Case history - Two stage, low-rate anaerobic treatment facility for South American alcochemical citric acid wastewater

This paper describes the case history of a two-stage, low-rate anaerobic tr eatment system at a South American alcochemical and citric acid plant. Envi ronmental concerns associated with land irrigation of a high-strength indus trial wastewater forced the plant to implement wastewater treatment. This p aper will also outline results from an on-site pilot study which was conduc ted to develop the design criteria for the full-scale system. The installed full-scale system will be described in detail, including the plant s physical layout, design parameters, system performance, biogas prod uction and utilization, and some of its unique aspects. Among these is the use of a floating biofilter (bagasse) on the second stage to eliminate any nuisance odours from off gases. All biogas generated in the first stage is collected, with a significant po rtion drawn off and burned in a retrofitted 8000 kW boiler to generate proc ess steam. The excess biogas is flared. Effluent from the treatment system is combined with other low-strength process plant streams and discharged to a river. During the first year of operation, performance has been very good, with ch emical oxygen demand (COD), biochemical oxygen demand (BOD), and total susp ended solids (TSS) removals averaging 74 percent, 93 percent, and 70 percen t, respectively. The corresponding GOD, BOD, and TSS results obtained in th e pilot study were 74 percent, 96 percent, and 70 percent, respectively, an d agree very well with those being obtained in full scale. (C) 1998 Publish ed by Elsevier Science Ltd. All rights reserved.