Wastewater treatment odor control is about far more than keeping bad smells at bay. It’s about ensuring that local communities and nearby ecosystems are kept safe from toxic emissions, as well as giving onsite personnel a safe and pleasant place to work. It’s a crucial consideration during the wastewater treatment and management process.
Read on and discover more about odor control in wastewater treatment, including why it’s so important and how it works.
Understanding Wastewater Odor and Odor Control
Before we get started, let’s look at what wastewater odor actually is. In a very basic sense, wastewater odor is any bad smell produced by the process of treating the waste influent or by the waste itself. As this water tends to contain materials that humans find unpleasant, even the odors the water produces naturally can pose a serious problem for local communities. When waste materials are broken down during treatment, more intense odors are released at an even greater volume, exacerbating the problem.
In a more scientific sense, most odors are produced by one particular gas that is released during processing – hydrogen sulfide (H₂S). As H₂S has no color, it is invisible in the air. However, it does have a very strong smell. In addition to this, hydrogen sulfide gas can be highly toxic to humans and animals, so wastewater processing plants have a duty to keep H₂S under control, removing it where possible and preventing leaks.
Other compounds can also cause bad odors. These include ammonia, sulfur dioxide, skatoles, mercaptans, amines, and indoles, all of which may be released during treatment or simply by stagnant areas of wastewater. These compounds may be toxic in higher concentrations.
Odor control is an issue right across the wastewater treatment process. From wastewater clarifiers and sedimentation basins to headworks, lift stations, and treatment lagoons, teams need to remain aware of odor levels and gas leakages.
Why Is Odor Control So Important During Wastewater Treatment?
Why is this such a big deal? Below are some of the key factors that make wastewater odor control so important.
- Odors make life unpleasant for local residents and anyone else who spends time in the local area.
- Odors may be caused by toxic gases, which can put human and animal life at risk.
- Odors may also be emitted by polluting chemicals that damage local ecosystems.
- Odors create a poor working environment for anyone onsite.
- Odors may be an indication that there are problems in the wastewater treatment process, making treatment inefficient or ineffective.
Odor Control Methods
We can view odor control in two ways – removal and prevention. Removal is a reactive response, taking away odors that have already been produced. Prevention is a more proactive process, reducing the amount of odor-causing compounds produced in the first place.
Removal of Odors
Firstly, let’s take a look at three methods of removing odors from wastewater.
Biological Treatment of Vapor
Vapor from the wastewater is fed into biotowers, which are filled with inorganic matter. The vapor filters through these towers, removing much of the H₂S gas. Not all odor-causing gases can be removed in this manner, so other forms of treatment may be required to comprehensively deal with all odors.
Vapor can be filtered through carbon-based media to remove odor-producing compounds. The carbon media are useful in adsorbing and removing H2S gas at low concentrations. This process will also remove higher concentrations of H₂S gas, but this will wear out the media quickly and the carbon will need to be replaced. Facility managers may use other forms of medium, deployed alongside the carbon, to achieve more comprehensive removal of odor-producing compounds from the vapor mixture.
Chemical scrubbing involves filtering the vapor through specially chosen chemical media in order to remove odor-causing compounds from the vapor. Removal is achieved through a process of dissolving and then absorbing (different from the adsorbing listed above) the compounds as they pass through the media. Chemical scrubbing may be better suited to treatment plants where the vapor levels fluctuate – unlike biological treatment, for example, which is better suited to applications with more consistent loads.
Prevention of Odors
Next, let’s examine how odors can be prevented to reduce the need for reactive removal during odor control.
Utilizing Aerobic Bacteria During Treatment
Using anaerobic bacteria – i.e., bacteria that digest waste in the absence of oxygen – to treat wastewater can result in unpleasant odors and the release of potentially harmful gases. This is due to the chemical reactions that take place when the bacteria break down the waste. Focusing on aerobic bacterial digestion – i.e., digestion in the presence of oxygen – can solve this problem. The byproducts of aerobic waste digestion tend to be less odorous and less toxic than those of anaerobic digestion.
Increasing Aeration within the Treatment Pool
The problem with shifting focus towards aerobic digestion is that parts of the wastewater treatment pool will naturally be devoid of oxygen. This results in anaerobic digestion, even if it is not desired. To combat this, facility teams can use aeration pipes and tubes, increasing the amount of available oxygen within the treatment tank itself.
Improving Circulation During Treatment
Even when aeration is improved, there is still the risk that oxygen-devoid areas may form within the treatment zone, particularly deep within the tank or down in the sludge layer. To prevent a resulting odor and toxic gas release, facility managers can work to improve the circulation of wastewater within the tank, ensuring that all of the waste is exposed to aerobic bacterial digestion and the conditions required to make this happen.
Explore Our Range of Wastewater Treatment and Odor Control Products
The Chemtech range is designed to support wastewater treatment facility managers and teams as they work to achieve optimal odor control and environmental safety. Explore our odor control product pages and find the solutions you need, or reach out to our team today and discover more.