Often considered a simple item, water is a living element of daily life, both in terms of personal health for users, industry and commerce. Whether focusing on water cleaning for drinking or wastewater treatment, Crowcon is proud to have provided a lot of users in the water industry with gas detection equipment; Keep workers safe all over the world.
Gas detectors should be suitable for the specific environment they need to operate. Accordingly, the water industry is a wet and dirty environment with many toxic and flammable risks as well as the risk of oxygen depletion.
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| Gas detection measurement in the field of clean water filtration and wastewater treatment |
Part 1 – Clean Water Purification Plant
Overview process:
- The process of clean water treatment is water treatment before general distribution, making it suitable for drinking. This water usually begins as groundwater or surface water:
- Groundwater: Water taken from the underground. This water tends to be relatively clean due to natural processes (natural filtration) and therefore only minimal cleaning is required
- Surface water: Water taken from surface sources (e.g., rivers and reservoirs). This water is in direct contact with the environment so it needs to be treated a lot.
Gas detection during cleaning
- The most common gas hazards during clean water treatment are oxygen depletion and exposure to disinfectants such as chlorine, ammonium and ozone.
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| Gas detection measurement in the field of filtration and clean water treatment |
Stage 1.1 – Obtaining water and storing
Process overview
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- Water is collected from surface sources and stored in open reservoirs or underground water drains. The reservoirs allow the mixing of water that has been collected at current levels thus diluting the contaminant. Water retention allows for improved water quality including the release of debris, with sunlight damaging organic matter and reducing bacteria.
- Water is then pumped into treatment facilities.
Gas detection
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- Water transport pipes require normal hygiene and safety checks, during this operation, many handheld gas detectors are used to ensure the safety of the workforce. Pre-in check-in must be completed before entering any restricted spaces and often O2, CO, H2S and CH4 are monitored. In essence, the limited spaces are small in size, so the handheld gas detector must also be neat and not entangle the user, and at the same time be able to withstand the wet and dirty environment that they must perform. Early and clear indicators of any increased gas monitored (or reduced oxygen) are of critical importance with large alarms and bright light alarms for users.
Stage 1.2 – Water Purification
Process overview
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- Screening is used to remove possible floating objects in the input water. This water is usually from open reservoirs and often consists of such matter as twigs, leaves and general litter.
- The initial inspection prevents these objects from causing other problems on the pipeline.
Gas detection
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- If the filtration area is clogged with different materials that they collect, then it is necessary to clean and maintain the operation. Due to the nature of the areas in question, it should be considered as a limited space, therefore it is required to equip a multi-quota gas detector to ensure the safety of workers. O2, H2S and CH4 are generally monitored and depending on the specific location, other gases may be part of the general requirement.
Stage 1.3 – Filtering
Process overview
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- Chemical precipitations are often added to link suspended substances. This is also known as ‘flocculation – flocculation or glue flocculation’. This makes the condensed particles larger and therefore easily removed before further processing. The ‘floc’ is removed and the water is ready for the next stage.
Stage 1.4 – Seding Tanks
Process overview
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- Water then passes through several sedimentary tanks, at each stage heavy sediment settles to the bottom while clean water passes through
- Aeration – Removes or reduces the level of unwanted compounds (e.g. H2S /CO2) from water, or oxidizes dissolved metals for easy removal.
- Carbon and ion exchange are also methods used by water treatment facilities to better remove particles.
Gas detection
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- The sedate tanks are usually ventilated naturally by taking them outdoors. If this is not the case, then fixed and/or portable monitoring for O2, H2S and CH4 is the minimum requirement that contributes to maintaining a safe working environment. Of course if, during a specific risk assessment, other gases are found in this area of the plant, then fixed and portable detectors may be required.
Stage 1.5 – Permeable Filtration
Process overview
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- Filtering – There are many different forms of filtration
- Granule activated carbon is an advanced system for removing pesticides, organic compounds, unpleasant tastes and odors
- Ozone is added to water to decompose pesticides, organic compounds, ozone also has antibacterial effects
- Fast force filter transmits water through a sand tank, which traps unwanted particles
- Slow sand filter transmits water slowly through fineer sand, removing smaller particles
- The above filtration methods will clean the water, improve the efficiency of the next stage.
Gas detection
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- When ozone is used as part of the filtration process it is usually created on the spot. Ozone is a toxic gas that is even at very low concentrations and therefore requires careful monitoring.The detector is fixed near the location of the Ozone generator or warehouse, linked to an on-site control system. provide media alarms and alarms to ensure notification in case of exit. Due to the nature of the ozone and the way in which it diffuses at normal temperatures, best practice also ensures the use of additional handheld detectors that monitor the user’s breathing area entering these areas.
Stage 1.6 – Final Processing
Process overview
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- Finally, water flows into a chemical contact tank, where disinfectants are added to kill bacteria.
- Chlorine (Cl2) remains the most common form of antiseptic.
- The addition of ammonia (NH3) to chlorine, forming more durable chloramines. Chlorine dioxide (ClO2) is mainly used as the original detergent for odorous surface water.
- Sodium hypochlorite is also added during this process
- Ozone is a very strong oxidative environment, destroying odors, bacteria and viruses.
- All chemicals have specific storage requirements specified locally or nationally.
- Sulphur dioxide can also be used to treat sewage containing chlorine before emiting ‘de-chlorinated’ water.
- Water is then pumped near the place of need and stored ready for use (e.g. in water towers).
Gas detection
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- The storage area of the chemicals used in the final processing stage needs to install a reliable gas detection system. Even mild leakage of chlorine, ammonia, sulfur dioxide or ozone is very harmful. The characteristics of the gas in question need to be considered when placing a fixed detector, which has a suitable exit point. Remote alarm and the ability to perform inter-dynamic action (e.g., turning on the ventilation fan, activating the valve automatically) can be used when a leak is detected. It is necessary to use portable gas detectors with appropriate toxic sensors in these areas to ensure the safety of workers.
Part 2 – Wastewater Treatment
Process overview
- The wastewater treatment process consists of various forms of liquid waste and the task of the treatment is to change it can return to the water cycle for reuse. Wastewater generated by humans and including washing water, feces, urine, laundry waste and processed industrial output as well as water on the road and rainwater flowing out can also include oil, grease and fuel. The process of wastewater treatment is often called the dirty water treatment process.
Gas detection
- Crowcon has been working with the wastewater treatment industry for more than 30 years, noticing harsh environments and various applications in this industry. Apply advanced technologies to ensure optimal solutions, focusing on improving safety both on and off site. The number and volume of toxic and flammable gases in this wastewater environment requires the use of both fixed gas detectors and handheld gas detectors.
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| Mobile and fixed gas measurement in wastewater treatment plant |
Stage 2.1 – Sources of wastewater
Process overview
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- Wastewater is collected from domestic and industrial, usually flushing and drainage routes. Manholes along distribution pipes allow inspection, cleaning and maintenance operations. The principle of natural force is used to transport wastewater along underground systems.
Gas detection
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- During the distribution of wastewater, limited spaces are very common. Flammable detection and H2S gas are common (MAY add CO//or CO2 in some applications) used for CSE. Cleaning and maintenance activities can cause workers to be exposed to toxic and flammable gases as well as oxygen deficiency. The use of handheld multi-indicators for inspection before entering dangerous spaces and continuous monitoring reduces risks for workers.
Stage 2.2 – Pumping station
Process overview
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- Pumping stations are often un man-controlled; Designed to treat raw wastewater from underground load distribution pipes. Sewage is introduced and contained in an underground pit, commonly known as a wet well. Traditional sewage pumping stations combine both a wet and dry well, which is a certain internal distance apart. The pump is installed under the ground on the background of the dry well with suction doors below the water level at the start of the pump. When the sewage level rises to a pre-defined point, the pump lifts the sewage into one drain to move to the next station.
Gas detection
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- Since many pumping stations are unman overmanded, both fixed and mobile monitoring methods are often used.
- The fixed system with on-site installed control panel provides clear light and sound warnings about the danger level of gas as well as inter-dynamic control such as ventilation fan activation. Fixed application focus solutions are capable of monitoring gas levels just above different wet water levels, alerting the workforce to hazards before entering the pumping station.
- The well area is a limited space and requires the use of an appropriate multi-quota gas detector in accordance with local or company requirements and/or regulations on limited space intrusion.
Stage 2.3 – Filtering
Process overview
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- After passing through several pumping stations, the wastewater enters the treatment plant. At this time it consists of substances along the line, such as wood, stone and other materials. The initial screening process eliminates this, preventing these dirty objects from going to the next stage.
Gas detection
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- If the screening of areas becomes clogged, it should be required for cleaning and maintenance. Due to the nature of the areas in question, it should be considered as limited space, thus require multi-quota gas detection devices to ensure the safety of workers. O2, H2S and CH4 are generally monitored and depending on the specific location, other gases may also need to be monitored.
Stage 2.4 – Primary Processing
Process overview
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- Sewage then enters a series of long, parallel concrete barrels, each of which is divided into two parts. The filtration tank allows the deposition of solids, the water levels will be divided vertically, the water will vibrate and come into contact with the air, which makes some dissolved gases, such as hydrogen sulphide, escape from the water. Air is pumped through the water. When the organic matter is decomposed it consumes oxygen, the contact will replenish oxygen to ensure the released gases continue to be released. The discharge of oxygen through water also makes suspended organic material treated. This particle is pumped out of the tank and taken to the landfill.
Gas detection
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- The sedate tanks are usually ventilated naturally by taking them outdoors. If this is not the case, then fixed and/or portable gas monitoring for O2, H2S and CH4 is minimal to contribute to maintaining a safe working environment. Of course if, during a specific risk assessment, other gases are detected in this area of the plant, then additional fixed and portable detectors may be required.
Stage 2.5A – Second Processing
Process overview
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- Second-rate processing facilitates biodegrading and reduces residual organic matter. Sewage enters a set of cleaning substances where sludge (the heavy, organic part of the sewage) settles from the sewage and is pumped out of the tank. Some water is removed in a step called thickening and then the sludge is treated in a large tank called digesters (see later on sludge treatment). When the sludge settles to the bottom of the cleaning tank, light materials will rise to the surface, this ‘scum’ consists of grease, oil, plastics and soap. It will be separated from the surface of the sewage.
Gas detection
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- When biodegradation consumes oxygen, it is possible to create oxygen depletion zones in processing areas. Since these tanks are usually open to other parts, the use of Portable Oxygen Gas Meters for O2 ensures worker safety. If the tanks are closed, then fixed detectors are used to ensure a safe working environment.
Stage 2.5B – Sludge Treatment
Process overview
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- Sludge is the result of wastewater treatment, which is residual organic matter and dead bacteria used during treatment or biological waste removed from the wastewater being treated. Sludge is often transferred to gas decomposition systems, where it is heated to encourage bacteria to produce biogas. There are many constituent gases in Biogas:
- Methane: 58.5%
- Carbon Dioxide: 40%
- Nitrogen: 1%
- Oxygen: 0.5%
- Hydrogen Sulphide: 3000ppm
- Hydrogen: 40ppm
Gas detection
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- While decomposition takes place in closed tanks, high levels of CH4 and H2S mean that pellistor methane detectors will be ineffective when gas escapes. An infrared type methane detection machine should be used in this environment to ensure a safe working environment. Use of fixed and portable meters in this area of the plant is common.
Stage 2.6A – Final treatment for water
Process overview
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- Finally, sewage flows into the chemical contact tank, where chemicals (e.g. chlorine) are added to kill bacteria, which can be dangerous to health, just as in swimming pools. Chlorine is almost eliminated because bacteria are destroyed, but sometimes it must be disabled by adding other chemicals. This activity protects fish and other marine life because treated water (known as sewage) is then discharged into local rivers or oceans.
- Other forms of disinfectant also used include chloramines, chlorine dioxide, sodium hypochlorite (hypo) and ozone.
Gas detection
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- All chemicals have specific storage requirements specified locally or nationally. The escape from chlorine, ammonia, sulfur dioxide or ozone is also very harmful. Fixed gas detection is required to ensure monitored storage areas, typically involving external alarms (sounders & beacons) to ensure workers are notified of any increase in gas levels as well as inter-dynamic control capabilities such as ventilation fan activation. Specific on-site risk assessment should be focused including gas characteristics; For example, chlorine weighs 2.3 times more than air and tends to fly near the ground and can be absorbed by porous material. Therefore, handheld meters with the ability to monitor specific gases for storage areas need to be equipped.
Stage 2.6B – Power Plant
Process overview
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- Water companies have become increasingly involved in the creation of electricity from sludge because high levels of methane represent a rich source of energy. Some facilities have an on-site power plant (internal combustion engine) that is used to convert biogas gas into electricity. Electricity can be used for on-site consumption and for sale to the national grid. In addition, biogas is used directly to provide fuel to heat other decomposition systems. High levels of methane in two forms show a rich source of energy.
Gas detection
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- Bio gas that arises through decomposition must be stored and ‘cleaned’ before use. This creates the need to equip fixed and portable detection equipment. Regular “leak detection” polls take place to ensure the integrity of containers and distribution tubes.
trans by TESIN VIETNAM
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