Settling/Sedimentation Followed by Sorption with <i>Pinus sylvestris</i> Sawdust as “Green” Sorbent: On-Site Treatment of a Real Industrial Wastewater

Abstract

Whereas the pulp and paper industrial sector—considered the second highest consumer of freshwater in Europe—has already been provided with sufficient wastewater characterization and treatment technologies, other wood-based industries (e.g. furniture, floor production), which do not use water for manufacturing processes, generate different wastewater streams after : 1) cleaning/washing of machinery that applies adhesives and coatings onto wood surfaces; 2) cleaning/washing of machinery that applies specific products for the curing phase of adhesives; 3) cleaning/washing of sharp planar blades used for the sawn process and to prepare wood surfaces for the adhesive application; 4) cleaning/washing of the floor; 5) cleaning/washing of trucks and vehicles. The dilution of low-volumes of highly polluted wastewater is not acceptable any longer since conventional treatment plants are not designed for these types of industrial wastewater. There is a need for proper characterization, treatability studies, designing and testing alternative small size and cost-effective treatment systems for on-site implementation. Treatment systems based on sorption mechanisms are flexible, easy to operate and generate less sludge and several low-cost sorbents generated by forestry activities have advantageous physico-chemical characteristics. The current paper presents the preliminary results from a pilot treatment system consisting of an equalization tank, settling/sedimentation and two sorption reactors in parallel using Pinus sylvestris sawdust as sorbent implemented as part of an integrated water management plan in a wood-floor industry. The simple to operate and cost-effective pilot treatment system performs satisfactorily during an initial period of operation. The study shows an average 39% - 54% reduction of TPH; 17% - 38% reduction of oil; 2% - 15% of reduction of COD and; 11% - 74% reduction of most toxic metals but for Co, Ni and Zn in the system B. Based on these results, Pinus sylvestris sawdust is a potential low-cost and abundant material to be considered for industrial wastewater treatment plants.