Abstract Sewage sludge is a by-product of the sewage treatment plants. Because of
its richness in nutrients and for several environmental and economic reasons, this
waste by-product is widely used as a fertilizer for agricultural purposes under
specific conditions. This practice might be hazardous since this waste includes
many known and unknown non-biodegradable and harmful pollutants, especially
emerging organic contaminants (EOCs), as well as cultivable and non-cultivable
pathogens. The present work is aiming at (1) providing information on the nature of
sludge in terms of persistent pollutants and cultivable and non-cultivable microbiota
generated by the currently implemented treatment processes, (2) analyzing the
consequences of the agricultural valorization on ecosystem biodiversity and soil
fertility, and (3) addressing and discussing the economic, ethical, and environmental
benefits or damage of this type of valorization. These issues need full consideration
by policy makers regarding the agricultural use of this waste by-product in terms of
irrigation with treated domestic wastewater or sludge land spreading as soil fertilizer
and plant growth promoter.
Keywords Economy, Ecotoxicity, Emerging organic contaminants, Ethics,
Irrigation, Land spreading, Metagenomics uncultured pathogens and parasites,
Microbiome, Micropollutants, Sewage sludge
1 Introduction
The human access to drinking water and sanitation is a universal right since water is
a vital resource for life and indispensable for the economy and the development of
nations. The protection of water resources and their sustainable use is becoming a
global issue to thwart consequences of population growth, increased urbanization,
and tourism and climate change with the risk of drought. The treatment and “reuse”
of sewage is among the possible solutions to solve the problem of water availability
for future generations as the world’s demand for safe and healthy food and water is
rapidly increasing [1]. According to the United Nations, the world’s population is
estimated to be 9.7 billion in 2050. Hence, preventing the degradation of soil
ecosystems and water resources must be a priority to consider for the next
decades [2].
Current estimates show the daily water consumption of an individual varies
according to the country and the environment (urban or rural); it can be excessive
(600 L day
À1 , in the USA), average (150 to 165 L day
À1 , in France), low (80 to
120 L day
À1 , in developing countries), or very low (<40 L day
À1 , in rural areas)
[3]. After use, the wastewater (WW) is discharged into the sewage system to join
WW treatment plants (WWTPs) where it will be purified. WW undergoes a series of
mechanical, physicochemical, and biological processes to produce clean water that
meets environmental quality standards, preventing stream and river eutrophication
50
E. Ammar et al.
its richness in nutrients and for several environmental and economic reasons, this
waste by-product is widely used as a fertilizer for agricultural purposes under
specific conditions. This practice might be hazardous since this waste includes
many known and unknown non-biodegradable and harmful pollutants, especially
emerging organic contaminants (EOCs), as well as cultivable and non-cultivable
pathogens. The present work is aiming at (1) providing information on the nature of
sludge in terms of persistent pollutants and cultivable and non-cultivable microbiota
generated by the currently implemented treatment processes, (2) analyzing the
consequences of the agricultural valorization on ecosystem biodiversity and soil
fertility, and (3) addressing and discussing the economic, ethical, and environmental
benefits or damage of this type of valorization. These issues need full consideration
by policy makers regarding the agricultural use of this waste by-product in terms of
irrigation with treated domestic wastewater or sludge land spreading as soil fertilizer
and plant growth promoter.
Keywords Economy, Ecotoxicity, Emerging organic contaminants, Ethics,
Irrigation, Land spreading, Metagenomics uncultured pathogens and parasites,
Microbiome, Micropollutants, Sewage sludge
1 Introduction
The human access to drinking water and sanitation is a universal right since water is
a vital resource for life and indispensable for the economy and the development of
nations. The protection of water resources and their sustainable use is becoming a
global issue to thwart consequences of population growth, increased urbanization,
and tourism and climate change with the risk of drought. The treatment and “reuse”
of sewage is among the possible solutions to solve the problem of water availability
for future generations as the world’s demand for safe and healthy food and water is
rapidly increasing [1]. According to the United Nations, the world’s population is
estimated to be 9.7 billion in 2050. Hence, preventing the degradation of soil
ecosystems and water resources must be a priority to consider for the next
decades [2].
Current estimates show the daily water consumption of an individual varies
according to the country and the environment (urban or rural); it can be excessive
(600 L day
À1 , in the USA), average (150 to 165 L day
À1 , in France), low (80 to
120 L day
À1 , in developing countries), or very low (<40 L day
À1 , in rural areas)
[3]. After use, the wastewater (WW) is discharged into the sewage system to join
WW treatment plants (WWTPs) where it will be purified. WW undergoes a series of
mechanical, physicochemical, and biological processes to produce clean water that
meets environmental quality standards, preventing stream and river eutrophication
50
E. Ammar et al.