Correlation of laboratory and installed drainage system solid transport measurements

Abstract

The transport of solids in 'horizontal' above ground drainage pipes was the subject of an investigation, based upon the measurement of both sterile 'model' solid velocity and 'live' waste load velocity, aimed at the establishment of a sound basis for the development of a comprehensive empirical drainage design method linked directly to installed drainage system solid transport measurements. Initial laboratory investigations were directed towards the assessment of various 'model' solid materials, with regard to comparative potential use with respect to drainage research. Results suggested a 'calibration' approach to the development of a design method to be a viable proposition, while a 'direct simulation' approach was found to be impracticable. Two installed branch drainage systems were monitored which served male and female W.C. cubicles in the entrance waiting-area of a large London hospital. A considerable body of data was compiled with respect to both facility usage patterns and drainage system loading. Transport performance data, classified according to waste load type, was processed to yield comparisons to the general form of relationships previously reported in relation to 'model' solid transport. It was concluded that the proportional rate of occurrence of the different types of waste load must be a prime consideration in any design method, and the premise that solid deposition should be avoided was confirmed. Solid transport mechanisms, as associated with each of the different types of 'live' waste load material and sterile 'model'. were detailed, and the relevance to 'live' waste load performance, of previous 'model' solid transport equations (which suggest 'linear' deceleration over substantial pipe lengths), was demonstrated. The study was concluded with the presentation of specific design performance recommendations, based upon the installed drainage system transport measurements, which data may be employed, initially, as the basis for a 'calibration' approach to laboratory based drainage research, and subsequently, as the basis for a comprehensive empirical drainage design method.