Journal of Cold Regions Engineering

A full-scale experimental plant intended for local treatment of septic sludge, situated in northern Sweden, is presented in this paper. The concept investigated included natural freezing, thawing, and drying in combination with composting. The experimental plant consisted of an undrained freezing-thawing-drying bed and a heat-insulated composter. About 500 L of fresh sludge, with a dry matter (DM) content of 4–5%, collected from a septic tank employed by one family, was transferred to the freezing-thawing-drying bed in the beginning of November 1996. During the winter months, the sludge froze and then thawed in the middle of May 1997. During a drying period of three weeks, the DM content increased from 10.6–21.3 to 25–95%. The final sludge volume and weight were 180 L and 54 kg, respectively. Approximate concentrations of nitrogen, phosphorus and total organic carbon of the dried sludge were determined to be 23, 5.9, and 346 g/kg DM. From June until the end of August, the sludge was cocomposted with kitchen refuse. Within two weeks, the composting temperature exceeded 65°C. The measured composting temperature indicated a high pathogen die-off, but before this concept can be suggested as an alternative to conventional septic sludge treatment, further studies should be conducted, including direct measurements of pathogens. The concept, however, has proved to be of interest in cold regions due to its simple construction and operation.

A review and comparison of two numerical ice jam profile models is provided. The first is the RIVJAM model, developed at the National Water Research Institute in Canada. The second is the ICEJAM model, which was developed at the University of Alberta and which forms the basis of the solution algorithm in the ice jam calculation routine recently implemented in HEC-RAS. Both the RIVJAM and ICEJAM models solve an ice jam stability equation in conjunction with one-dimensional, steady, gradually varied flow, and both have the capacity to compute profiles for equilibrium and nonequilibrium ice jams. The focus of the investigation is to compare the analytical equations solved, the numerical solution approaches, the required boundary conditions, and the relative sensitivity of the models' calibration parameters. Similarities between the models' governing equations and solution techniques are illustrated through direct comparison of the analytical equations and through model application. Differences between the models' boundary conditions and relative success of calibration are illustrated through the application to case studies.

A large outburst flood from a glacial terminal moraine lake can cause severe damage to downstream communities. This paper presents a study on the outbursts of glacial terminal moraine lakes in the upper Nainchu River basin of Tibet. This study includes an investigation of the number, size, and distribution of glacial terminal moraine lakes; analysis of climatic and geographic factors that contribute to glacial lake outbursts; investigations of the outburst potential of the three largest lakes in the Nainchu River basin; simulations of floods that might occur from the glacial lakes; and a description of the monitoring and flood warning system setup.