Different methods and technologies for improving environmental impact across air, water, waste etc.

Question 1

How does a bag filter work?

Answer 1

1) Gas stream is passed through a fabric filter which has smaller pores
2) This filter then collects the large particles and clean air passes through and out
3) The particles are removed by shaking them or by replacing the filter as the filter will get full and won’t work
4) Can be used for dust, smoke, fumes

Question 2

What are the various local exhaust ventilation systems?

Answer 2

• Enclosing hood
• Receiving hood
• Capturing hood

Question 3

What is meant by an ‘enclosing hood’?

Answer 3

Full: This is a fully enclosed (either room or area) where the operator and process are enclosed e..g for paint spraying.

Partial: have openings for material/operator to access e.g. fume cupboards.

More effective than a capturing hood

Question 4

What is meant by a ‘Receiving hood’?

Answer 4

• Usually takes places outside of the hood
• It receives the contaminated cloud which has speed and direction usually process-generated.
• Hoods can be fixed or moveable
• Example= canopy hood over a hot process

Question 5

What is meant be a ‘Capturing hood’?

Answer 5

• Process, source & contaminant cloud is outside the hood
• Generates airflow at and around source to capture and draw in contaminant-laden air. Can be fixed or moveable so is as near to source as possible
• Most common local exhaust ventilation system

Question 6

How do gravitational separators work?

Answer 6

• Accelerate spin given to contaminated gas stream so that it throws dust particles to the wall of the equipment and falls into a hopper
• Common = cyclone dust separator
• Centrifugal force can enhance it

Question 7

How do electrostatic precipitators/separators work?

Answer 7

• Closely spaced parallel wires between metal plates which carry high voltage and when air stream enters it causes a voltage difference and gives the particles charge
• The particles with a charge then are attracted to their opposite poles and pull to them and stick, allowing clean air to pass
• Disposed of via shaking/vibrating in a hopper
• Can collect dust, smoke and fumes

Question 8

What is the use of magnetic separators?

Answer 8

• Installed into the product feed lines to remove any ferrous metal contaminates especially if risk of explosions.
• Fully enclosed to avoid dusting and reduce fugitive emissions

Question 9

How do wet scrubbers work?

Answer 9

• Contaminated air flowing upwards against a cascade of water or an acid/alkaline solution.
• Soluble gases and particles removed (via absorbents)and cleaned air flows out of top. Horizontal plates give large surface area to improve efficiency.
• Contaminated solution removed from base and treated separately.
• Can be used to remove vapours and gases e.g. SO2, dust etc. Can include those which may form explosive mix.

Question 10

What is Flue Gas Desulphurisation? (FGD)

Answer 10

-The use of limestone slurry that reacts with the sulphur dioxide passing through, enabling removal of this contaminant

Question 11

How do packed scrubbers work?

Answer 11

• Packed beds of broken stone, ceramic, metal etc.
• Remove gaseous or vaporous pollutants from an air stream by contacting the contaminated air stream with a scrubbing liquor that absorbs or chemically reacts with the pollutants.
• Cleaned air discharged to atmosphere and the contaminated scrubbing liquor is either disposed of correctly or reused

Question 12

What are High Energy Venturi Scrubbers?

Answer 12

• Remove fine dust particles from industrial air streams

- Often installed to remove fine particles from hazardous, volatile or corrosive gas streams

Question 13

How does a ‘Water Wall’ work?

Answer 13

• Level of water rises and closes off direct air flow at rear of unit by the vacuum effect of the air extractor
• Weight of water causes permanent collapsing wave effect in which contaminated air is drawn and any particles are captured and settle out in water reservoir at the base of system
• Residues removed for disposal

Question 14

How do ‘Carbon adsorbers’ work?

Answer 14

• Adsorber is activated by thermal or chemical processing to develop open port structure in small carbon particles
• The resulting large ratio of surface area to weight provides large receptive area where gas molecules can be bound/adsorbed onto solid materials
• Can be used for pollution control and solvent recovery
• Activated charcoal useful for intercepting offensive odours, recovering solvents or trapping gases/vapours

Question 15

What is meant by a bund?

Answer 15

• An area contained by a rectangular wall built upon a concrete slab in which storage tanks are placed
• Should be impervious to any spillage/leak
• Shouldn’t be connected to any drains or watercourse or discharging incorrectly

Question 16

What is the use of 3 stage interceptors for avoiding water source contamination?

Answer 16

• Improves the quality of effluent discharged to sewer or to surface water
• Prevents drain blockages
• Use of float switches enable oil/water separation as oil floats to top due to density

Question 17

What are proprietary absorbents?

Answer 17

Similar to sand purpose to soak up spillages/leaks but are available in granules, sheets and pillows

Question 18

What is the purpose of drain seals?

Answer 18

Seal drains or pipes to retain any contaminants that may have gone into watercourse. Should be easily accessible to put on if such incident occurs

Question 19

What are booms?

Answer 19

• Designed for use on watercourses but also to isolate/divert/contain spillages
• Absorbent booms= absorbent material suitable for hydrocarbons and aqueous chemicals
• Plastic= inflated with air or water

Question 20

What is cake filtration?

Answer 20

• When filtered material cakes upon filter. Smaller particles travel through porous cake and get trapped deeper in the cake
• Cake removed when no longer permeable to allow liquid flow
• Disposed in landfill or for use in agriculture

Question 21

What is deep-bed filtration?

Answer 21

Cylindrical or rectangular packed bed through which suspension to be filtered passes through. Clean air passes through top after packed beds.

Question 22

What is membrane filtration?

Answer 22

When water passes through the membrane only (like reverse osmosis). Dissolved and suspended material is retained by process

Question 23

What is meant by incineration of waste?

Answer 23

The controlled burning/combustion of wastes at high temp to reduce the volume

Question 24

What is meant by compaction of waste?

Answer 24

A well-developed and reliable volume reduction technology mainly for processing solid man-made, low-level waste

Question 25

What is meant by cementation of waste?

Answer 25

Cementing, using specially formulated grouts, to immobilise radioactive material
It is then suitable for storage and disposal

Question 26

What is meant by vitrification?

Answer 26

The process of converting materials to glass, for processing high-level waste

Question 27

What are the 4 steps of the PDCA cycle and what does each stage mean?

Answer 27

1) PLAN; establish objectives & processes to deliver results in line with expected outputs
2) DO; implement plan, execute processes and measure output
3) CHECK; Study actual results collected in DO stage and compare against expected results from PLAN to determine any differences
4) ACT; Determine and implement corrective actions on significant differences between actual and planned results. Determine where to apply changes to continuously improve

Question 28

What are the stages for the ISO14001 Model for continual improvement?

Answer 28

1) Environmental Policy
2) Planning
3) Implementation
4) Operation
5) Checking
6) Corrective Actions
7) Management Review

Question 29

What are the key 7 components that need to be implemented to participate in EMAS?

Answer 29

1) Environmental Policy
2) Environmental Review
3) Environmental Programme
4) EMS
5) Environmental Audit Cycle
6) Environmental Statement
7) Validation

Question 30

What are the 6 stages of phased implementation needed to be assessed for ISO14001 certification?

Answer 30

1) Commit & establish baseline
2) Identify & ensure compliance
3) Develop objectives & targets
4) Implementation and operation of EMS
5) Checking, audit and review
6) Acknowledgement of EMS

Question 31

What is primary containment?

Answer 31

The tank or vessel in which material is stored

Question 32

What is secondary containment?

Answer 32

Used for local, remote or combined containment. Most cases local= a bund. These containments are either used in isolation or in combination with a bund to store more material.

Question 33

What is remote containment?

Answer 33

Where there is no bunding or if there is bunding but the risk of overspill caused by firefighting run-off water has been identified

Question 34

What is meant by composting in waste treatment?

Answer 34

Biological decomposition of organic matter in waste under controlled conditions

Question 35

What is meant by sanitary landfilling?

Answer 35

Controlled burial of waste

Question 36

What is meant by gasification?

Answer 36

Biological decomposition of organic matter in waste to obtain methane and other gases

Question 37

What is meant by pyrolysis?

Answer 37

High temp conversion of organic materials in absence of O2 to obtain combustible by-products