Wastewater has different origins, it can be domestic, rainwater, household, industrial or agricultural. In order to reduce the impact of human activity on the environment, this wastewater is treated in Polluted Water Treatment Plants (PWTPs) before being released into the environment. According to the Ministry of Ecological Transition, in 2019, France had more than 22 000 wastewater treatment plants, offering a total treatment capacity of 105 million Population Equivalents (p.e. - dimensioning of wastewater treatment systems taking into account the quantity of wastewater emitted per person per day and their pollutant load). In other words, French PWTPs are capable to treat more than 22 million cubic metres of wastewater per day.
Wastewater is treated in several stages. The first stage, the pre-treatment, eliminates most of the suspended solid waste (sand, wood scraps, grease). Primary treatments removes suspended solids through physical processes. Finally, the secondary treatment eliminates matter in solution in water (organic matter, mineral substances) thanks to the action of microorganisms.
The treatment of wastewater generates the production of various residues known as sludge. Today, the production of this sludge in France amounts more than 1 million tons of dry matter. More than 70% of this sludge is used as a fertiliser in agriculture or as a raw material for biogas. The remaining 30% is incinerated (F. Roussel, 2020).
Most of the wastewater comes from domestic use and therefore has a relatively high toilet paper load. The latter is composed exclusively of cellulose and represents more than 23% of suspended solids (C. EME, C. Boutin, 2015). In 2016, a French person consumed an average of 146L of drinking water per day, or about 53.4m3 per year (EauFrance, 2018), and consumed, on average, about 6.4kg of toilet paper per year (Statista, 2018). As toilet paper is essentially made of cellulose fibres, its recovery would represent an abundant source of raw material for France, amounting to approximately 670 000 tonnes per year, and would make it possible to reduce sludge production. Thus, this recycled product would be in line with national objectives and would enable many French companies to reduce the use of fossil resources, particularly oil, and thus lower their carbon footprint.
In addition, France has a positive cellulose import balance in 2019 (International Trade Center, 2020). This recycled cellulose would be a substitute material for raw cellulose in various products such as newspapers, clothing, asphalt bitumen, bioplastics and biocomposites. It could therefore be used in various sectors, and reduce France's dependence, or even reverse its trade balance. In the Plastics sector, cellulose could be incorporated into the biocomposites that make up the products intended for the automobile, up to 5 to 10 kg per car (Andrieu A. 2019). In the Bioplastics sector, 40 to 100% of the cellulose fibres recovered would be used for the manufacture of plastics (French Association for the Development of Bioplastics, s.d). Finally, cellulose could be used in the Building and Public Works (BTP) sector as an additive for bitumen asphalt binder, to the extent of 0.3 to 5% (Bellatrache et al., 2018 and Techniques Routières, 2013).
Recycling is at the heart of current political debates with, in particular, the law n°2020-105 of 10 February 2020 relating to the fight against waste and the circular economy. As a result, cellulosic recovery within wastewater is a major lever for action in France. The use and incorporation of materials from recycling would be a way forward that has already proved its worth in several European countries, notably the Netherlands and Germany, and is about to emerge in France.
Article produced by YEC Vitae in collaboration with PVS GmbH and CirTec.
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