What are emerging pollutants?
Emerging pollutants are defined as new chemicals without regulatory status and a poor understanding of their environmental and health impacts. The major sources of environmentally relevant emerging contaminants are primarily wastewater treatment plants, effluents and secondarily terrestrial run-offs (roofs, pavement, roads, and agricultural land). Contaminants do not need to be persistent in the environment to cause negative effects, a common phenomenon, as their high transformation/removal rates are compensated by their continuous introduction into the environment.
Many pharmaceuticals and personal care products detected in the environment can be considered emerging contaminants, as they are not addressed by published health standards. However, the word “emerging,” used in the context of contaminants detected at low levels in water, should not be confused with the word “emergency,” which often connotes cause for immediate alarm. Some of the terms used to refer to different classes of emerging contaminants include:
- Pharmaceuticals and personal care products (PPCPs)
- Endocrine disrupting chemicals (EDCs)
- Organic wastewater contaminants (OWCs)
- Persistent organic pollutants (POPs)
- Contaminants of emerging concern (CECs)
- Microconstituents
- Nanomaterials
Occurrence
A large number of studies have investigated the fate of EOCs in groundwater following infiltration of waste waters (sewage and industrial) as well as contaminated surface water sources, and to date provides the largest body of research regarding the sources and fate of EOCs in the subsurface. The work has been carried out in many countries including Germany, USA, UK, Denmark, Spain, Italy, Austria, Israel and France. Compared to other freshwater resources the occurrence of emerging pollutants in groundwater is poorly characterised.
While it is clear from reviewing the literature that the vast majority of groundwater resources do not contain emerging pollutants in concentrations that would be considered toxic and/or harmful, due to natural attenuation and dilution mechanisms, there is a large variety of EOCs found in groundwater proximal to important direct and indirect sources (e.g. artificial recharge and surface water), and in some cases the concentrations are significant (>100 ng/L). Figure 1 illustrates source-pathway-receptor approach to understand the arrival of emerging pollutants to groundwater bodies.
Point-source pollution originates from discrete locations whose inputs into aquatic systems can often be defined in a spatially discrete manner. The spatial extent or plume of pollution is therefore generally more constrained. Important examples include industrial effluents (e.g. manufacturing plants, hospitals, food processing plants), municipal sewage treatment plants and combined sewage-storm-water overflows, resource extraction (mining), waste disposal sites (landfill sites, industrial impoundments, farm waste lagoons) and buried septic tanks. Diffuse pollution, in contrast, originates from poorly defined, diffuse sources that typically occur over broad geographical scales. Examples of diffuse source pollution include agricultural runoff from bio-solids and manure sources, storm-water and urban runoff, leakage from reticulated urban sewerage systems and diffuse aerial deposition. These sources of pollution can be characterised as: i) covering larger geographical scales, ii) having generally lower environmental loading compared to point sources, iii) having higher potential for natural attenuation in the soil and subsurface, iv) and are poorly defined with less direct/obvious links back to the ‘polluter’, as such they continue to be a real challenge to monitor, regulate and assess their impact on groundwater resources. The combined toxicity of multiple contaminants is not well understood at present. In addition, there are a number of key emerging pollutants that have a global footprint, and are frequently detected in groundwater resources.
Prioritisation in DEMEAU project: list of selected compounds
The European Union needs data to implement new directives in order to prevent and manage pollution of aquatic environments. In that sense, some research projects, such as for example the DEMEAU project, will play an important role in helping regulators and water managers to test new innovative solutions to remove emerging pollutants from water and wastewater.
The DEMEAU project selected 12 emerging pollutants based on the following criteria:
- Commonly found in wastewater and drinking water supplies
- Environmental relevance
- Broad spectrum of chemical and physical properties
- Range from good to bad elimination by tested technologies (O3 and/or UV/H2O2)
- Existence of analytical methods by project partners
Chemical properties of selected organic trace substances.
Compound |
Chemical formula |
Function |
MW |
log Kow (unchanged) |
log D at pH 7.4 |
pKa |
charge at pH 7 |
Benzotriazole |
corrosion inhibitor in the atmosphere and underwater |
119 |
1,4 |
1,2 |
1.1, 8.6 |
0 |
|
Bezafibrate |
Fibrate drug used for the treatment of hyperlipidaemia |
361,8 |
4,3 |
0,7 |
3,4 |
-1 |
|
Carbamazepine |
anti-seizure medication |
236,1 |
2,5 |
2,7 |
- |
0 |
|
Epoxi-carbamazepine |
Metabolite of Carbamazepine |
252 |
- |
- |
- |
- |
|
Diclofenac |
nonsteroidal anti-inflammatory drug used to treat pain and inflammation |
295 |
4,5 |
1 |
4,2 |
-1 |
|
Gemfibrozil |
Fibrate drug to treat high cholesterol and triglyceride levels in people with pancreatitis |
250.33 |
- |
- |
- |
- |
|
Iopromide |
Contrast medium commonly used in radiographic studies |
790,9 |
-1,74 |
-1,74 |
11,1 |
0 |
|
Metroprolol |
beta-blocker used to treat angina (chest pain) and hypertension |
267,2 |
1,9 |
-0,1 |
9,5 |
1 |
|
Phenazone |
Analgesic, a non-steroidal anti-inflammatory drug and an antipyretic |
188,1 |
0,4 |
0,3 |
1,4 |
0 |
|
Primidone |
Anticonvulsant in the treatment of partial and generalized seizures |
218,1 |
1,12 |
1,12 |
11,5 |
0 |
|
Sulfamethoxazole |
Sulfonamide bacteriostatic antibiotic. |
253,1 |
0,9 |
-0,2 |
1.8, 5.6 |
-1 |
|
Trimethoprim |
Bacteriostatic antibiotic used mainly in the prevention and treatment of urinary tract infections |
290,1 |
0,9 |
0,6 |
7,2 |
0,5 |