Tertiary treatment of urban wastewater: effect on antibiotic resistance

ESAMUR conference, Murcia, November 16-17 2017

Luigi RizzoUniversity of Salerno

Department of Civil Engineering

Fisciano (SA), Italy

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SummaryWastewater reuse, main challenges and EU regulation

Antibiotic resistance (AR), AR transfer mechanisms and AR in urban wastewater treatment plants (UWWTPs)

Tertiary treatment in UWWTPs

Effect of disinfection processes on AR

Advanced oxidation processes (AOPs)

Effect of photo driven AOPs on AR (ARB&Gs)

Conclusions

Acknowledgements

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Wastewater reuse

Gap between water sources (poor) and water demand (high) in several countries ask for alternative sources.

Wastewater (ww) reuse can contribute to fill the gap but ….

… concern for treated ww safety.

Regulations on ww reuse exist in some countries but a EU regulation is missing.

EU is working to a regulation: EU minimum quality standards for ww reuse… (JRC technical report).

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Main challenges in ww treatment for agricultural reuse

Depend on the country/geographical area, technology availability, treatment costs etc...

(In developed countries) research is working to find effective tertiary treatment methods to make treated ww safer: through an effective inactivation of pathogens;

reduced effluent toxicity;

by minimizing the formation and/or removing disinfection by products (DBPs);

effectively removing contaminants of emerging concern (CECs);

and, more recently, through the control of antibiotic resistance spread.

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EU wastewater reuse regulation (?)EU minimum quality standards

for wastewater reuse…SCHEER and EFSA scientific

advices on JRC report

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In the opinion of the SCHEER, the report inadequately addresses (i) contaminants of emerging concern (CECs), (ii) antibiotic resistance spread through urban wastewater treatment plants’ (UWWTPs) effluents, and (iii) possible risks associated with disinfection and/or advanced treatment of urban wastewater (e.g. formation of disinfection by products and related toxicity). Therefore the SCHEER is of the opinion that, in its current form, the minimum quality requirements proposed provide insufficient protection both to environmental and human health. 

The European Food Safety Authority recommends that: … and (10) critical discussion on the importance of the uptake and accumulation of chemical contaminants, including compounds of emerging concern and disinfectant by‐products, and the possible consequences for human and animal health, is included.

Antibiotic resistance

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Antibiotic resistance

Antibiotic resistance (AR) has become an ongoing clinical and public health issue of concern worldwide (WHO 2014).

Depending on the scenario, failing to tackle AR treat will mean that (Taylor et al., 2014):the world population by 2050 may decrease by 11 million (if

resistance rates will be successfully addressed) and 444 million (a world with no effective antimicrobial drugs) than it would otherwise be in the absence of AR.

the world economy would be smaller by between 0.06% and 3.10%, again depending on the scenario, and world Gross Domestic Product losses may result in a cumulative loss that ranges between $2.1 trillion and $124.5 trillion.

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AR transfer mechanisms

8/24Dodd 2012. J. Environ. Monit.  14, 1754‐1771

Antibiotic resistance in UWWTPs

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Tertiary treatment in UWWTPsMechanical

pre‐treatment Primary settlingRaw urbanwastewater

Biological process

Secondary settling

Tertiary/advancedtreatment

Sludge treatment

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•Filtration (F)

•(F +) adsorption

•F + membranes

•(F +) AOPs

•(F+) disinfection

Tertiary treatment in UWWTPsDisinfection processes

Chlorination

UV-C radiation

Peracetic acid

Physical processesRapid granular filtration

Membranes (UF, MF, NF*)

Physico-chemical processesAdsorption (typically PAC, GAC)

Advanced oxidation processes (AOPs)Ozonation, UV/H2O2, photo-Fenton … etc.Poor or no effect high effect 11/24

Effect on CECs             AR        Bacteria

*

Advanced oxidation processes (AOPs)

… have been widely investigated in the removal of organic and inorganic contaminants from water/wastewater as well as disinfection processes;

Among AOPs, photo driven processes, including photo-Fenton and UV/H2O2 as well as heterogeneous photocatalytic processes (e.g., UV/TiO2) have been found to be effective in the inactivation of a wide range of bacteria;

AOPs produce radical species (e.g., hydroxyl radicals (HO)).

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Effect of photo driven AOPs on ARB

Effect of solar photo-Fenton on multi-drug resistant E. coli strain (ampicillin, ciprofloxacin, tetracycline)

Ferro et al. App. Cat. B 178 (2015) 65–7313/24

Effect of photo driven AOPs on ARB Effect of H2O2/sunlight (a), TiO2/sunlight and TiO2/H2O2/sunlight (b) processes

on multi-drug resistant E. coli strain (ampicillin, ciprofloxacin, tetracycline)

(a) (b)

Ferro et al. App. Cat. B 178 (2015) 65–7314/24

Effect of photo driven AOPs on ARB

Comparison between Cl2 (1 mg/L, A) and sunligth/H2O2 (50 mg/L, B)

Fiorentino et al. J. Photochem. Photob. B 148 (2015) 43–5015/24

Wastewater disinfection by AOPs: ARB regrowth

Total and AR E.Coli regrowth: comparison between solar/H2O2 (50 mg/L) and chlorination (Cl2, 1 mg/L)

Fiorentino et al. J. Photochem. Photob. B 148 (2015) 43–5016/24

Effect of conventional disinfection on ARGsBacterial cells damaged by disinfection processes can release mobile genetic elements that may transfer AR to non‐resistant recipient cells 

Although conventional and new disinfection processes can be effective in the inactivation of ARB, they may be not effective in controlling AR spread. In particular: Conventional disinfection processes (namely, chlorination, UV‐C 

radiation and ozonation) can eventually remove ARGs … but under not realistic operative conditions (in terms of oxidant/disinfectant concentration, UV radiation);

A few investigations at full scale showed that chlorine and UV‐C disinfection do not significantly affect ARGs abundance;

Only a few works investigated the effect of AOPs on ARGs and results depend on target AOP and ARGs. 17/24

Effect of photo driven AOPs on ARGs Effect of sunlight/H2O2 process on selected AR E. coli strain and ARGs

(intracellular and total DNA) in aqueous suspension

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Effect of photo driven AOPs on ARGs

Effect of sunlight/H2O2 process on selected AR E. coli strain and ARGs (intracellular and total DNA) in aqueous suspension

Intracellular DNA Total DNA

(Ferro et al., 2016, Journal of Hazardous Materials doi:10.1016/j.jhazmat.2016.03.014) 19/24

0.529 mmol H2O2/L

Effect of photo driven AOPs on ARGs

Effect of sunlight/H2O2 process on indigenous AR E. coli* and ARGs (in intracellular and total DNA) in urban ww.

20/24*8 mg/L of ampicillin, 0.064 mg/L of ciprofloxacin, 8 mg/L of tetracycline

Effect of photo driven AOPs on ARGs Effect of sunlight/H2O2 process on indigenous AR E. coli and ARGs (in

intracellular and total DNA) in urban ww.

(Ferro et al., 2016, Science of the Total Environment 560‐561, 29‐35)

Intracellular DNA Total DNA

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Conclusions Needs for effective tertiary treatment methods to make reused ww safer

to minimize risk for human health;

Needs for (a useful) EU regulation on ww reuse that can ensure the same safety level among EU countries;

Further studies need to understand:The effect of AOPs on the potential of AR transfer (ARB&Gs and mobile

genetic elements release in the effluent).

If potential AR transfer can actually result into a real AR transfer to humans through the environment (water, ww reuse, crops irrigation, soils, plant uptake).

On going research efforts on ww reuse and AR (details in Researchgateand official webpages):NEREUS COST Action (ES1403, http://www.nereus-cost.eu/)

ANSWER (H2020-MSCA-ITN-2015, http://www.answer-itn.eu/)

Italy-China project on ww disinfection and AR (MAE, PGR04089) 22/24

Acknowledgements ESAMUR and Pedro José Simón Andreu

University of Salerno: Giovanna Ferro, Antonino Fiorentino,

Stefano Castiglione, Francesco Guarino, Angela Cicatelli

Plataforma Solar de Almeria: Pilar Fernandez-Ibanez,

Inmaculada Polo-Lopez, María Castro Alferez

Funding:

FARB projects

SFERA program

COST Action NEREUS

ANSWER project

Italy-China project23/24

Thankyou

ANSWER project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie

grant agreement No. 675530

The content herein reflect only the author’s views and the Research Executive Agency is not responsible for any use that may be made of the information it contains. 

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Luigi RizzoUniversity of Salerno

Department of Civil Engineering

(l.rizzo@unisa.it)