ANAEROBIC TREATMENT OF DISTILLERY WASTEWATER
Abstract:A conventional thermophilic anaerobic digester was converted to a thermophilic high-rate hybrid anaerobic reactor for treating distillery wastewater of the Il-San distillery in Pusan, Korea. At loading rates of 5.45 to 15.02kg/m3/d, the hybrid reactor had been operating successfully without any system upset since May 1995 until August 1999. During this period the reactor has demonstrated soluble chemical oxygen demand (sCOD) removal efficiencies of 85 to 91% and total COD (tCOD) removal efficiencies of 72 to 84%. The product gas had methane content of 59 to 68%. Total COD removal rates were 4.31 to 5.43, 6.26 to 6.89 and 9.03 to 9.78kgtCOD/m3/d for tapioca, corn, and naked-barley wastewater, respectively. Soluble COD removal rates ranged from 3.75 to 4.79, 3.28 to 4.89 and 5.57 to 6.21kgsCOD/m3/d for tapioca, corn, and naked-barley wastewater, respectively. The hybrid reactor was capable of handling very high SS input and demonstrated SS removal efficiencies of 9 to 16, 35 to 49, and 60 to 71% for tapioca, corn, and naked-barley wastewater, respectively.
There are unknown substances in naked-barley wastewater toxic to anaerobic microorganisms. Treating naked-barley wastewater for 26 days continuously at an average tCOD loading rate of 11.08kg/m3/d, however, the hybrid reactor did not experience any deterioration in either COD removal efficiency or gas production rate. During this period, average removal efficiencies of tCOD and sCOD were 84% and 91%, respectively and the biogas production rate averaged 6.61 ˜7.57m3/m3reactor/d while producing 0.57˜0.69m3biogas/kgtCODrem. (at standard conditions of 0°C and 1atm pressure). When treating tapioca and corn wastewater, the reactor showed average gas production rate of 0.53 to 0.69 and 0.62 to 0.71m3/kgtCODrem.(at standard conditions), respectively. Biogas production rates ranged from 3.18 to 3.46 and 4.91 to 5.22m3/m3 reactor/d for tapioca and corn wastewater, respectively.
During the month of September 1999, reactor pH gradually dropped to 6.4 and sCOD removal efficiency dropped to 80% from usual value of 90%. During the month of October 1999, reactor pH and alkalinity dropped sharply and emergency NaOH addition had to be done. After 7 days of NaOH addition and reduced influent flow rate, the hybrid reactor recovered but the reactor could not perform as before. Since clogging (and thus, short-circuiting) in the hybrid reactor was suspected as the reason for this reactor failure, two tracer tests with LiCl were performed on March and July 2000 in order to estimate the degree of clogging. Operation results of the thermophilic high-rate hybrid reactor since start-up are presented and discussed along with the results of two tracer tests.
Document Type: Research Article
Publication date: January 1, 2001
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