Étude de différentes approches visant au recyclage des eaux de lavage d’un procédé de traitement de contenants de PEHD post-consommation

Abstract

The recovery of HDPE residual materials requires them to be cleaned. This washing requires the consumption of a large quantity of water. The municipality’s regulatory constraints require the company to treat its water. In order to reduce water consumption per production unit, this wash water can be recycled as long as it does not disturb the recovery process. In this perspective, the research project aims to evaluate the characteristics of wash water in order to find an appropriate technology to increase the recycling of the water resource. The Soleno recycling plant specializes in the recycling and recovery of HDPE plastic waste for the control and management of rainwater. The goal of the project is to propose a ranking of the scenarios of the wash water treatment process which will allow an increase in the recirculation of this water, and to decrease the consumption of the natural water resource. To achieve this goal, the first objective is to quantify the consumption of wash water as well as the chemical and physical parameters that characterize it. The second objective is to estimate the efficiency of potential technologies for the treatment of wash water. Finally, the methodology of the third objective is the use of the satisfaction analysis method, to allow the ranking of technologies according to multidimensional criteria (technical, social, economic and environmental). The complexity of the project and the choice of a technology comes from the heterogeneity of the composition of the wash water and the interactions of the different compounds between them in relation to the treatment processes. The characterization highlighted the variations of wash water flows (4.6m3/d-10.2m3/d) as well as a high organic load with little biodegradability (BOD5/COD=30%). The characteristics of the water to be treated are, for COD, 96 g-O2/L, of which 71% (±3.1%) are soluble. The SS concentration is 28 g/L of which 48% (± 13 g/L) is volatile in the form of VSS. The variation of the contaminants depends on the origin of the raw material to be recycled and the charges are based on the production characteristics. Tests have shown that dry pretreatment of HDPE flakes prior to washing reduces the mass of contaminants to be washed as well as the water required. Nanofiltration, photocatalysis and electrocoagulation can achieve the treatment objectives, but have important limitations in the industrial context. The analysis of all the results shows that the treatment by evaporation followed by condensation associated with the energetic recovery of residue from the wash water is the system that offers the greatest satisfaction for the industry.

Date	3 Feb 2022
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Robert Hausler (Supervisor)