Cellulosic materials recovery from municipal wastewater: from treatment plants to the market

IntroductionCellulose is the most abundant available biopolymer (up to 1011 t/annum production) with a high molecular weight (Kumar et al., 2020 ). Cellulose is a long linear polysaccharide polymer consisting of β-1,4-linked glucose units (C5H8O4)m, and exhibits in structural cell wall tissues of all higher plans and some algae, while some bacteria also excrete cellulose. Considering the increasing demand for lignocellulosic raw materials in a huge number of industries, undervalued side streams with a high potential should be well utilized in order to embrace a more circular economy approach that reduces waste and allows for the continual use and re-use of resources (Keijsers et al., 2013; Puyol et al., 2017). For thousands of years, mankind process cellulose derived from plants in the production of pulp, paper, and derivatives. With the adoption of toilet paper in modern societies, cellulose fibers became a primary insoluble substrate entering wastewater treatment plants (WWTPs). In the last decade, cellulose recovery from wastewater has become a topic of interest which has attracted a remarkable attention leading to considerable investments (Palmieri et al., 2019; Ruiken et al., 2013). By introducing a microsieving (mesh size