Gas Hazards in Wastewater

Water is vital to our daily lives, both for personal and domestic use and industrial/commercial applications making water sites both numerous and widespread. Despite the quantity and location of water sites, only two environments predominate, and these are quite specific. They are clean water and wastewater. This blog details gas risks encountered at wastewater sites and how they may be mitigated. 

The wastewater industry is always wet, with temperatures between 4 and 20oc near the water and rarely far from that limited temperature range even away from the immediate location of the wastewater. 90%+ relative humidity, 12 +/- 8oc, atmospheric pressure, with multiple toxic and flammable gas hazards and the risk of oxygen depletion. Gas detectors must be chosen to suit the specific environment in which they operate, and whilst high humidity is generally challenging to all instrumentation, the constant pressure, moderate temperatures and narrow temperature range is a far greater benefit to safety instrumentation. 

Gas Hazards  

The main gases of concern in wastewater treatment plants are: 

  • Methane 
  • Hydrogen sulphide 
  • Carbon dioxide  
  • Reduced levels of oxygen 

Hydrogen sulphide, methane and carbon dioxide are the by-products of the decomposition of organic materials that exist in the waste flows feeding the plant. The build-up of these gases may lead to the lack of oxygen, or in some cases, explosion when coupled with a source of ignition. 

Hydrogen sulphide (H2S)

Hydrogen sulphide is a common product of the biodegradation of organic matter; pockets of H2S can collect in rotting vegetation, or sewage itself, and be released when disturbed. Workers in sewerage and wastewater plants and pipework can be overcome by H2S, with fatal consequences. Its high toxicity is the main danger of H2S. Prolonged exposure to 2-5 parts per million (ppm) H2S can cause nausea and headaches and bring tears to the eyes. H2S is an anaesthetic, hence at 20ppm, symptoms include fatigue, headaches, irritability, dizziness, temporary loss of the sense of smell and impaired memory. Severity of symptoms increase with concentration as nerves shut down, through coughing, conjunctivitis, collapse and rapid unconsciousness. Exposure at higher levels can result in rapid knock down and death. Prolonged exposure to low levels of H2S may cause chronic illness or can also kill. Because of this, many gas monitors will have both instantaneous and TWA (Time-Weighted Average) alerts. 

Methane (CH4)

Methane is a colourless, highly flammable gas that is the primary component of natural gas, also referred to as biogas. It can be stored and/or transported under pressure as a liquid-gas. CH4 is a greenhouse gas that is also encountered in normal atmospheric conditions at a rate of approximately 2 parts per million (ppm). High exposure can lead to slurred speech, vision problems and memory loss. 

Oxygen (O2)

The normal concentration of oxygen in the atmosphere is approximately 20.9% volume. In the absence of adequate ventilation, the level of oxygen can be reduced surprisingly quickly by breathing and combustion processes. Olevels may also be depleted due to dilution by other gases such as carbon dioxide (also a toxic gas), nitrogen or helium, and chemical absorption by corrosion processes and similar reactions. Oxygen sensors should be used in environments where any of these potential risks exist. When locating oxygen sensors, consideration needs to be given to the density of the diluting gas and the “breathing” zone (nose level). 

Safety Considerations 

Risk assessment

Risk assessment is critical, as you need to be aware of the environment that you are entering and thus working in. Therefore, understanding the applications and identifying the risks regarding all safety aspects. Focusing on gas monitoring, as part of the risk assessment, you need to be clear on what gases may be present. 

Fit for purpose

There is a variety of applications within the water treatment process, giving the need to monitor multiple gases, including carbon dioxide, hydrogen sulphide, chlorine, methane, oxygen, ozone and chlorine dioxide. Gas detectors are available for single or multiple gas monitoring, making them practical for different applications as well as making sure that, if conditions change (such as sludge is stirred up, causing a sudden increase in hydrogen sulphide and flammable gas levels), the worker is still protected. 

Legislation  

European Commission Directive 2017/164 issued in January 2017, established a new list of indicative occupational exposure limit values (IOELVs). IOELV are health-based, non-binding values, derived from the most recent scientific data available and considering the availability of reliable measurement techniques. The list includes carbon monoxide, nitrogen monoxide, nitrogen dioxide, sulphur dioxide, hydrogen cyanide, manganese, diacetyl and many other chemicals. The list is based on Council Directive 98/24/EC that considers the protection of the health and safety of workers from the risks related to chemical agents in the workplace. For any chemical agent for which an IOELV has been set at Union level, Member States are required to establish a national occupational exposure limit value. They also are required to take into account the Union limit value, determining the nature of the national limit value in accordance with national legislation and practice. Member States will be able to benefit from a transitional period ending at the latest on 21 August 2023. 

The Health and Safety Executive (HSE) state that each year several workers will suffer from at least one episode of work-related illness. Although, most illnesses are relatively mild cases of gastroenteritis, there is also a risk for potentially fatal diseases, such as leptospirosis (Weil’s disease) and hepatitis. Even though these are reported to the HSE, there could be significant under-reporting as there is often failure to recognise the link between illness and work. 

Our solutions  

Elimination of these gas hazards is virtually impossible, so permanent workers and contractors must depend on reliable gas detection equipment to protect them. Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include T4x, Clip SGD, Gasman, Tetra 3, Gas-Pro, T4 and Detective+. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard, Xgard Bright and IRmax. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions that measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the wastewater industry our panels include Gasmaster.   

To find out more on the gas hazards in wastewater visit our industry page for more information. 

Transportation and Key Gas Challenges 

The transportation sector is one of the largest industries in the world, spanning a variety of applications. The sector offers services concerned with the movement of people and cargo of all types, across air freight and logistics, airlines and airport services, road and rail, transportation infrastructure, trucking, highways, rail tracks, and marine ports and services. 

Gas hazards during transportation  

The transport of dangerous goods is regulated in order to prevent, accidents involving people or property, damage to the environment. There a numerous gas hazards including the transportation of hazardous material, air conditioning emissions, cabin combustion and hangar leaks.  

The transportation of hazardous materials poses a risk to those involved. There are nine classification areas specified by the United Nations (UN) including explosives, gases, flammable liquids and solids, oxidising substances, toxic substances, radioactive materials, corrosive substances and miscellaneous goods. With the risk of an accident occurring being more likely when transporting these materials. Although the biggest cause for concern within the industry being the transportation of non-flammable non-toxic gas is asphyxiation. As a slow leak in a storage container can drain all of the oxygen in the air and cause the individuals in the environment to suffocate. 

Leaks within aircraft hangars and fuel storage areas of highly explosive aviation fuel is an area that must be monitored to prevent fires, equipment damage, and at the worst fatalities. It is essential to choose a suitable gas detection solution that focuses on the aircraft rather than the aircraft hangar, avoids false alarms, and can monitor large areas. 

Not only is it the external environment that faces gas risks in transportation, those working in the sector also face similar challenges. Air conditioning emissions poses a gas hazard threat due to the burning of fossil fuels leading to a subsequent emission of carbon monoxide (CO). high levels of CO in a confined area such as a vehicle cabin, of more than the normal level (30ppm) or an oxygen level below normal (19%) can result in dizziness, feeling and being sick, tiredness and confusion, stomach pain, shortness of breath and difficulty breathing. Therefore, proper ventilation in these spaces with the assistance of a gas detector is paramount to ensuring the safe of those working in the transportation industry.  

Similarly, in the air sector cabin combustion and fuselage fires, in the central portion of an airplane, poses a real threat. Although flame retardant materials are applied, if a fire does start the cabin’s trim and fittings can still generate toxic gases and vapours that could be more dangerous than the fire itself. Inhalation of harmful gases caused by a fire in these environments tend to be the main direct cause of fatalities.  

Transportation Standards and Certifications 

Each mode of transport, (road, rail, air, sea and inland waterway) has its own regulations but they are generally harmonized with the United Nations Economic Commission for Europe (UNECE). The Hazardous Materials Transportation Act (HMTA), enacted in the USA in 1975, states that regardless of the type of transportation, any company whose goods fall into one of the nine categories specified as hazardous by the UN, must comply with the regulations or risk fines and penalties. 

Those working in the transport sector in the UK must comply with the requirements laid out in the UN Model Regulations which assigns each dangerous substance or article a specific class that correlates how dangerous it is. It does this via the packing group (PG) classification, according to PG I, PG II or PG III. 

From an European standpoint the International Carriage of Dangerous Goods by Road (ADR) governs the regulations on how to classify, pack, label and certify dangerous goods. It also comprises vehicle and tank requirements and other operational requirements. The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations (2009) also is relevant in England, Wales and Scotland. 

Other relevant regulations include the International Carriage of Dangerous Goods by Inland Navigation (ADN), the International Maritime Dangerous Goods (IMDG) and The International Civil Aviation Organization’s (ICAO) Technical Instruction 

Our solution 

Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include T4x, Clip SGD, Gasman, Tetra 3, Gas-pro, T4. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard, Xgard Bright, IRmax. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions which are able to measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the transportation industry our panels include Gasmaster and Vortex 

To find out more on the dangers of gas hazards in transportation visit our industry page for more information.  

T4x a Compliance 4-gas monitor 

It is vital to ensure that the gas sensor you employ is fully optimised and reliable in the detection and accurate measurement of flammable gas and vapours, whatever environment or workplace it is within, is of the utmost importance. 

Fixed or portable? 

Gas detectors come in a range of different forms, most commonly they are known as fixed, portable or transportable, in which these devices are designed to meet the needs of the user and environment whilst protecting the safety of those within it.  

Fixed detectors are implemented as permanent fixtures within an environment to provide ongoing monitoring of plant and equipment. According to guidance from the Health and Safety Executive (HSE) these types of sensors are particularly helpful where there is the possibility of a leak into an enclosed or partially enclosed space which could lead to the accumulation of flammable gases. The International Gas Carrier Code (IGC Code) states that gas detection equipment should be installed to monitor the integrity of the environment that it is to monitor and should be tested in accordance with the recognised standards. This is to ensure that the fixed gas detection system operates effectively, timely and accurate calibration of the sensors is critical. 

Portable detectors normally come as a small, handheld device that can be used within smaller environments, confined spaces, to trace leaks or early warnings to the presence of flammable gas and vapour within hazardous areas. Transportable detectors are not handheld, but they are easily moved from place to place to act as a monitor ‘stand-in’ whilst a fixed sensor is undergoing maintenance. 

What is a compliance 4-gas monitor? 

Gas sensors are primarily optimised for detecting specific gases or vapours through design or calibration. It is desirable that a toxic gas sensor, for example one detecting carbon monoxide or hydrogen sulphide, provides an accurate indication of the target gas concentration rather than a response to another interfering compound. Personal safety monitors often combine several sensors for protecting the user against specific gas risks. However, a ‘Compliance 4-Gas monitor’ comprises sensors for measuring levels of carbon monoxide (CO) hydrogen sulphide (H2S), oxygen (O2) and flammable gases; normally methane (CH4) in one device.  

The T4x monitor with the ground-breaking MPS™ sensor is able to provide protection from CO, H2S, O2 risks with accurate measurement of multiple flammable gases and vapours utilising a basic methane calibration. 

Is there a need for a compliance 4-gas monitor? 

Many of the flammable gas sensors deployed in conventional monitors are optimized for detecting a specific gas or vapour through calibration but will respond to many other compounds. This is problematic and potentially dangerous as the gas concentration indicated by the sensor will not be accurate and may indicate a higher (or more dangerously) and lower concentration of gas/vapour than is present. With workers often potentially exposed to risks from multiple flammable gases and vapours within their workplace, it is incredibly important to ensure that they are protected through the implementation of an accurate and reliable sensor. 

How is the T4x portable 4-in-1 gas detector different? 

To ensure ongoing reliability and accuracy of the T4x detector. The detector utilises the  MPS™ (Molecular Property Spectrometry) Sensor functionality within its robust unit that provides a range of features to ensure safety. It offers protection against the four common gas hazards: carbon monoxide, hydrogen sulphide, flammable gases and oxygen depletion, whilst The T4x multi gas detector now comes with improved detection of pentane, hexane and other long chain hydrocarbons. It comprises a large single button and easy-to-follow menu system to enable ease of use for those wearing gloves, who’ve undergone minimal training. Tough, yet portable, the T4x detector features an integrated rubber boot and an optional clip-on filter that can be easily removed and replaced when needed. These features allow the sensors to remain protected even within the dirtiest environments, to ensure they can constant. 

A unique benefit to the T4x detector is that it ensures toxic gas exposure is calculated accurately throughout an entire shift, even if it is switched off momentarily, during a break or when travelling to another site. The TWA feature allows for uninterrupted and disrupted monitoring, So, when powering up, the detector begins again from zero, as if starting a new shift and ignores all previous measurements. The T4x allows the user the option to include previous measurements from within the correct time frame. The detector is not just reliable in terms of accurate detection and measurement of four gases, it is also dependable due to its battery life. It lasts for 18 hours and is useful for usage across multiple or longer shifts without requiring charging as regularly.  

During usage the T4 employs a handy ‘traffic light’ display offering constant visual assurance that it is operating soundly and conforming to the site bump test and calibration policy. The bright green and red Positive Safety LEDs are visible to all and, as a result, offer a quick, simple and comprehensive indication of the monitor’s status to both the user and others around them. 

T4x helps operations teams focus on more value adding tasks by reducing the number of sensor replacements by 75% and increasing sensor reliability. Through ensuring compliance across site T4x helps health and safety managers by eliminating the need to ensure each device is calibrated for the relevant flammable gas as it accurately detects 19 at once. Being poison resistant and with battery life doubled, operators are more likely to never be without a device. T4x reduces the 5-year total cost of ownership by over 25% and saves 12g of lead per detector which makes it much easier to recycle at the end of its life. 

Overall, through the combination of three sensors (including two new sensor technologies MPS and Long-life O2) within an already popular portable multi-gas detector. Crowcon allowed for the enhancement of safety, cost-effectiveness and efficiency of individual units and entire fleets. The new T4x offers longer life with a higher accuracy for gas hazard detection whilst providing a more sustainable build than ever before.