Equipments and Devices for Environmental Monitoring and Pollution Control
Pollution control devices include:
• Dust collection system
• Baghouse
• Cyclones
• Electrostatic precipitators
• Scrubbers
• Spray tower
• Sewage treatment
• Vapour recovering systems
Separators are devices that are used to control particulate matters. Particulate matters are common pollutants present in the emission of an industry. They have applications in the emission of an industry and in mechanical operation for dust control such as pulverizing, grinding, blending, wood work and other dusty operations e.t.c.
There three types of devices which are commonly used as internal separators, they are:
• Gravitational settling chambers
• Cyclone separators
• Baghouse filter (cloth screen or fabric filters)
Gravitational settling chambers
They are used to separate larger particles size greater than 50 microns. A stream of dust laden gas is passed into the settling chambers where the velocity of the gas is suddenly reduced as a result of the dust particles that settle down and it is collected through a hopper at the bottom. The collection efficiency of the settling chambers can be increased by installing a series of settling chambers in parallel.
Advantages of gravitational settling chambers
• It is cheaper to maintain and install
• It has low energy consumption
• It is very easy to maintain
• Very simple technology is required
• Ensures dry and continuous disposal of solid particles.
Disadvantages of gravitational settling chambers
• It requires large space for installation
• It is not highly efficient
Cyclonic Separators
Cyclonic separation is a method of removing particulates from air, gas or liquid stream without the use of filters through vortex separation. Rotational effects and gravity is used to separate mixture of solid and liquid. A high speed rotating (air) flow is established within a cylindrical or conical container called Cyclone. Air flow in a helical pattern beginning from the top of the cyclone and ending at the bottom of the cyclone, before exiting the cyclone. Large particles fall to the bottom of the cyclone where they can be removed. As the rotating flow moves towards the narrow end of the cyclone, the rotational radius of the stream is reduced, separating smaller particles. Large scale cyclones are used in sawmills to remove sawdust from extracted air. Cyclones are also used in oil refineries to separate oil from gases.
Advantage of Cyclonic Separators
• Simple technology
• Low cost maintenance
• High efficiency
• It is easy to maintain
• Low energy consumption
Disadvantages of Cyclonic Separators
• It cannot collect particles between 5-10 microns effectively
• Equipment can be subjected to severe corrosion and abrasion.
Fabric Filters (Baghouse or Cloth Screen Filter)
These are devices by which gas is purified through various filtering cloths (cotton wool, chemical filters) or fabric filters. A typical baghouse fiter consist of tabular bag or an envelope mounted in a manner that the particle laden gas passing through the filter get deposited on the inside surface of the bags which are dusted by shaking at regular interval. The dusts are collected in a hopper at the bottom. Bag filters have high efficiency but the filters are required to be cleared and changed at regular intervals. Baghouse filter can be used to remove particulates out of air and gas release from commercial processes or combustion from electricity generation power plants, steel mill, pharmaceutical industries, food manufacturers and chemical industries use baghouse to control emission.
Advantages of Fabric Filters (Baghouse or Cloth Screen Filter)
• High collection efficiency for particles of all sizes, especially those smaller than 10 microns in size
• Simple construction and operation
• Low energy consumption
• Dry disposal of collected materials.
Disadvantages of Fabric Filters (Baghouse or Cloth Screen Filter)
• It is difficult to maintain
• The equipment is usually large, therefore occupying a lot of space.
POLLUTION CONTROL PRACTICES
Pollution control practices include: recycling, regulation, restriction, reusing, reducing, preventing, composting, recovery, mitigation e.t.c.
RECYCLING
Recycling is the process of using waste material to form a new product to prevent waste of potential useful materials. Recycling is also the collection of a product by the public and return of this material to the industrial sector. Examples of recycling are the collection of newspapers and aluminium cans by the individuals and their eventual return to paper manufacturers them and sell to members of the public. The recycling process requires the participation of the public, since the public must perform the separation step.
Regulation
Regulation is the process of enacting laws or rules to protect the environment from adverse effect of pollution. Many nations enact legislation to regulate various types of pollution as well as to mitigate adverse effects of pollution. The purpose of environmental regulations on pollution control is set to maximum levels of the pollutants to be released into the environment and to prosecute offenders of pollution control laws. Regulation helps in environmental monitoring.
Development of New Technologies for Pollution Control
In this age and time, science and technology are advancing at an alarming rate. The rapid development of science and technology brings considerate benefits to human beings, but it also brings environmental pollution and energy shortage. With advances in technology to exploit more energy (including fossil, fuel, coal, natural gas and so on) to meet the demand of the growing population. The more population we have, the more energy we need. With the expansion of industrialization, requirement for energy worldwide has increased. We have a great need for energy because of rapid growth of our economy.
Environmental pollution can be reduced by green technology, renewable and clean energy such as solar energy to solve energy crisis. But these new technologies need a large amount for investment, research and development. Most countries cannot afford it. Therefore these methods are infeasible in the short term e.g of new technology is nano-porous fibres, it traps carbon dioxide and other pollutants so they can be removed and recycled back into the production process.
GIS for Pollution Detection
Geographical information system (GIS) was established in 1960 in Canada from Canadian information system, it was implemented in 1964 by Tomhinson. It gained awareness in 1980. The use, training and popularity of GIS grew in 1980. GIS is a system for capturing, storing, checking, manipulating, analysis and displaying of data that are spatially referenced to the earth. GIS can also be defined as computer based set of procedures used to store and manipulate geographical data. GIS is an information technology and advanced technique of investigation.
GIS is used by environmental researchers, urban management, business world, government and non-governmental programmes e.t.c. GIS can be applied in environmental planning and monitoring in conservation area planning, land use planning, air quality monitoring and water quality monitoring e.t.c.
AIR SAMPLER
Air sampling devices are used to detect smoke, particulates and gases. The equipment used, selected and its siting is determined by the problem being studied and the purpose to be served. Monitoring instruments for measurement of pollution include:
Pollutants Measurement Method
Carbon monoxide (CO) gas chromatography, non-dispersive infra-red, spectrophotometry
Sulphur dioxide ultraviolet pulsed fluorescence, flame photometric dilution or permeation tube calibrators
Ozone ultraviolet spectrophotometer, gas phase, chemiluminiscence, gas
Phase titration (GPT), calibrators
Nitrogen dioxide chemiluminiscence, permeation or GPT calibrators
Lead (Pb) high volume sampler and atomic absorption analysis
Suspend particulate matter high volume sampler and weight determination
Hydrocarbons flame ionization and gas chromatography, calibration with methane
gas tank.
Environmental Monitoring Laboratories
Environmental monitoring laboratories are laboratory that deals with measurement, sampling, analysis, observation and evaluation of pollution levels in air, water, soil, food and living organisms in an environment.
Environmental monitoring provides pollution information and data.
Environmental monitoring could make one predict the possible hazards that will be generated in future.
Environmental monitoring laboratories sees to the level at which industries or polluters comply with laid standards.
Environmental monitoring guide environmental impact assessment procedures, it also gives useful advice and suggestion to industries on how to manage their waste.
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