Environmental assessment of solar photo-Fenton processes in combination with nanofiltration for the removal of micro-contaminants from real wastewaters

Alejandro Gallego-Schmid,Raphael Ricardo Zepon Tarpani,Sara Miralles-Cuevas,Alejandro Cabrera-Reina,Sixto Malato,Adisa Azapagic

doi:10.1016/j.scitotenv.2018.09.361

Alejandro Gallego-Schmid, Raphael Ricardo Zepon Tarpani + Show 4 more

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https://doi.org/10.1016/j.scitotenv.2018.09.361

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Abstract

Scarcity of water and concerns about the ecotoxicity of micro-contaminants are driving an interest in the use of advanced tertiary processes in wastewater treatment plants. However, the life cycle environmental implications of these treatments remain uncertain. To address this knowledge gap, this study evaluates through life cycle assessment the following four advanced process options for removal of micro-contaminants from real effluents: i) solar photo-Fenton (SPF) operating at acidic pH; ii) acidic SPF coupled with nanofiltration (NF); iii) SPF operating at neutral pH; and iv) neutral SPF coupled with NF. The results show that acidic SPF coupled with NF is the best option for all 15 impacts considered. For example, its climate change potential is almost three times lower than that of the neutral SPF process (311 vs 928 kg CO2 eq./1000 m3 of treated effluent). The latter is the worst option for 12 impact categories. For the remaining three impacts (acidification, depletion of metals and particulate matter formation), acidic SPF without NF is least sustainable; it is also the second worst option for seven other impacts. Neutral SPF with NF is the second worst technology for climate change, ozone and fossil fuel depletion as well as marine eutrophication. In summary, both types of SPF perform better environmentally with than without NF and the acidic SPF treatment is more sustainable than the neutral version. Thus, the results of this work suggest that ongoing efforts on developing neutral SPF should instead be focused on further improvements of its acidic equivalent coupled with NF. These results can also be used to inform future development of policy related to the removal of micro-contaminants from wastewater.

Highlights

Water quality and availability are of an increasing concern in many regions worldwide, calling for a better management of water resources (FAO, 2007; OECD, 2012)
Neutral solar photo-Fenton (SPF) is the worst option for 12 of the 15 impact categories, while acidic SPF coupled with NF is the best alternative for all the impacts
Acidic SPF is more environmentally sustainable than its neutral equivalent. Both types of SPF have lower impacts if they are coupled with NF than if they are stand-alone

Summary

Introduction

Water quality and availability are of an increasing concern in many regions worldwide, calling for a better management of water resources (FAO, 2007; OECD, 2012). An exception is Switzerland, which has set an 80% reduction target for the release of micro-contaminants from MWTPs (including primary, secondary and tertiary treatment) with any of the following characteristics (Eggen et al, 2014): i) serving capacity N80,000 people; ii) serving capacity N24,000 people and discharging into sensitive waters or drinking reservoirs; or iii) serving capacity N8000 people and a contribution N10% of the dry-weather flow in the receiving waters This is expected to affect 123 MWTPs nationally and reduce the total load of microcontaminants discharged to the environment by 50% (Mulder et al, 2015). There is a need for more scientific evidence on the impacts that these substances may cause in water bodies, as well as for systematic monitoring of some of the compounds (Taylor and Senac, 2014; NRMMC, 2015)

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