Wastewater generated by the wooden floor industry : Treatability investigation applying individual and coupled technologies

Abstract: During the last half-century a growing concern has taken place in the world regarding water shortage and public health associated to water pollution. Safe discharges of industrial effluents and water reuse within the industry have been encouraged and several initiatives have promoted the development of wastewater treatment technologies with the main focus on industrial sectors that generate large volumes of wastewater. On the other hand, searching for onsite technological options to treat small volumes of highly polluted wastewaters generated by industrial sectors that have no water in their production processes (i.e. wooden floor and furniture industry) has been neglected. To minimize and prevent environmental effects through innovative approaches, onsite treatment options for wastewater generated by cleaning/washing activities in a wooden floor industry in Sweden have been investigated. It was found that different wastewater streams generated after cleaning/washing of machinery and surfaces at different stages of the wooden floor production can pose negative effects to aquatic organisms. Since they are intermittently and manually generated, these wastewater streams have high variability both in volumes and chemical composition. During treatability studies, equalization/sedimentation process was found to be an important pre-treatment step responsible for reduction of chemical oxygen demand (COD) of about 19%. Sorption/filtration with activated carbon and anaerobic biological treatment were found to be technically feasible for both COD and formaldehyde removal. Wood fly ash (waste material with negligible cost) showed moderate sorption efficiency as compared to commercial activated carbon and leaching of secondary pollutants might prevent the use of this material unless pretreatment is carried out. In the anaerobic treatment process, the treatment efficiency of COD in an anaerobic baffled reactor  (ABR) was decreased 50% when the C/N ratio dropped below 3. A successful treatment of the cleaning wastewater with soluble COD removal of about 83% and FA removal higher than 99% was achieved by the ABR operated with hydraulic retention time (HRT) of 5 days. Mole ratio of Mg:N:P and pH were key parameters for ammonium precipitation in the wastewater. At Mg:N:P of 1:1:1 or higher and pH of 8.0, the highest ammonium removal (83%) was achieved. Combinations of treatment processes (e.g. sorption and electrocoagulation or biological treatment and chemical precipitation) improved the quality of the final effluent. However, process optimization is still required in order to improve even more the quality of the final effluent and reduce operation and maintenance costs. From the water reuse/recycle perspective, the application of advanced oxidation in combination with the above-mentioned processes seems to be a promising approach.