Tai lieu 4 ( Mô Hình Lan Truyền Ô Nhiễm Trong Đất)

Từ kết quả nghiên cứu đáy các bãi rác cho thấy hầu hết các bãi rác chưa được xây dựng đúng tiêu chuẩn. Hệ số thấm của nền đất dưới các bãi rác khoảng 106 đến 104 cms chưa đạt yêu cầu kỹ thuật. Hầu hết các bãi rác đều gây ô nhiễm môi trường nước xung quanh và vượt ngưỡng yêu cầu so với quy chuẩn nước thải của bãi chôn lấp chất thải Mô hình lan truyền bằng thực nghiệm và Geoslope đều cho thấy tầm quan trọng của lớp đáy bãi rác, với độ chặt lớn, hệ số thấm nhỏ có khả năng kìm hãm và ngăn chặn được các chất ô nhiễm. Tuy nhiên nước thấm qua đất dung trọng 1,55 (gcm3); 1,6 (gcm3); 1,65 (gcm3) có nồng độ COD, chì và cadimi vẫn vượt ngưỡng cho phép. Nước thấm qua đất có dung trọng 1,7 (gcm3), đạt 98% độ chặt tiêu chuẩn có nồng độ COD đạt tiêu chuẩn so với quy chuẩn nước thải của bãi chôn lấp chất thải, tuy nhiên vẫn vượt ngưỡng so với tiêu chuẩn nước mặt và nước tưới tiêu, gấp 410 lần. Nồng độ chì, đồng và kẽm đạt tiêu chuẩn cho nước sinh hoạt và tưới tiêu. Nồng độ cadimi vượt ngưỡng so với tiêu chuẩn cho nước sinh hoạt. Kết quả mô phỏng sự lan truyền chất ô nhiễm theo chiều sâu dưới đáy bãi rác bằng Geoslope cho thấy với nền đất được đầm chặt đạt hệ số nén K98, hệ số thấm đạt khoảng k = 109 cms: thì chất ô nhiễm không bị phát tán hoặc phát tán với độ sâu rất nhỏ dưới 10m

Practical methods assessment of risk related

to transportation of dangerous

goods by pipelines

Mieczysław Borysiewicz

Institute of Atomic Energy ,

Otwock-Świerk

The risk connected with

transportation

¾ Main hazardous related to transportation

of liquid (oil or refining products) in case

of leakage is derived from flammable and toxin substances Flammable is of great

importance for safety whereas toxic is

dangerous for environmental

¾ It’s necessary to take into account many elements while consideration of hazardous sources

The most important are:

Physical-chemical substance properties, connected with flammable and toxic – it’s necessary to

consider components of product in detail

Size leakage depends on:

‹ diameter of pipeline, product density, pressure in pipeline, topography and duration time of leakage,

‹ material properties and mechanisms of damages, which are factors forming leakage,

Table 1A

100 -

12 39

49

%

100 0,773

0,089 0,285

0,359 TOTAL

60,9 0,445

0,054 0,173

0,218

Outside impact

1,8 0,013

0,002 0,005

0,006

Natural hazard

11,5 0,085

0,01 0,033

0,042

Corrosion

6,4 0,047

0,006 0,018

0,023

Operating errors

19,4 0,143

0,017 0,056

0,07

Mechanism

damage

Whole Crack

Hole Leak

Percent Appear damages / 1000 km-year

Frequency of failures pipelines for derivatives of liquid oil substances

100 -

12 39

49

%

100 0,42

0,051 0,164

0,206 TOTAL

31,3 0,132

0,016 0,051

0,064

Outside impact

3,1 0,013

0,002 0,005

0,006

Natural hazard

20,2 0,085

0,01 0,033

0,042

Corrosion

11,2 0,047

0,006 0,018

0,023

Operating errors

34,2 0,143

0,017 0,056

0,07

Mechanism

damage

Whole Crack

Hole Leak

Percent Appear damages / 1000 km-year

Reason failure

B Frequency failures petroleum pipelines of thickness from 5 to 10 mm

Table 1B

Frequency of failures pipelines for derivatives of liquid oil substances

100 -

12 39

49

%

100

0, 303 0,037

0,118 0,148

TOTAL

4,9 0,015

0,002 0,006

0,007

Outside impact

3,3 0,013

0,002 0,005

0,006

Natural hazard

29,5 0,085

0,01 0,033

0,042

Corrosion

16,4 0,047

0,006 0,018

0,023

Operating errors

45,9 0,143

0,017 0,056

0,07

Mechanism

damage

Whole Crack

Hole Leak

Percent Appear damages / 1000 km-year

Reason failure

C Frequency failures petroleum pipelines of thickness from 10 to 15

mm

Table 1C

Frequency of failures pipelines for derivatives of liquid oil substances

0,289 0,354

0,387 0,42

TOTAL

0,0013 0,066

0,099 0,132

Outside impact

0,013 0,013

0,013 0,013

Natural hazard

0,085 0,085

0,085 0,085

Corrosion

0,047 0,047

0,047 0,047

Operating errors

0,143 0,143

0,143 0,143

Mechanism damage

3m 2m

1,5m 0,9m

Deep of pipeline Reason failure

Frequency failures petroleum pipelines in depend on deep pipeline

Table 2

Estimate velocity discharge

For velocity discharge from pipeline transportation liquid have impact

coefficients such as:

Scenarios of failures

The scenarios can be split into two groups:

¾ scenarios leading to fires and explosions

¾ scenarios leading to pollution of environment (ground water, wet ground, soil)

One can get probabilities of individual

scenarios by defining data determining

probabilities of particular environmental

conditions and applying quantitative

principles of analysis of events tree

Fires and explosions

In case fires and explosions it is necessary

to consider three possibilities:

¾ pool fire – liquid fire, which formed leakage area,

¾ flash fire (fire of vapour plume), fire of gas

or mixed vapour with air without

overpressure,

¾ vapour cloud explosion: cased by ignition with overpressure

Fires and explosion

¾ Probability of pipeline (with oil) explosion is not big even in case of great leakage In the DoT

(Department of Transport USA) data until now only one such event has been registered But it

is estimated that in fire can appear in 4% and 6% of leakages

¾ Maximum distance of vapour cloud fire can be estimated as 1.4% volume of plume in air

Examples calculation for fires

Table 1 Pool fire of petrol – late ignition

30 96

25 63

19 73

53 53

Medium clay

10mm

65 45

46 30

Medium clay

168mm

110 126

70 78

85 100

100 100

Medium clay

219mm

126 78

100 164

Medium clay

324mm

126 126

78 78

100 100

205 205

Medium clay

406mm

Zone radius for 10kw/m2 (m)

Length of flame (m)

Pool area (m)

Velocity discharge (kg/s)

Soil type Hole

diameter

Tabel 2 Pool fire of petrol – Early ignition

19 17

11 5,3

10mm

40 31

26 30

168mm

67 47

48 100

219mm

83 56

62 164

324mm

91,2 60

68,9 205

406mm

Zone radius for 10kw/m2 (m)

Length of flame (m)

Pool area (m)

Velocity discharge (kg/s)

Hole diameter

Examples calculation for fires

Table 3 Probability of ignition sources

Leakage – big hole Crack

Probabilities for failure scenarios

diagrams below

generating by these trees are also

¾ Events tree for pipeline rupture and medium hole (rural).

Probabilities for failure scenarios

¾ Events tree for leakages (rural).

Probabilities for failure scenarios

¾ Events tree for pipeline rupture and medium hole (urban area).

Probabilities for failure scenarios

¾ Events tree for leakages (urban area).

Probabilities for failure scenarios

Hazard of environment

Releases of hydrocarbon fuel from pipelines can cause different

consequences for:

• biological life in water and soil

• surface water

• soil and geology

• using rural terrain etc

Modeling pollutants in porous media

interpretation, including assumption about

homogeneous flow in ground water in given

direction and homogenous parameters

• Example of that model is a simple model of

hydrocarbon pools, HSSM [Charbeneau Randall J., Weaver James W., Lien Bob K., Kerr Robert S., US EPA, The hydrocarbon Spill Screening Model (HSSM), 1995], available in Institute of

Atomic Energy in Swierk

Modeling pollutants in porous media

are discharged nearly ground surface and transported down

through aeration zone up to level of ground water.

spread in horizontal direction Components of hydrocarbon lens are dissolved in ground water flowing under the lens These

components arise stain, which can pollute wells and other

sensitive receptors which are located in flow direction.

on quantity of light liquids in non-aqueous phase liquid,

coefficients of phases distribution, velocity flow of ground water etc The results of this model should be taken as rough

approximation, as many other approximations have been used in the model.

Modeling pollutants in porous media

• Another considered physical problem is

pollutions of porous media in case of discharge

of organic substances – the so-called

non-aqueous liquid phase (NAPL) in under surface heterogeneous granulated soils

• The organic liquids can be lighter than water

(LNAPL i.e., based on hydrocarbon petrol) or heavier than water (DNAPL i.e., based on

chloral hydrocarbon)

Modeling pollutants in porous media

Three basic mechanisms of spreading pollutants of

organic liquids on upper layer ground are:

caused by gravity and capillary forces.

precipitating of source in aeration zone In case of organic liquids heavier than water, their components are picked out by wet

ground.

where increase of density of gas causes motion down Division between pollutants phases: aqueous and gas additionally

increases potential of components which causes particles

migration

• The spreading pollutions NAPL in under surface groundcaused by surface realase

Modeling pollutants in porous media

into consideration all three mechanisms of

transport pollutants that can be used to calculate pollutions of soil and ground water as a result of release of oil derivates is a model applied in

computer program NAPL Simulator [GuarnacciaJoseph, Pinder George, Fishman Mikhail, Kerr Robert S., US EPA, EPA/600/R-97/102, NAPL-Simulator, 1997], applied in Institute of Atomic Energy in Swierk too]