Mercury in Wastewater: Sources and Detection Solutions

Mercury is a naturally occurring heavy metal that acts as a powerful neurotoxin, yet it is still causing global issues. This is especially true within wastewater, as its presence within waterways is a major environmental and public health hazard due to the fact that it is highly toxic and bioaccumulates within the food chain.

Once mercury enters aquatic ecosystems, bacteria convert it into an even more potent form: methylmercury. This form of mercury will then build up in fish tissue and work its way up the food chain, risking wildlife and, eventually, humans.

Humans are most often exposed to mercury through eating contaminated fish. Methylmercury crosses the blood-brain barrier and can even cause significant damage to the nervous system of young children and fetuses, which can lead to developmental delays.

In adults, it can also damage the nervous and cardiovascular systems as well as the kidneys. In addition to these dangers, mercury persists within aquatic environments. Overall, this means the metal poses severe health and environmental risks. In many cases, mercury enters the waterways via wastewater from municipal sewage or industrial discharge.

Key sources of mercury introduction into aquatic systems include chemical manufacturing, coal-fired power plants, chlor-alkali plants and metal smelting. Municipal wastewater is often contaminated by residential products, such as thermometers and batteries.

The Impact of Mercury on Wastewater Systems and the Environment

Mercury’s impact within wastewater systems should not be underestimated. In reality, mercury in wastewater is a persistent issue that can have significant environmental consequences. Mercury can and does lead to environmental damage that risks the health of humans and wildlife alike.

The following is a look at some of the ways mercury impacts wastewater systems and the environment:

Biomagnification: As mentioned briefly, mercury builds up as it moves through the food chain. This process is referred to as biomagnification. Large predators such as otters, eagles and predatory fish consume smaller fish with mercury within their bodies. This leads to the development of toxic levels of mercury within the apex predators, far exceeding the amount of metal that is in the surrounding water.
Aquatic Life Toxicity: Mercury also impacts aquatic biota, meaning that it can cause chronic or toxic effects on aquatic life. These elevated levels of mercury can interfere with fish reproduction, overall behavior and, eventually, alter the biodiversity of an entire ecosystem.
Methylation in Anoxic Environments: Wastewater often contains high amounts of nutrients that can lead to algal blooms. These blooms then decompose, which can promote the conversion of mercury into methylmercury, which is a particularly toxic form of mercury. This form is easily absorbed by organisms via the bloodstream.
Widespread Contamination: Domestic wastewater inputs and historically large industrial discharges have resulted in long-term contamination of water-laid sediments. Consequently, mercury contamination and persistent pollution is widespread enough to merit advisories on the consumption of fish in some major bodies of water.
Plant and Ecosystem Stress: Mercury contamination also reduces the diversity of plants and organisms within aquatic habitats, which disrupts the foundational balance of an entire ecosystem.

Regulatory Guidelines for Mercury Discharge in Wastewater

Obviously, with the knowledge that mercury discharge or the presence of mercury within waterways is so detrimental, there are regulatory guidelines in place when it comes to mercury discharge in wastewater. There are two levels of these protections in place, accounting for global and domestic restrictions.

Global Regulations:

Minamata Convention on Mercury: This global treaty, the Minamata Convention on Mercury, includes the United States and more than 140 other countries and is a legally binding restriction on mercury that has phased out mercury mines, emissions and various mercury-containing products. Its goal is to protect human health and promote a safe environment by controlling anthropogenic releases and emissions. The treaty involves mandates on mercury-added products, such as specific lamps, batteries and thermometers. It also regulates industrial sectors such as waste incineration and chloralkali.
Basel Convention: Another broad transborder movement is the Basel Convention, which provides management guidelines for mercury waste, better ensuring it is handled safely and separated properly by trained personnel.

Domestic Regulations: United States National Regulations

Clean Water Act (CWA): The Clean Water Act (CWA) requires industries to procure permits in order to discharge pollutants into the water. These limitations and guidelines are strictly enforced across various sectors including dental offices (they must use amalgam separators), battery manufacturing and electric power plants.
Safe Drinking Water Act (SDWA): The SDWA guidelines set the maximum contaminant level for drinking water as it relates to the presence of mercury at 2 parts per billion. This is a restriction level designed to help prevent the public from mercury exposure.
Clean Air Act (CAA): Another regulation within the United States is the CAA. This reduces airborne emissions through National Emission Standards for Hazardous Air Pollutants (NESHAP) as part of the Mercury and Air Toxics Standards (MATS). This restricts emissions from oil-fired power and coal-fired power plants.
Resource Conservation and Recovery Act (RCRA) and Mercury Export Ban Act: The RCRA oversees the generation, transformation and disposal of hazardous mercury waste. The Mercury Export Ban Act goes even further, prohibiting the export of elemental mercury to reduce the global commercial supply.

Key Industrial Requirements and Restrictions

Power Generation and Incineration: Commercial incinerators and coal-fired power plants may contribute to airborne mercury. Therefore, they are required to adhere to MATS standards to restrict stack emissions.
Chlor-Alkali Plants: National emission standards are strictly enforced when it comes to mercury-cell chlor-alkali facilities.
Dental Offices: Dental amalgam can be a central source of mercury discharge within publicly owned municipal wastewater treatment facilities. Regulations exist to oversee the installation and maintenance of amalgam separators, which are designed to capture mercury from waste before it enters these public sewers.

Non-Compliance Consequences

Industries found in non-compliance in terms of their mercury waste face several financial penalties, legal liabilities and more. Violations may trigger immediate enforcement actions that can lead to forced facility shutdowns, reputational damage for the company, operational downtime and financial loss.

Regulatory bodies such as the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) impose strict guidelines and worker protection laws. Some industries are also required to operate under the EPA National Pollutant Discharge Elimination System (NPDES).

If they breach mercury limits, they can lose discharge permits. In addition, non-compliance in terms of mercury disposal can exceed tens of thousands of dollars per violation and even result in criminal charges and felony convictions in some cases. Industries might also be faced with paying remediation costs like site assessment, along with soil or groundwater cleanup as well as long-term environmental monitoring costs, which could reach a total of millions of dollars for a facility in violation.

Mercury Detection Technologies

The latest technology in mercury detection focuses primarily on real-time field monitoring, automation and high sensitivity. Regulatory methods are based on measurement tools like cold vapor atomic fluorescence spectroscopy (CVAFS) and cold vapor atomic absorption spectroscopy (CVAAS).

The following explores mercury detection technologies and how each is used in various industries:

Cold Vapor Atomic Fluorescence Spectroscopy (CVAFS): This is one of the latest detection methods for discovering ultra-trace amounts of mercury. CVAFS can detect mercury down to less than sub-parts per trillion. This tool is vital for EPA Method 1631E compliance. It works by utilizing oxidation, purge and trap methodologies, and gold amalgamation for its superior sensitivity.
Cold Vapor Atomic Absorption Spectroscopy (CVAAS): This method is widely used to measure mercury in water and wastewater. CVAAS converts mercury in the sample to elemental mercury vapor, which passes through an absorption cell where the amount of light absorbed is measured to determine mercury concentration. The technique is used in EPA methods including Method 245.1 and Method 7470A for mercury analysis in aqueous samples.
Direct Mercury Analysis (DMA): As another testing option for trace amounts of mercury, DMA utilizes thermal decomposition atomic absorption spectrometry to bypass the complex acid digestion step. This provides rapid and accurate results, which adhere to EPA Method 7473.
Portable and Real-Time Monitoring: Portable survey meters including CVAAS devices are fitted with kits to allow real-time testing and immediate hazard assessment on site without having to ship samples to a lab. Modular platforms like automated IoT modules provide lab-accurate, continued monitoring in the field. This can set an instant threshold for early spill detection.

Generally, when it comes to mercury detection, absorption, precipitation and membrane filtration are primarily employed — at least in terms of separation and pre-concentration detection techniques. These methods work to isolate and concentrate trace mercury from even complex samples like natural water or industrial wastewater before testing is done — thus, improving the sensitivity of instruments like atomic absorption or fluorescence spectroscopy.

The Role of Industrial Wastewater Management in Mercury Management

Industrial waste managers and wastewater companies must ensure that their facilities are mindful of mercury discharges and maintain compliance with all regulatory bodies, adhering to local and federal limits. The core responsibilities — not only for wastewater management in general, but also the facilities across the board — are to focus on the following:

Source Reduction and Elimination: Wastewater management should include a measure of self-auditing that considers the facilities’ equipment and looks to replace items like thermometers, mercury-tilt switches and fluorescent lights with mercury-free alternatives as part of product substitution. Supply chain policies should also establish mercury-free purchasing policies, and global mandates like the Minamata Convention on Mercury should be followed.
Emission and Capture Technologies: Mercury removal units (MRUs) and industrial scrubbers like pollution control devices should be utilized within a facility. In terms of wastewater, specifically, facilities should use separators to capture mercury before it enters waterways.
Waste Management and Storage: Segregation, storage requirements, and waste handling regulations and procedures should always be followed to help ensure facility compliance and proper wastewater management.
Worker Health, Safety and Monitoring: Vapor monitoring, personal protective equipment (PPE), spill kits and comprehensive training are yet another way for managers to keep their facilities safe and to prevent excess mercury from entering waterways. This also includes best management practices that oversee operational rules, chemical segregation, spill-response protocols and further employee training to prevent mercury from entering wastewater.

AGS Scientific Is Here to Help

Mercury in wastewater is a problem that demands an innovative solution. Thankfully, at AGS Scientific, we can help you create effective management strategies to mitigate mercury pollution. Since 2003, we have specialized in mercury analysis and more, offering advanced technology and an 80% reduction in generated waste.

When wondering how to choose the right mercury analyzer, we can set you up with the right information to best serve your industry and help you find the right mercury analyzers for your needs. The accuracy of our instruments makes them indispensable not only in the laboratory but for field use as well.