Every time we wash our clothes, take medication, irrigate crops, or generate effluent from manufacturing, people create apotential pathway connecting chemical use to the wider environment. Wastewater sits at the centre of this connection, carrying a complex mixture of contaminants through treatment systems and, ultimately, into rivers, lakes, groundwater, and coastal ecosystems. Understanding how wastewater transports, transforms, and removes chemical pollutants is therefore critical for protecting environmental and human health. As pressures from urbanisation, industrialisation, population growth, and climate change continue to increase, developing effective and sustainable wastewater solutions has become one of the defining environmental challenges of the twenty-first century.
As you work through this module, you will explore how wastewater treatment contributes to reducing chemical pollution, why treatment effectiveness varies, and how integrated approaches combining prevention, treatment, innovation, and collaboration can help protect both ecosystems and human health.
Although many people associate wastewater solely with sewage, it is a much broader term that includes water from homes, hospitals, laboratories, industrial facilities, agriculture, aquaculture, and urban runoff. The types of chemicals found in wastewater are highly diverse. Domestic wastewater may contain ingredients from personal care products, detergents, cleaning agents, and pharmaceuticals. Commercial and healthcare facilities contribute medicines, solvents, contrast agents, and specialist treatment chemicals. Agricultural activities introduce nutrients, pesticides, and veterinary medicines, while urban runoff can carry heavy metals, hydrocarbons, de-icing salts, and other pollutants. Some of these substances break down naturally, whereas others are persistent and may remain in the environment long after they are released.
To reduce these impacts, wastewater is typically treated through a series of stages. Primary treatment removes suspended solids and particle-bound contaminants through physical processes such as screening and sedimentation. Secondary treatment uses microorganisms to break down biodegradable organic material and reduce nutrient concentrations. Tertiary treatment applies more advanced technologies, including filtration, oxidation, membrane processes, and disinfection, to target pathogens and trace contaminants that remain after earlier stages.
Despite these treatment processes, no single technology is effective for all pollutants. Different contaminants behave differently depending on their chemical properties, such as persistence, solubility, and ability to bind to solids. Some pharmaceuticals and industrial chemicals can be removed efficiently, whereas others may persist even after advanced treatment. Consequently, understanding both the chemistry of pollutants and the mechanisms of treatment is essential when designing solutions.
An increasingly important principle in pollution management is preventing contaminants from entering wastewater in the first place. Source-control measures, such as waste separation technologies, sustainable drainage systems, reedbeds, wetlands, and other nature-based solutions, can reduce pollution before it reaches treatment facilities. Where prevention is not possible, a combination of biological, physical, and chemical treatment technologies can help minimise environmental impacts. Ultimately it’s important to match the solutions for wastewater to the local situation and chemical mixtures being addressed.
Susan Zappala at the JNCC in the UK gives an overview of the removal of chemicals in wastewater treatment
Key Reading
Gardner et. al., 2012. The significance of hazardous chemicals in wastewater treatment works effluents. Science of The Total Environment Vol 437: 363-372
Kogut et. al., 2026. A Critical Review of Domestic Wastewater Pollutants: Exposure Pathways and Treatment Technologies. Clean Technologies, 8(3): 73. https://doi.org/10.3390/cleantechnol8030073
Al-Rajhi and Abdelghany. 2024. Innovative strategies for wastewater treatment: harnessing green technologies for sustainable resource recovery. a review. Front. Environ. Sci. Vol 13. https://doi.org/10.3389/fenvs.2025.1696485
Environment Agency, 2025. Blog. Regulating the water industry: legal powers and duties. 19 June. Retrieved on 19 Aug 2026 from https://environmentagency.blog.gov.uk/2025/06/19/regulating-the-water-industry-legal-powers-and-duties/
Environment Agency, 2026. Written evidence from the Environment Agency (PPM0011) Environmental and Climate Change Committee: Pet Parasite Medication Environment Agency Written Evidence (May 2026). Retrieved on 19 Aug 2026 from https://committees.parliament.uk/writtenevidence/167373/pdf/
Sims. 2022. Chemicals of concern: a prioritisation and early warning system for England. Royal Society of Chemistry. Environmental Chemistry Group—Bulletin—July. Retrieved on 19 Aug from https://www.envchemgroup.com/uploads/1/0/0/2/100278594/eb35.pdf