Wastewater treatment basins represent a major challenge at an environmental level, since they emit Volatile Organic Compounds (VOC) emissions and generate odours due to the degradation of organic matter, which affect both people working at the plant, as well as the communities around and the environment.
Whenever wastewater basins are open to the atmosphere, odorous emissions of these VOC compounds occur. Aeration of biological wastewater treatment basins, stirring operations, open buffer tanks, settling tanks, flocculation equipment, API separators and wastewater stripping facilities are activities that need special attention. In all of these cases, the emission of pollutants may be shifted from the water basin to the atmosphere. And in order to treat that, a waste gas treatment becomes vital.
The sectors affected
Refineries and petrochemical plants need to treat the wastewater they use for their production daily activities. Other main sectors affected by industrial wastewater emissions are currently chemical plants, pharmaceutical production sites, etc.
With increasing industrial activity, increased levels of treatment before discharging industrial wastewater is needed.
Effects of industrial wastewater
Some of the potential effects of industrial wastewater on the atmosphere are the following:
- VOC emissions (including halogenated compounds), evaporating from the water
- Evaporation/formation of odours (for example: H2S, NH3)
- Aerosol formation
- Drift of potentially hazardous microorganisms from the treatment plant
- If biogas is generated and not used as fuel for energy supply, it usually gets flared, causing emissions to the atmosphere
The polluting VOC compounds
Basins for Wastewater treatment are the origin of greenhouse gas polluting emissions, such as benzene, toluene, aliphatic compounds, methane (CH4) and other organic volatile substances which hugely rise ozone depletion in comparison to carbon dioxide (CO2). Apart from those, inorganic volatile compounds are also present in wastewater. Most common components emitted on surface water are Benzene, Toluene, Xylene, Methane, Benzoapyrene, Pyrene, Aliphatic hydrocarbons, Heavy weight hydrocarbons, etc.
Most of non-methane volatile organic compounds (NMVOC) emissions happening in the chemical sector are diffuse or fugitive emissions or occur during storage, and these type of sources are very difficult to quantify and measure.
It is important to treat industrial wastewater properly and effectively, but also the treatment of surface water volatile emissions become crucial, so that potentially harmful pollutants in all its phases (liquid and gas) are not released into the environment.
The most suitable technology solution
Industrial wastewater emissions generated from petrochemical and refinery treatment basins must be eliminated with specific technology whose objective is to transform the gaseous polluting compounds into H2O and acceptable quantities of CO2, leading to a huge reduction on the environment impact even in the surrounding population. Such technologies are Regenerative Thermal Oxidizers, also known as RTO systems.
Regenerative Thermal Oxidizer (RTO)
What is an RTO?
A Regenerative Thernal Oxidizer (RTO) unit is a piece of equipment designed to eliminate Volatile Organic Compounds (VOCs). Essentially, it is formed of three towers with ceramic beds, where energy is recovered, and a combustion chamber in which the temperature is kept constant in order to enable oxidation. The organic compounds it eliminates consist primarily of carbon and hydrogen: consequently, when they react with oxygen they form carbon dioxide and water. The combustion chamber incorporates a burner that normally uses natural gas to raise the temperature inside the chamber, although other fuels (fuel oil, diesel oil, etc.) can also be used.
How RTO equipment works
In a Regenerative Thermal Oxidation (RTO) system, the contaminated air to be treated is sucked in by the main fan, which is usually located upstream of the oxidiser, although for processes with high concentrations of suspended particles the fan is usually located downstream of the oxidiser.
The fan then pushes the air to be treated through the first ceramic tower. In this first tower, the air is heated along with the ceramic media. When the air has passed through the ceramic bed, it reaches the combustion chamber, where the oxidation takes place. For gases without halogenated compounds, the temperature is usually around 800 ºC – 900 ºC; however, for gases that contain halogenated compounds, the temperature needs to be around 1100 ºC in order to ensure full oxidation. In each instance, the temperature will depend on the compounds that are to be treated.
At the same time, as air to be treated enters the first chamber, the now-oxidised air is passed through the second ceramic tower, in order to transfer its heat to the ceramic media. This cools the gas and heats the ceramic bed. After passing through the second tower, the air – now free from pollutants – is sent up the flue.
The third ceramic tower is used to recirculate the purged elements, as all of the air must be oxidised during the valve sequencing.
The sequencing procedure is repeated periodically, every 45-90 seconds, in order to make sure each tower is operating in the same way.
Systems with three ceramic towers are the most common, although you can find RTOs with two towers and even some that have five towers.
The benefits of installing an RTO
The advantages of installing an RTO lie in the ability to optimise your energy use while maintaining the same level of efficiency for eliminating VOCs. This is due to the fact that the ceramic towers are able to store a large amount of energy during each sequence, which in turn serves to heat the air or gas that is being treated. In fact, thermal efficiency can reach levels of 90-95 %.
This means that under normal operating conditions, fuel gas is not consumed, as the process is autothermal. An autothermal process is one in which the combustion chamber maintains its operating temperature without needing to burn energy from an external source (i.e. fuel). This is because the energy released by the VOCs as they oxidise is sufficient to keep the chamber at a high temperature.
An RTO system can be installed in a wide variety of industrial applications, including the chemical, pharmaceutical and petrochemical sectors, storage tank facilities, the oil and gas, paint, coatings and construction industries, and many other sectors where VOCs are an issue.
The specific advantages of a Tecam RTO system
- High-quality finishes designed to increase durability
- Materials that can be adapted in line with the atmospheric criteria and the requirements of the customer
- Components sourced from first-class suppliers and partners that are internationally renowned for their reliability
- Cold-tested at our assembly facilities in order to minimise problems and unforeseen incidents during assembly at your plant
- Equipped with proprietary software, 100 % integrated
- Online remote monitoring system for maximum speed of access in the event of a breakdown
- Special valves that guarantee 99.9 % hermetic sealing
- Low cost of operation and maintenance
- Rapid supply and customer service
- Levels of adaptability and service that only Tecam can provide
We can say that in today’s critical environmental situation, it is more important than ever to properly and effectively treat all kinds of waste, including industrial wastewater. It is vital to prevent potentially harmful contaminants from being released into the atmosphere, causing harm to people and the environment. In that sense, Regenerative Thermal Oxidation (RTO) stands as the most suitable, efficient technical solution to eliminate industrial wastewater COV emissions, for a clean and safe environment.
For further information on this topic, please contact us at firstname.lastname@example.org or +34 93 428 11 54.