The urban water sector and emerging contaminants

Pollutants and contaminants complicate the wastewater treatment process, so understanding emerging contaminants is vital for urban water.

Wastewater treatment plants are designed to treat water before it is discharged into waterways. Pollutants and contaminants complicate this process, so understanding emerging contaminants is vital for the urban water sector.

Whether we like it or not, wastewater treatment plants (WWTPs) are an essential gateway between the community and the environment. Wastewater treatment plants accept, manage, and treat water on behalf of the community on its journey to the broader environment. In recent times, the focus for WWTP effluent has expanded away from managing the familiar nutrient and microbiological contaminants to include the more challenging contaminants of emerging concern (CEC).

It is known that many contaminants, including CEC, enter wastewater from industrial sources, such as trade waste. Trade waste can include wastewater from a diverse set of industries, ranging from food manufacturing to chemical manufacturing to metalworking to waste management (including landfill leachate). The list goes on. However, this is only part of the story.

Many CECs enter sewers as the result of normal human activities: preparation and cooking of food, bathing, laundry, managing our health with medications and supplements, exercise, and leisure activities, to name a few. For many of these contaminants, human activity results in a constant flux of contaminants to wastewater. That these contaminants are derived from domestic sources does not change WWTP operators’ obligation to manage the contaminants.

Scheduling specific chemicals on the Industrial Chemicals Environmental Management Standard (IChEMS) is registered under Australia’s obligations under the Stockholm Convention. It seems likely to result in more chemicals being prohibited in Australia (unless specifically exempt) and thus prohibited from being released into the environment. There is concern that water utilities will then effectively be responsible for releasing prohibited chemicals into the environment.

The Queensland Water Directorate (qldwater) and its members – the state’s water and sewerage service providers – are tackling the problem of CEC in treated wastewater from two directions.

Source control for emerging contaminants

Contaminants in wastewater are diverse. Everything we eat, drink, medicate our bodies with, wash off our bodies, wash off our clothes, and use to clean our homes makes its way into the sewer. Because of this, wastewater is a cocktail of chemicals. Wastewater treatment plants are designed to remove nutrients and pathogens, but they are not effective at destroying some contaminants.

This includes some chemicals, such as PFAS and its precursors. These are especially topical now because of the release of a Draft PFAS National Environment Management Plan (NEMP) 3.0, which included proposed limits for PFAS in biosolids for the first time. Biosolids are what remains of microorganisms after the digestion of organic matter during wastewater treatment. They are a valuable fertiliser and soil improver for agriculture.

About half of the PFAS that ends up in biosolids and treated wastewater comes from domestic sources because it is present in many everyday products, from food packaging to cosmetics and textiles.

Another example is galaxolide, a fragrance compound used in everything from cleaning products to cosmetics. The recent Review of the NSW Biosolids Guidelines proposed limits for galaxolide in biosolids for the first time for a chemical exclusively sourced from domestic wastewater.

This means that the most effective method for many contaminants may be to control the chemicals at the source, such as eliminating the contaminant from products used in the community.

With this in mind, the qldwater Consortium for Research and Advocacy on Contaminants has developed the Chemical Concoctions website. This website seeks to educate the public about the hidden sources of contaminants in their homes. It also gives people information about their choices as consumers to reduce the amount that makes it into wastewater.

Trade waste control

The other source of CEC in wastewater is trade waste. Trade waste discharges to sewers are typically managed through trade waste agreements with the local water and sewerage service provider. The agreements usually specify limits for common sewage parameters (including biological oxygen demand (BOD), ammonia, grease, and pH). These are typically determined by the impact a discharger’s wastewater stream will have on a wastewater treatment plant.

However, many trade waste sites are also known contributors of untreatable chemicals. For example, landfill leachate is commonly accepted as a trade waste stream. They can be high in pesticides, hydrocarbons, flame retardants, and PFAS. These sites are expected to have high levels of BOD, ammonia, nitrogen, and phosphorous.

Landfill leachate is an obvious source of CEC via trade waste, but many CEC are unknowingly discharged in trade waste and can affect the quality of the treated wastewater. If trade waste sources can be identified, there may be opportunities to substitute for or otherwise reduce problematic chemicals. This can facilitate releasing contaminants that pose the greatest environmental risk.

With this in mind, a “Cheat Sheet” has been developed to support the sewerage service providers, employees, and customers in making informed decisions on reducing the impact of emerging contaminants, especially for trade waste. Data was sourced from the WaterRA Emerging Chemicals Database for National Awareness (Echidna) database to view the most common pollutants in wastewater and their risk based on a mix of bioaccumulation, persistence, and toxicity rankings.

The data has been refined to include chemical usage and focus on a mix of the most common and/or potentially hazardous. Further data for the presence, types, and sources of contaminants pinpoint industries of concern to focus on.

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