DEMEAU’s Work Area 1 conducted a study review on trace organic removal rates in different Managed Aquifer Recharge (MAR) sites. The review concluded that redox and residence time conditions are part of the key parameters that are able to estimate emerging pollutants removal. MAR enables storage of water in periods of good resource quantity and it offers natural degradation of some pollutants, although some trace organic compounds have shown to be poorly degradable or may be removed only under specific conditions. Therefore, emerging pollutants are of special concern in Managed Aquifer Recharge (MAR) with reclaimed waste water.
This study intends to develop a European approach for MAR authorisation through the identification of the optimum MAR characteristics to ensure a minimum environmental impact related to trace organics and other pollutants.
A comprehensive review of more than 40 scientific papers and books has been carried out related to attenuation of emerging substances during MAR. For this purpose, twelve compounds have been selected representing emerging pollutants commonly found in wastewater and in drinking water that are of environmental relevance:
- Benzotriazole (Industrial chemical and pharmaceutical)
- Bezafibrate (Pharmaceutical, androgens)
- Carbamazepine (Pharmaceutical, androgens)
- Epoxi-carbamazepine (Pharmaceutical, androgens)
- Diclofenac (Pharmaceutical, non-steroidal anti-inflammatories)
- Gemfibrozil (Pharmaceutical, androgens)
- Iopromide (X-Ray contrast media)
- Metroprolol (Pharmaceutical, ß-adrenergic blockers)
- Phenazone (Pharmaceutical, analgesic)
- Primidone (Pharmaceutical, anticonvulsant)
- Sulfamethoxazole (Pharmaceutical, antibiotic)
- Trimethoprim (Pharmaceutical, antibiotic)
The research focused on these twelve selected compounds and has previously identified specific indicators of influencing removal of emerging substances as:
- MAR type
- Aquifer type
- Redox conditions
- DOC/TOC
- Residence time
- Concentration of the emerging substance in source water (initial concentration)
- Temperature
- Percentage of attenuation
- Compound characteristics
The review resulted in a Removal Condition Matrix that presents for each of the chosen emerging substances the conditions influencing the attenuation in MAR systems and the degree of expected removal under these conditions. As concluded from the Removal Conditions Matrix, the specific redox and residence time conditions required to achieve best removal of the selected contaminants have been analysed. 5 of the 12 trace organic compounds studied show high removal rates independent of redox conditions or residence time. The rest of the studied compounds require specific conditions to achieve best removal rates in MAR systems. For example, Benzotriazole shows some attenuation in nitrate and iron-manganese reduction conditions when residence time is longer than 6 months. Primidone shows no removal in any circumstance (Figure 1) and can be used as a tracer.
Figure 1: Substance removal is a function of chemical reduction conditions and residence time in the aquifer, here shown for Primidone.
On the other hand, other parameters as organic matter might influence on emerging pollutants removal as well, but available data was not enough to achieve significant conclusions in this study.
In conclusion, the review contributes to design site specific MAR systems to enhance emerging pollutants removal. For further information see Deliverable D12.1.