of the stations exceeded one of the permanent monitoring criteria
of microplastics retained
unique method for analysing micropollutants in water and sludge
Undesirable substances, detectable in the environment at very low concentrations (µg/L, ng/L), called micropollutants, may have at these values negative impacts on living organisms because of their toxicity, persistence and bioaccumulation. They are organic or inorganic, biodegradable or not.
In water, this contamination results from the partial treatment of micropollutants by urban and industrial wastewater treatment plants. Current treatments are mainly focused on the removal of carbon, nitrogen, phosphorus and some locally identified micropollutants. They are not adapted to a set of commonly used micropollutants that are thus discharged into the natural environment.
During the 2016 RSDE campaign, 87% of the stations exceeded one of the permanent monitoring criteria, and phytopharmaceutical molecules were identified in 30 to 60% of the wastewater treatment plant (WWTP) outputs. It should be noted that 90% of micropollutants are of pharmaceutical origin and come from domestic discharges (source OFB).
The cost for micropollutants removal is consequently between €60,000 and €200,000 per kg of phytopharmaceutical substances eliminated for drinking water production. The cost of restoring the good status of water bodies exceeds far the cost of environment quality monitoring . In 2007-2010, WFD monitoring in Europe cost an average of 30.5 million euros per year plus 15 million euros for additional monitoring networks, compared to 27 billion euros for restoration measures for 2010-2015.
Switzerland, for its part, has amended its federal law on water protection since 2015 to make it compulsory to remove at least 80% of certain micropollutants from the outlets of wastewater treatment plants that discharge into sensitive environmental places. The additional cost of treatment is estimated at 10 to 30% of the cost of conventional treatment.
Plastic debris is now a very important environmental problem and the risk of plastic microparticles becoming a public health problem exists because of their proven presence in tap water or bottled water. A recent WHO report (“Microplastics in drinking-water”, 2019) downplays this risk, but calls for more research focusing on the fraction of microparticles smaller than 150 microns, whichare able to cross epithelial barriers and penetrate deep into human organs. Thus a fraction of microparticles and plastic nanoparticles are concerned.
Since treated wastewater is a major source of plastic microparticles in surface waters (another source being stormwater discharged into lakes and rivers), there is a need to monitor the retention efficiency of microparticles in both wastewater treatment plants and stormwater.
Studies on micropollutants from wastewater treatment plants have shown their high presence in sludge matrices (AMPERES, SMS…) and indeed, this part adsorbed on the solid fraction must be quantified for a correct evaluation of the fate of micropollutants. The micropollutants concentration in the sludge depends on both the primary treatment and the physico-chemical properties of the molecules (hydrophobic and electrostatic interactions). The costs and lack of reliable solutions for quantifying micropollutants in complex matrices are currently an obstacle to the development of efficient technologies for their removal.