ANAEROBIC TREATMENT OF CONDENSATES: TRIAL AT A DOMTAR PAPERS KRAFT PULP AND PAPER MILL

摘要

In 1998, the Domtar Papers pulp and paper mill in Windsor investigated the potentialfor treatment of contaminated kraft mill condensates using anaerobic treatment. Theobjectives of this project were to assess the technical feasibility of the replacement ofthe steam stripper by anaerobic treatment; provide basic information for design of ananaerobic treatment of condensates; provide information on treated condensate qualityfor eventual reuse. The project involved extensive chemical characterisation of thecondensates followed by treatability tests. The tests included laboratory bench testsand on-site pilot testing using direct feed from the process. The treatability testing wasdone in collaboration with Biothane Corporation. Characterisation showed that theorganic content of the condensates was essentially methanol as expected but that thefoul evaporator condensates had high sulfide contents.It was found that undiluted foul condensates at the Windsor mill are toxic to theanaerobic biomass due to the high concentrations of sulfides. Treatment of combinedcondensates is possible at an approximate volumetric loading of 10-12 g/L/d COD withgood production of biogas (0.35 L/g of COD removed) and excellent methanol removal(better than 95 %). The biogas produced is of excellent fuel quality with close to 90%methane but high sulfide content (close to 4%).Implementation of kraft mill contaminated condensate treatment using anaerobictreatment is considered to be technically feasible based on this work; design of a fullscale system would require particular attention to protection of the biomass from toxicshocks caused by process upsets. Further work would also be required to gain a betterunderstanding of factors affecting treatment performance.