Acceptable Lead Levels in Wastewater and the Need for Removal

Acceptable Lead Levels in Wastewater and the Need for Removal

Lead (Pb) is a heavy metal that is well-known for its high toxicity and the hazards it presents to human, plant, and animal life. Given the risks posed by lead entering waterways and drinking water supplies, discharge of lead-contaminated wastewater streams is heavily regulated across most regions of the world. In this article, we’ll take a look at the limits and acceptable levels of lead in industrial wastewater, and explore the most common reasons why a facility might implement a lead removal strategy.

What are the main reasons for removing lead from wastewater?

While industrial uses of the metal have shifted over time, today, lead is important to the production of acid batteries, metal plating and finishing, printed circuit boards, ammunition, ceramics, glass, non-household paints and pigments, and other products. These and other operations result in wastewater streams that can contain concentrations of lead that far exceed safe exposure levels—sometimes by many thousands of times over. 

Industrial effluents can contain dissolved lead, as well as various lead compounds, such as lead salts, oxides, and sulfides. When contaminated wastewater is improperly discharged to waterways or to wastewater treatment facilities, lead can make its way into aquatic and terrestrial ecosystems. Over time, lead can accumulate in sediments, soils, plants, and animals, with consequences such as inhibited plant growth and contamination of drinking water and food supplies. In humans, even small amounts of lead in food or water can cause a number of health problems, including acute lead poisoning, as well as chronic conditions such as nerve damage, paralysis, cancer, colic, impaired cognitive function, and infertility, among other conditions.

As such, the biggest underlying reason that facilities need to remove lead from industrial effluents is to protect the public against the environmental and health risks associated with lead toxicity. We’ll take a closer look at the specific factors that compel or motivate facilities to seek lead removal options in the following sections.

Compliance with wastewater discharge permit limitations

To mitigate the public health risks and environmental impacts of lead, many nations maintain regulations that stipulate limits on lead in drinking water and industrial effluents.  In the United States, the Environmental Protection Agency (US EPA) is responsible for regulating lead limits in industrial effluent streams. An industrial facility must comply with relevant discharge limitations, as the failure to do so can result in substantial fines and serious legal repercussions.

Lead limits and enforcement strategies may differ depending upon the way in which a facility chooses to handle its effluent streams. The US EPA, for example, makes a distinction between direct dischargers that release effluents directly to waterways, and indirect dischargers that route effluents to wastewater treatment facilities. Direct dischargers are subject to US EPA enforcement by means of National Pollutant Discharge Elimination System (NPDES) permits. While the NPDES permitting process is particular to the US, other regions of the world have similar compliance, monitoring, and enforcement programs. Put simply, if you plan to discharge wastewater to public waterways, you will need to obtain the proper discharge license or permit, and implement a lead removal strategy to stay in compliance with the lead limits applicable to your facility. In the US, the daily maximum and/or monthly average lead limits will be defined in your NPDES permit, along with requirements for sampling and testing your wastewater.

NPDES limits on lead are based on US regulatory standards, which are complex, and range quite a bit depending upon industrial sector, treatment approach, and production volume. For both the electroplating and metal finishing industries, for example, the average monthly concentration of lead in effluent streams is limited to around 0.4 mg/L. Limits for other industries are defined differently, as is the case for the nonferrous metals manufacturing industry, where lead limits are scalable based on a facility’s production volume. As such, effluent limits for metals manufacturers are written as the number of pounds of lead in an effluent stream per billion pounds of lead-containing product (e.g. bullion, sinter, slag, etc.). Effluent limits on lead differ widely depending upon the specific types of metal products produced, although most types of primary lead producers can expect a monthly average limit of less than 300 pounds of effluent lead per billion pounds of lead product produced. At the low end, some facilities may be limited to zero lead content in their effluent streams, while on the high end, some types of refineries could have a monthly average limits that are much higher.

In summary, you will need to implement some means of lead removal as part of your wastewater treatment strategy if your facility discharges wastewater directly to waterways and your lead content exceeds applicable daily or monthly regulatory limits on lead content.

Compliance with wastewater treatment facility requirements

Many industrial facilities choose to discharge wastewater to a centralized wastewater treatment facility, such as municipal sewers or publicly-owned treatment works (POTW). But receiving facilities aren’t always equipped to treat industrial effluents for toxic materials like lead or other heavy metals. As a result, elevated lead levels can persist following treatment, where they may pollute waterways or contaminate drinking water supplies.

In order to prevent these types of disasters, centralized treatment plants usually require discharging facilities to meet certain wastewater quality standards to ensure predictable and safe plant function. In short, if your facility discharges to a POTW or sewer and your effluent contains lead, you will likely need to remove lead from your wastewater prior to discharge.

In the US, this is regulated by the US EPA’s National Pretreatment Program, which grants receiving facilities the power to administer wastewater discharge permits and enforce their own limits on lead. This is because centralized treatment facilities must themselves comply with US EPA limits on lead and other contaminants. US regulatory standards for centralized treatment facilities are complex, and lead limits range somewhat depending on the types of waste streams received by the treatment facility. In general, however, US regulatory codes limit centralized treatment facilities to a monthly average of less than 0.3 milligrams of lead per liter of wastewater. Given these stringent guidelines, a receiving facility may require an industrial facility to reduce lead content to levels that can be safely managed by the wastewater treatment technology in place at the POTW. Failure to adhere to pretreatment requirements can jeopardize existing wastewater discharge agreements with the receiving facility, and can result in fines or legal action.

Reclamation and recycling

While regulatory compliance is the chief reason that industrial facilities seek lead removal solutions, there are sometimes added benefits for doing so, including the ability to recover stream constituents. In fact, industrial facilities are increasingly implementing recycling and reclamation initiatives aimed at separating out certain constituents from process water or wastewater streams so that they can be recycled or reused. These reclamation strategies can help facilities to meet regulatory guidelines or permit requirements, while also providing economic advantages by cutting consumption of materials and source water, and by reducing the volume of liquid and solid wastes.   

Separation technologies can be used to reclaim lead and lead compounds for recycling and reuse, and they can also be used to remove lead to ensure that other stream constituents can be reused.  In other words, if your facility is looking for ways to cut costs and improve material utilization efficiency, then reclamation may be worth considering as part of a lead removal strategy.  

Can SAMCO help?

SAMCO has over 40 years’ experience custom-designing and manufacturing wastewater treatment systems, so please feel free to reach out to us with your questions. For more information or to get in touch, contact us here. You can also visit our website to set up a call with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for a separation or wastewater treatment system to meet your lead removal needs.

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