Stopping Micropollutants at their Source
We explain the origins of micropollutants entering the environment and how they can be prevented.
Micropollutants arrive in the environment through multiple routes, but one of the main sources is wastewater from industrial processing. There are currently 100,000 commercially registered compounds in Europe and there is little in place to stop the residue from the majority of these eventually entering the water cycle.
Also known as priority substances, micropollutants are present in products and processes that are part of daily life in an industrialised world – medication, personal care products, technology, clothing, pesticides and fertilisers. These substances are problematic when they have toxic, persistent and bioaccumulative properties.
They are emitted in wastewater from all manner of manufacturing plants including pharmaceutical, chemical, electronics and agrochemical. Leachate from landfill sites where unprocessed waste is dumped can also be a source.
Municipal treatment plants serve as centralised collection points for industrial wastewater, stormwater and domestic sewage and are in the sights of regulators seeking to diminish the impact of toxic substances on the ecosystem.
Analytical techniques have vastly improved over the last decade and are increasingly detecting micropollutants in the aquatic environment down to extremely low concentrations, even one nanogram per litre. Secondary treated effluent discharged from wastewater treatment plants into receiving waters has consequently been identified as a major source of toxic substances in the environment.
Existing biological wastewater treatment plants were designed prior to the development of modern analytical techniques and were not expected to remove trace levels of micropollutants. The presence of micropollutants in the environment has been linked to toxic biological effects in fish and mammals including estrogenicity, mutagenicity and genotoxicity.
The feminisation of male fish is one example relating to the impact on aquatic species exposed to endocrine disrupting compounds. Another serious concern is the rise of antibiotic-resistant organisms that could affect human health.
Reducing micropollutant concentrations requires a multi-stranded long-term strategy and the EU Water Framework Directive, adopted across Europe in 2000, has created an opportunity for enforcement of more stringent regulations. This is reflected elsewhere in the world, especially in Asia where Chinese factory managers risk imprisonment for breaching compliance and polluting the environment.
Source control measures like adoption of non-toxic chemical alternatives and agricultural management to reduce polluted water running off land will certainly play a role in reducing priority substances in watercourses. However, advanced on-site technologies for wastewater treatment will also play a vital role.
To date tertiary treatment has proven prohibitively expensive, especially where combined wastewater and stormwater collection generates great volumes for treatment. Advanced oxidation processes (AOPs), such as ozone, provide one way of screening out micropollutants but are energy intensive and expensive for most applications.
This means there is a great opportunity for the development of lower cost technologies to provide the additional treatment required to eliminate micropollutants before they enter the environment or, even better, before they exit the industrial site. One of very few alternatives to AOPs is Arvia’s Nyex process, which is currently being piloted with one of the UK’s largest utilities and deployed in a range of industrial applications.
Nyex uniquely combines oxidation and adsorption to tackle hard-to-treat substances. The results of the trials will be available in the near future – watch out for some very good news for the water industry, manufacturers and the environment.