoxygenation (rD) Waste flow, QW

rD = k1 Lt = k1 L0 e-k1t 

Rate of reaeration (rR) rR = k2 (O2 deficit) = k2 (S-C) = k2D

Upstream flow, Qr u

k1 : deoxygenation const. = BOD rate constant k2: reaeration coeff. =3.9 u0.5 /H1.5

Assuming Plug flow

S: saturation DO

Distant, x or Time, t

C: current DO 

Rate of increase of the deficit = rD –rR dD/dt= k1L0e-k1t - k2D y’ +p(x)y=q(x) 14

Streeter-Phelps oxygen sag curve k1 L0 D = ─── ( e-k1t –e-k2t ) + D0 e-k2t k2 - k1 S

saturation Initial deficit D0

rR

D

rD DOmin xc or tc rD > rR

Time or distance rD = rR

rD < rR

15

Excessive BOD saturation

DO

Minimum acceptable DO, typically 1~2 mg/L

unhealthy

anaerobic

Distance



Fish driven elsewhere or die



Anaerobic process produces less desirable end products



Seasonal flow fluctuations change BOD concentration



Streeter-Phelps equation not applicable 16

Temperature effects DO

Waste outlet

Distance 





When temperature increase, decay rate increase but saturated value drops and aeration slows down. Streams that have enough DO in winter may have unacceptable deficit during summer. Adverse impact from power plant. 17

4

Estuaries UNESCO definition A semi-enclosed coastal body of water having free connection to the open sea and within which sea water is measurably diluted with fresh water deriving from land drainage US NOAA/DOI definition (for MPA management purpose) Part of a river or stream or other body of water having unimpaired connection with the open sea, where the sea water is measurably diluted with fresh water derived from land drainage, and extending upstream to where ocean derived salts measure less than 0.5 parts per thousand during the period of average annual low flow. 18

Importance of estuary 

Major populations reside on many of the estuaries around the world.  





1/3 of U.S. population lives and works close to estuaries; 7 of the 10 largest metropolitan areas border estuarine areas (N.Y., Tokyo, London, Shanghai, Buenos Aires, Osaka, L.A.)

Intertidal grass and mangrove roots provide shelter for the small shrimp, crabs, lobster, and other marine life that need protection from predation by larger fish during the early stages of their life cycle. High primary and secondary productivity lead to increases in commercial fisheries. Estimated that 6080% of all commercial fishes depend on estuaries for part or all of their life cycle. 19

Geological formation type of estuary 1. 2. 3. 4.

Drowned river mouth (Ria 溺灣) Bar-build Fjord (峽灣) Tectonic

(Garrison, 2005) 20

Geological formation type of estuary 

Drowned river mouth estuary 





Formed at the mouth of a river when melting glaciers in temperate latitudes flooded river valleys Rising sea levels push seawater back during the last great rise in sea level. Typically resemble a V-shaped river channel, usually less than 20 m deep, with an accompanying floodplain

(Garrison, 2005)

21

Geological formation type of estuary 

Bar-build estuary 





A broad, shallow estuarine system where flow of water between the estuary and coastal ocean is restricted by a sand bar paralleling the shore line. Sand bar generally built up to the point where the wave action is stopped. The streams or rivers flowing into bar-built estuaries typically have a very low water volume during most of the year. The bars may grow into barrier beaches or islands and the estuary can become permanently blocked.

(Garrison, 2005)

22

Geological formation type of estuary 

Fjord estuary 





Forms when glaciers made a deep scouring cut in the coast line as they moved down toward the sea, usually deep with steep sides. A sill or rock bar is situated at the mouth of the fjord having been deposited there when the glacier receded. Fjords are found throughout Canada, Chile, New Zealand, Greenland, Norway, Siberia, and Scotland. Garrison, 2005

23

Geological formation type of estuary 

Tectonic estuary 





Result from major geological events such as faulting, volcanic eruption, and landslides when part of the coastline moves up or down. When depression sinks below sea level, ocean water may rush in and fill it. Typically very deep and surrounded by mountainous areas. San Francisco Bay is the best-known estuary formed by tectonic activity.

Garrison, 2005

24

Estuary comparison 



Drowned river mouth and bar-built estuaries 

depths generally less than 50 meters



sand or mud bottoms



found along older, tectonically passive coastlines

Fjords and tectonic estuaries 

Fjords tend to have a moderately high input of freshwater. Very little seawater flows into the fjord because of the sill.



depths may extend far beyond 50 meters in some parts



rocky bottoms



found along rugged, tectonically active coastlines

25

Mixing in estuary Oceanographic classification: according to their circulation properties and the steady state salinity distribution 



Most important types 

Salt wedge estuary



Well-mixed estuary



Partially-mix estuary



Stratified estuary



Reverse estuary

The VR/VT ratio determines the estuary type, not the absolute values of VR or VT 

VR, river volume: the volume of freshwater that enters from the river during one tidal period



VT, tidal volume: the volume of water brought into the estuary by the tide and removed over each tidal cycle

26

Mixing in estuary 

Salt wedge estuary  





VR >> VT, or there are no tides at all mixing is restricted to the thin transition layer between the fresh water at the top and the "wedge" of salt water underneath. Pool mixing for pollutants.

Well-mixed estuary 





VT >> VR, tidal mixing dominates the entire estuary complete mix achieves locally between surface and bottom; uniform vertical salinity profiles show Better pollutants dissipation

(Garrison, 2005)

27

Mixing in estuary 

Partially mixed estuary 





share properties of both salt-wedge and well-mixed estuaries salt water is mixed upward and fresh water is mixed downward, but gradient not as sharp as with a salt wedge

Stratified estuary 





Ex. Fjords: typically deep and have a large salt water reservoir below the upper layer Entrainment is a one-way process, so no fresh water is mixed downward Worse pollutants dilution

(Garrison, 2005) 28

Mixing in estuary 

Reverse estuary Formed along arid coast when river cease to flow  Evaporation at upstream will cause water to flow from the ocean to the estuary 



Intermittent estuaries 

(Garrison, 2005)

Many estuaries change their classification type because of highly variable rainfall over the catchment area of their river input 29

Resident time of estuary 



Circulation in estuary 

River flow out to sea



Tidal rise and ebb

Net seaward flow may be small 

Ex. Thames estuary, London Ebbing tide: downstream 15 km Rising tide: upstream 13 km Net movement: 2 km seaward





(Clark, 2001)

Needs a month at the head of estuary to reach the ocean Small dilution capacity, pronounced O2 sag, anoxic zone may appear, migratory fish may not pass through

30

Settlement in estuary 

 



Rate of settling of particles depends on the their size and de ns i t y ,andt hevi s c os i t yandve l oc i t yofwat e r .St oke s ’ equation can be used to calculate settling velocity. Flow velocity slow down at estuary Sudden change in salinity cause natural particles to flocculate and settle, i.e., compression of electric double layers. Sedimentation takes place in estuary, leading to the development of extensive mud-flats containing organic materials, metals, and so on. 31

Cheasapeake Bay 





The largest estuary in the United States (166,534 km2) In the 1970s, the Bay contained one of the planet's first marine dead zones (hypoxia), oxygen was so depleted that it cannot support life, resulting in massive fish kills. Loss of aquatic vegetation has depleted the habitat for many of the bay's animal creatures. (Garrison, 2005)

32

Marine Eutrophication

5

(Clark, 2001)

33

Nutrient enrichment in natural waters 

Enrichment 



Many wastes entering sea are plant nutrients, i.e., nitrate and phosphate



Urban run-offs



Fertilizer from intensive farming area

Eutrophication 



Natural eutrophication in regions of upwelling: nutrientrich deep ocean water rise to surface, e.g. E. China Sea Anthropogenic eutrophication is result of nutrient pollution of natural waters, e.g., lakes, rivers, estuaries, bays, coastal waters 34

Definition 

NOAA definition (National Ocean & Atmosphere Admin.) a process in which the addition of nutrients to water bodies stimulates algal growth. In recent decades, human activities have greatly accelerated nutrient inputs, causing the excessive growth of algae and leading to degraded water quality and associated impairments



EEA Definition (European Environment Agency) Enhanced primary production due to excess supply of nutrients from human activities, independent of the natural productivity level for the area in question 35

Causes of eutrophication Perturbation of N & P biogeochemical cycles  Synthetic fertilizers  Burning of fossil fuels  Forest burning  Monoculture of legumes (豆類植物)  Animal wastes and manure  Sewage: Sewage treatment reduces BOD and some P inputs but no significant reduction of N  Loss of wetland (main denitrifying)

36

Sources of nutrients 

Point sources: Wastewater drains  Domestic Sewage  Sewage treatment plants  Livestock production  Storm sewers  Can monitor & regulate or treat 



Non-point sources: Agricultural runoff  Manure spreading  Atmospheric deposition  Urban runoff & septic leachate  Seasonal effects, e.g. rainfall, meltwater  Major source of N & P to surface waters  Diffuse, difficult to monitor or manage 

37

Example of animal wastes

38

Important nutrients N, P, Si  

  



Ratios N:P and N: Si are especially important Redfield ratio N:P = 16:1  N limited when < 16:1  P limited when >16:1 P most important in freshwater lakes N is usually limiting nutrient in coastal waters and estuaries. P limitation has been documented in coastal waters and estuaries: Si availability controls diatom growth. Dams and upstream eutrophication in rivers traps Si in sediments before it reaches estuaries which may shift algae community. 39

Consequences of eutrophication 

Ecological       



Ocean Hypoxia/Anoxia Increased harmful algae blooms (HAB) Increased turbidity Loss of sea grass and kelp beds Damage to coral reef Decreased biodiversity Marine mammal & seabird deaths

Socio-Economic    

Decreased fisheries and aquaculture yields Contamination of aquifers, taste, odor, NO3- &NO2Increased risk of poisoning of animals including humans by algal toxins Loss of tourism revenues 40

Unexpected consequences of organic loading 







Fisheries benefits with increase in organic discharges in Seto Sea Increase in seabirds in Wadden Sea with high organic inputs Number of sea ducks declines as Thames estuary restored. Ocean dumping of sewage sludge results in increase of sea bird. (Clark, 2001) 41

6

Public health risks Beach can be closed temporarily due to sewage contamination 80 million people visit the beaches of Los Angeles and Orange Counties each year, and according to a new study by researchers at UCLA and Stanford, as many as 1.5 million of those visitors are sickened by bacterial pollution, resulting in millions of dollars in public health costs. 42

Pathogens 



Pathogens in sewage 

Enteric bacteria, e.g., Salmonella, Shigella



Virus, e.g., polio, hepatitis virus, rotavirus



Protozoa, e.g., Giadia, Cryptosporidium



Eggs of intestine parasites

Routes of infection: contamination on bathing water or seafood 

Through contacts with or incidental ingestion (cut/skin abrasion)





Consumption of contaminated seafood

Survival of pathogen in seawater 

Bacteria can become dormant



Virus can be very persistent

43

Risk of contaminated food 

Eggs of Parasites 

 

 

High risk if sewage or sludge used in salad crops. Di s c har gewas t e st os e amayc ompl e t epar as i t e s ’ l i f ec yc l eandl e ad to infection of human when consuming infected sea products. Problems are greatest in tropical countries, e.g., Southeast Asia

Seafood 



Hookworm and tapeworm are resistant to drying and may persist in crude sewage and sewage sludge

Higher risk for filter feeders, e.g., bivalve mollusks. Accumulate human pathogens on gills.



Depuration is required before marketing.



Crustaceans and fish do not presents risks.

Biotoxin: 

Due to harmful algae 44

Beach monitoring in US 







The BEACH Act (Beaches Environmental Assessment and Coastal Health) of 2000 required coastal states and states bordering the Great Lakes to adopt EPA's most current recommended bacteria criteria to better protect beach bathers from harmful pathogens. 

E Coli.



Enterococci

Beach notification actions are usually either 

A beach advisory, warning people of possible risks of swimming



Closing a beach for public swimming.

In 2007, of the 3,602 coastal beaches in US that were monitored, 1,167 (32%) had at least one advisory or closing. 94% of beach notification actions reported during the 2007 swimming season were a week or less.

45

Beach monitoring in Taiwan 項目

採樣日期 採樣天候

大腸桿菌群 腸球菌群 (菌落數/100毫升) (菌落數/100毫升) 30 小於10

試分級

福隆

97.9.1



新金山

97.9.1



33

小於10



崎頂

97.9.1



450

290

尚可

通霄

97.9.1



13

10

大安

97.9.1



3100

280

馬沙溝

97.9.1



小於10

小於10

優 不符甲類標 準 優

西子灣

97.8.31



180

29



旗津

97.9.1



11

12



杉原

97.8.31



小於10

小於10



墾丁跳石 (南灣休憩 區海岸)

97.9.1



小於10

小於10





46

Sewage treatment

7

The sewage treatment involves three stages, called primary, secondary and tertiary treatment. First, the solids are separated from the wastewater stream. Then dissolved biological matter is progressively converted into a solid mass by using microorganisms. Finally, the biological solids are neutralized then disposed of or re-used, and the treated water may be disinfected chemically or physically. The final effluent can be discharged into a stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf course, green way or park. 47

Typical wastewater quality and treatment scheme Parameter

Conc. (mg/L)

BOD

100 ~ 300

COD

250 ~ 1000

TDS

200 ~ 1000

SS

100 ~ 350

TKN

20 ~ 80

TP

5 ~ 20

Water is typically > 99.9%

(Clark, 2001)

48

Primary treatment (physical) 



Screening: remove large float objects that may damage pumps and clog pipes, e.g., bar screen, fine mesh screen Grit chamber:  



Primary clarifier 

  

 

Horizontal velocity typically 0.3 m/sec; detention time 45~90 sec Allow sand, grit (s.g. = 1.3~2.7) and other heavy materials to settle out. Flow speed is reduced sufficiently to allow most of the SS to settle out by gravity Detention time: 2~ 3 hours SS removal: 50~65 % BOD removal: 25~40 %

Odor/VOCs controls (volatile organic matters) Flow equalization 49

Secondary treatment (biological) 

Trickling filter (滴濾池) 





Biological tower: plastic media was used to increase the surface area of biofilm; equivalent treatment to rock beds with smaller land area.

Activated sludge process 



WW is sprayed on the surface of coarse rocks, forming biofilm that adsorbs and consumes organics in the water as it percolates through the bed

Activated sludge and a large amount of air is pumped into the tank to enhance the biodegradation of wastewater



Remove more BOD than trickling filter



Detention time: 6 ~ 8 hours;

Secondary clarifier: 

Effluent: BOD and SS typically 30/30



Sludge was recycled back to AS or diverted to further treatment.

50

Tertiary treatment (advanced) 

Residual SS remove:  



Nutrient removal  



N: Ammonia oxidation; nitrification/denitrification; stripping P: Chemical precipitation; biological phosphors removal

Toxic compounds and refractory organics  



granular medium filtration Membrane Microfiltration (MF); ultrafiltration (UF)

Carbon absorption Chemical oxidation

Dissolved solid   

Chemical precipitation Ion exchange Nano filtration (NF); reverse osmosis (RO) 51

Disinfection  

Selective destruction of disease causing organisms Chlorine and its compounds (Cl2, ClO2, NaOCl)   



Ozone  



Effective mixing, contact time, residual are important to achieve effective bacteria kill. Contact time: typically 15~45 min. CT value; N/N0 = (1+0.23CT)-3 Very reactive; deep and covered contact chambers are used Not persistent in the effluent

Ultraviolet (uv)   

Safe, no hazardous chemicals are used Low contact time (20 ~ 30 seconds with low-pressure lamps) SS in the wastewater can render UV disinfection ineffective 52

River pollution 

Greatest volume of organics to be disposed of: Urban: human sewage  Intense farming: animal wastes 



River water BOD Unpolluted: < 2 mg/L  Grossly polluted: > 10 mg/L 



River pollution index (RPI) BOD, DO, NH3-N, SS  Four tiers 

(www.epa.gov.tw) 53

River pollution index (RPI) Parameter

未(稍)受污染

輕度污染

中度污染

嚴重污染

DO

> 6.5

4.6~6.5

2.0~4.5

< 2.0

BOD

< 3.0

3.0 ~ 4.9

5.0 ~ 15

> 15

SS

< 20.0

20 ~ 49

50 ~ 100

> 100

NH3-N

< 0.5

0.5 ~ 0.99

1.0 ~ 3.0

> 3.0

Score

1

3

6

10

RPI

6

Ex. 96/5/3 鹽水溪橋(河口)  DO=1.2; BOD=9.5; SS=34; NH3-N=14.8  RPI= (10+6+3+10)/4=7.25 (嚴重污染) 54

Ocean Outfall

8

Ocean and large lake, e.g., the Great Lake, provide extensive assimilation capacity that used by many communities for wastewater disposal. Typically, carries to an offshore discharge point by a laid on/buried pipe, or tunnel.

55

Density of seawater 

Density of seawater frequently expressed in σt unit, σt = real density –1000 g/L

(Metcalf & Eddy, 1991) 56

Wastewater discharge plume in the ocean 







Initial mixing zone (nearfield) Initial mixing involves effluent buoyancy, ambient stratification, and current. Buoyant plume forms and rapidly rise to the water column If ambient water stratified: Entrained deep denser water which reduces bouyancy If ambient water weakly or not stratified (as in winter): plume rises to surface Beyond initial zone (farfield) carries away by ambient current and dilute through diffusion

(Metcalf & Eddy, 1991) 57

Los Angeles Hyperion Treatment Plant

(From Hyperion Treatment Plant report)

58

(www.parsons.com)

59

San Diego South Bay Ocean Outfall 

Project Duration: 1986 –2000



Constructed Value: $ 133 Million





Capacity: average dry weather flows of 660,000 CMD and peak flows of 1,260,000 CMD Extends 3.5 miles offshore and discharges effluent in approximately 100 feet of water



Tunnel boring machine was used to excavate the tunnel



The tunnel has an 11 foot diameter and is 19,000 feet long



Barges were used as platforms to trench the ocean floor, install pipe,





The 1.5 miles of exposed pipeline was covered with more than 400,000 tons of ballast rock to protect the outfall from ocean waves and ship anchors Tunneling minimized environmental impacts to a local salt marsh and barrier dune habitat, a major refuge for birds and wildlife 60

(Metcalf & Eddy, 1991) 61

(Metcalf & Eddy, 1991) 62

(Metcalf & Eddy, 1991) 63

(Metcalf & Eddy, 1991) 64

(Metcalf & Eddy, 1991) 65

(Metcalf & Eddy, 1991) 66

Consequence of organics charged to marine environment

9

67

Consequence of organics charged to estuaries Thames estuary case: a history of pollution and recovery Year

Conditions

~ 1820

Important Salmon river

1820~50

Progressed overloaded

1850s

Foul smelling and devoid fish

1890s

Outfalls reduced and sewer piped to treatment plants. Sludge dumped at sea

1900

Remarked improvement in water quality

1950s

Population growth out runs plant capacity. 30km of anoxic stretch

1964~76

Expansion of treatment plants

1979

Dramatic rise of oxygen, benthic fauna, and fish 68

Thames estuary case

(Clark, 2001) 69

Consequence of organics charged to sea 

Case study of sludge dumping sites Barrow Deep  Garroch Head  New York Bight 



Accumulation can be measured by Organic contents of sediments  Heavy metal concentrations, e.g., silver  Spores forming bacteria 

70

Barrow Deep dumping site, outside Thames estuary UK

(Clark, 2001)    

Dispersive site, strong bottom current and high water exchange 5 million ton/year since 1890s ~ 1998 No local effects, only some small patches of slightly elevated organics. Organic enrichment the southern North Sea

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Garroch Head dumping site, west of Scotland

  

Cumulative site in area of weak current 1.5 million ton/year since 1974 ~ 1998 Severe but localized impact on the seabed

(Clark, 2001)

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New York Bight dumping site

 

“12-mi l es i t e ”( 1924-86): 50 m deep, 10 million ton/year Evident of organic enrichment and metal accumulation “106-mile s i t e ”( 1985-92): 2500 m deep, 8 million ton/year Dispersed over 10,000 km2

(Clark, 2001)

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(Clark, 2001)

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Effect on benthic organisms 







Ocean sludge dumping has a direct effect on the benthic fauna, which is exposed to he sedimentation of particulate matter rich in nutrients and bacteria. Smothering by PMs and reduction of DO due to enhanced bacteria activities excludes more sensitive species Opportunist species, e.g., Capitella capitata (小頭蟲), become dominant and outcompete other species; diversity decreases at the discharge site. Capitella can be indicator species for organic pollution

(Clark, 2001) 75

10

Regulations GESAMP put sewage discharge to sea top of its list of concern due to high public health risk. Many deaths reported annually in area with poor hygiene.

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Standard for commercial/recreational uses

(Clark, 2001)

In Taiwan, coliform groups as indicator  Effluent standards: < 200,000~300,000 CFU/100 mL  Ocean outfall standards: < 5,000,000~10,000,000 CFU/100 mL  Ocean environment: < 1000 CFU/100 mL

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