Treatment of Hospital Wastewater Using Activated Sludge with Extended Aeration

Hospital wastewater is of a complex nature and is generally discharged into urban sewage systems. This study evaluated the removal efficiency of organic and biological contaminants from a hospital wastewater treatment plant using extended aeration activated sludge. The study was conducted at a treatment plant scale, with 14 hours of feed. The plant consists of a pre-filter, a collector and crumbler tank, a homogenization tank, two biological reactors of 80 000 liters capacity each, two settlers and a contact disinfection chamber. Three flow rates of 3 L/s, 4 L/s and 5 L/s were tested in each biological reactor, with application of three concentrations of residual chlorine with sodium hypochlorite to the effluent of the settling tanks (0.3 ppm, 0.4 ppm and 0.5 ppm). The removal ef-ficiency of suspended solids varied according to flow rate. The reactor with a flow rate of 3 L/s and 0.5 ppm of residual chlorine achieved the highest removal of suspended solids (91.95%), biological oxygen demand (97.52%) and fecal coliforms (99.99%). Finally, the quality of the hospital wastewater is within the limits of the national and international environmental quality thresholds.