Anaerobic treatment of human waste in northern communities

Abstract

Many communities in Canada's northern areas rely on a trucked supply of water and pickup of human waste from bucket toilets or holding tanks. The high capital costs of conventional piped water and gravity sewer systems and the lack of funds necessitate the continued use of trucked systems for many years, particularly in the smaller settlements in permafrost regions. Promising methods of cheaper piped collection of wastes, such as vacuum and pressure sewers, may be used in the near future. Both require only small quantities of water for the transport of solids. Human wastes in plastic bags ("honey bags") are now disposed of at a dump, in waste pits, or lagoons. Satisfactory treatment methods for these strong wastes and for wastes from holding tanks, vacuum, and pressure sewers are needed.Results of a 5 year study simulating a waste pit in permafrost show that it merely serves as a holding tank and does not provide satisfactory treatment. Pathogens are likely to remain viable in such a pit for many years. Anaerobic digestion of undiluted human waste has been found feasible at 20 °C, but is not likely to be a practical and economical solution for communities using trucked systems. Properly located, constructed, and operated waste pits are recommended for these situations.Anaerobic digestion of vacuum sewer wastes, which are much less dilute than sewage, is feasible at a temperature of 20 °C and with a minimum detention time of 30 days. The process may be applicable at lower temperatures, provided a high proportion of methane bacteria is maintained in the reactor. This may be accomplished either by longer detention time or through the anaerobic contact process. It is recommended that a pilot installation be constructed together with a vacuum sewer system in a northern community using anaerobic digestion as the method of treatment of vacuum sewer wastes.