Characterization and biological treatment of pickling industry wastewater

Pickling industry wastewaters present unique difficulties in biological tre atment because of high salt content (3-6% salt). Conventional activated slu dge cultures disintegrate or loose microbial activity as a result of plasmo lysis at salt concentrations above 1%. In order to overcome adverse effects of salt in pickling wastewater, salt tolerant bacteria (Halobacter halobiu m) was added to activated sludge culture and used in biological treatment o f the wastewater in an activated sludge unit. After characterization and nutrient balancing of the wastewater, an activat ed sludge unit was used in laboratory to investigate the effects of major p rocess variables such as sludge age and hydraulic residence time on perform ance of the system. Single stage and two stage activated processes were use d for the treatment of the pickling wastewater. More than 95% of COD remova l was obtained with a single stage process at a sludge age of theta (c) = 1 0 d and hydraulic residence time of theta (H) = 30 h. Similar results were obtained with the two stage process, when sludge ages and hydraulic residen ce times for each stage were theta (c1) = theta (c2) = 10 d, and theta (H1) = theta (H2) = 15 h, respectively. Kinetic coefficients were determined an d the design equations were developed by using the experimental data.