Reducing Toxicity in Wastewater and Achieving Regulatory Compliance at Industrial Facilities

Wastewater released by industrial facilities is subject to significant environmental regulations. The primary goal of these regulations is to prevent contaminants and toxins from entering surface water, groundwater and other sources of drinking water, which then must be treated by municipal water treatment plants.

Ozone advanced oxidation processes (AOP) offer exceptional benefits for industrial facilities working to reduce toxicity in wastewater and achieve regulatory compliance. Ozone AOP can help companies lower their environmental risk, reduce legal and compliance costs and enhance their sustainability profile.

What regulations target industrial wastewater?

Industrial facilities that discharge into “waters of the United States” will likely require a National Pollutant Discharge Elimination System (NPDES) permit. As a component of the NPDES program, the National Pretreatment Program addresses the discharge of industrial wastewater to municipal wastewater treatment systems, with standards that vary from state to state and city to city. The EPA’s Effluent Limitations Guidelines currently apply to 59 industrial categories, and some industrial facilities may be subject to the Spill Prevention, Control, and Countermeasure (SPCC) rule, if they store, transfer, use or consume oil or oil products, such as diesel fuel, gasoline, lube oil, hydraulic oil, adjuvant oil, crop oil, vegetable oil or animal fat. There are also numerous state and local regulations that affect industrial wastewater.

What wastewater toxicity testing is required by industrial facilities?

Part of the oversight of the National Pollutant Discharge Elimination System requires that facilities conduct wastewater toxicity testing on their effluent – specifically, they are to regularly perform Whole Effluent Toxicity (WET) tests.

The WET test measures the effects of facility wastewater on specific test organisms – specifically, their ability to survive, grow and reproduce. As opposed to testing for a specific chemical, WET is the aggregate toxic effect of a facility’s effluent on living organisms. By observing this effect, the effluent’s impact on an ecosystem and water safety can be understood.

There are two basic types of WET tests: acute and chronic. Acute tests measure the immediate impact (such as mortality) of effluent on life forms that act as representatives of a general aquatic setting, and the test duration is usually 24, 48 or 96 hours. Chronic tests measure the longer-term impact of effluent, such as survivability, growth, mobility, fecundity, reproduction and teratogenicity (embryonic abnormalities). For chronic tests in freshwater settings, the test duration of between four and eight days. For chronic testing on marine/estuarine organisms, the test duration is between one hour and nine days.

The required frequency of a WET test is determined by a facility’s discharge permit and can range from monthly to annually, depending on substances handled by the facility and their potential risk. Only third-party certified labs can perform these tests.

What is the risk to industrial facilities of releasing contaminated wastewater?

Industrial plants that do not adequately treat their wastewater expose themselves to litigation and regulatory fines, which have an immediate negative impact on profitability. Industrial facilities that pass along contaminated wastewater to their local municipal treatment plants are pushing their external costs to governments and taxpayers, which can result in reputational and political damage.

What is ozone?

A pale blue gas, ozone (O3) is composed of three oxygen atoms and is the most powerful oxidizing agent permitted for use in water treatment. Ozone has a fast reaction time, no added chemicals and reduced disinfection by-products. It’s an unstable compound, a reactive oxygen species, that degrades organic and inorganic substances in wastewater. In industrial settings, ozone water treatment can significantly reduce (or even completely remove) contaminants, toxins and many other pollutants from water in a vast range of industrial and municipal applications. Ozone can be generated onsite and introduced into the wastewater to oxidize a wide variety of inorganic, organic and microbiological problems including contaminants of emerging concern, 1,4-dioxane, micropollutants and cyanobacteria mycotoxins.

How does ozone AOP treat industrial wastewater?

Ozone AOP can be added to an existing traditional water treatment system to meet regulations without redesigning a completely new system and is an appealing option for industrial wastewater treatment. Ozone is composed of three oxygen atoms, and when introduced into the wastewater, it can eliminate a wide variety of inorganic, organic and microbiological toxins. Ozone can be generated onsite with an ozone generator, which uses energy to create ozone by separating oxygen molecules (O₂) into oxygen atoms (O), which react with other oxygen molecules (O₂) to form ozone (O3). A high voltage alternating current is applied across a dielectric discharge gap that contains an oxygen-bearing feed gas. When ozone is dissolved in water, highly reactive hydroxyl radicals form. These radicals have excellent oxidizing capacity on pollutants and molecules including metals, surfactants, phenols, hydrocarbons, cyanide, pharmaceutical micropollutants, 1,4 dioxane and others.

What is the benefit of piloting an ozone AOP system?

Wastewater and water treatment systems are a significant investment, so piloting the treatment before committing to a permanent installation is critically advised. De Nora has containerized, plug-and-play versions of our products with lab-scale testing that facilities can use for a limited period of time to confirm that it will produce the desired results.

One size most certainly does not fit all when it comes to industrial wastewater treatment, and piloting can overcome the challenges of variability presented by seasonality, weather, space allotment, regulatory targets and other unique factors faced by specific plants. Piloting also offers the opportunity to adjust certain parameters to design a system that will deliver the right treatment for the specific application. Piloting ensures that a plant invests properly and for the long term.

Case study: West Virginia facility surpasses compliance requirements with ozone AOP

A West Virginia manufacturing facility needed to reduce wastewater toxicity by 50% to meet state requirements for discharging into the Ohio River. Its average water characteristics included a chemical oxygen demand (COD) of 100-140 ppm, total suspended solids (TSS) of less than 30 and 4-7 ppm of surfactants.

Granular activated carbon was rejected due to high operating cost. UV was not applicable due to low UV transmittance and high organics content. The facility ultimately decided to pilot an ozone treatment system due to its ability to oxidize the majority of the molecules causing toxicity.

The system dramatically reduced the plant’s TUc (chronic toxicity units) to as low as 0, far surpassing state regulatory requirements and reducing the risk of fines and litigation. The pilot has now been converted into a permanent installation.

Why work with De Nora?

De Nora has developed and delivered ozone generators for water treatment and advanced oxidation processes for industrial applications since the 1970s, supporting customers from design to commissioning and aftersales. We design single components to complete packaged systems that generate up to 6,000 pounds (113 kg/h) of ozone per day. With more than 1,500 Capital Controls Ozone Generators installed around the world, we support customers with on-site piloting and lab-scale testing in containerized plug-and-play pilot packages.